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Tripp TR, McDougall RM, Frankish BP, Wiley JP, Lun V, MacInnis MJ. Contraction intensity affects NIRS-derived skeletal muscle oxidative capacity but not its relationships to mitochondrial protein content or aerobic fitness. J Appl Physiol (1985) 2024; 136:298-312. [PMID: 38059287 DOI: 10.1152/japplphysiol.00342.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 11/16/2023] [Accepted: 12/02/2023] [Indexed: 12/08/2023] Open
Abstract
To further refine the near-infrared spectroscopy (NIRS)-derived measure of skeletal muscle oxidative capacity in humans, we sought to determine whether the exercise stimulus intensity affected the τ value and/or influenced the magnitude of correlations with in vitro measures of mitochondrial content and in vivo indices of exercise performance. Males (n = 12) and females (n = 12), matched for maximal aerobic fitness per fat-free mass, completed NIRS-derived skeletal muscle oxidative capacity tests for the vastus lateralis following repeated contractions at 40% (τ40) and 100% (τ100) of maximum voluntary contraction, underwent a skeletal muscle biopsy of the same muscle, and performed multiple intermittent isometric knee extension tests to task failure to establish critical torque (CT). The value of τ100 (34.4 ± 7.0 s) was greater than τ40 (24.2 ± 6.9 s, P < 0.001), but the values were correlated (r = 0.688; P < 0.001). The values of τ40 (r = -0.692, P < 0.001) and τ100 (r = -0.488, P = 0.016) correlated with myosin heavy chain I percentage and several markers of mitochondrial content, including COX II protein content in whole muscle (τ40: r = -0.547, P = 0.006; τ100: r = -0.466, P = 0.022), type I pooled fibers (τ40: r = -0.547, P = 0.006; τ100: r = -0.547, P = 0.006), and type II pooled fibers (τ40: r = -0.516, P = 0.009; τ100: r = -0.635, P = 0.001). The value of τ40 (r = -0.702, P < 0.001), but not τ100 (r = -0.378, P = 0.083) correlated with critical torque (CT); however, neither value correlated with W' (τ40: r = 0.071, P = 0.753; τ100: r = 0.054, P = 0.812). Overall, the NIRS method of assessing skeletal muscle oxidative capacity is sensitive to the intensity of skeletal muscle contraction but maintains relationships to whole body fitness, isolated limb critical intensity, and mitochondrial content regardless of intensity.NEW & NOTEWORTHY Skeletal muscle oxidative capacity measured using near-infrared spectroscopy (NIRS) was lower following high-intensity compared with low-intensity isometric knee extension contractions. At both intensities, skeletal muscle oxidative capacity was correlated with protein markers of mitochondrial content (in whole muscle and pooled type I and type II muscle fibers) and critical torque. These findings highlight the importance of standardizing contraction intensity while using the NIRS method with isometric contractions and further demonstrate its validity.
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Affiliation(s)
- Thomas R Tripp
- Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | | | | | - J Preston Wiley
- Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
- Faculty of Kinesiology, University of Calgary Sport Medicine Centre, Calgary, Alberta, Canada
| | - Victor Lun
- Faculty of Kinesiology, University of Calgary Sport Medicine Centre, Calgary, Alberta, Canada
| | - Martin J MacInnis
- Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
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2
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Van Vossel K, Hardeel J, Van de Casteele F, de Jager S, Lievens E, Boone J, Derave W. Muscle typology influences the number of repetitions to failure during resistance training. Eur J Sport Sci 2023; 23:2021-2030. [PMID: 37092841 DOI: 10.1080/17461391.2023.2207077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/25/2023]
Abstract
This study examined whether muscle typology (muscle fibre type composition) is related to maximal strength and whether it can explain the high inter-individual variability in number of repetitions to failure during resistance training. Ninety-five resistance training novices (57 males) were assessed for their maximal isometric knee extension strength and muscle typology. Muscle typology was estimated by measuring carnosine in the soleus, gastrocnemius and/or vastus lateralis using proton magnetic resonance spectroscopy. Forty-four subjects (22 males) performed dynamic strength tests (1RM) and 3 sets of leg extensions and curls to failure (60%1RM) to determine the association between muscle typology and (total) number of repetitions. Twenty-one subjects performed additional biceps curls and triceps extensions (60%1RM) to assess influence of exercise, 23 subjects performed additional leg extensions and curls at 80% and 40%1RM to evaluate influence of training load. There was a weak but significant relationship between muscle typology and maximal isometric strength (r = 0.22, p = 0.03) favouring the fast typology individuals. Slow and fast typology individuals did not differ in upper arm and upper leg 1RM. Total number of repetitions was related to muscle typology at 80% (r = -0.42; p = 0.04) and 60% (p = -0.44; p = 0.003) but not at 40%1RM. Slow typology individuals performed more repetitions to failure at 60%1RM in the leg extension (p = 0.03), leg curl (p = 0.01) and biceps curl (p = 0.02). In conclusion, muscle typology has a small contribution to maximal isometric strength but not dynamic strength and partly determines the number of repetitions to failure during resistance training. This insight can help individualizing resistance training prescriptions.
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Affiliation(s)
- Kim Van Vossel
- Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium
| | - Julie Hardeel
- Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium
| | | | - Sarah de Jager
- Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium
| | - Eline Lievens
- Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium
| | - Jan Boone
- Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium
| | - Wim Derave
- Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium
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3
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Van Vossel K, Hardeel J, Van de Casteele F, Van der Stede T, Weyns A, Boone J, Blemker SS, Lievens E, Derave W. Can muscle typology explain the inter-individual variability in resistance training adaptations? J Physiol 2023; 601:2307-2327. [PMID: 37038845 DOI: 10.1113/jp284442] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Accepted: 04/03/2023] [Indexed: 04/12/2023] Open
Abstract
Considerable inter-individual heterogeneity exists in the muscular adaptations to resistance training. It has been proposed that fast-twitch fibres are more sensitive to hypertrophic stimuli and thus that variation in muscle fibre type composition is a contributing factor to the magnitude of training response. This study investigated if the inter-individual variability in resistance training adaptations is determined by muscle typology and if the most appropriate weekly training frequency depends on muscle typology. In strength-training novices, 11 slow (ST) and 10 fast typology (FT) individuals were selected by measuring muscle carnosine with proton magnetic resonance spectroscopy. Participants trained both upper arm and leg muscles to failure at 60% of one-repetition maximum (1RM) for 10 weeks, whereby one arm and leg trained 3×/week and the contralateral arm and leg 2×/week. Muscle volume (MRI-based 3D segmentation), maximal dynamic strength (1RM) and fibre type-specific cross-sectional area (vastus lateralis biopsies) were evaluated. The training response for total muscle volume (+3 to +14%), fibre size (-19 to +22%) and strength (+17 to +47%) showed considerable inter-individual variability, but these could not be attributed to differences in muscle typology. However, ST individuals performed a significantly higher training volume to gain these similar adaptations than FT individuals. The limb that trained 3×/week had generally more pronounced hypertrophy than the limb that trained 2×/week, and there was no interaction with muscle typology. In conclusion, muscle typology cannot explain the high variability in resistance training adaptations when training is performed to failure at 60% of 1RM. KEY POINTS: This study investigated the influence of muscle typology (muscle fibre type composition) on the variability in resistance training adaptations and on its role in the individualization of resistance training frequency. We demonstrate that an individual's muscle typology cannot explain the inter-individual variability in resistance training-induced increases in muscle volume, maximal dynamic strength and fibre cross-sectional area when repetitions are performed to failure. Importantly, slow typology individuals performed a significantly higher training volume to obtain similar adaptations compared to fast typology individuals. Muscle typology does not determine the most appropriate resistance training frequency. However, regardless of muscle typology, an additional weekly training (3×/week vs. 2×/week) increases muscle hypertrophy but not maximal dynamic strength. These findings expand on our understanding of the underlying mechanisms for the large inter-individual variability in resistance training adaptations.
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Affiliation(s)
- Kim Van Vossel
- Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium
| | - Julie Hardeel
- Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium
| | | | - Thibaux Van der Stede
- Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium
- Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - Anneleen Weyns
- Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium
| | - Jan Boone
- Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium
| | - Silvia Salinas Blemker
- Department of Biomedical Engineering, University of Virginia, Charlottesville, VA, USA
- Springbok Analytics, Charlottesville, VA, USA
| | - Eline Lievens
- Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium
| | - Wim Derave
- Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium
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4
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Festa RR, Monsalves-Álvarez M, Cancino J, Jannas-Vela S. Prescription of High-intensity Aerobic Interval Training Based on Oxygen Uptake Kinetics. Int J Sports Med 2023; 44:159-168. [PMID: 35995143 DOI: 10.1055/a-1929-0295] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Endurance training results in diverse adaptations that lead to increased performance and health benefits. A commonly measured training response is the analysis of oxygen uptake kinetics, representing the demand of a determined load (speed/work) on the cardiovascular, respiratory, and metabolic systems, providing useful information for the prescription of constant load or interval-type aerobic exercise. There is evidence that during high-intensity aerobic exercise some interventions prescribe brief interval times (<1-min), which may lead to a dissociation between the load prescribed and the oxygen uptake demanded, potentially affecting training outcomes. Therefore, this review explored the time to achieve a close association between the speed/work prescribed and the oxygen uptake demanded after the onset of high-intensity aerobic exercise. The evidence assessed revealed that at least 80% of the oxygen uptake amplitude is reached when phase II of oxygen uptake kinetics is completed (1 to 2 minutes after the onset of exercise, depending on the training status). We propose that the minimum work-time during high-intensity aerobic interval training sessions should be at least 1 minute for athletes and 2 minutes for non-athletes. This suggestion could be used by coaches, physical trainers, clinicians and sports or health scientists for the prescription of high-intensity aerobic interval training.
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Affiliation(s)
- Raúl Ricardo Festa
- Laboratorio de Fisiología del Ejercicio y Metabolismo, Escuela de Kinesiología, Universidad Finis Terrae, Santiago, Chile
| | | | - Jorge Cancino
- Laboratorio de Fisiología del Ejercicio y Metabolismo, Escuela de Kinesiología, Universidad Finis Terrae, Santiago, Chile
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5
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Petrick HL, Brownell S, Vachon B, Brunetta HS, Handy RM, van Loon LJC, Murrant CL, Holloway GP. Dietary nitrate increases submaximal SERCA activity and ADP transfer to mitochondria in slow-twitch muscle of female mice. Am J Physiol Endocrinol Metab 2022; 323:E171-E184. [PMID: 35732003 DOI: 10.1152/ajpendo.00371.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Rapid oscillations in cytosolic calcium (Ca2+) coordinate muscle contraction, relaxation, and physical movement. Intriguingly, dietary nitrate decreases ATP cost of contraction, increases force production, and increases cytosolic Ca2+, which would seemingly necessitate a greater demand for sarcoplasmic reticulum Ca2+ ATPase (SERCA) to sequester Ca2+ within the sarcoplasmic reticulum (SR) during relaxation. As SERCA is highly regulated, we aimed to determine the effect of 7-day nitrate supplementation (1 mM via drinking water) on SERCA enzymatic properties and the functional interaction between SERCA and mitochondrial oxidative phosphorylation. In soleus, we report that dietary nitrate increased force production across all stimulation frequencies tested, and throughout a 25 min fatigue protocol. Mice supplemented with nitrate also displayed an ∼25% increase in submaximal SERCA activity and SERCA efficiency (P = 0.053) in the soleus. To examine a possible link between ATP consumption and production, we established a methodology coupling SERCA and mitochondria in permeabilized muscle fibers. The premise of this experiment is that the addition of Ca2+ in the presence of ATP generates ADP from SERCA to support mitochondrial respiration. Similar to submaximal SERCA activity, mitochondrial respiration supported by SERCA-derived ADP was increased by ∼20% following nitrate in red gastrocnemius. This effect was fully attenuated by the SERCA inhibitor cyclopiazonic acid and was not attributed to differences in mitochondrial oxidative capacity, ADP sensitivity, protein content, or reactive oxygen species emission. Overall, these findings suggest that improvements in submaximal SERCA kinetics may contribute to the effects of nitrate on force production during fatigue.NEW & NOTEWORTHY We show that nitrate supplementation increased force production during fatigue and increased submaximal SERCA activity. This was also evident regarding the high-energy phosphate transfer from SERCA to mitochondria, as nitrate increased mitochondrial respiration supported by SERCA-derived ADP. Surprisingly, these observations were only apparent in muscle primarily expressing type I (soleus) but not type II fibers (EDL). These findings suggest that alterations in SERCA properties are a possible mechanism in which nitrate increases force during fatiguing contractions.
