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Poredoš D, Jenko Pražnikar Z, Kozinc Ž. Acute Effects of Beetroot Juice Supplementation on Isometric Muscle Strength, Rate of Torque Development and Isometric Endurance in Young Adult Men and Women: A Randomized, Double-Blind, Controlled Cross-Over Pilot Study. Nutrients 2022; 14:nu14224759. [PMID: 36432445 PMCID: PMC9692807 DOI: 10.3390/nu14224759] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Revised: 11/07/2022] [Accepted: 11/08/2022] [Indexed: 11/12/2022] Open
Abstract
This study was conducted to investigate the effect of concentrated beetroot juice on isometric strength and knee extensor muscle endurance in healthy adults. We conducted a randomized cross-over, double-blind experiment in which participants (18 healthy, physically active adults, 9 men, 9 women) consumed either concentrated beetroot juice (140 mL) or low-nitrate control supplement 2.5 h before the measurement. Isometric maximum strength (peak torque), explosive strength (isometric rate of torque development), and strength endurance at 50% of peak torque were measured on an isometric dynamometer. The results showed that concentrated beetroot juice had no effect on the maximum voluntary isometric strength and rate of torque development of the knee extensors. The only exception was the maximum rate of torque development, for which a positive influence was demonstrated only in men. As for the endurance of the knee extensors, the supplement had a positive effect in men (endurance time increased from 86.4 ± 46.1 s to 103.4 ± 53.7 s; p = 0.022), but not in women. The absence of effect on maximal voluntary strength is consistent with previous research. One the other hand, improvements in endurance and rate of torque development in men only point to an important aspect of a previously under-researched area of sex-specific responses to nitrate supplementation.
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Affiliation(s)
- David Poredoš
- Faculty of Health Sciences, University of Primorska, Polje 42, SI-6310 Izola, Slovenia
| | - Zala Jenko Pražnikar
- Andrej Marušič Institute, University of Primorska, Muzejski trg 2, SI-6000 Koper, Slovenia
| | - Žiga Kozinc
- Faculty of Health Sciences, University of Primorska, Polje 42, SI-6310 Izola, Slovenia
- Andrej Marušič Institute, University of Primorska, Muzejski trg 2, SI-6000 Koper, Slovenia
- Correspondence:
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Abdalla LHP, Broxterman RM, Barstow TJ, Greco CC, Denadai BS. W' reconstitution rate at different intensities above critical torque: the role of muscle size and maximal strength. Exp Physiol 2021; 106:1909-1921. [PMID: 34288192 DOI: 10.1113/ep089638] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Accepted: 07/16/2021] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Do muscle size, maximal force and exercise intensity influence the recovery time constant for the finite impulse above critical torque (τIET' )? What is the main finding and its importance? Muscle size and maximal strength have different influences on the parameters of the hyperbolic torque-time to task failure relationship. Greater muscle size and maximal strength, as well as exercise at an intensity of 60% MVC, prolong τIET' during intermittent isometric exercise. ABSTRACT Muscle perfusion and O2 delivery limitations through muscle force generation appear to play a major role in defining the hyperbolic torque-time to task failure (Tlim ) relationship. Therefore, we aimed to determine the influence of muscle size and maximal strength on the recovery time constant for the finite impulse above critical torque (τIET' ). Ten men participated in the study and performed intermittent isometric tests until task-failure (Tlim ) for the knee-extensors (KE) (35% and 60% maximal voluntary contraction (MVC)) and plantar flexors (PF) (60% MVC). The τIET' was determined for each of these Tlim tests using the IET'BAL model. The IET' (9738 ± 3080 vs. 2959 ± 1289 N m s) and end-test torque (ET)(84.5 ± 7.1 vs. 74.3 ± 12.7 N m) were significantly lower for PF compared to KE (P < 0.05). Exercise tolerance (Tlim ) was significantly longer for PF (239 ± 81 s) than KE (150 ± 55 s) at 60% MVC, and significantly longer for KE at 35% MVC (641 ± 158 s) than 60% MVC. The τIET' was significantly faster at 35% MVC (641 ± 177 s) than 60% MVC (1840 ± 354 s) for KE, both of which were significantly slower than PF at 60% MVC (317 ± 102 s). This study showed that τIET' during intermittent isometric exercise is slower with greater muscle size and maximal strength.
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Affiliation(s)
| | - Ryan Michael Broxterman
- Department of Internal Medicine, University of Utah, Salt Lake City, UT, USA.,Geriatric Research, Education and Clinical Center, VA Medical Center, Salt Lake City, UT, USA
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Lopez C, Taivassalo T, Berru MG, Saavedra A, Rasmussen HC, Batra A, Arora H, Roetzheim AM, Walter GA, Vandenborne K, Forbes SC. Postcontractile blood oxygenation level-dependent (BOLD) response in Duchenne muscular dystrophy. J Appl Physiol (1985) 2021; 131:83-94. [PMID: 34013753 PMCID: PMC8325615 DOI: 10.1152/japplphysiol.00634.2020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 04/28/2021] [Accepted: 05/13/2021] [Indexed: 11/22/2022] Open
Abstract
Duchenne muscular dystrophy (DMD) is characterized by a progressive replacement of muscle by fat and fibrous tissue, muscle weakness, and loss of functional abilities. Impaired vasodilatory and blood flow responses to muscle activation have also been observed in DMD and associated with mislocalization of neuronal nitric oxide synthase mu (nNOSμ) from the sarcolemma. The objective of this study was to determine whether the postcontractile blood oxygen level-dependent (BOLD) MRI response is impaired in DMD and correlated with established markers of disease severity in DMD, including MRI muscle fat fraction (FF) and clinical functional measures. Young boys with DMD (n = 16, 5-14 yr) and unaffected controls (n = 16, 5-14 yr) were evaluated using postcontractile BOLD, FF, and functional assessments. The BOLD response was measured following five brief (2 s) maximal voluntary dorsiflexion contractions, each separated by 1 min of rest. FFs from the anterior compartment lower leg muscles were quantified via chemical shift-encoded imaging. Functional abilities were assessed using the 10 m walk/run and the 6-min walk distance (6MWD). The peak BOLD responses in the tibialis anterior and extensor digitorum longus were reduced (P < 0.001) in DMD compared with controls. Furthermore, the anterior compartment peak BOLD response correlated with function (6MWD ρ = 0.87, P < 0.0001; 10 m walk/run time ρ = -0.78, P < 0.001) and FF (ρ = -0.52, P = 0.05). The reduced postcontractile BOLD response in DMD may reflect impaired microvascular function. The relationship observed between the postcontractile peak BOLD response and functional measures and FF suggests that the BOLD response is altered with disease severity in DMD.NEW & NOTEWORTHY This study examined the postcontractile blood oxygen level-dependent (BOLD) response in boys with Duchenne muscular dystrophy (DMD) and unaffected controls, and correlated this measure to markers of disease severity. Our findings indicate that the postcontractile BOLD response is impaired in DMD after brief muscle contractions, is correlated to disease severity, and may be valuable to implement in future studies to evaluate treatments targeting microvascular function in DMD.
