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Tymko MM, Drapeau A, Vieira-Coelho MA, Labrecque L, Imhoff S, Coombs GB, Langevin S, Fortin M, Châteauvert N, Ainslie PN, Brassard P. Acute isometric and dynamic exercise do not alter cerebral sympathetic nerve activity in healthy humans. J Cereb Blood Flow Metab 2024:271678X241248228. [PMID: 38613232 DOI: 10.1177/0271678x241248228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 04/14/2024]
Abstract
The impact of physiological stressors on cerebral sympathetic nervous activity (SNA) remains controversial. We hypothesized that cerebral noradrenaline (NA) spillover, an index of cerebral SNA, would not change during both submaximal isometric handgrip (HG) exercise followed by a post-exercise circulatory occlusion (PECO), and supine dynamic cycling exercise. Twelve healthy participants (5 females) underwent simultaneous blood sampling from the right radial artery and right internal jugular vein. Right internal jugular vein blood flow was measured using Duplex ultrasound, and tritiated NA was infused through the participants' right superficial forearm vein. Heart rate was recorded via electrocardiogram and blood pressure was monitored using the right radial artery. Total NA spillover increased during HG (P = 0.049), PECO (P = 0.006), and moderate cycling exercise (P = 0.03) compared to rest. Cerebral NA spillover remained unchanged during isometric HG exercise (P = 0.36), PECO after the isometric HG exercise (P = 0.45), and during moderate cycling exercise (P = 0.94) compared to rest. These results indicate that transient increases in blood pressure during acute exercise involving both small and large muscle mass do not engage cerebral SNA in healthy humans. Our findings suggest that cerebral SNA may be non-obligatory for exercise-related cerebrovascular adjustments.
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Affiliation(s)
- Michael M Tymko
- Integrative Cerebrovascular and Environmental Physiology SB Laboratory, Department of Human Health and Nutritional Sciences, College of Biological Science, University of Guelph, Guelph, Canada
- Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, Canada
| | - Audrey Drapeau
- Department of Kinesiology, Faculty of Medicine, Université Laval, Québec, Canada
- Institut universitaire de cardiologie et de pneumologie de Québec-Université Laval, Québec, Canada
| | - Maria Augusta Vieira-Coelho
- Department of Biomedicine, Pharmacology and Therapeutics Unit, Faculty of Medicine, University of Porto, Portugal
- Department of Psychiatry and Mental Health, University Hospital Center of São João, Porto, Portugal
| | - Lawrence Labrecque
- Department of Kinesiology, Faculty of Medicine, Université Laval, Québec, Canada
- Institut universitaire de cardiologie et de pneumologie de Québec-Université Laval, Québec, Canada
| | - Sarah Imhoff
- Department of Kinesiology, Faculty of Medicine, Université Laval, Québec, Canada
- Institut universitaire de cardiologie et de pneumologie de Québec-Université Laval, Québec, Canada
| | - Geoff B Coombs
- Department of Kinesiology, Faculty of Science, McMaster University, Hamilton, Canada
| | - Stephan Langevin
- Institut universitaire de cardiologie et de pneumologie de Québec-Université Laval, Québec, Canada
| | - Marc Fortin
- Institut universitaire de cardiologie et de pneumologie de Québec-Université Laval, Québec, Canada
| | - Nathalie Châteauvert
- Institut universitaire de cardiologie et de pneumologie de Québec-Université Laval, Québec, Canada
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, Canada
| | - Patrice Brassard
- Department of Kinesiology, Faculty of Medicine, Université Laval, Québec, Canada
- Institut universitaire de cardiologie et de pneumologie de Québec-Université Laval, Québec, Canada
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2
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Teixeira AL, Vianna LC. The exercise pressor reflex: An update. Clin Auton Res 2022; 32:271-290. [PMID: 35727398 DOI: 10.1007/s10286-022-00872-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 05/25/2022] [Indexed: 02/07/2023]
Abstract
The exercise pressor reflex is a feedback mechanism engaged upon stimulation of mechano- and metabosensitive skeletal muscle afferents. Activation of these afferents elicits a reflex increase in heart rate, blood pressure, and ventilation in an intensity-dependent manner. Consequently, the exercise pressor reflex has been postulated to be one of the principal mediators of the cardiorespiratory responses to exercise. In this updated review, we will discuss classical and recent advancements in our understating of the exercise pressor reflex function in both human and animal models. Particular attention will be paid to the afferent mechanisms and pathways involved during its activation, its effects on different target organs, its potential role in the abnormal cardiovascular response to exercise in diseased states, and the impact of age and biological sex on these responses. Finally, we will highlight some unanswered questions in the literature that may inspire future investigations in the field.