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Affiliation(s)
- Heather L Petrick
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
- Department of Human Biology, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht, the Netherlands
| | - Stuart Brownell
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Bayley Vachon
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Henver S Brunetta
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
- Department of Physiological Sciences, Federal University of Santa Catarina, Santa Catarina, Brazil
| | - Rachel M Handy
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Luc J C van Loon
- Department of Human Biology, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht, the Netherlands
| | - Coral L Murrant
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Graham P Holloway
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
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6
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Barclay CJ, Launikonis BS. A mathematical model to quantify RYR Ca2+ leak and associated heat production in resting human skeletal muscle fibers. J Gen Physiol 2022; 154:213077. [PMID: 35311921 PMCID: PMC9037342 DOI: 10.1085/jgp.202112994] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Accepted: 02/06/2022] [Indexed: 02/02/2023] Open
Abstract
Cycling of Ca2+ between the sarcoplasmic reticulum (SR) and myoplasm is an important component of skeletal muscle resting metabolism. As part of this cycle, Ca2+ leaks from the SR into the myoplasm and is pumped back into the SR using ATP, which leads to the consumption of O2 and generation of heat. Ca2+ may leak through release channels or ryanodine receptors (RYRs). RYR Ca2+ leak can be monitored in a skinned fiber preparation in which leaked Ca2+ is pumped into the t-system and measured with a fluorescent dye. However, accurate quantification faces a number of hurdles. To overcome them, we developed a mathematical model of Ca2+ movement in these preparations. The model incorporated Ca2+ pumps that move Ca2+ from the myoplasm to the SR and from the junctional space (JS) to the t-system, Ca2+ buffering by EGTA in the JS and myoplasm and by buffers in the SR, and Ca2+ leaks from the SR into the JS and myoplasm and from the t-system into the myoplasm. The model accurately simulated Ca2+ uptake into the t-system, the relationship between myoplasmic [Ca2+] and steady-state t-system [Ca2+], and the effect of blocking RYR Ca2+ leak on t-system Ca2+ uptake. The magnitude of the leak through the RYRs would contribute ∼5% of the resting heat production of human muscle. In normal resting fibers, RYR Ca2+ leak makes a small contribution to resting metabolism. RYR-focused pathologies have the potential to increase RYR Ca2+ leak and the RYR leak component of resting metabolism.
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7
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Abstract
A hallmark of adaptation in humans and other animals is our ability to control how we think and behave across different settings. Research has characterized the various forms cognitive control can take-including enhancement of goal-relevant information, suppression of goal-irrelevant information, and overall inhibition of potential responses-and has identified computations and neural circuits that underpin this multitude of control types. Studies have also identified a wide range of situations that elicit adjustments in control allocation (e.g., those eliciting signals indicating an error or increased processing conflict), but the rules governing when a given situation will give rise to a given control adjustment remain poorly understood. Significant progress has recently been made on this front by casting the allocation of control as a decision-making problem. This approach has developed unifying and normative models that prescribe when and how a change in incentives and task demands will result in changes in a given form of control. Despite their successes, these models, and the experiments that have been developed to test them, have yet to face their greatest challenge: deciding how to select among the multiplicity of configurations that control can take at any given time. Here, we will lay out the complexities of the inverse problem inherent to cognitive control allocation, and their close parallels to inverse problems within motor control (e.g., choosing between redundant limb movements). We discuss existing solutions to motor control's inverse problems drawn from optimal control theory, which have proposed that effort costs act to regularize actions and transform motor planning into a well-posed problem. These same principles may help shed light on how our brains optimize over complex control configuration, while providing a new normative perspective on the origins of mental effort.
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8
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Akberdin IR, Kiselev IN, Pintus SS, Sharipov RN, Vertyshev AY, Vinogradova OL, Popov DV, Kolpakov FA. A Modular Mathematical Model of Exercise-Induced Changes in Metabolism, Signaling, and Gene Expression in Human Skeletal Muscle. Int J Mol Sci 2021; 22:10353. [PMID: 34638694 PMCID: PMC8508736 DOI: 10.3390/ijms221910353] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Revised: 09/04/2021] [Accepted: 09/22/2021] [Indexed: 11/29/2022] Open
Abstract
Skeletal muscle is the principal contributor to exercise-induced changes in human metabolism. Strikingly, although it has been demonstrated that a lot of metabolites accumulating in blood and human skeletal muscle during an exercise activate different signaling pathways and induce the expression of many genes in working muscle fibres, the systematic understanding of signaling-metabolic pathway interrelations with downstream genetic regulation in the skeletal muscle is still elusive. Herein, a physiologically based computational model of skeletal muscle comprising energy metabolism, Ca2+, and AMPK (AMP-dependent protein kinase) signaling pathways and the expression regulation of genes with early and delayed responses was developed based on a modular modeling approach and included 171 differential equations and more than 640 parameters. The integrated modular model validated on diverse including original experimental data and different exercise modes provides a comprehensive in silico platform in order to decipher and track cause-effect relationships between metabolic, signaling, and gene expression levels in skeletal muscle.
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Affiliation(s)
- Ilya R. Akberdin
- Department of Computational Biology, Scientific Center for Information Technologies and Artificial Intelligence, Sirius University of Science and Technology, 354340 Sochi, Russia; (I.N.K.); (S.S.P.); (R.N.S.); (F.A.K.)
- BIOSOFT.RU, LLC, 630090 Novosibirsk, Russia
- Department of Natural Sciences, Novosibirsk State University, 630090 Novosibirsk, Russia
- Federal Research Center Institute of Cytology and Genetics SB RAS, 630090 Novosibirsk, Russia
| | - Ilya N. Kiselev
- Department of Computational Biology, Scientific Center for Information Technologies and Artificial Intelligence, Sirius University of Science and Technology, 354340 Sochi, Russia; (I.N.K.); (S.S.P.); (R.N.S.); (F.A.K.)
- BIOSOFT.RU, LLC, 630090 Novosibirsk, Russia
- Laboratory of Bioinformatics, Federal Research Center for Information and Computational Technologies, 633010 Novosibirsk, Russia
| | - Sergey S. Pintus
- Department of Computational Biology, Scientific Center for Information Technologies and Artificial Intelligence, Sirius University of Science and Technology, 354340 Sochi, Russia; (I.N.K.); (S.S.P.); (R.N.S.); (F.A.K.)
- BIOSOFT.RU, LLC, 630090 Novosibirsk, Russia
- Laboratory of Bioinformatics, Federal Research Center for Information and Computational Technologies, 633010 Novosibirsk, Russia
| | - Ruslan N. Sharipov
- Department of Computational Biology, Scientific Center for Information Technologies and Artificial Intelligence, Sirius University of Science and Technology, 354340 Sochi, Russia; (I.N.K.); (S.S.P.); (R.N.S.); (F.A.K.)
- BIOSOFT.RU, LLC, 630090 Novosibirsk, Russia
- Department of Natural Sciences, Novosibirsk State University, 630090 Novosibirsk, Russia
- Laboratory of Bioinformatics, Federal Research Center for Information and Computational Technologies, 633010 Novosibirsk, Russia
| | | | - Olga L. Vinogradova
- Institute of Biomedical Problems of the Russian Academy of Sciences, 123007 Moscow, Russia;
| | - Daniil V. Popov
- Institute of Biomedical Problems of the Russian Academy of Sciences, 123007 Moscow, Russia;
| | - Fedor A. Kolpakov
- Department of Computational Biology, Scientific Center for Information Technologies and Artificial Intelligence, Sirius University of Science and Technology, 354340 Sochi, Russia; (I.N.K.); (S.S.P.); (R.N.S.); (F.A.K.)
- BIOSOFT.RU, LLC, 630090 Novosibirsk, Russia
- Laboratory of Bioinformatics, Federal Research Center for Information and Computational Technologies, 633010 Novosibirsk, Russia
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9
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Abstract
Abstract. Attaining sports or health goals requires not only high motivation but also the willpower to translate sport-behavior intentions into successful action. This volitional regulation calls for the mobilization of effort to overcome obstacles in the pursuit of goals. The present article provides a theoretical and empirical overview of motivation intensity theory ( Brehm & Self, 1989 ) – a conceptual framework that makes clear and testable predictions about effort mobilization in various contexts. First, we present the guiding principles of this theory and its operationalizations by measures of effort-related cardiovascular reactivity and physical handgrip force. Second, we review a selection of empirical tests of the basic assumptions of this theory and the impact of psychological moderator variables such as affect, fatigue, pain, and personality on effort mobilization. Finally, we discuss important implications of these findings for the sports and health domains and make suggestions for future research.
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10
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Hering GO, Stepan J. The Maximal Lactate Steady State Workload Determines Individual Swimming Performance. Front Physiol 2021; 12:668123. [PMID: 33981254 PMCID: PMC8107465 DOI: 10.3389/fphys.2021.668123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Accepted: 03/31/2021] [Indexed: 11/13/2022] Open
Abstract
The lactate threshold (LT) and the strongly related maximal lactate steady state workload (MLSSW) are critical for physical endurance capacity and therefore of major interest in numerous sports. However, their relevance to individual swimming performance is not well understood. We used a custom-made visual light pacer for real-time speed modulation during front crawl to determine the LT and MLSSW in a single-exercise test. When approaching the LT, we found that minute variations in swimming speed had considerable effects on blood lactate concentration ([La-]). The LT was characterized by a sudden increase in [La-], while the MLSSW occurred after a subsequent workload reduction, as indicated by a rapid cessation of blood lactate accumulation. Determination of the MLSSW by this so-called "individual lactate threshold" (ILT)-test was highly reproducible and valid in a constant speed test. Mean swimming speed in 800 and 1,500 m competition (S-Comp) was 3.4% above MLSSW level and S-Comp, and the difference between S-Comp and the MLSSW (Δ S-Comp/MLSSW) were higher for long-distance swimmers (800-1,500 m) than for short- and middle-distance swimmers (50-400 m). Moreover, Δ S-Comp/MLSSW varied significantly between subjects and had a strong influence on overall swimming performance. Our results demonstrate that the MLSSW determines individual swimming performance, reflects endurance capacity in the sub- to supra-threshold range, and is therefore appropriate to adjust training intensity in moderate to severe domains of exercise.
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Affiliation(s)
- Gernot O Hering
- Department of Sport and Health Science, University of Konstanz, Konstanz, Germany
| | - Jens Stepan
- Department of Sport and Health Science, University of Konstanz, Konstanz, Germany.,Department of Obstetrics and Gynaecology, Paracelsus Medical University, Salzburg, Austria
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11
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Cao T, Jin JP. Evolution of Flight Muscle Contractility and Energetic Efficiency. Front Physiol 2020; 11:1038. [PMID: 33162892 PMCID: PMC7581897 DOI: 10.3389/fphys.2020.01038] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2020] [Accepted: 07/29/2020] [Indexed: 12/19/2022] Open
Abstract
The powered flight of animals requires efficient and sustainable contractions of the wing muscles of various flying species. Despite their high degree of phylogenetic divergence, flight muscles in insects and vertebrates are striated muscles with similarly specialized sarcomeric structure and basic mechanisms of contraction and relaxation. Comparative studies examining flight muscles together with other striated muscles can provide valuable insights into the fundamental mechanisms of muscle contraction and energetic efficiency. Here, we conducted a literature review and data mining to investigate the independent emergence and evolution of flight muscles in insects, birds, and bats, and the likely molecular basis of their contractile features and energetic efficiency. Bird and bat flight muscles have different metabolic rates that reflect differences in energetic efficiencies while having similar contractile machinery that is under the selection of similar natural environments. The significantly lower efficiency of insect flight muscles along with minimized energy expenditure in Ca2+ handling is discussed as a potential mechanism to increase the efficiency of mammalian striated muscles. A better understanding of the molecular evolution of myofilament proteins in the context of physiological functions of invertebrate and vertebrate flight muscles can help explore novel approaches to enhance the performance and efficiency of skeletal and cardiac muscles for the improvement of human health.
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Affiliation(s)
| | - J.-P. Jin
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI, United States
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12
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Reggiani C. Caffeine as a tool to investigate sarcoplasmic reticulum and intracellular calcium dynamics in human skeletal muscles. J Muscle Res Cell Motil 2020; 42:281-289. [PMID: 32034582 DOI: 10.1007/s10974-020-09574-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Accepted: 01/30/2020] [Indexed: 12/23/2022]
Abstract
Caffeine is worldwide used for its power to increase cognitive and physical performance. The ergogenic effects of caffeine, however, do not depend on a direct action on muscles. Actually, the actions of caffeine on skeletal muscles, take place at millimolar concentrations which are far above the micromolar level reached after a regular consumption of coffee or similar drinks, and close to a lethal concentration. At millimolar concentrations caffeine exerts a powerful effect on sarcoplasmic reticulum (SR) activating the release of calcium via ryanodine receptors and, possibly, inhibiting calcium reuptake. For this reason caffeine has become a valuable tool for studying SR function and for diagnostics of SR related muscle disorders. This review aims to briefly describe the effects and the mechanism of action of caffeine on sarcoplasmic reticulum and to focus on its use to study intracellular calcium dynamics in human muscle fibers in physiological and pathological conditions.
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Affiliation(s)
- Carlo Reggiani
- Department of Biomedical Sciences, University of Padova, Via Marzolo 3, 35131, Padua, Italy. .,ZRS-Science and Research Center, Koper, Slovenia.
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13
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P i-induced muscle fatigue leads to near-hyperbolic power-duration dependence. Eur J Appl Physiol 2019; 119:2201-2213. [PMID: 31399839 DOI: 10.1007/s00421-019-04204-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Accepted: 08/01/2019] [Indexed: 12/20/2022]
Abstract
PURPOSE Consequences of combining three ideas proposed previously by other authors: (1) that there exists a critical power (CP), above which no steady state in [Formula: see text]O2 (oxygen consumption) and metabolites can be achieved in voluntary constant-power exercise; (2) that muscle fatigue is related to decreased exercise efficiency (increased [Formula: see text]O2/power output ratio); and (3) that Pi (inorganic phosphate) is the main fatigue-related metabolite are investigated. METHODS A previously-developed computer model of the skeletal muscle bioenergetic system is used. It was assumed in computer simulations that skeletal muscle work terminates when cytosolic Pi (inorganic phosphate) exceeds a certain critical level. RESULTS Simulated changes in muscle [Formula: see text]O2, cytosolic ADP, pH, PCr and Pi as a function of time at various ATP usage activities (corresponding to power outputs) agreed well with experimental data. Computer simulations resulted in a fourth previously-published idea: (4) that the power-duration relationship describing the dependence of power output (PO) on the time to exhaustion of voluntary constant-power exercise at a given PO has a (near-)hyperbolic shape. CONCLUSIONS Pi is a major factor contributing to muscle fatigue, as such an assumption leads to a (near-)hyperbolic shape of the power-duration relationship, at least for exercise duration of ~ 1-10 min. Thus, a potential mechanism underlying the power-duration relationship shape is offered that was absent in the literature. Other factors/mechanisms, such as cytosol acidification, glycogen stores depletion and central fatigue can contribute to this relationship, especially in longer exercises.