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Affiliation(s)
- Christopher Lopez
- Department of Physical Therapy, University of Florida, Gainesville, Florida
| | - Tanja Taivassalo
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida
| | - Maria G Berru
- Department of Physical Therapy, University of Florida, Gainesville, Florida
| | - Andres Saavedra
- Department of Physical Therapy, University of Florida, Gainesville, Florida
| | - Hannah C Rasmussen
- Department of Physical Therapy, University of Florida, Gainesville, Florida
| | - Abhinandan Batra
- Department of Physical Therapy, University of Florida, Gainesville, Florida
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida
| | - Harneet Arora
- Department of Physical Therapy, University of Florida, Gainesville, Florida
| | - Alex M Roetzheim
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida
| | - Glenn A Walter
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida
| | - Krista Vandenborne
- Department of Physical Therapy, University of Florida, Gainesville, Florida
| | - Sean C Forbes
- Department of Physical Therapy, University of Florida, Gainesville, Florida
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A thermodynamic function of glycogen in brain and muscle. Prog Neurobiol 2020; 189:101787. [PMID: 32151532 DOI: 10.1016/j.pneurobio.2020.101787] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 01/30/2020] [Accepted: 03/03/2020] [Indexed: 11/20/2022]
Abstract
Brain and muscle glycogen are generally thought to function as local glucose reserves, for use during transient mismatches between glucose supply and demand. However, quantitative measures show that glucose supply is likely never rate-limiting for energy metabolism in either brain or muscle under physiological conditions. These tissues nevertheless do utilize glycogen during increased energy demand, despite the availability of free glucose, and despite the ATP cost of cycling glucose through glycogen polymer. This seemingly wasteful process can be explained by considering the effect of glycogenolysis on the amount of energy obtained from ATP (ΔG'ATP). The amount of energy obtained from ATP is reduced by elevations in inorganic phosphate (Pi). Glycogen utilization sequesters Pi in the glycogen phosphorylase reaction and in downstream phosphorylated glycolytic intermediates, thereby buffering Pi elevations and maximizing energy yield at sites of rapid ATP consumption. This thermodynamic effect of glycogen may be particularly important in the narrow, spatially constrained astrocyte processes that ensheath neuronal synapses and in cells such as astrocytes and myocytes that release Pi from phosphocreatine during energy demand. The thermodynamic effect may also explain glycolytic super-compensation in brain when glycogen is not available, and aspects of exercise physiology in muscle glycogen phosphorylase deficiency (McArdle disease).
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Muddle TW, Magrini MA, Colquhoun RJ, Luera MJ, Tomko PM, Jenkins ND. Impact of Fatiguing, Submaximal High- vs. Low-Torque Isometric Exercise on Acute Muscle Swelling, and Echo Intensity in Resistance-Trained Men. J Strength Cond Res 2019; 33:1007-1019. [DOI: 10.1519/jsc.0000000000003033] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Gelabert-Rebato M, Wiebe JC, Martin-Rincon M, Gericke N, Perez-Valera M, Curtelin D, Galvan-Alvarez V, Lopez-Rios L, Morales-Alamo D, Calbet JAL. Mangifera indica L. Leaf Extract in Combination With Luteolin or Quercetin Enhances VO 2peak and Peak Power Output, and Preserves Skeletal Muscle Function During Ischemia-Reperfusion in Humans. Front Physiol 2018; 9:740. [PMID: 29937737 PMCID: PMC6002676 DOI: 10.3389/fphys.2018.00740] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Accepted: 05/28/2018] [Indexed: 12/15/2022] Open
Abstract
It remains unknown whether polyphenols such as luteolin (Lut), mangiferin and quercetin (Q) have ergogenic effects during repeated all-out prolonged sprints. Here we tested the effect of Mangifera indica L. leaf extract (MLE) rich in mangiferin (Zynamite®) administered with either quercetin (Q) and tiger nut extract (TNE), or with luteolin (Lut) on sprint performance and recovery from ischemia-reperfusion. Thirty young volunteers were randomly assigned to three treatments 48 h before exercise. Treatment A: placebo (500 mg of maltodextrin/day); B: 140 mg of MLE (60% mangiferin) and 50 mg of Lut/day; and C: 140 mg of MLE, 600 mg of Q and 350 mg of TNE/day. After warm-up, subjects performed two 30 s Wingate tests and a 60 s all-out sprint interspaced by 4 min recovery periods. At the end of the 60 s sprint the circulation of both legs was instantaneously occluded for 20 s. Then, the circulation was re-opened and a 15 s sprint performed, followed by 10 s recovery with open circulation, and another 15 s final sprint. MLE supplements enhanced peak (Wpeak) and mean (Wmean) power output by 5.0-7.0% (P < 0.01). After ischemia, MLE+Q+TNE increased Wpeak by 19.4 and 10.2% compared with the placebo (P < 0.001) and MLE+Lut (P < 0.05), respectively. MLE+Q+TNE increased Wmean post-ischemia by 11.2 and 6.7% compared with the placebo (P < 0.001) and MLE+Lut (P = 0.012). Mean VO2 during the sprints was unchanged, suggesting increased efficiency or recruitment of the anaerobic capacity after MLE ingestion. In women, peak VO2 during the repeated sprints was 5.8% greater after the administration of MLE, coinciding with better brain oxygenation. MLE attenuated the metaboreflex hyperpneic response post-ischemia, may have improved O2 extraction by the Vastus Lateralis (MLE+Q+TNE vs. placebo, P = 0.056), and reduced pain during ischemia (P = 0.068). Blood lactate, acid-base balance, and plasma electrolytes responses were not altered by the supplements. In conclusion, a MLE extract rich in mangiferin combined with either quercetin and tiger nut extract or luteolin exerts a remarkable ergogenic effect, increasing muscle power in fatigued subjects and enhancing peak VO2 and brain oxygenation in women during prolonged sprinting. Importantly, the combination of MLE+Q+TNE improves skeletal muscle contractile function during ischemia/reperfusion.
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Affiliation(s)
- Miriam Gelabert-Rebato
- Department of Physical Education and Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain
- Nektium Pharma, Las Palmas de Gran Canaria, Spain
| | | | - Marcos Martin-Rincon
- Department of Physical Education and Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain
| | | | - Mario Perez-Valera
- Department of Physical Education and Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain
| | - David Curtelin
- Department of Physical Education and Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain
| | - Victor Galvan-Alvarez
- Department of Physical Education and Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain
| | - Laura Lopez-Rios
- Department of Physical Education and Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain
| | - David Morales-Alamo
- Department of Physical Education and Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain
| | - Jose A. L. Calbet
- Department of Physical Education and Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain
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Broxterman RM, Hureau TJ, Layec G, Morgan DE, Bledsoe AD, Jessop JE, Amann M, Richardson RS. Influence of group III/IV muscle afferents on small muscle mass exercise performance: a bioenergetics perspective. J Physiol 2018; 596:2301-2314. [PMID: 29644702 DOI: 10.1113/jp275817] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Accepted: 03/28/2018] [Indexed: 12/19/2022] Open
Abstract
KEY POINTS This investigation assessed the influence of group III/IV muscle afferents on small muscle mass exercise performance from a skeletal muscle bioenergetics perspective. Group III/IV muscle afferent feedback was attenuated with lumbar intrathecal fentanyl during intermittent isometric single-leg knee-extensor all-out exercise, while 31 P-MRS was used to assess skeletal muscle bioenergetics. Attenuation of group III/IV muscle afferent feedback improved exercise performance during the first minute of exercise, due to an increase in total ATP production with no change in the ATP cost of contraction. However, exercise performance was not altered during the remainder of the protocol, despite a sustained increase in total ATP production, due to an exacerbated ATP cost of contraction. These findings reveal that group III/IV muscle afferents directly limit exercise performance during small muscle mass exercise, but, due to their critical role in maintaining skeletal muscle contractile efficiency, with time, the benefit of attenuating the muscle afferents is negated. ABSTRACT The direct influence of group III/IV muscle afferents on exercise performance remains equivocal. Therefore, all-out intermittent isometric single-leg knee-extensor exercise and phosphorous magnetic resonance spectroscopy (31 P-MRS) were utilized to provide a high time resolution assessment of exercise performance and skeletal muscle bioenergetics in control conditions (CTRL) and with the attenuation of group III/IV muscle afferent feedback via lumbar intrathecal fentanyl (FENT). In both conditions, seven recreationally active men performed 60 maximal voluntary quadriceps contractions (MVC; 3 s contraction, 2 s relaxation), while knee-extensor force and 31 P-MRS were assessed during each MVC. The cumulative integrated force was significantly greater (8 ± 6%) in FENT than CTRL for the first minute of the all-out protocol, but was not significantly different for the second to fifth minutes. Total ATP production was significantly greater (16 ± 21%) in FENT than CTRL throughout the all-out exercise protocol, due to a significantly greater anaerobic ATP production (11 ± 13%) in FENT than CTRL with no significant difference in oxidative ATP production. The ATP cost of contraction was not significantly different between FENT and CTRL for the first minute of the all-out protocol, but was significantly greater (29 ± 34%) in FENT than in CTRL for the second to fifth minutes. These findings reveal that group III/IV muscle afferents directly limit exercise performance during small muscle mass exercise, but, due to their critical role in maintaining skeletal muscle contractile efficiency, with time, the benefit from muscle afferent attenuation is negated.
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Affiliation(s)
- Ryan M Broxterman
- Geriatric Research, Education, and Clinical Center, Salt Lake City VAMC, UT, USA.,Department of Internal Medicine, University of Utah, Salt Lake City, UT, USA
| | - Thomas J Hureau
- Geriatric Research, Education, and Clinical Center, Salt Lake City VAMC, UT, USA.,Department of Internal Medicine, University of Utah, Salt Lake City, UT, USA
| | - Gwenael Layec
- Department of Internal Medicine, University of Utah, Salt Lake City, UT, USA.,Center on Aging, University of Utah, Salt Lake City, UT, USA
| | - David E Morgan
- Department of Anesthesiology, University of Utah, Salt Lake City, UT, USA
| | - Amber D Bledsoe
- Department of Anesthesiology, University of Utah, Salt Lake City, UT, USA
| | - Jacob E Jessop
- Department of Anesthesiology, University of Utah, Salt Lake City, UT, USA
| | - Markus Amann
- Geriatric Research, Education, and Clinical Center, Salt Lake City VAMC, UT, USA.,Department of Internal Medicine, University of Utah, Salt Lake City, UT, USA.,Center on Aging, University of Utah, Salt Lake City, UT, USA.,Department of Anesthesiology, University of Utah, Salt Lake City, UT, USA.,Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, UT, USA
| | - Russell S Richardson
- Geriatric Research, Education, and Clinical Center, Salt Lake City VAMC, UT, USA.,Department of Internal Medicine, University of Utah, Salt Lake City, UT, USA.,Center on Aging, University of Utah, Salt Lake City, UT, USA.,Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, UT, USA
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Broxterman RM, Layec G, Hureau TJ, Morgan DE, Bledsoe AD, Jessop JE, Amann M, Richardson RS. Bioenergetics and ATP Synthesis during Exercise: Role of Group III/IV Muscle Afferents. Med Sci Sports Exerc 2018; 49:2404-2413. [PMID: 28767527 DOI: 10.1249/mss.0000000000001391] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
PURPOSE The purpose of this study was to investigate the role of the group III/IV muscle afferents in the bioenergetics of exercising skeletal muscle beyond constraining the magnitude of metabolic perturbation. METHODS Eight healthy men performed intermittent isometric knee-extensor exercise to task failure at ~58% maximal voluntary contraction under control conditions (CTRL) and with lumbar intrathecal fentanyl to attenuate group III/IV leg muscle afferents (FENT). Intramuscular concentrations of phosphocreatine (PCr), inorganic phosphate (Pi), diprotonated phosphate (H2PO4), adenosine triphosphate (ATP), and pH were determined using phosphorous magnetic resonance spectroscopy (P-MRS). RESULTS The magnitude of metabolic perturbation was significantly greater in FENT compared with CTRL for [Pi] (37.8 ± 16.8 vs 28.6 ± 8.6 mM), [H2PO4] (24.3 ± 12.2 vs 17.9 ± 7.1 mM), and [ATP] (75.8% ± 17.5% vs 81.9% ± 15.8% of baseline), whereas there was no significant difference in [PCr] (4.5 ± 2.4 vs 4.4 ± 2.3 mM) or pH (6.51 ± 0.10 vs 6.54 ± 0.14). The rate of perturbation in [PCr], [Pi], [H2PO4], and pH was significantly faster in FENT compared with CTRL. Oxidative ATP synthesis was not significantly different between conditions. However, anaerobic ATP synthesis, through augmented creatine kinase and glycolysis reactions, was significantly greater in FENT than in CTRL, resulting in a significantly greater ATP cost of contraction (0.049 ± 0.016 vs 0.038 ± 0.010 mM·min·N). CONCLUSION Group III/IV muscle afferents not only constrain the magnitude of perturbation in intramuscular Pi, H2PO4, and ATP during small muscle mass exercise but also seem to play a role in maintaining efficient skeletal muscle contractile function in men.