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14
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Cheng AJ, Hwee DT, Kim LH, Durham N, Yang HT, Hinken AC, Kennedy AR, Terjung RL, Jasper JR, Malik FI, Westerblad H. Fast skeletal muscle troponin activator CK-2066260 increases fatigue resistance by reducing the energetic cost of muscle contraction. J Physiol 2019; 597:4615-4625. [PMID: 31246276 PMCID: PMC6851859 DOI: 10.1113/jp278235] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Accepted: 06/26/2019] [Indexed: 01/26/2023] Open
Abstract
Key points Skeletal muscle fatigue limits performance in various physical activities, with exercise intolerance being a key symptom in a broad spectrum of diseases. We investigated whether a small molecule fast skeletal troponin activator (FSTA), CK‐2066260, can mitigate muscle fatigue by reducing the cytosolic free [Ca2+] required to produce a given submaximal force and hence decreasing the energy requirement. Isolated intact single mouse muscle fibres and rat muscles in‐situ treated with CK‐2066260 showed improved muscle endurance., which was accompanied by decreased ATP demand and reduced glycogen usage. CK‐2066260 treatment improved in‐vivo exercise capacity in healthy rats and in a rat model of peripheral artery insufficiency. In conclusion, we show that the FSTA CK‐2066260 effectively counteracts muscle fatigue in rodent skeletal muscle in vitro, in situ, and in vivo. This may translate to humans and provide a promising pharmacological treatment to patients suffering from severe muscle weakness and exercise intolerance.
Abstract Skeletal muscle fatigue limits performance during physical exercise and exacerbated muscle fatigue is a prominent symptom among a broad spectrum of diseases. The present study investigated whether skeletal muscle fatigue is affected by the fast skeletal muscle troponin activator (FSTA) CK‐2066260, which increases myofibrillar Ca2+ sensitivity and amplifies the submaximal force response. Because more force is produced for a given Ca2+, we hypothesized that CK‐2066260 could mitigate muscle fatigue by reducing the energetic cost of muscle activation. Isolated single mouse muscle fibres were fatigued by 100 repeated 350 ms contractions while measuring force and the cytosolic free [Ca2+] or [Mg2+] ([Mg2+]i). When starting fatiguing stimulation at matching forces (i.e. lower stimulation frequency with CK‐2066260): force was decreased by ∼50% with and by ∼75% without CK‐2066260; [Mg2+]i was increased by ∼10% with and ∼32% without CK‐2066260, reflecting a larger decrease in [ATP] in the latter. The glycogen content in in situ stimulated rat muscles fatigued by repeated contractions at matching forces was about two times higher with than without CK‐2066260. Voluntary exercise capacity, assessed by rats performing rotarod exercise and treadmill running, was improved in the presence of CK‐2066260. CK‐2066260 treatment also increased skeletal muscle fatigue resistance and exercise performance in a rat model of peripheral artery insufficiency. In conclusion, we demonstrate that the FSTA CK‐2066260 mitigates skeletal muscle fatigue by reducing the metabolic cost of force generation. Skeletal muscle fatigue limits performance in various physical activities, with exercise intolerance being a key symptom in a broad spectrum of diseases. We investigated whether a small molecule fast skeletal troponin activator (FSTA), CK‐2066260, can mitigate muscle fatigue by reducing the cytosolic free [Ca2+] required to produce a given submaximal force and hence decreasing the energy requirement. Isolated intact single mouse muscle fibres and rat muscles in‐situ treated with CK‐2066260 showed improved muscle endurance., which was accompanied by decreased ATP demand and reduced glycogen usage. CK‐2066260 treatment improved in‐vivo exercise capacity in healthy rats and in a rat model of peripheral artery insufficiency. In conclusion, we show that the FSTA CK‐2066260 effectively counteracts muscle fatigue in rodent skeletal muscle in vitro, in situ, and in vivo. This may translate to humans and provide a promising pharmacological treatment to patients suffering from severe muscle weakness and exercise intolerance.
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Affiliation(s)
- Arthur J Cheng
- Department of Physiology and Pharmacology, Karolinska Institutet, 171 77, Stockholm, Sweden
| | - Darren T Hwee
- Research and Early Development, Cytokinetics, Inc., South San Francisco, CA, 94080, USA
| | - Leo H Kim
- Research and Early Development, Cytokinetics, Inc., South San Francisco, CA, 94080, USA
| | - Nickie Durham
- Research and Early Development, Cytokinetics, Inc., South San Francisco, CA, 94080, USA
| | - Hsiao T Yang
- Department of Biomedical Sciences, University of Missouri, Columbia, MO, 65211, USA
| | - Aaron C Hinken
- Research and Early Development, Cytokinetics, Inc., South San Francisco, CA, 94080, USA
| | - Adam R Kennedy
- Research and Early Development, Cytokinetics, Inc., South San Francisco, CA, 94080, USA
| | - Ronald L Terjung
- Department of Biomedical Sciences, University of Missouri, Columbia, MO, 65211, USA
| | - Jeffrey R Jasper
- Research and Early Development, Cytokinetics, Inc., South San Francisco, CA, 94080, USA
| | - Fady I Malik
- Research and Early Development, Cytokinetics, Inc., South San Francisco, CA, 94080, USA
| | - Håkan Westerblad
- Department of Physiology and Pharmacology, Karolinska Institutet, 171 77, Stockholm, Sweden
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15
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Allard NAE, Schirris TJJ, Verheggen RJ, Russel FGM, Rodenburg RJ, Smeitink JAM, Thompson PD, Hopman MTE, Timmers S. Statins Affect Skeletal Muscle Performance: Evidence for Disturbances in Energy Metabolism. J Clin Endocrinol Metab 2018; 103:75-84. [PMID: 29040646 DOI: 10.1210/jc.2017-01561] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Accepted: 10/03/2017] [Indexed: 02/08/2023]
Abstract
CONTEXT Statin myopathy is linked to disturbances in mitochondrial function and exercise intolerance. OBJECTIVES To determine whether differences exist in exercise performance, muscle function, and muscle mitochondrial oxidative capacity and content between symptomatic and asymptomatic statin users, and control subjects. DESIGN Cross-sectional study. SETTING Department of Physiology, Radboud University Medical Center. PARTICIPANTS Long-term symptomatic and asymptomatic statin users, and control subjects (n = 10 per group). INTERVENTIONS Maximal incremental cycling tests, involuntary electrically stimulated isometric quadriceps-muscle contractions, and biopsy of vastus lateralis muscle. MAIN OUTCOMES MEASURED Maximal exercise capacity, substrate use during exercise, muscle function, and mitochondrial energy metabolism. RESULTS Peak oxygen uptake, maximal work load, and ventilatory efficiency were comparable between groups, but both statin groups had a depressed anaerobic threshold compared with the control group (P = 0.01). Muscle relaxation time was prolonged in both statin groups compared with the control group and rate of maximal force rise was decreased (Ptime×group < 0.001 for both measures). Mitochondrial activity of complexes II and IV was lower in symptomatic statin users than control subjects and tended to be lower for complex (C) III (CII: P = 0.03; CIII: P = 0.05; CIV: P = 0.04). Mitochondrial content tended to be lower in both statin groups than in control subjects. CONCLUSION Statin use attenuated substrate use during maximal exercise performance, induced muscle fatigue during repeated muscle contractions, and decreased muscle mitochondrial oxidative capacity. This suggests disturbances in mitochondrial oxidative capacity occur with statin use even in patients without statin-induced muscle complaints.
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Affiliation(s)
- Neeltje A E Allard
- Department of Physiology, Radboud University Medical Center, Nijmegen, Netherlands
| | - Tom J J Schirris
- Department of Pharmacology and Toxicology, Radboud University Medical Center, Nijmegen, Netherlands
- Centre for Systems Biology and Bioenergetics, Radboud Center for Mitochondrial Medicine, Radboud University Medical Center, Nijmegen, Netherlands
| | - Rebecca J Verheggen
- Department of Physiology, Radboud University Medical Center, Nijmegen, Netherlands
| | - Frans G M Russel
- Department of Pharmacology and Toxicology, Radboud University Medical Center, Nijmegen, Netherlands
- Centre for Systems Biology and Bioenergetics, Radboud Center for Mitochondrial Medicine, Radboud University Medical Center, Nijmegen, Netherlands
| | - Richard J Rodenburg
- Centre for Systems Biology and Bioenergetics, Radboud Center for Mitochondrial Medicine, Radboud University Medical Center, Nijmegen, Netherlands
- Nijmegen Center for Mitochondrial Disorders, Department of Pediatrics, Radboud University Medical Center, Nijmegen, Netherlands
| | - Jan A M Smeitink
- Centre for Systems Biology and Bioenergetics, Radboud Center for Mitochondrial Medicine, Radboud University Medical Center, Nijmegen, Netherlands
- Nijmegen Center for Mitochondrial Disorders, Department of Pediatrics, Radboud University Medical Center, Nijmegen, Netherlands
| | - Paul D Thompson
- Division of Cardiology, Hartford Hospital, Hartford, Connecticut
| | - Maria T E Hopman
- Department of Physiology, Radboud University Medical Center, Nijmegen, Netherlands
| | - Silvie Timmers
- Department of Physiology, Radboud University Medical Center, Nijmegen, Netherlands
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Chang YH, Ting LH. Mechanical evidence that flamingos can support their body on one leg with little active muscular force. Biol Lett 2017; 13:rsbl.2016.0948. [PMID: 28539457 DOI: 10.1098/rsbl.2016.0948] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Accepted: 05/03/2017] [Indexed: 11/12/2022] Open
Abstract
Flamingos (Phoenicopteridae) often stand and sleep on one leg for long periods, but it is unknown how much active muscle contractile force they use for the mechanical demands of standing on one leg: body weight support and maintaining balance. First, we demonstrated that flamingo cadavers could passively support body weight on one leg without any muscle activity while adopting a stable, unchanging, joint posture resembling that seen in live flamingos. By contrast, the cadaveric flamingo could not be stably held in a two-legged pose, suggesting a greater necessity for active muscle force to stabilize two-legged versus one-legged postures. Our results suggest that flamingos engage a passively engaged gravitational stay apparatus (proximally located) for weight support during one-legged standing. Second, we discovered that live flamingos standing on one leg have markedly reduced body sway during quiescent versus alert behaviours, with the point of force application directly under the distal joint, reducing the need for muscular joint torque. Taken together, our results highlight the possibility that flamingos stand for long durations on one leg without exacting high muscular forces and, thus, with little energetic expenditure.
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17
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Roberts LD, Ashmore T, McNally BD, Murfitt SA, Fernandez BO, Feelisch M, Lindsay R, Siervo M, Williams EA, Murray AJ, Griffin JL. Inorganic Nitrate Mimics Exercise-Stimulated Muscular Fiber-Type Switching and Myokine and γ-Aminobutyric Acid Release. Diabetes 2017; 66:674-688. [PMID: 28028076 DOI: 10.2337/db16-0843] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Accepted: 12/18/2016] [Indexed: 11/13/2022]
Abstract
Exercise is an effective intervention for the prevention and treatment of type 2 diabetes. Skeletal muscle combines multiple signals that contribute to the beneficial effects of exercise on cardiometabolic health. Inorganic nitrate increases exercise efficiency, tolerance, and performance. The transcriptional regulator peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α) coordinates the exercise-stimulated skeletal muscle fiber-type switch from glycolytic fast-twitch (type IIb) to oxidative slow-twitch (type I) and intermediate (type IIa) fibers, an effect reversed in insulin resistance and diabetes. We found that nitrate induces PGC1α expression and a switch toward type I and IIa fibers in rat muscle and myotubes in vitro. Nitrate induces the release of exercise/PGC1α-dependent myokine FNDC5/irisin and β-aminoisobutyric acid from myotubes and muscle in rats and humans. Both exercise and nitrate stimulated PGC1α-mediated γ-aminobutyric acid (GABA) secretion from muscle. Circulating GABA concentrations were increased in exercising mice and nitrate-treated rats and humans; thus, GABA may function as an exercise/PGC1α-mediated myokine-like small molecule. Moreover, nitrate increased circulating growth hormone levels in humans and rodents. Nitrate induces physiological responses that mimic exercise training and may underlie the beneficial effects of this metabolite on exercise and cardiometabolic health.
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MESH Headings
- Adipocytes/drug effects
- Adipocytes/metabolism
- Aged
- Aminoisobutyric Acids
- Animals
- Beta vulgaris
- Chromatography, Liquid
- Double-Blind Method
- Female
- Fibronectins/drug effects
- Fibronectins/metabolism
- Fruit and Vegetable Juices
- Gas Chromatography-Mass Spectrometry
- Growth Hormone/metabolism
- Humans
- Immunohistochemistry
- In Vitro Techniques
- Insulin Resistance
- Male
- Mass Spectrometry
- Mice
- Mice, Transgenic
- Middle Aged
- Muscle Fibers, Fast-Twitch/drug effects
- Muscle Fibers, Fast-Twitch/metabolism
- Muscle Fibers, Skeletal/drug effects
- Muscle Fibers, Skeletal/metabolism
- Muscle Fibers, Slow-Twitch/drug effects
- Muscle Fibers, Slow-Twitch/metabolism
- Muscle, Skeletal/drug effects
- Muscle, Skeletal/metabolism
- Nitrates/pharmacology
- Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha/drug effects
- Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha/genetics
- Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha/metabolism
- Physical Conditioning, Animal
- Rats
- Rats, Wistar
- Transcriptome
- gamma-Aminobutyric Acid/drug effects
- gamma-Aminobutyric Acid/metabolism
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Affiliation(s)
- Lee D Roberts
- Leeds Institute of Cardiovascular and Metabolic Medicine, Faculty of Medicine and Health, University of Leeds, Leeds, U.K.
- Medical Research Council-Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, U.K
- Department of Biochemistry and Cambridge Systems Biology Centre, University of Cambridge, Cambridge, U.K
| | - Tom Ashmore
- Department of Biochemistry and Cambridge Systems Biology Centre, University of Cambridge, Cambridge, U.K
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, U.K
| | - Ben D McNally
- Medical Research Council-Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, U.K
- Department of Biochemistry and Cambridge Systems Biology Centre, University of Cambridge, Cambridge, U.K
| | - Steven A Murfitt
- Department of Biochemistry and Cambridge Systems Biology Centre, University of Cambridge, Cambridge, U.K
| | - Bernadette O Fernandez
- Faculty of Medicine, Clinical and Experimental Sciences, University of Southampton, Southampton General Hospital, Southampton, U.K
| | - Martin Feelisch
- Faculty of Medicine, Clinical and Experimental Sciences, University of Southampton, Southampton General Hospital, Southampton, U.K
| | - Ross Lindsay
- Department of Biochemistry and Cambridge Systems Biology Centre, University of Cambridge, Cambridge, U.K
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, U.K
| | - Mario Siervo
- Human Nutrition Research Centre, Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, U.K
| | - Elizabeth A Williams
- Human Nutrition Unit, Department of Oncology, Faculty of Medicine, Dentistry and Health, University of Sheffield, Sheffield, U.K
| | - Andrew J Murray
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, U.K
| | - Julian L Griffin
- Medical Research Council-Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, U.K
- Department of Biochemistry and Cambridge Systems Biology Centre, University of Cambridge, Cambridge, U.K
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Piperine's mitigation of obesity and diabetes can be explained by its up-regulation of the metabolic rate of resting muscle. Proc Natl Acad Sci U S A 2016; 113:13009-13014. [PMID: 27799519 DOI: 10.1073/pnas.1607536113] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We identify a target for treating obesity and type 2 diabetes, the consumption of calories by an increase in the metabolic rate of resting skeletal muscle. The metabolic rate of skeletal muscle can be increased by shifting myosin heads from the super-relaxed state (SRX), with a low ATPase activity, to a disordered relaxed state (DRX), with a higher ATPase activity. The shift of myosin heads was detected by a change in fluorescent intensity of a probe attached to the myosin regulatory light chain in skinned skeletal fibers, allowing us to perform a high-throughput screen of 2,128 compounds. The screen identified one compound, which destabilized the super-relaxed state, piperine (the main alkaloid component of black pepper). Destabilization of the SRX by piperine was confirmed by single-nucleotide turnover measurements. The effect was only observed in fast twitch skeletal fibers and not in slow twitch fibers or cardiac tissues. Piperine increased ATPase activity of skinned relaxed fibers by 66 ± 15%. The Kd was ∼2 µM. Piperine had little effect on the mechanics of either fully active or resting muscle fibers. Previous work has shown that piperine can mitigate both obesity and type 2 diabetes in rodent models of these conditions. We propose that the increase in resting muscle metabolism contributes to these positive effects. The results described here show that up-regulation of resting muscle metabolism could treat obesity and type 2 diabetes and that piperine would provide a useful lead compound for the development of these therapies.
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19
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Pirkmajer S, Chibalin AV. Na,K-ATPase regulation in skeletal muscle. Am J Physiol Endocrinol Metab 2016; 311:E1-E31. [PMID: 27166285 DOI: 10.1152/ajpendo.00539.2015] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Accepted: 05/02/2016] [Indexed: 12/17/2022]
Abstract
Skeletal muscle contains one of the largest and the most dynamic pools of Na,K-ATPase (NKA) in the body. Under resting conditions, NKA in skeletal muscle operates at only a fraction of maximal pumping capacity, but it can be markedly activated when demands for ion transport increase, such as during exercise or following food intake. Given the size, capacity, and dynamic range of the NKA pool in skeletal muscle, its tight regulation is essential to maintain whole body homeostasis as well as muscle function. To reconcile functional needs of systemic homeostasis with those of skeletal muscle, NKA is regulated in a coordinated manner by extrinsic stimuli, such as hormones and nerve-derived factors, as well as by local stimuli arising in skeletal muscle fibers, such as contractions and muscle energy status. These stimuli regulate NKA acutely by controlling its enzymatic activity and/or its distribution between the plasma membrane and the intracellular storage compartment. They also regulate NKA chronically by controlling NKA gene expression, thus determining total NKA content in skeletal muscle and its maximal pumping capacity. This review focuses on molecular mechanisms that underlie regulation of NKA in skeletal muscle by major extrinsic and local stimuli. Special emphasis is given to stimuli and mechanisms linking regulation of NKA and energy metabolism in skeletal muscle, such as insulin and the energy-sensing AMP-activated protein kinase. Finally, the recently uncovered roles for glutathionylation, nitric oxide, and extracellular K(+) in the regulation of NKA in skeletal muscle are highlighted.
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Affiliation(s)
- Sergej Pirkmajer
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia; and
| | - Alexander V Chibalin
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
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20
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Richter M, Gendolla G, Wright R. Three Decades of Research on Motivational Intensity Theory. ADVANCES IN MOTIVATION SCIENCE 2016. [DOI: 10.1016/bs.adms.2016.02.001] [Citation(s) in RCA: 109] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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21
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Haider G, Folland JP. Nitrate supplementation enhances the contractile properties of human skeletal muscle. Med Sci Sports Exerc 2015; 46:2234-43. [PMID: 24681572 DOI: 10.1249/mss.0000000000000351] [Citation(s) in RCA: 120] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
PURPOSE Dietary nitrate supplementation positively affects cardiovascular function at rest and energy metabolism during exercise in humans and has recently also been reported to markedly enhance the in vitro contractile properties of mouse fast-twitch muscle. The aim of this study was to investigate the effects of short-term nitrate supplementation on the in vivo contractile properties of the skeletal muscle and voluntary muscle function of humans. METHODS In a double-blind, randomized, crossover design, 19 healthy untrained men (21 ± 3 yr) ingested a nitrate-rich concentrated beetroot juice (NIT; nitrate dosage, approximately 9.7 mmol·d) and a placebo (PLA) for seven consecutive days. After the last supplementation dose, force was recorded while participants completed a series of voluntary and involuntary (electrically evoked) unilateral isometric contractions of the knee extensors. RESULTS NIT enhanced the peak force response to low-frequency electrical stimulation, as follows: maximal twitch (NIT, 149 ± 41 N, vs PLA, 138 ± 37 N; P = 0.008; effect size, r (ES) = 0.56) and submaximal 1- to 20-Hz contractions (5%-10%, ES = 0.53-0.63). Whereas explosive (rising phase) force production during the first 50 ms of evoked maximal twitch and octet contractions (eight electrical impulses at 300 Hz) was also 3%-15% greater after NIT compared with that after PLA (P = 0.023-0.048, ES = 0.52-0.59), explosive voluntary force remained similar (P = 0.510, ES = 0.16). Maximum voluntary force was also unchanged after NIT (P = 0.539, ES = 0.15). CONCLUSIONS These results indicate that 7 d of dietary nitrate supplementation enhanced the in vivo contractile properties of the human skeletal muscle. Specifically, nitrate supplementation improved excitation-contraction coupling at low frequencies of stimulation and enhanced evoked explosive force production but did not affect maximum or explosive voluntary force production in untrained individuals.
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Affiliation(s)
- Georg Haider
- School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UNITED KINGDOM
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22
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de Winter JM, Joureau B, Sequeira V, Clarke NF, van der Velden J, Stienen GJ, Granzier H, Beggs AH, Ottenheijm CA. Effect of levosimendan on the contractility of muscle fibers from nemaline myopathy patients with mutations in the nebulin gene. Skelet Muscle 2015; 5:12. [PMID: 25949787 PMCID: PMC4422316 DOI: 10.1186/s13395-015-0037-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 04/01/2015] [Indexed: 11/25/2022] Open
Abstract
Background Nemaline myopathy (NM), the most common non-dystrophic congenital myopathy, is characterized by generalized skeletal muscle weakness, often from birth. To date, no therapy exists that enhances the contractile strength of muscles of NM patients. Mutations in NEB, encoding the giant protein nebulin, are the most common cause of NM. The pathophysiology of muscle weakness in NM patients with NEB mutations (NEB-NM) includes a lower calcium-sensitivity of force generation. We propose that the lower calcium-sensitivity of force generation in NEB-NM offers a therapeutic target. Levosimendan is a calcium sensitizer that is approved for use in humans and has been developed to target cardiac muscle fibers. It exerts its effect through binding to slow skeletal/cardiac troponin C. As slow skeletal/cardiac troponin C is also the dominant troponin C isoform in slow-twitch skeletal muscle fibers, we hypothesized that levosimendan improves slow-twitch muscle fiber strength at submaximal levels of activation in patients with NEB-NM. Methods To test whether levosimendan affects force production, permeabilized slow-twitch muscle fibers isolated from biopsies of NEB-NM patients and controls were exposed to levosimendan and the force response was measured. Results No effect of levosimendan on muscle fiber force in NEB-NM and control skeletal muscle fibers was found, both at a submaximal calcium level using incremental levosimendan concentrations, and at incremental calcium concentrations in the presence of levosimendan. In contrast, levosimendan did significantly increase the calcium-sensitivity of force in human single cardiomyocytes. Protein analysis confirmed that the slow skeletal/cardiac troponin C isoform was present in the skeletal muscle fibers tested. Conclusions These findings indicate that levosimendan does not improve the contractility in human skeletal muscle fibers, and do not provide rationale for using levosimendan as a therapeutic to restore muscle weakness in NEB-NM patients. We stress the importance of searching for compounds that improve the calcium-sensitivity of force generation of slow-twitch muscle fibers. Such compounds provide an appealing approach to restore muscle force in patients with NEB-NM, and also in patients with other neuromuscular disorders. Electronic supplementary material The online version of this article (doi:10.1186/s13395-015-0037-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Josine M de Winter
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center Amsterdam, De Boelelaan 1118, 1081, BT Amsterdam, The Netherlands
| | - Barbara Joureau
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center Amsterdam, De Boelelaan 1118, 1081, BT Amsterdam, The Netherlands
| | - Vasco Sequeira
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center Amsterdam, De Boelelaan 1118, 1081, BT Amsterdam, The Netherlands
| | - Nigel F Clarke
- INMR, The Children's Hospital at Westmead and Discipline of Paediatrics & Child Health, University of Sydney, Cnr Hawkesbury Road & Hainsworth Street, Sydney, Australia
| | - Jolanda van der Velden
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center Amsterdam, De Boelelaan 1118, 1081, BT Amsterdam, The Netherlands
| | - Ger Jm Stienen
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center Amsterdam, De Boelelaan 1118, 1081, BT Amsterdam, The Netherlands ; Department of Physics and Astronomy, Faculty of Science, VU University, De Boelelaan 1105, Amsterdam, The Netherlands
| | - Henk Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, 1333 N. Martin Avenue, Tucson, USA
| | - Alan H Beggs
- Division of Genetics and Genomics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, 25 Shattuck Street, Boston, USA
| | - Coen Ac Ottenheijm
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center Amsterdam, De Boelelaan 1118, 1081, BT Amsterdam, The Netherlands ; Department of Cellular and Molecular Medicine, University of Arizona, 1333 N. Martin Avenue, Tucson, USA
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Layec G, Bringard A, Le Fur Y, Micallef JP, Vilmen C, Perrey S, Cozzone PJ, Bendahan D. Opposite effects of hyperoxia on mitochondrial and contractile efficiency in human quadriceps muscles. Am J Physiol Regul Integr Comp Physiol 2015; 308:R724-33. [PMID: 25695290 DOI: 10.1152/ajpregu.00461.2014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Accepted: 02/10/2015] [Indexed: 01/06/2023]
Abstract
Exercise efficiency is an important determinant of exercise capacity. However, little is known about the physiological factors that can modulate muscle efficiency during exercise. We examined whether improved O2 availability would 1) impair mitochondrial efficiency and shift the energy production toward aerobic ATP synthesis and 2) reduce the ATP cost of dynamic contraction owing to an improved neuromuscular efficiency, such that 3) whole body O2 cost would remain unchanged. We used (31)P-magnetic resonance spectroscopy, surface electromyography, and pulmonary O2 consumption (V̇o2p) measurements in eight active subjects during 6 min of dynamic knee-extension exercise under different fractions of inspired O2 (FiO2 , 0.21 in normoxia and 1.0 in hyperoxia). V̇o2p (755 ± 111 ml/min in normoxia and 799 ± 188 ml/min in hyperoxia, P > 0.05) and O2 cost (P > 0.05) were not significantly different between normoxia and hyperoxia. In contrast, the total ATP synthesis rate and the ATP cost of dynamic contraction were significantly lower in hyperoxia than normoxia (P < 0.05). As a result, the ratio of the rate of oxidative ATP synthesis from the quadriceps to V̇o2p was lower in hyperoxia than normoxia but did not reach statistical significance (16 ± 3 mM/ml in normoxia and 12 ± 5 mM/ml in hyperoxia, P = 0.07). Together, these findings reveal dynamic and independent regulations of mitochondrial and contractile efficiency as a consequence of O2 availability in young active individuals. Furthermore, muscle efficiency appears to be already optimized in normoxia and is unlikely to contribute to the well-established improvement in exercise capacity induced by hyperoxia.