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Affiliation(s)
- Ryan M Broxterman
- 1Geriatric Research, Education, and Clinical Center, Salt Lake City Veteran's Affairs Medical Center, Salt Lake City, UT; 2Department of Internal Medicine, University of Utah, Salt Lake City, UT; 3Department of Anesthesiology, University of Utah, Salt Lake City, UT; and 4Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, UT
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Muscle fatigue: general understanding and treatment. Exp Mol Med 2017; 49:e384. [PMID: 28983090 PMCID: PMC5668469 DOI: 10.1038/emm.2017.194] [Citation(s) in RCA: 276] [Impact Index Per Article: 39.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2017] [Revised: 05/20/2017] [Accepted: 05/23/2017] [Indexed: 12/19/2022] Open
Abstract
Muscle fatigue is a common complaint in clinical practice. In humans, muscle fatigue can be defined as exercise-induced decrease in the ability to produce force. Here, to provide a general understanding and describe potential therapies for muscle fatigue, we summarize studies on muscle fatigue, including topics such as the sequence of events observed during force production, in vivo fatigue-site evaluation techniques, diagnostic markers and non-specific but effective treatments.
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Osada T, Mortensen SP, Rådegran G. Mechanical compression during repeated sustained isometric muscle contractions and hyperemic recovery in healthy young males. J Physiol Anthropol 2015; 34:36. [PMID: 26520798 PMCID: PMC4628366 DOI: 10.1186/s40101-015-0075-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 10/12/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND An elevated intramuscular pressure during a single forearm isometric muscle contraction may restrict muscle hyperemia. However, during repeated isometric exercise, it is unclear to what extent mechanical compression and muscle vasodilatation contribute to the magnitude and time course of beat-to-beat limb hemodynamics, due to alterations in leg vascular conductance (LVC). METHODS In eight healthy male subjects, the time course of both beat-to-beat leg blood flow (LBF) and LVC in the femoral artery was determined between repeated 10-s isometric thigh muscle contractions and 10-s muscle relaxation (a duty cycle of 20 s) for steady-state 120 s at five target workloads (10, 30, 50, 70, and 90% of maximum voluntary contraction (MVC)). The ratio of restricted LBF due to mechanical compression across workloads was determined by the formula (relaxation LBF--contraction LBF)/relaxation LBF (%). RESULTS The exercise protocol was performed completely by all subjects (≤ 50% MVC), seven subjects (≤ 70% MVC), and two subjects (≤ 90% MVC). During a 10-s isometric muscle contraction, the time course in both beat-to-beat LBF and LVC displayed a fitting curve with an exponential increase (P < 0.001, r (2) ≥ 0.956) at each workload but no significant difference in mean LBF across workloads and pre-exercise. During a 10-s muscle relaxation, the time course in both beat-to-beat LBF and LVC increased as a function of workload, followed by a linear decline (P < 0.001, r (2) ≥ 0.889), that was workload-dependent, resulting in mean LBF increasing linearly across workloads (P < 0.01, r (2) = 0.984). The ratio of restricted LBF can be described as a single exponential decay with an increase in workload, which has inflection point distinctions between 30 and 50% MVC. CONCLUSIONS In a 20-s duty cycle of steady-state repeated isometric muscle contractions, the post-contraction hyperemia (magnitude of both LBF and LVC) during muscle relaxation was in proportion to the workload, which is in agreement with previous findings. Furthermore, time-dependent beat-to-beat muscle vasodilatation was seen, but not restricted, during isometric muscle contractions through all target workloads. Additionally, the relative contribution of mechanical obstruction and vasodilatation to the hyperemia observed in the repeated isometric exercise protocol was non-linear with regard to workload. In combination with repeated isometric exercise, the findings could potentially prove to be useful indicators of circulatory adjustment by mechanical compression for muscle-related disease.
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Affiliation(s)
- Takuya Osada
- Department of Sports Medicine for Health Promotion, Tokyo Medical University, 6-1-1, Shinjuku, Shinjuku-ku, Tokyo, 160-8402, Japan. .,Cardiac Rehabilitation Center, Tokyo Medical University Hospital, 6-7-1, Nishishinjuku, Shinjuku-ku, Tokyo, 160-0023, Japan. .,The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, DK-2100, Copenhagen Ø, Denmark.
| | - Stefan P Mortensen
- The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, DK-2100, Copenhagen Ø, Denmark.,Department of Cardiovascular and Renal Research, University of Southern Denmark, DK-5000, Odense, Denmark
| | - Göran Rådegran
- The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, DK-2100, Copenhagen Ø, Denmark.,Department of Clinical Sciences Lund, Cardiology, Lund University, SE-221 85, Lund, Sweden.,The Section for Heart Failure and Valvular Disease, The Heart and Lung Clinic, Skåne University Hospital, Lund, Sweden
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12
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McNeil CJ, Allen MD, Olympico E, Shoemaker JK, Rice CL. Blood flow and muscle oxygenation during low, moderate, and maximal sustained isometric contractions. Am J Physiol Regul Integr Comp Physiol 2015; 309:R475-81. [PMID: 26084698 PMCID: PMC4591373 DOI: 10.1152/ajpregu.00387.2014] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Accepted: 06/15/2015] [Indexed: 11/22/2022]
Abstract
A reduction of blood flow to active muscle will precipitate fatigue, and sustained isometric contractions produce intramuscular and compartmental pressures that can limit flow. The present study explored how blood flow and muscle oxygenation respond to isometric contractions at low, moderate, and maximal intensities. Over two visits, 10 males (26 ± 2 yr; means ± SD) performed 1-min dorsiflexion contractions at 30, 60, and 100% of maximal voluntary contraction (MVC) torque. Doppler ultrasound of the anterior tibial artery was used to record arterial diameter and mean blood velocity and to calculate absolute blood flow. The tissue oxygenation index (TOI) of tibialis anterior was acquired with near-infrared spectroscopy (NIRS). There was a progressive increase in blood flow at 30% MVC (peak of 289 ± 139% resting value), no change from rest until an increase in the final 10 s of exercise at 60% MVC (peak of 197 ± 102% rest), and an initial decrease (59 ± 30% resting value) followed by a progressive increase at 100% MVC (peak of 355 ± 133% rest). Blood flow was greater at 30 and 100% than 60% MVC during the last 30 s of exercise. TOI was ∼63% at rest and, within 30 s of exercise, reached steady-state values of ∼42%, ∼22%, and ∼22% for 30, 60, and 100% MVC, respectively. Even maximal contraction of the dorsiflexors is unable to cause more than a transient decrease of flow in the anterior tibial artery. Unlike dynamic or intermittent isometric exercise, our results indicate blood flow is not linearly graded with intensity or directly coupled with oxygenation during sustained isometric contractions.
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Affiliation(s)
- Chris J McNeil
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
| | - Matti D Allen
- School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario, Canada
| | - Eric Olympico
- School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario, Canada
| | - J Kevin Shoemaker
- School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario, Canada; Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada; and
| | - Charles L Rice
- School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario, Canada; Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada
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13
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Abstract
PURPOSE The aim of this study was to investigate the effect of obesity on neuromuscular fatigue in adolescent girls. METHODS Twelve lean (13.6 ± 0.8 years) and 12 obese (13.9 ± 0.9 years) girls repeated 5-s maximal voluntary contractions (MVC) of the knee extensors until the generated torque reached 55 % of its initial value. Magnetic stimulations were delivered to the femoral nerve every five MVCs to follow the course of voluntary activation (VA) and potentiated twitch torque (Qtwpot). RESULTS Torque reached 55 % of its initial value after 52.6 ± 20.4 and 74.9 ± 22.8 repetitions in obese and lean girls, respectively (p < 0.01). Furthermore, the decline of VA was smaller in obese girls (p < 0.001). In contrast, Qtwpot decreased to a greater extent in obese girls (p < 0.05). CONCLUSIONS Obese girls fatigue faster than their lean counterparts. The peripheral factors mainly account for fatigue in obese girls, whereas central factors are mainly involved in lean girls.
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14
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Allen MD, Kimpinski K, Doherty TJ, Rice CL. Decreased muscle endurance associated with diabetic neuropathy may be attributed partially to neuromuscular transmission failure. J Appl Physiol (1985) 2015; 118:1014-22. [PMID: 25663671 DOI: 10.1152/japplphysiol.00441.2014] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Accepted: 02/03/2015] [Indexed: 01/25/2023] Open
Abstract
Diabetic polyneuropathy (DPN) can cause muscle atrophy, weakness, contractile slowing, and neuromuscular transmission instability. Our objective was to assess the response of the impaired neuromuscular system of DPN in humans when stressed with a sustained maximal voluntary contraction (MVC). Baseline MVC and evoked dorsiflexor contractile properties were assessed in DPN patients (n = 10) and controls (n = 10). Surface electromyography was used to record tibialis anterior evoked maximal compound muscle action potentials (CMAPs) and neuromuscular activity during MVCs. Participants performed a sustained isometric dorsiflexion MVC for which task termination was determined by the inability to sustain ≥60% MVC torque. The fatigue protocol was immediately followed by a maximal twitch, with additional maximal twitches and MVCs assessed at 30 s and 2 min postfatigue. DPN patients fatigued ∼21% more quickly than controls (P < 0.05) and featured less relative electromyographic activity during the first one-third of the fatigue protocol compared with controls (P < 0.05). Immediately following fatigue, maximal twitch torque was reduced similarly (∼20%) in both groups, and concurrently CMAPs were reduced (∼12%) in DPN patients, whereas they were unaffected in controls (P > 0.05). Twitch torque and CMAP amplitude recovered to baseline 30 s postfatigue. Additionally, at 30 s postfatigue, both groups had similar (∼10%) reductions in MVC torque relative to baseline, and MVC strength recovered by 2 min postfatigue. We conclude DPN patients possess less endurance than controls, and neuromuscular transmission failure may contribute to this greater fatigability.
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Affiliation(s)
- Matti D Allen
- School of Medicine, Queen's University, Kingston, Ontario, Canada; School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada; School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario, Canada;
| | - Kurt Kimpinski
- Department of Clinical Neurological Sciences, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada
| | - Timothy J Doherty
- School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario, Canada; Department of Clinical Neurological Sciences, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada; Department of Physical Medicine and Rehabilitation, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada; and
| | - Charles L Rice
- School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario, Canada; Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada
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15
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Ishii H, Nishida Y. Effect of Lactate Accumulation during Exercise-induced Muscle Fatigue on the Sensorimotor Cortex. J Phys Ther Sci 2014; 25:1637-42. [PMID: 24409038 PMCID: PMC3885857 DOI: 10.1589/jpts.25.1637] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Accepted: 07/22/2013] [Indexed: 01/09/2023] Open
Abstract
[Purpose] During exercise, skeletal muscle motor units are recruited based on afferent
sensory input following peripheral metabolic by-product accumulation. The purpose of this
study was to investigate whether lactate plays a role in conveying fatigue-related
information to the brain. [Subjects] Eleven healthy adults participated in this study.