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Affiliation(s)
- Gwenael Layec
- Aix-Marseille Université, Centre National de la Recherche Scientifique, Center for Magnetic Resonance in Biology and Medicine, UMR 7339, Marseille, France; Division of Geriatrics, Department of Medicine, University of Utah, Salt Lake City, Utah; Geriatric Research, Education, and Clinical Center, George E. Whalen Veterans Affairs Medical Center, Salt Lake City, Utah;
| | - Aurélien Bringard
- Département des Neurosciences Fondamentales, Centre Médical Universitaire, University of Geneva, Geneva, Switzerland
| | - Yann Le Fur
- Aix-Marseille Université, Centre National de la Recherche Scientifique, Center for Magnetic Resonance in Biology and Medicine, UMR 7339, Marseille, France
| | - Jean-Paul Micallef
- Movement To Health (M2H), EuroMov, Montpellier-1 University, Montpellier, France; and Institut National de la Santé et de la Recherche Médicale ADR 08, Montpellier, France
| | - Christophe Vilmen
- Aix-Marseille Université, Centre National de la Recherche Scientifique, Center for Magnetic Resonance in Biology and Medicine, UMR 7339, Marseille, France
| | - Stéphane Perrey
- Movement To Health (M2H), EuroMov, Montpellier-1 University, Montpellier, France; and
| | - Patrick J Cozzone
- Aix-Marseille Université, Centre National de la Recherche Scientifique, Center for Magnetic Resonance in Biology and Medicine, UMR 7339, Marseille, France
| | - David Bendahan
- Aix-Marseille Université, Centre National de la Recherche Scientifique, Center for Magnetic Resonance in Biology and Medicine, UMR 7339, Marseille, France
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Miller MS, Bedrin NG, Ades PA, Palmer BM, Toth MJ. Molecular determinants of force production in human skeletal muscle fibers: effects of myosin isoform expression and cross-sectional area. Am J Physiol Cell Physiol 2015; 308:C473-84. [PMID: 25567808 DOI: 10.1152/ajpcell.00158.2014] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Skeletal muscle contractile performance is governed by the properties of its constituent fibers, which are, in turn, determined by the molecular interactions of the myofilament proteins. To define the molecular determinants of contractile function in humans, we measured myofilament mechanics during maximal Ca(2+)-activated and passive isometric conditions in single muscle fibers with homogenous (I and IIA) and mixed (I/IIA and IIA/X) myosin heavy chain (MHC) isoforms from healthy, young adult male (n = 5) and female (n = 7) volunteers. Fibers containing only MHC II isoforms (IIA and IIA/X) produced higher maximal Ca(2+)-activated forces over the range of cross-sectional areas (CSAs) examined than MHC I fibers, resulting in higher (24-42%) specific forces. The number and/or stiffness of the strongly bound myosin-actin cross bridges increased in the higher force-producing MHC II isoforms and, in all isoforms, better predicted force than CSA. In men and women, cross-bridge kinetics, in terms of myosin attachment time and rate of myosin force production, were independent of CSA, although women had faster (7-15%) kinetics. The relative proportion of cross bridges and/or their stiffness was reduced as fiber size increased, causing a decline in specific force. Results from our examination of molecular mechanisms across the range of physiological CSAs explain the variation in specific force among the different fiber types in human skeletal muscle, which may have relevance to understanding how various physiological and pathophysiological conditions modulate single-fiber and whole muscle contractility.
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Affiliation(s)
- Mark S Miller
- Department of Molecular Physiology and Biophysics, College of Medicine, University of Vermont, Burlington, Vermont; Department of Kinesiology, School of Public Health and Health Sciences, University of Massachusetts, Amherst, Massachusetts
| | - Nicholas G Bedrin
- Department of Molecular Physiology and Biophysics, College of Medicine, University of Vermont, Burlington, Vermont
| | - Philip A Ades
- Department of Medicine, College of Medicine, University of Vermont, Burlington, Vermont; and
| | - Bradley M Palmer
- Department of Molecular Physiology and Biophysics, College of Medicine, University of Vermont, Burlington, Vermont
| | - Michael J Toth
- Department of Molecular Physiology and Biophysics, College of Medicine, University of Vermont, Burlington, Vermont; Department of Medicine, College of Medicine, University of Vermont, Burlington, Vermont; and
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25
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Skeletal muscle work efficiency with age: the role of non-contractile processes. Clin Sci (Lond) 2014; 128:213-23. [PMID: 25134525 DOI: 10.1042/cs20140274] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Although skeletal muscle work efficiency probably plays a key role in limiting mobility of the elderly, the physiological mechanisms responsible for this diminished function remain incompletely understood. Thus, in the quadriceps of young (n=9) and old (n=10) subjects, we measured the cost of muscle contraction (ATP cost) with 31P-magnetic resonance spectroscopy (31P-MRS) during (i) maximal intermittent contractions to elicit a metabolic demand from both cross-bridge cycling and ion pumping and (ii) a continuous maximal contraction to predominantly tax cross-bridge cycling. The ATP cost of the intermittent contractions was significantly greater in the old (0.30±0.22 mM·min-1·N·m-1) compared with the young (0.13±0.03 mM·min-1·N·m-1, P<0.05). In contrast, at the end of the continuous contraction protocol, the ATP cost in the old (0.10±0.07 mM·min-1·N·m-1) was not different from the young (0.06±0.02 mM·min-1·N·m-1, P=0.2). In addition, the ATP cost of the intermittent contractions correlated significantly with the single leg peak power of the knee-extensors assessed during incremental dynamic exercise (r=-0.55; P<0.05). Overall, this study reveals an age-related increase in the ATP cost of contraction, probably mediated by an excessive energy demand from ion pumping, which probably contributes to both the decline in muscle efficiency and functional capacity associated with aging.
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26
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Medeiros WM, Fernandes MCT, Azevedo DP, de Freitas FFM, Amorim BC, Chiavegato LD, Hirai DM, O'Donnell DE, Neder JA. Oxygen delivery-utilization mismatch in contracting locomotor muscle in COPD: peripheral factors. Am J Physiol Regul Integr Comp Physiol 2014; 308:R105-11. [PMID: 25477423 DOI: 10.1152/ajpregu.00404.2014] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Central cardiorespiratory and gas exchange limitations imposed by chronic obstructive pulmonary disease (COPD) impair ambulatory skeletal muscle oxygenation during whole body exercise. This investigation tested the hypothesis that peripheral factors per se contribute to impaired contracting lower limb muscle oxygenation in COPD patients. Submaximal neuromuscular electrical stimulation (NMES; 30, 40, and 50 mA at 50 Hz) of the quadriceps femoris was employed to evaluate contracting skeletal muscle oxygenation while minimizing the influence of COPD-related central cardiorespiratory constraints. Fractional O₂ extraction was estimated by near-infrared spectroscopy (deoxyhemoglobin/myoglobin concentration; deoxy-[Hb/Mb]), and torque output was measured by isokinetic dynamometry in 15 nonhypoxemic patients with moderate-to-severe COPD (SpO2 = 94 ± 2%; FEV₁ = 46.4 ± 10.1%; GOLD II and III) and in 10 age- and gender-matched sedentary controls. COPD patients had lower leg muscle mass than controls (LMM = 8.0 ± 0.7 kg vs. 8.9 ± 1.0 kg, respectively; P < 0.05) and produced relatively lower absolute and LMM-normalized torque across the range of NMES intensities (P < 0.05 for all). Despite producing less torque, COPD patients had similar deoxy-[Hb/Mb] amplitudes at 30 and 40 mA (P > 0.05 for both) and higher deoxy-[Hb/Mb] amplitude at 50 mA (P < 0.05). Further analysis indicated that COPD patients required greater fractional O₂ extraction to produce torque (i.e., ↑Δdeoxy-[Hb/Mb]/torque) relative to controls (P < 0.05 for 40 and 50 mA) and as a function of NMES intensity (P < 0.05 for all). The present data obtained during submaximal NMES of small muscle mass indicate that peripheral abnormalities contribute mechanistically to impaired contracting skeletal muscle oxygenation in nonhypoxemic, moderate-to-severe COPD patients.
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Affiliation(s)
- Wladimir M Medeiros
- Pulmonary Function and Clinical Exercise Physiology Unit (SEFICE), Respiratory Division, Department of Medicine, School of Medicine, Federal University of São Paulo (UNIFESP), São Paulo, Brazil
| | - Mari C T Fernandes
- Pulmonary Function and Clinical Exercise Physiology Unit (SEFICE), Respiratory Division, Department of Medicine, School of Medicine, Federal University of São Paulo (UNIFESP), São Paulo, Brazil
| | - Diogo P Azevedo
- Pulmonary Function and Clinical Exercise Physiology Unit (SEFICE), Respiratory Division, Department of Medicine, School of Medicine, Federal University of São Paulo (UNIFESP), São Paulo, Brazil
| | - Flavia F M de Freitas
- Pulmonary Function and Clinical Exercise Physiology Unit (SEFICE), Respiratory Division, Department of Medicine, School of Medicine, Federal University of São Paulo (UNIFESP), São Paulo, Brazil
| | - Beatriz C Amorim
- Pulmonary Function and Clinical Exercise Physiology Unit (SEFICE), Respiratory Division, Department of Medicine, School of Medicine, Federal University of São Paulo (UNIFESP), São Paulo, Brazil
| | - Luciana D Chiavegato
- Pulmonary Function and Clinical Exercise Physiology Unit (SEFICE), Respiratory Division, Department of Medicine, School of Medicine, Federal University of São Paulo (UNIFESP), São Paulo, Brazil
| | - Daniel M Hirai
- Pulmonary Function and Clinical Exercise Physiology Unit (SEFICE), Respiratory Division, Department of Medicine, School of Medicine, Federal University of São Paulo (UNIFESP), São Paulo, Brazil; Laboratory of Clinical Exercise Physiology (LACEP), Division of Respiratory and Critical Care Medicine, Department of Medicine, Queen's University, Kingston, Canada; and
| | - Denis E O'Donnell
- Respiratory Investigation Unit (RIU), Division of Respiratory and Critical Care Medicine, Department of Medicine, Queen's University, Kingston, Canada
| | - J Alberto Neder
- Pulmonary Function and Clinical Exercise Physiology Unit (SEFICE), Respiratory Division, Department of Medicine, School of Medicine, Federal University of São Paulo (UNIFESP), São Paulo, Brazil; Laboratory of Clinical Exercise Physiology (LACEP), Division of Respiratory and Critical Care Medicine, Department of Medicine, Queen's University, Kingston, Canada; and
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Dutka TL, Lamboley CR, Murphy RM, Lamb GD. Acute effects of taurine on sarcoplasmic reticulum Ca2+ accumulation and contractility in human type I and type II skeletal muscle fibers. J Appl Physiol (1985) 2014; 117:797-805. [DOI: 10.1152/japplphysiol.00494.2014] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Taurine occurs in high concentrations in muscle and is implicated in numerous physiological processes, yet its effects on many aspects of contractility remain unclear. Using mechanically skinned segments of human vastus lateralis muscle fibers, we characterized the effects of taurine on sarcoplasmic reticulum (SR) Ca2+ accumulation and contractile apparatus properties in type I and type II fibers. Prolonged myoplasmic exposure (>10 min) to taurine substantially increased the rate of accumulation of Ca2+ by the SR in both fiber types, with no change in the maximum amount accumulated; no such effect was found with carnosine. SR Ca2+ accumulation was similar with 10 or 20 mM taurine, but was significantly slower at 5 mM taurine. Cytoplasmic taurine (20 mM) had no detectable effects on the responsiveness of the Ca2+ release channels in either fiber type. Taurine caused a small increase in Ca2+ sensitivity of the contractile apparatus in type I fibers, but type II fibers were unaffected; maximum Ca2+-activated force was unchanged in both cases. The effects of taurine on SR Ca2+ accumulation 1) only became apparent after prolonged cytoplasmic exposure, and 2) persisted for some minutes after complete removal of taurine from the cytoplasm, consistent with the hypothesis that the effects were due to an action of taurine from inside the SR. In summary, taurine potentiates the rate of SR Ca2+ uptake in both type I and type II human fibers, possibly via an action from within the SR lumen, with the degree of potentiation being significantly reduced at low physiological taurine levels.