[Methods] Subjects performed handgrip exercises at 10%, 30%, and 50% maximal voluntary
contraction for 120 s. They were monitored for brachial artery blood pressure, respiratory
quotient, muscle fatigue (integrated electromyogram, median power frequency), blood
lactate levels, muscle blood flow, and brain activity. [Results] The handgrip exercise
protocol caused significant muscle fatigue based on 28% and 37% reductions in median power
frequency detected at 30% and 50% maximal voluntary contraction, respectively. Subjects
exhibited intensity-dependent increases in blood pressure, respiratory quotient, muscle
blood flow, and circulating lactate concentrations. Furthermore, brain activity increased
at 30% and 50% maximal voluntary contraction. Multiple regression analysis identified
muscle blood flow at 30% maximal voluntary contraction and lactate at 50% maximal
voluntary contraction with standardized partial regression coefficients of −0.64 and 0.75,
respectively. [Conclusion] These data suggest that blood lactate concentration and muscle
blood flow, which reflect muscle metabolism, may convey load intensity information to the
brain during muscle fatigue.
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Affiliation(s)
- Hideaki Ishii
- Doctoral Program, Rehabilitation Sciences, Seirei Christopher University, Japan ; Department of Rehabilitation, Nursing Home Hamamatsu Jyujinosono, Japan
| | - Yusuke Nishida
- Doctoral Program, Rehabilitation Sciences, Seirei Christopher University, Japan
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16
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Abstract
Skeletal muscle fatigue is defined as the fall of force or power in response to contractile activity. Both the mechanisms of fatigue and the modes used to elicit it vary tremendously. Conceptual and technological advances allow the examination of fatigue from the level of the single molecule to the intact organism. Evaluation of muscle fatigue in a wide range of disease states builds on our understanding of basic function by revealing the sources of dysfunction in response to disease.
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Affiliation(s)
- Jane A Kent-Braun
- Department of Kinesiology, University of Massachusetts-Amherst, Amherst, Massachusetts, USA.
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17
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Laughlin MH, Davis MJ, Secher NH, van Lieshout JJ, Arce-Esquivel AA, Simmons GH, Bender SB, Padilla J, Bache RJ, Merkus D, Duncker DJ. Peripheral circulation. Compr Physiol 2013; 2:321-447. [PMID: 23728977 DOI: 10.1002/cphy.c100048] [Citation(s) in RCA: 174] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Blood flow (BF) increases with increasing exercise intensity in skeletal, respiratory, and cardiac muscle. In humans during maximal exercise intensities, 85% to 90% of total cardiac output is distributed to skeletal and cardiac muscle. During exercise BF increases modestly and heterogeneously to brain and decreases in gastrointestinal, reproductive, and renal tissues and shows little to no change in skin. If the duration of exercise is sufficient to increase body/core temperature, skin BF is also increased in humans. Because blood pressure changes little during exercise, changes in distribution of BF with incremental exercise result from changes in vascular conductance. These changes in distribution of BF throughout the body contribute to decreases in mixed venous oxygen content, serve to supply adequate oxygen to the active skeletal muscles, and support metabolism of other tissues while maintaining homeostasis. This review discusses the response of the peripheral circulation of humans to acute and chronic dynamic exercise and mechanisms responsible for these responses. This is accomplished in the context of leading the reader on a tour through the peripheral circulation during dynamic exercise. During this tour, we consider what is known about how each vascular bed controls BF during exercise and how these control mechanisms are modified by chronic physical activity/exercise training. The tour ends by comparing responses of the systemic circulation to those of the pulmonary circulation relative to the effects of exercise on the regional distribution of BF and mechanisms responsible for control of resistance/conductance in the systemic and pulmonary circulations.
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Affiliation(s)
- M Harold Laughlin
- Department of Medical Pharmacology and Physiology, and the Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri, USA.
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18
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Mohamad NI, Nosaka K, Cronin J. Maximizing Hypertrophy: Possible Contribution of Stretching in the Interset Rest Period. Strength Cond J 2011. [DOI: 10.1519/ssc.0b013e3181fe7164] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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19
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Green JG, Stannard SR. Active recovery strategies and handgrip performance in trained vs. untrained climbers. J Strength Cond Res 2010; 24:494-501. [PMID: 20072048 DOI: 10.1519/jsc.0b013e3181c06af3] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Isometric contractions, such as occurring during rock climbing, occlude blood flow to the active musculature. The ability to maximize forearm blood flow between such contractions is a likely determinant of intermittent handgrip performance. This study aimed to test the hypothesis that intermittent isometric handgrip performance is improved by 2 common active recovery strategies suggested to increase muscle blood flow. On 6 separate occasions, 9 trained indoor rock climbers and 9 untrained participants undertook a fatiguing, intermittent, isometric handgrip exercise bout consisting of sets of 6 contractions (approximately 33% of maximal voluntary contraction [MVC] force), each 3-second long separated by a 1-second rest. Between sets, participants were allowed 9-second recovery performing passive rest, "shaking out" (vigorously shaking the hand), or grasping a handgrip vibration machine, each with or without forearm occlusion. Performance was assessed by pre- and post-exercise MVC trials and a 20-contraction post-exercise handgrip time trial (TT20). Trained climbers exhibited significantly greater handgrip MVC force and intermittent exercise capacity than untrained (p < 0.01). There was no effect of recovery strategy on any measure (p > 0.05). Trained climbers were more affected by occlusion than untrained in MVC (p < 0.05) and TT20 (p < 0.01). Shaking out and low-frequency vibration are unlikely to affect rock climbing performance. It is recommended that rock climbers and their coaches focus on optimizing body position rather than compromising body position to allow for shaking out.
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Affiliation(s)
- Jackson G Green
- Institute of Food, Nutrition and Human Health, Massey University, Palmerston, New Zealand.