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Affiliation(s)
- T. L. Dutka
- Department of Zoology, La Trobe University, Melbourne, Victoria, Australia; and
| | - C. R. Lamboley
- Institute of Sport, Exercise and Active Living (ISEAL), Victoria University, Melbourne, Victoria, Australia
| | - R. M. Murphy
- Department of Zoology, La Trobe University, Melbourne, Victoria, Australia; and
| | - G. D. Lamb
- Department of Zoology, La Trobe University, Melbourne, Victoria, Australia; and
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28
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Richter M. Goal pursuit and energy conservation: energy investment increases with task demand but does not equal it. MOTIVATION AND EMOTION 2014. [DOI: 10.1007/s11031-014-9429-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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29
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Christie AD, Tonson A, Larsen RG, DeBlois JP, Kent JA. Human skeletal muscle metabolic economy in vivo: effects of contraction intensity, age, and mobility impairment. Am J Physiol Regul Integr Comp Physiol 2014; 307:R1124-35. [PMID: 25163917 DOI: 10.1152/ajpregu.00083.2014] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
We tested the hypothesis that older muscle has greater metabolic economy (ME) in vivo than young, in a manner dependent, in part, on contraction intensity. Twenty young (Y; 24±1 yr, 10 women), 18 older healthy (O; 73±2, 9 women) and 9 older individuals with mild-to-moderate mobility impairment (OI; 74±1, 7 women) received stimulated twitches (2 Hz, 3 min) and performed nonfatiguing voluntary (20, 50, and 100% maximal; 12 s each) isometric dorsiflexion contractions. Torque-time integrals (TTI; Nm·s) were calculated and expressed relative to maximal fat-free muscle cross-sectional area (cm2), and torque variability during voluntary contractions was calculated as the coefficient of variation. Total ATP cost of contraction (mM) was determined from flux through the creatine kinase reaction, nonoxidative glycolysis and oxidative phosphorylation, and used to calculate ME (Nm·s·cm(-2)·mM ATP(-1)). While twitch torque relaxation was slower in O and OI compared with Y (P≤0.001), twitch TTI, ATP cost, and economy were similar across groups (P≥0.15), indicating comparable intrinsic muscle economy during electrically induced isometric contractions in vivo. During voluntary contractions, normalized TTI and total ATP cost did not differ significantly across groups (P≥0.20). However, ME was lower in OI than Y or O at 20% and 50% MVC (P≤0.02), and torque variability was greater in OI than Y or O at 20% MVC (P≤0.05). These results refute the hypothesis of greater muscle ME in old age, and provide support for lower ME in impaired older adults as a potential mechanism or consequence of age-related reductions in functional mobility.
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Affiliation(s)
- Anita D Christie
- Department of Kinesiology, University of Massachusetts, Amherst, Massachusetts
| | - Anne Tonson
- Department of Kinesiology, University of Massachusetts, Amherst, Massachusetts
| | - Ryan G Larsen
- Department of Kinesiology, University of Massachusetts, Amherst, Massachusetts
| | - Jacob P DeBlois
- Department of Kinesiology, University of Massachusetts, Amherst, Massachusetts
| | - Jane A Kent
- Department of Kinesiology, University of Massachusetts, Amherst, Massachusetts
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30
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Shi S, Liu H, Bai X, Cao Y. Pressing the nerve alters muscle fiber types of the peroneus longus in rats: preliminary evidence for external anal sphincteroplasty. Med Sci Monit 2014; 20:752-7. [PMID: 24807024 PMCID: PMC4020912 DOI: 10.12659/msm.884037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Background Studies have demonstrated that anal reconstruction with a gracilis graft pressing the dominant nerve could be used to treat fecal incontinence. However, the detailed mechanism by this remains unknown. Herein, we evaluated the alteration in muscle fiber types and contractility of the peroneus longus muscle in rats after pressing its dominant nerves. Material/Methods The rat soleus and peroneus longus were exposed during surgery. The superficial peroneal nerve was pressed so that the peroneus longus temporarily lost its innervation. The epimysium between the soleus and the peroneus longus was removed. The end point of the soleus was cut off and the epimysium of the contact surfaces of the soleus and the peroneus longus were sutured. Five months later, peroneus longus contractility was recorded by the myograph system, and types of muscle fibers were observed using the myosin ATPase staining method. Results The skeletal muscle fiber type underwent adaptive changes due to double innervations with both fast and slow muscle nerves. Compared with other groups, the percentage of type I fibers in the peroneus longus increased significantly in the group of rats with the pressure on the nerve and removal of the sarcolemma. The maximal contraction and relaxation time at the single twitch and complete tetanus of the peroneus longus were also increased. Conclusions Our results show that pressing dominant nerves alter the skeletal muscle fiber types of the peroneus longus, which lead to increased maximal contraction and relaxation time, and significantly improve the ability in resistance to fatigue in rats. This study provides a basis for future clinical studies for external anal sphincter reconstruction using gracilis grafts that are doubly innervated by pressing on its dominant nerve.
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Affiliation(s)
- Song Shi
- Department of General Surgery, The First Affiliated Hospital, Xian Jiaotong University College of Medicine, Xian, China (mainland)
| | - Hao Liu
- Department of General Surgery, The First Affiliated Hospital, Xian Jiaotong University College of Medicine, Xian, China (mainland)
| | - Xiaobin Bai
- Department of General Surgery, The First Affiliated Hospital, Xian Jiaotong University College of Medicine, Xian, China (mainland)
| | - Yongxiao Cao
- Department of Pharmacology, Xi'an Jiaotong University College of Medicine, Xi'an, China (mainland)
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31
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Lamboley CR, Murphy RM, McKenna MJ, Lamb GD. Sarcoplasmic reticulum Ca2+ uptake and leak properties, and SERCA isoform expression, in type I and type II fibres of human skeletal muscle. J Physiol 2014; 592:1381-95. [PMID: 24469076 DOI: 10.1113/jphysiol.2013.269373] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The Ca(2+) uptake properties of the sarcoplasmic reticulum (SR) were compared between type I and type II fibres of vastus lateralis muscle of young healthy adults. Individual mechanically skinned muscle fibres were exposed to solutions with the free [Ca(2+)] heavily buffered in the pCa range (-log10[Ca(2+)]) 7.3-6.0 for set times and the amount of net SR Ca(2+) accumulation determined from the force response elicited upon emptying the SR of all Ca(2+). Western blotting was used to determine fibre type and the sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) isoform present in every fibre examined. Type I fibres contained only SERCA2 and displayed half-maximal Ca(2+) uptake rate at ∼pCa 6.8, whereas type II fibres contained only SERCA1 and displayed half-maximal Ca(2+) uptake rate at ∼pCa 6.6. Maximal Ca(2+) uptake rate was ∼0.18 and ∼0.21 mmol Ca(2+) (l fibre)(-1) s(-1) in type I and type II fibres, respectively, in good accord with previously measured SR ATPase activity. Increasing free [Mg(2+)] from 1 to 3 mM had no significant effect on the net Ca(2+) uptake rate at pCa 6.0, indicating that there was little or no calcium-induced calcium release occurring through the Ca(2+) release channels during uptake in either fibre type. Ca(2+) leakage from the SR at pCa 8.5, which is thought to occur at least in part through the SERCA, was ∼2-fold lower in type II fibres than in type I fibres, and was little affected by the presence of ADP, in marked contrast to the larger SR Ca(2+) leak observed in rat muscle fibres under the same conditions. The higher affinity of Ca(2+) uptake in the type I human fibres can account for the higher relative level of SR Ca(2+) loading observed in type I compared to type II fibres, and the SR Ca(2+) leakage characteristics of the human fibres suggest that the SERCAs are regulated differently from those in rat and contribute comparatively less to resting metabolic rate.
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Affiliation(s)
- C R Lamboley
- Department of Zoology, La Trobe University, Melbourne, Victoria 3086, Australia.
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Abstract
Muscular exercise requires transitions to and from metabolic rates often exceeding an order of magnitude above resting and places prodigious demands on the oxidative machinery and O2-transport pathway. The science of kinetics seeks to characterize the dynamic profiles of the respiratory, cardiovascular, and muscular systems and their integration to resolve the essential control mechanisms of muscle energetics and oxidative function: a goal not feasible using the steady-state response. Essential features of the O2 uptake (VO2) kinetics response are highly conserved across the animal kingdom. For a given metabolic demand, fast VO2 kinetics mandates a smaller O2 deficit, less substrate-level phosphorylation and high exercise tolerance. By the same token, slow VO2 kinetics incurs a high O2 deficit, presents a greater challenge to homeostasis and presages poor exercise tolerance. Compelling evidence supports that, in healthy individuals walking, running, or cycling upright, VO2 kinetics control resides within the exercising muscle(s) and is therefore not dependent upon, or limited by, upstream O2-transport systems. However, disease, aging, and other imposed constraints may redistribute VO2 kinetics control more proximally within the O2-transport system. Greater understanding of VO2 kinetics control and, in particular, its relation to the plasticity of the O2-transport/utilization system is considered important for improving the human condition, not just in athletic populations, but crucially for patients suffering from pathologically slowed VO2 kinetics as well as the burgeoning elderly population.
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Affiliation(s)
- David C Poole
- Departments of Kinesiology, Anatomy, and Physiology, Kansas State University, Manhattan, Kansas, USA.
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33
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Gong G, Wang W. Confocal imaging of single mitochondrial superoxide flashes in intact heart or in vivo. J Vis Exp 2013:e50818. [PMID: 24300235 DOI: 10.3791/50818] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Mitochondrion is a critical intracellular organelle responsible for energy production and intracellular signaling in eukaryotic systems. Mitochondrial dysfunction often accompanies and contributes to human disease. Majority of the approaches that have been developed to evaluate mitochondrial function and dysfunction are based on in vitro or ex vivo measurements. Results from these experiments have limited ability in determining mitochondrial function in vivo. Here, we describe a novel approach that utilizes confocal scanning microscopy for the imaging of intact tissues in live aminals, which allows the evaluation of single mitochondrial function in a real-time manner in vivo. First, we generate transgenic mice expressing the mitochondrial targeted superoxide indicator, circularly permuted yellow fluorescent protein (mt-cpYFP). Anesthetized mt-cpYFP mouse is fixed on a custom-made stage adaptor and time-lapse images are taken from the exposed skeletal muscles of the hindlimb. The mouse is subsequently sacrificed and the heart is set up for Langendorff perfusion with physiological solutions at 37 °C. The perfused heart is positioned in a special chamber on the confocal microscope stage and gentle pressure is applied to immobilize the heart and suppress heart beat induced motion artifact. Superoxide flashes are detected by real-time 2D confocal imaging at a frequency of one frame per second. The perfusion solution can be modified to contain different respiration substrates or other fluorescent indicators. The perfusion can also be adjusted to produce disease models such as ischemia and reperfusion. This technique is a unique approach for determining the function of single mitochondrion in intact tissues and in vivo.
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Affiliation(s)
- Guohua Gong
- Mitochondria and Metabolism Center, Department of Anesthesiology and Pain Medicine, University of Washington
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34
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Lamboley CR, Murphy RM, McKenna MJ, Lamb GD. Endogenous and maximal sarcoplasmic reticulum calcium content and calsequestrin expression in type I and type II human skeletal muscle fibres. J Physiol 2013; 591:6053-68. [PMID: 24127619 DOI: 10.1113/jphysiol.2013.265900] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The relationship between sarcoplasmic reticulum (SR) Ca(2+) content and calsequestrin (CSQ) isoforms was investigated in human skeletal muscle. A fibre-lysing assay was used to quantify the endogenous Ca(2+) content and maximal Ca(2+) capacity of the SR in skinned segments of type I and type II fibres from vastus lateralis muscles of young healthy adults. Western blotting of individual fibres showed the great majority contained either all fast or all slow isoforms of myosin heavy chain (MHC), troponins C and I, tropomyosin and SERCA, and that the strontium sensitivity of the force response was closely indicative of the troponin C isoform present. The endogenous SR Ca(2+) content was slightly lower in type I compared to type II fibres (0.76 ± 0.03 and 0.85 ± 0.02 mmol Ca(2+) per litre of fibre, respectively), with virtually all of this Ca(2+) evidently being in the SR, as it could be rapidly released with a caffeine-low [Mg(2+)] solution (only 0.08 ± 0.01 and <0.07 mmol l(-1), respectively, remaining). The maximal Ca(2+) content that could be reached with SR Ca(2+) loading was 1.45 ± 0.04 and 1.79 ± 0.03 mmol l(-1) in type I and type II fibres, respectively (P < 0.05). In non-lysed skinned fibres, where the SR remained functional, repeated cycles of caffeine-induced Ca(2+) release and subsequent Ca(2+) reloading similarly indicated that (i) maximal SR Ca(2+) content was lower in type I fibres than in type II fibres (P < 0.05), and (ii) the endogenous Ca(2+) content represented a greater percentage of maximal content in type I fibres compared to type II fibres (∼59% and 41%, respectively, P < 0.05). Type II fibres were found on average to contain ∼3-fold more CSQ1 and ∼5-fold less CSQ2 than type I fibres (P < 0.001). The findings are consistent with the SR Ca(2+) content characteristics in human type II fibres being primarily determined by the CSQ1 abundance, and in type I fibres by the combined amounts of both CSQ1 and CSQ2.
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Affiliation(s)
- C R Lamboley
- G. D. Lamb: Department of Zoology, La Trobe University, Melbourne, Victoria 3086, Australia.