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20
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Adamo DE, Khodaee M, Barringer S, Johnson PW, Martin BJ. Low mean level sustained and intermittent grip exertions: influence of age on fatigue and recovery. ERGONOMICS 2009; 52:1287-1297. [PMID: 19662553 DOI: 10.1080/00140130902984935] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The goal of this study was to quantify localised muscle fatigue resulting from low mean levels of exertion in younger (< 40 years) and older (> 50 years) adults. Fatigue, elicited in the finger flexor muscles by intermittent (10% mean maximum voluntary contraction (MVC)) and sustained (8% MVC) handgrip exercises, was quantified by a muscle twitch force response before, immediately after and during 3 h following exercise. Despite greater mean loads, recovery time was shorter following intermittent than sustained contractions, which suggests that recovery from fatigue is more sensitive to rest within the work cycle than mean work. The more pronounced effects for younger than older individuals following the sustained exertion indicate that changes in muscle fibre type composition might predispose older individuals to be more resistant to fatigue resulting from sustained contractions of low level. Performing hand exertion tasks requiring low mean force levels contributes to similar long-lasting fatigue effects regardless of gender and age. Intermittent periods of complete rest reduce muscle fatigue. Since fatigue was not perceived during recovery from the tested sustained and intermittent contractions, subjective evaluations may not be a reliable indicator of localised muscle fatigue.
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Affiliation(s)
- D E Adamo
- Institute of Gerontology, Department of Health Sciences, Wayne State University, Detroit, Michigan 48202, USA
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21
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Physiological effects of the TASER® C2 conducted energy weapon. Forensic Sci Med Pathol 2009; 5:189-98. [PMID: 19598011 DOI: 10.1007/s12024-009-9100-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2009] [Accepted: 06/03/2009] [Indexed: 10/20/2022]
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22
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Hunter SK, Griffith EE, Schlachter KM, Kufahl TD. Sex differences in time to task failure and blood flow for an intermittent isometric fatiguing contraction. Muscle Nerve 2009; 39:42-53. [PMID: 19086076 DOI: 10.1002/mus.21203] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The purpose of this study was to compare the time to task failure, postcontraction hyperemia, and vascular conductance of young men and women for a submaximal intermittent fatiguing contraction performed with the handgrip muscles. Twenty men and 20 women (mean +/- SD: 22 +/- 4 years) performed an isometric contraction at 50% of maximal voluntary contraction (MVC) (6-s contraction, 4-s rest) until task failure. Forearm venous occlusion plethysmography was used to estimate the peak blood flow (after 10-min occlusion) and blood flow at rest after 6-s submaximal contractions of varying intensities, and during an intermittent fatiguing contraction at 1-min intervals and task failure. The time to task failure was longer for the women compared with the men (408 +/- 205 s vs. 297 +/- 57 s, P < 0.05). Postcontraction hyperemia and vascular conductance were greater for men than for women after nonfatiguing 6-s submaximal contractions performed at 20%, 40%, 50%, 60%, and 80% of MVC force (P < 0.05). In contrast, hyperemia and vascular conductance were similar for both genders when measured at 50 s into the fatiguing contraction, at each minute thereafter, and at task failure. Regression analysis indicated that the rate of electromyographic activity and perceived exertion were the significant predictors of the time to task failure. The longer time to task failure for women compared with men for an intermittent fatiguing contraction with handgrip muscles was not explained by postcontraction hyperemia or vascular conductance with fatigue.
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Affiliation(s)
- Sandra K Hunter
- Department of Physical Therapy, Marquette University, Milwaukee, Wisconsin 53233, USA.
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23
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Wigmore DM, Befroy DE, Lanza IR, Kent-Braun JA. Contraction frequency modulates muscle fatigue and the rate of myoglobin desaturation during incremental contractions in humans. Appl Physiol Nutr Metab 2008; 33:915-21. [PMID: 18923566 DOI: 10.1139/h08-085] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The metabolic cost of force production, and therefore the demand for oxygen, increases with intensity and frequency of contraction. This study investigated the interaction between fatigue and oxygenation, as reflected by deoxymyoglobin (dMb), during slow and rapid rhythmic isometric contractions having the same duty cycles and relative force-time integrals (FTIs). We used 1H magnetic resonance spectroscopy and measures of dorsiflexor muscle force to compare dMb and fatigue (fall of maximal voluntary force, MVC) in 11 healthy adults (29 +/- 7 y) during 16 min of slow (4 s contraction, 6 s relaxation) and rapid (1.2 s, 1.8 s) incremental (10%-80% MVC) contractions. We tested the hypotheses that (i) the rate of Mb desaturation would be faster in rapid than in slow contractions and (ii) fatigue, Mb desaturation, and the fall in FTI would be greater, and PO2 (oxygen tension) lower, at the end of rapid contractions than at the end of slow contractions. Although dMb increased more quickly during rapid contractions (p = 0.05), it reached a plateau at a similar level in both protocols (approximately 42% max, p = 0.49), likely due to an inability to further increase force production and thus metabolic demand. Despite the similar dMb at the end of both protocols, fatigue was greater in rapid (56.6% +/- 2.7% baseline) than in slow (69.5% +/- 4.0%, p = 0.01) contractions. These results indicate that human skeletal muscle fatigue during incremental isometric contractions is in part a function of contraction frequency, possibly due to metabolic inhibition of the contractile process.
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Affiliation(s)
- Danielle M Wigmore
- Department of Kinesiology, University of Massachusetts, Amherst, MA 01003, USA
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24
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Smith JL, Butler JE, Martin PG, McBain RA, Taylor JL. Increased ventilation does not impair maximal voluntary contractions of the elbow flexors. J Appl Physiol (1985) 2008; 104:1674-82. [DOI: 10.1152/japplphysiol.01358.2007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Exercise performance is impaired by increased respiratory work, yet the mechanism for this is unclear. This experiment assessed whether neural drive to an exercising muscle was affected by cortically driven increases in ventilation. On each of 5 days, eight subjects completed a 2-min maximal voluntary contraction (MVC) of the elbow flexor muscles, followed by 4 min of recovery, while transcranial magnetic stimulation tested for suboptimal neural drive to the muscle. On 1 day, subjects breathed without instructions under normocapnia. During the 2-min MVC, ventilation was ∼3.5 times that at rest. On another day, subjects breathed without instruction under hypercapnia. During the 2-min MVC, ventilation was ∼1.5 times that on the normocapnic day. On another 2 days under normocapnia, subjects voluntarily matched their breathing to the uninstructed breathing under normocapnia and hypercapnia using target feedback of the rate and inspiratory volume. On a fifth day under normocapnia, the volume feedback was set to each subject's vital capacity. On this day, ventilation during the 2-min MVC was approximately twice that on the uninstructed normocapnic day (or ∼7 times rest). The experimental manipulations succeeded in producing voluntary and involuntary hyperpnea. However, maximal voluntary force, fatigue and voluntary activation of the elbow flexor muscles were unaffected by cortically or chemically driven increases in ventilation. Results suggest that any effects of increased respiratory work on limb exercise performance are not due to a failure to drive both muscle groups optimally.