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Bombardier E, Smith IC, Gamu D, Fajardo VA, Vigna C, Sayer RA, Gupta SC, Bal NC, Periasamy M, Tupling AR. Sarcolipin trumps β-adrenergic receptor signaling as the favored mechanism for muscle-based diet-induced thermogenesis. FASEB J 2013; 27:3871-8. [PMID: 23752204 DOI: 10.1096/fj.13-230631] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Sarcolipin (SLN) regulates muscle-based nonshivering thermogenesis and is up-regulated with high-fat feeding (HFF). To investigate whether other muscle-based thermogenic systems compensate for a lack of Sln and to firmly establish SLN as a mediator of diet-induced thermogenesis (DIT), we measured muscle and whole-body energy expenditure in chow- and high-fat-fed Sln(-/-) and wild-type (WT) mice. Following HFF, resting muscle metabolic rate (VO2, μl/g/s) was increased similarly in WT (0.28±0.02 vs. 0.31±0.03) and Sln(-/-) (0.23±0.03 vs. 0.35±0.02) mice due to increased sympathetic nervous system activation in Sln(-/-) mice; however, whole-body metabolic rate (VO2, ml/kg/h) was lower in Sln(-/-) compared with WT mice following HFF but only during periods when the mice were active in their cages (WT, 2894±87 vs. Sln(-/-), 2708±61). Treatment with the β-adrenergic receptor (β-AR) antagonist propranolol during HFF completely prevented muscle-based DIT in Sln(-/-) mice; however, it had no effect in WT mice, resulting in greater differences in whole-body metabolic rate and diet-induced weight gain. Our results suggest that β-AR signaling partially compensates for a lack of SLN to activate muscle-based DIT, but SLN is the primary and more effective mediator.
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Affiliation(s)
- Eric Bombardier
- University of Waterloo, Department of Kinesiology, 200 University Ave. W., ON, Canada N2L 3G1
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Cheng AJ, Place N, Bruton JD, Holmberg HC, Westerblad H. Doublet discharge stimulation increases sarcoplasmic reticulum Ca2+ release and improves performance during fatiguing contractions in mouse muscle fibres. J Physiol 2013; 591:3739-48. [PMID: 23690559 DOI: 10.1113/jphysiol.2013.257188] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Double discharges (doublets) of motor neurones at the onset of contractions increase both force and rate of force development during voluntary submaximal contractions. The purpose of this study was to examine the role of doublet discharges on force and myoplasmic free [Ca(2+)] ([Ca(2+)]i) during repeated fatiguing contractions, using a stimulation protocol mimicking the in vivo activation pattern during running. Individual intact fibres from the flexor digitorum brevis muscle of mice were stimulated at 33°C to undergo 150 constant-frequency (five pulses at 70 Hz) or doublet (an initial, extra pulse at 200 Hz) contractions at 300 ms intervals. In the unfatigued state, doublet stimulation resulted in a transient (∼10 ms) approximate doubling of [Ca(2+)]i, which was accompanied by a greater force-time integral (∼70%) and peak force (∼40%) compared to constant frequency contractions. Moreover, doublets markedly increased force-time integral and peak force during the first 25 contractions of the fatiguing stimulation. In later stages of fatigue, addition of doublets increased force production but the increase in force production corresponded to only a minor portion of the fatigue-induced reduction in force. In conclusion, double discharges at the onset of contractions effectively increase force production, especially in early stages of fatigue. This beneficial effect occurs without additional force loss in later stages of fatigue, indicating that the additional energy cost induced by doublet discharges to skeletal muscle is limited.
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Affiliation(s)
- Arthur J Cheng
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden, 171 77.
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Venturelli M, Richardson RS. Point: Skeletal muscle mechanical efficiency does increase with age. J Appl Physiol (1985) 2013; 114:1108-9. [DOI: 10.1152/japplphysiol.01438.2012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- Massimo Venturelli
- Department of Medicine, Division of Geriatrics, University of Utah, Salt Lake City, Utah (e-mail: )
- Department of Neurological, Neuropsychological, Morphological and Movement Sciences, University of Verona, Verona, Italy
| | - Russell S. Richardson
- Department of Medicine, Division of Geriatrics, University of Utah, Salt Lake City, Utah (e-mail: )
- Geriatric Research, Education and Clinical Center, George E. Whalen VA Medical Center, Salt Lake City, Utah
- Department of Exercise and Sport Science, University of Utah, Salt Lake City, Utah
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NIKOOYAN ALIA, VEEGER HEJ, WESTERHOFF PETER, BERGMANN GEORG, VAN DER HELM FRANSCT. RELATIVE CONTRIBUTION OF DIFFERENT MUSCLE ENERGY CONSUMPTION PROCESSES IN AN ENERGY-BASED MUSCLE LOAD SHARING COST FUNCTION. J MECH MED BIOL 2013. [DOI: 10.1142/s0219519413500097] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The aim of this study is to quantify the relative contributions of two muscle energy consumption processes (the detachment of cross-bridges and calcium-pumping) incorporated in a recently developed muscle load sharing cost function, namely the energy-based criterion, by using in vivo measured glenohumeral-joint reaction forces (GH-JRFs). Motion data and in vivo GH-JRFs were recorded for four patients carrying an instrumented shoulder implant while performing abduction and forward flexion motions up to their maximum possible arm elevations. Motion data were used as the input to the delft shoulder and elbow model for the estimation of GH-JRFs. The widely used stress as well as the energy-based cost functions were adopted as the load sharing criteria. For the energy-based criterion, simulations were run for a wide range of different weight parameters (determining the relative contribution of the two energy processes) in the neighborhood of the previously assumed parameters for each subject and motion. The model-predicted and in vivo-measured GH-JRFs were compared for all model simulations. Application of the energy-based criterion with new identified parameters resulted in significant (two-tailed p < 0.05, post-hoc power ~ 0.3) improvement (on average ~20%) of the model-predicted GH-JRFs at the maximal arm elevation compared to when using either the stress or the pre-assumed form of the energy-based criterion. About 25% of the total energy consumption was calculated for the calcium-pumping process at maximal muscle activation level when using the new parameters. This value was comparable to the corresponding ones reported in the previous literature. The identified parameters are recommended to be used instead of their predecessors.
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Affiliation(s)
- ALI A. NIKOOYAN
- Department of Biomechanical Engineering, Delft University of Technology, Mekelweg 2, Delft 2628CD, The Netherlands
| | - HEJ VEEGER
- Department of Biomechanical Engineering, Delft University of Technology, Mekelweg 2, Delft 2628CD, The Netherlands
- Research Institute Move, VU Amsterdam, Van der Boechorststraat 9, 1081BT Amsterdam, The Netherlands
| | - PETER WESTERHOFF
- Julius Wolff Institut, Charité, Universitätsmedizin, Augustenburger Platz 1, 13353 Berlin, Germany
| | - GEORG BERGMANN
- Julius Wolff Institut, Charité, Universitätsmedizin, Augustenburger Platz 1, 13353 Berlin, Germany
| | - FRANS C. T. VAN DER HELM
- Department of Biomechanical Engineering, Delft University of Technology, Mekelweg 2, Delft 2628CD, The Netherlands
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Levine S, Bashir MH, Clanton TL, Powers SK, Singhal S. COPD elicits remodeling of the diaphragm and vastus lateralis muscles in humans. J Appl Physiol (1985) 2012; 114:1235-45. [PMID: 23264538 DOI: 10.1152/japplphysiol.01121.2012] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
A profound remodeling of the diaphragm and vastus lateralis (VL) occurs in patients with moderate-to-severe chronic obstructive pulmonary disease (COPD). In this mini-review, we discuss the following costal diaphragm remodeling features noted in patients with moderate-to-severe COPD: 1) deletion of serial sarcomeres, 2) increased proportion of slow-twitch fibers, 3) fast-to-slow isoform shift in sarco(endo)plasmic reticulum Ca(2+)-ATPase, 4) increased capacity of oxidative metabolism, 5) oxidative stress, and 6) myofiber atrophy. We then present the sole feature of diaphragm remodeling noted in mild-to-moderate COPD under the heading "MyHC and contractile remodeling noted in mild-to-moderate COPD." The importance of VL remodeling in COPD patients as a prognostic indicator as well as a major determinant of the ability to carry out activities of daily living is well accepted. We present the remodeling of the VL noted in COPD patients under the following headings: 1) Decrease in proportion of slow-twitch fibers, 2) Decreased activity of oxidative pathways, 3) Oxidative and nitrosative stress, and 4) Myofiber atrophy. For each of the remodeling features noted in both the VL and costal diaphragm of COPD patients, we present mechanisms that are currently thought to mediate these changes as well as the pathophysiology of each remodeling feature. We hope that our mechanistic presentation stimulates research in this area that focuses on improving the ability of COPD patients to carry out increased activities of daily living.
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Affiliation(s)
- Sanford Levine
- Department of Surgery, University of Pennsylvania, Philadelphia, Pennsylvania 19035, USA.
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40
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Abstract
Summary
Much research in comparative physiology is now performed using ‘omics’ tools and many results are interpreted in terms of the effects of changes in gene expression on energy metabolism. However, ‘metabolism’ is a complex phenomenon that spans multiple levels of biological organization. In addition rates and directions of flux change dynamically under various physiological circumstances. Within cells, message level cannot be equated with protein level because multiple mechanisms are at play in the ‘regulatory hierarchy’ from gene to mRNA to enzyme protein. This results in many documented instances wherein change in mRNA levels and change in enzyme levels are unrelated. It is also known from metabolic control analysis that the influence of single steps in pathways on flux is often small. Flux is a system property and its control tends to be distributed among multiple steps. Consequently, change in enzyme levels cannot be equated with change in flux. Approaches developed by Hans Westerhoff and colleagues, called ‘hierarchical regulation analysis’, allow quantitative determination of the extent to which ‘hierarchical regulation’, involving change in enzyme level, and ‘metabolic regulation’, involving the modulation of the activity of preexisting enzyme, regulate flux. We outline these approaches and provide examples to show their applicability to problems of interest to comparative physiologists.
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Affiliation(s)
- Raul K. Suarez
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA 93106-9610, USA
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Evolving concepts on the age-related changes in "muscle quality". J Cachexia Sarcopenia Muscle 2012; 3:95-109. [PMID: 22476917 PMCID: PMC3374023 DOI: 10.1007/s13539-011-0054-2] [Citation(s) in RCA: 103] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Accepted: 12/26/2011] [Indexed: 01/06/2023] Open
Abstract
The deterioration of skeletal muscle with advancing age has long been anecdotally recognized and has been of scientific interest for more than 150 years. Over the past several decades, the scientific and medical communities have recognized that skeletal muscle dysfunction (e.g., muscle weakness, poor muscle coordination, etc.) is a debilitating and life-threatening condition in the elderly. For example, the age-associated loss of muscle strength is highly associated with both mortality and physical disability. It is well-accepted that voluntary muscle force production is not solely dependent upon muscle size, but rather results from a combination of neurologic and skeletal muscle factors, and that biologic properties of both of these systems are altered with aging. Accordingly, numerous scientists and clinicians have used the term "muscle quality" to describe the relationship between voluntary muscle strength and muscle size. In this review article, we discuss the age-associated changes in the neuromuscular system-starting at the level of the brain and proceeding down to the subcellular level of individual muscle fibers-that are potentially influential in the etiology of dynapenia (age-related loss of muscle strength and power).
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42
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McKay JL, Ting LH. Optimization of muscle activity for task-level goals predicts complex changes in limb forces across biomechanical contexts. PLoS Comput Biol 2012; 8:e1002465. [PMID: 22511857 PMCID: PMC3325175 DOI: 10.1371/journal.pcbi.1002465] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2011] [Accepted: 02/22/2012] [Indexed: 01/08/2023] Open
Abstract
Optimality principles have been proposed as a general framework for understanding motor control in animals and humans largely based on their ability to predict general features movement in idealized motor tasks. However, generalizing these concepts past proof-of-principle to understand the neuromechanical transformation from task-level control to detailed execution-level muscle activity and forces during behaviorally-relevant motor tasks has proved difficult. In an unrestrained balance task in cats, we demonstrate that achieving task-level constraints center of mass forces and moments while minimizing control effort predicts detailed patterns of muscle activity and ground reaction forces in an anatomically-realistic musculoskeletal model. Whereas optimization is typically used to resolve redundancy at a single level of the motor hierarchy, we simultaneously resolved redundancy across both muscles and limbs and directly compared predictions to experimental measures across multiple perturbation directions that elicit different intra- and interlimb coordination patterns. Further, although some candidate task-level variables and cost functions generated indistinguishable predictions in a single biomechanical context, we identified a common optimization framework that could predict up to 48 experimental conditions per animal (n = 3) across both perturbation directions and different biomechanical contexts created by altering animals' postural configuration. Predictions were further improved by imposing experimentally-derived muscle synergy constraints, suggesting additional task variables or costs that may be relevant to the neural control of balance. These results suggested that reduced-dimension neural control mechanisms such as muscle synergies can achieve similar kinetics to the optimal solution, but with increased control effort (≈2×) compared to individual muscle control. Our results are consistent with the idea that hierarchical, task-level neural control mechanisms previously associated with voluntary tasks may also be used in automatic brainstem-mediated pathways for balance.