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25
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Rudroff T, Staudenmann D, Enoka RM. Electromyographic measures of muscle activation and changes in muscle architecture of human elbow flexors during fatiguing contractions. J Appl Physiol (1985) 2008; 104:1720-6. [PMID: 18356480 DOI: 10.1152/japplphysiol.01058.2007] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The study compared changes in intramuscular and surface recordings of EMG amplitude with ultrasound measures of muscle architecture of the elbow flexors during a submaximal isometric contraction. Ten subjects performed a fatiguing contraction to task failure at 20% of maximal voluntary contraction force. EMG activity was recorded in biceps brachii, brachialis, and brachioradialis muscles using intramuscular and surface electrodes. The rates of increase in the amplitude of the surface EMG for the long and short heads of biceps brachii and brachioradialis were greater than those for the intramuscular recordings measured at different depths. The amplitude of the intramuscular recordings from three muscles increased at a similar rate (P = 0.13), as did the amplitude of the three surface recordings from two muscles (P = 0.83). The increases in brachialis thickness (27.7 +/- 5.7 to 30.9 +/- 3.5 mm; P < 0.05) and pennation angle (10.9 +/- 3.5 to 16.5 +/- 4.8 degrees ; P = 0.003) were not associated with the increase in intramuscular EMG amplitude (P > 0.58). The increase in brachioradialis thickness (22.8 +/- 4.8 to 25.5 +/- 3.4 mm; P = 0.0075) was associated with the increase in the amplitude for one of two intramuscular EMG signals (P = 0.007, r = 0.79). The time to failure was more strongly associated with the rate of increase in the amplitude of the surface EMG than that for the intramuscular EMG, which suggests that the surface measurement provides a more appropriate measure of the change in muscle activation during a fatiguing contraction.
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Affiliation(s)
- Thorsten Rudroff
- Dept. of Integrative Physiology, Univ. of Colorado, Boulder, CO 80309-0354, USA.
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26
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Gonzales JU, Thompson BC, Thistlethwaite JR, Harper AJ, Scheuermann BW. Forearm blood flow follows work rate during submaximal dynamic forearm exercise independent of sex. J Appl Physiol (1985) 2007; 103:1950-7. [PMID: 17932302 DOI: 10.1152/japplphysiol.00452.2007] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To test the hypothesis that sex influences forearm blood flow (FBF) during exercise, 15 women and 16 men of similar age [women 24.3 +/- 4.0 (SD) vs. men 24.9 +/- 4.5 yr] but different forearm muscle strength (women 290.7 +/- 44.4 vs. men 509.6 +/- 97.8 N; P < 0.05) performed dynamic handgrip exercise as the same absolute workload was increased in a ramp function (0.25 W/min). Task failure was defined as the inability to maintain contraction rate. Blood pressure and FBF were measured on separate arms during exercise by auscultation and Doppler ultrasound, respectively. Muscle strength was positively correlated with endurance time (r = 0.72, P < 0.01) such that women had a shorter time to task failure than men (450.5 +/- 113.0 vs. 831.3 +/- 272.9 s; P < 0.05). However, the percentage of maximal handgrip strength achieved at task failure was similar between sexes (14% maximum voluntary contraction). FBF was similar between women and men throughout exercise and at task failure (women 13.6 +/- 5.3 vs. men 14.5 +/- 4.9 ml.min(-1).100 ml(-1)). Mean arterial pressure was lower in women at rest and during exercise; thus calculated forearm vascular conductance (FVC) was higher in women during exercise but similar between sexes at task failure (women 0.13 +/- 0.05 vs. men 0.11 +/- 0.04 ml.min(-1).100 ml(-1).mmHg(-1)). In conclusion, the similar FBF during exercise was achieved by a higher FVC in the presence of a lower MAP in women than men. Still, FBF remained coupled to work rate (and presumably metabolic demand) during exercise irrespective of sex.
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Affiliation(s)
- Joaquin U Gonzales
- Cardiopulmonary and Metabolism Research Laboratory, Department of Kinesiology, The University of Toledo, Toledo, OH 43606, USA
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27
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Damon BM, Hornberger JL, Wadington MC, Lansdown DA, Kent-Braun JA. Dual gradient-echo MRI of post-contraction changes in skeletal muscle blood volume and oxygenation. Magn Reson Med 2007; 57:670-9. [PMID: 17390346 PMCID: PMC4437703 DOI: 10.1002/mrm.21191] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Analysis of post-contraction MRI signal intensity (SI) transients may allow noninvasive studies of microvascular reactivity and blood oxygenation recovery. The purpose of this study was to determine the physiological basis for post-contraction changes in short-echo (6 ms) and long-echo (46 ms) gradient-echo (GRE) MRI signals (S(6) and S(46), respectively). Six healthy subjects were studied with the use of dual GRE MRI and near-infrared spectroscopy (NIRS). S(6), S(46), total hemoglobin concentration ([THb]), and oxyhemoglobin saturation (%HbO(2)) were measured before, during, and after 2 and 8 s dorsiflexion maximal voluntary contractions, and 5 min of proximal arterial occlusion. The changes in S(6) and [THb] after the 2-s contractions were similar to those following 8-s contractions, but changes in %HbO(2) and S(46) were greater following 8-s contractions than after the 2-s contractions. [THb] and S(6) did not change during and following 5 min of arterial occlusion, but %HbO(2) and S(46) were both significantly depressed at similar occlusion durations. Also, distance measures indicated similarity between S(6) and [THb] and between S(46) and %HbO(2). We conclude that following brief human skeletal muscle contractions, changes in S(6) primarily reflect changes in blood volume and changes in S(46) primarily reflect changes in blood oxygenation.
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Affiliation(s)
- Bruce M Damon
- Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA.
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