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Affiliation(s)
| | - Lena H. Ting
- The Wallace H. Coulter Department of Biomedical Engineering, Emory University and the Georgia Institute of Technology, Atlanta, Georgia, United States of America
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43
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Specific effects of endurance and sprint training on protein expression of calsequestrin and SERCA in mouse skeletal muscle. J Muscle Res Cell Motil 2012; 33:123-30. [PMID: 22466636 DOI: 10.1007/s10974-012-9290-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Accepted: 03/16/2012] [Indexed: 10/28/2022]
Abstract
Calsequestrin (CSQ) is the main Ca²⁺ binding protein inside the sarcoplasmic reticulum (SR) of skeletal and cardiac muscle. The present study demonstrates the specific effects of different training regimens on CSQ isoform 1 (CSQ1, the primary isoform) and SR Ca²⁺-ATPase (SERCA1, 2) expression in various skeletal muscles of mouse. CSQ1, SERCA1, and SERCA2 protein expression was determined with Western blot in m. soleus (SOL), m. extensor digitorum longus (EDL), m. gastrocnemius (GAS), m. rectus femoris (RF), and m. tibialis anterior (TA) muscles after completing a 6-week endurance or sprint training program. Endurance training induced decrease in CSQ1 concentration in SOL (p < 0.001) and in SERCA1 levels in GAS (p < 0.05), whereas increase in CSQ1 expression was detected in EDL (p < 0.01). After sprint training the concentration of CSQ1 increased in GAS (p < 0.01) and EDL (p < 0.01). Additionally, sprint exercise induced an increase in SERCA1 in GAS (p < 0.001) and a decline in TA (p < 0.05). SERCA2 was up-regulated with sprint training in GAS (p < 0.01). Myosin heavy chain (MHC) based fibre type composition altered differently depending on the muscle and the training regimen.These results indicate that (1) diverse training strategies used affect differently CSQ1 and SERCA1 concentrations in the skeletal muscle, (2) the regulation of CSQ1 and SERCA1 does not necessary follow the fast-slow definition despite the correlation between MHC isoforms, and (3) the changes in CSQ1 concentration occur prior to SERCA1 or SERCA2.
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44
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Majerczak J, Korostynski M, Nieckarz Z, Szkutnik Z, Duda K, Zoladz JA. Endurance training decreases the non-linearity in the oxygen uptake-power output relationship in humans. Exp Physiol 2012; 97:386-99. [DOI: 10.1113/expphysiol.2011.062992] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Jones AM, Grassi B, Christensen PM, Krustrup P, Bangsbo J, Poole DC. Slow component of VO2 kinetics: mechanistic bases and practical applications. Med Sci Sports Exerc 2012; 43:2046-62. [PMID: 21552162 DOI: 10.1249/mss.0b013e31821fcfc1] [Citation(s) in RCA: 230] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The V·O₂ slow component, a slowly developing increase in V·O₂ during constant-work-rate exercise performed above the lactate threshold, represents a progressive loss of skeletal muscle contractile efficiency and is associated with the fatigue process. This brief review outlines the current state of knowledge concerning the mechanistic bases of the V·O₂ slow component and describes practical interventions that can attenuate the slow component and thus enhance exercise tolerance. There is strong evidence that, during constant-work-rate exercise, the development of the V·O₂ slow component is associated with the progressive recruitment of additional (type II) muscle fibers that are presumed to have lower efficiency. Recent studies, however, indicate that muscle efficiency is also lowered (resulting in a "mirror-image" V·O₂ slow component) during fatiguing, high-intensity exercise in which additional fiber recruitment is unlikely or impossible. Therefore, it seems that muscle fatigue underpins the V·O₂ slow component, although the greater fatigue sensitivity of recruited type II fibers might still play a crucial role in the loss of muscle efficiency in both situations. Several interventions can reduce the magnitude of the V·O₂ slow component, and these are typically associated with an enhanced exercise tolerance. These include endurance training, inspiratory muscle training, priming exercise, dietary nitrate supplementation, and the inspiration of hyperoxic gas. All of these interventions reduce muscle fatigue development either by improving muscle oxidative capacity and thus metabolic stability or by enhancing bulk muscle O2 delivery or local Q·O₂-to-V·O₂ matching. Future honing of these interventions to maximize their impact on the V·O₂ slow component might improve sports performance in athletes and exercise tolerance in the elderly or in patient populations.
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Affiliation(s)
- Andrew M Jones
- Sport and Health Sciences, College of Life and Environmental Sciences, St. Luke's Campus, University of Exeter, Exeter, United Kingdom.
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46
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Dutka TL, Lamboley CR, McKenna MJ, Murphy RM, Lamb GD. Effects of carnosine on contractile apparatus Ca2+ sensitivity and sarcoplasmic reticulum Ca2+ release in human skeletal muscle fibers. J Appl Physiol (1985) 2012; 112:728-36. [DOI: 10.1152/japplphysiol.01331.2011] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
There is considerable interest in potential ergogenic and therapeutic effects of increasing skeletal muscle carnosine content, although its effects on excitation-contraction (EC) coupling in human muscle have not been defined. Consequently, we sought to characterize what effects carnosine, at levels attained by supplementation, has on human muscle fiber function, using a preparation with all key EC coupling proteins in their in situ positions. Fiber segments, obtained from vastus lateralis muscle of human subjects by needle biopsy, were mechanically skinned, and their Ca2+ release and contractile apparatus properties were characterized. Ca2+ sensitivity of the contractile apparatus was significantly increased by 8 and 16 mM carnosine (increase in pCa50 of 0.073 ± 0.007 and 0.116 ± 0.006 pCa units, respectively, in six type I fibers, and 0.063 ± 0.018 and 0.103 ± 0.013 pCa units, respectively, in five type II fibers). Caffeine-induced force responses were potentiated by 8 mM carnosine in both type I and II fibers, with the potentiation in type II fibers being entirely explicable by the increase in Ca2+ sensitivity of the contractile apparatus caused by carnosine. However, the potentiation of caffeine-induced responses caused by carnosine in type I fibers was beyond that expected from the associated increase in Ca2+ sensitivity of the contractile apparatus and suggestive of increased Ca2+-induced Ca2+ release. Thus increasing muscle carnosine content likely confers benefits to muscle performance in both fiber types by increasing the Ca2+ sensitivity of the contractile apparatus and possibly also by aiding Ca2+ release in type I fibers, helping to lessen or slow the decline in muscle performance during fatiguing stimulation.
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Affiliation(s)
- T. L. Dutka
- Department of Zoology, La Trobe University; and
| | - C. R. Lamboley
- Institute of Sport, Exercise and Active Living, Victoria University, Melbourne, Australia
| | - M. J. McKenna
- Institute of Sport, Exercise and Active Living, Victoria University, Melbourne, Australia
| | | | - G. D. Lamb
- Department of Zoology, La Trobe University; and
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47
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Abstract
Mammalian skeletal muscle comprises different fiber types, whose identity is first established during embryonic development by intrinsic myogenic control mechanisms and is later modulated by neural and hormonal factors. The relative proportion of the different fiber types varies strikingly between species, and in humans shows significant variability between individuals. Myosin heavy chain isoforms, whose complete inventory and expression pattern are now available, provide a useful marker for fiber types, both for the four major forms present in trunk and limb muscles and the minor forms present in head and neck muscles. However, muscle fiber diversity involves all functional muscle cell compartments, including membrane excitation, excitation-contraction coupling, contractile machinery, cytoskeleton scaffold, and energy supply systems. Variations within each compartment are limited by the need of matching fiber type properties between different compartments. Nerve activity is a major control mechanism of the fiber type profile, and multiple signaling pathways are implicated in activity-dependent changes of muscle fibers. The characterization of these pathways is raising increasing interest in clinical medicine, given the potentially beneficial effects of muscle fiber type switching in the prevention and treatment of metabolic diseases.
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Affiliation(s)
- Stefano Schiaffino
- Venetian Institute of Molecular Medicine, Department of Biomedical Sciences, University of Padova, Consiglio Nazionale delle Ricerche Institute of Neurosciences, and Department of Human Anatomy and Physiology, University of Padova, Padova, Italy
| | - Carlo Reggiani
- Venetian Institute of Molecular Medicine, Department of Biomedical Sciences, University of Padova, Consiglio Nazionale delle Ricerche Institute of Neurosciences, and Department of Human Anatomy and Physiology, University of Padova, Padova, Italy
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48
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Boone J, Bouckaert J, Barstow TJ, Bourgois J. Influence of priming exercise on muscle deoxy[Hb + Mb] during ramp cycle exercise. Eur J Appl Physiol 2011; 112:1143-52. [PMID: 21766226 DOI: 10.1007/s00421-011-2068-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Accepted: 06/29/2011] [Indexed: 10/18/2022]
Abstract
The aim of the present study was to gain better insight into the mechanisms underpinning the sigmoid pattern of deoxy[Hb + Mb] during incremental exercise by assessing the changes in the profile following prior high-intensity exercise. Ten physically active students performed two incremental ramp (25 W min(-1)) exercises (AL and LL, respectively) preceded on one occasion by incremental arm (10 W min(-1)) and on another occasion by incremental leg exercise (25 W min(-1)), which served as the reference test (RT). Deoxy[Hb + Mb] was measured by means of near-infrared spectroscopy and surface EMG was recorded at the Vastus Lateralis throughout the exercises. Deoxy[Hb + Mb], integrated EMG and Median Power Frequency (MdPF) were expressed as a function of work rate (W) and compared between the exercises. During RT and AL deoxy[Hb + Mb] followed a sigmoid increase as a function of work rate. However, during LL deoxy[Hb + Mb] increased immediately from the onset of the ramp exercise and thus no longer followed a sigmoid pattern. This different pattern in deoxy[Hb + Mb] was accompanied by a steeper slope of the iEMG/W-relationship below the GET (LL: 0.89 ± 0.11% W(-1); RT: 0.74 ± 0.08% W(-1); AL: 0.72 ± 0.10% W(-1)) and a more pronounced decrease in MdPF in LL (17.2 ± 4.5%) compared to RT (5.0 ± 2.1%) and AL (3.9 ± 3.2%). It was observed that the sigmoid pattern of deoxy[Hb + Mb] was disturbed when the ramp exercise was preceded by priming leg exercise. Since the differences in deoxy[Hb + Mb] were accompanied by differences in EMG it can be suggested that muscle fibre recruitment is an important underlying mechanism for the pattern of deoxy[Hb + Mb] during ramp exercise.
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Affiliation(s)
- Jan Boone
- Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium.
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49
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Layec G, Haseler LJ, Hoff J, Richardson RS. Evidence that a higher ATP cost of muscular contraction contributes to the lower mechanical efficiency associated with COPD: preliminary findings. Am J Physiol Regul Integr Comp Physiol 2011; 300:R1142-7. [PMID: 21307358 DOI: 10.1152/ajpregu.00835.2010] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Impaired metabolism in peripheral skeletal muscles potentially contributes to exercise intolerance in chronic obstructive pulmonary disease (COPD). We used (31)P-magnetic resonance spectroscopy ((31)P-MRS) to examine the energy cost and skeletal muscle energetics in six patients with COPD during dynamic plantar flexion exercise compared with six well-matched healthy control subjects. Patients with COPD displayed a higher energy cost of muscle contraction compared with the controls (control: 6.1 ± 3.1% of rest·min(-1)·W(-1), COPD: 13.6 ± 8.3% of rest·min(-1)·W(-1), P = 0.01). Although, the initial phosphocreatine resynthesis rate was also significantly attenuated in patients with COPD compared with controls (control: 74 ± 17% of rest/min, COPD: 52 ± 13% of rest/min, P = 0.04), when scaled to power output, oxidative ATP synthesis was similar between groups (6.5 ± 2.3% of rest·min(-1)·W(-1) in control and 7.8 ± 3.9% of rest·min(-1)·W(-1) in COPD, P = 0.52). Therefore, our results reveal, for the first time that in a small subset of patients with COPD a higher ATP cost of muscle contraction may substantially contribute to the lower mechanical efficiency previously reported in this population. In addition, it appears that some patients with COPD have preserved mitochondrial function and normal energy supply in lower limb skeletal muscle.
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Affiliation(s)
- Gwenael Layec
- Veterans Affairs Medical Center, 500 Foothill Dr., Salt Lake City, UT 84148, USA.
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50
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Suarez RK, M. LGH, Welch KC. The sugar oxidation cascade: aerial refueling in hummingbirds and nectar bats. J Exp Biol 2011; 214:172-8. [DOI: 10.1242/jeb.047936] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Summary
Most hummingbirds and some species of nectar bats hover while feeding on floral nectar. While doing so, they achieve some of the highest mass-specific values among vertebrates. This is made possible by enhanced functional capacities of various elements of the ‘O2 transport cascade’, the pathway of O2 from the external environment to muscle mitochondria. Fasted hummingbirds and nectar bats fly with respiratory quotients (RQs; ) of ∼0.7, indicating that fat fuels flight in the fasted state. During repeated hover-feeding on dietary sugar, RQ values progressively climb to ∼1.0, indicating a shift from fat to carbohydrate oxidation. Stable carbon isotope experiments reveal that recently ingested sugar directly fuels ∼80 and 95% of energy metabolism in hover-feeding nectar bats and hummingbirds, respectively. We name the pathway of carbon flux from flowers, through digestive and cardiovascular systems, muscle membranes and into mitochondria the ‘sugar oxidation cascade’. O2 and sugar oxidation cascades operate in parallel and converge in muscle mitochondria. Foraging behavior that favours the oxidation of dietary sugar avoids the inefficiency of synthesizing fat from sugar and breaking down fat to fuel foraging. Sugar oxidation yields a higher P/O ratio (ATP made per O atom consumed) than fat oxidation, thus requiring lower hovering per unit mass. We propose that dietary sugar is a premium fuel for flight in nectarivorous, flying animals.
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Affiliation(s)
- Raul K. Suarez
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA 93106, USA
| | - L. Gerardo Herrera M.
- Estación de Biología de Chamela, Instituto de Biología, Universidad Nacional Autónoma de México, Apartado Postal 21, San Patricio, Jalisco 48980, México
| | - Kenneth C. Welch
- Department of Biological Sciences, University of Toronto, Scarborough, Ontario M1C 1A4, Canada
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