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Affiliation(s)
- André L Teixeira
- NeuroV̇ASQ̇, Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, DF, Brasília, Brazil
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON, Canada
| | - Lauro C Vianna
- NeuroV̇ASQ̇, Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, DF, Brasília, Brazil.
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3
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Tarumi T, Yamabe T, Fukuie M, Zhu DC, Zhang R, Ogoh S, Sugawara J. Brain blood and cerebrospinal fluid flow dynamics during rhythmic handgrip exercise in young healthy men and women. J Physiol 2021; 599:1799-1813. [PMID: 33481257 DOI: 10.1113/jp281063] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Accepted: 01/12/2021] [Indexed: 01/06/2023] Open
Abstract
KEY POINTS The cerebral fluid response to exercise, including the arterial and venous cerebral blood flow (CBF) and cerebrospinal fluid (CSF), currently remains unknown. We used time-resolved phase-contrast magnetic resonance imaging to assess changes in CBF and CSF flow dynamics during moderate-intensity rhythmic handgrip (RHG) exercise in young healthy men and women. Our data demonstrated that RHG increases the cerebral arterial inflow and venous outflow while decreasing the pulsatile CSF flow during RHG. Furthermore, changes in blood stroke volume at the measured arteries, veins, and sinuses and CSF stroke volume at the cerebral aqueduct were positively correlated with each other during RHG. Male and female participants exhibited distinct blood pressure responses to RHG, but their cerebral fluid responses were similar. These results collectively suggest that RHG influences both CBF and CSF flow dynamics in a way that is consistent with the Monro-Kellie hypothesis to maintain intracranial volume-pressure homeostasis in young healthy adults. ABSTRACT Cerebral blood flow (CBF) increases during exercise, but its impact on cerebrospinal fluid (CSF) flow remains unknown. This study investigated CBF and CSF flow dynamics during moderate-intensity rhythmic handgrip (RHG) exercise in young healthy men and women. Twenty-six participants (12 women) underwent the RHG and resting control conditions in random order. Participants performed 3 sets of RHG, during which cine phase-contrast magnetic resonance imaging (PC-MRI) was performed to measure blood stroke volume (SV) and flow rate in the internal carotid (ICA) and vertebral (VA) arteries, the internal jugular vein (IJV), the superior sagittal (SSS) and straight sinuses (SRS), and CSF SV and flow rate in the cerebral aqueduct of Sylvius. Blood pressure, end-tidal CO2 (EtCO2 ), heart rate (HR), and respiratory rate were simultaneously measured during cine PC-MRI scans. Compared with control conditions, RHG showed significant elevations of HR, mean arterial pressure, and respiratory rate with a mild reduction of EtCO2 (all P < 0.05). RHG decreased blood SV in the measured arteries, veins, and sinuses and CSF SV in the aqueduct (all P < 0.05). Conversely, RHG increased blood flow in the ICA, VA, and IJV (all P < 0.05). At the aqueduct, RHG decreased the absolute CSF flow rate (P = 0.0307), which was calculated as a sum of the caudal and cranial CSF flow rates. Change in the ICA SV was positively correlated with changes in the IJV, SSS, SRS, and aqueductal SV during RHG (all P < 0.05). These findings demonstrate a close coupling between the CBF and CSF flow dynamics during RHG in young healthy adults.
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Affiliation(s)
- Takashi Tarumi
- Human Informatics and Interaction Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan.,Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki, Japan.,Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Texas, USA
| | - Takayuki Yamabe
- Human Informatics and Interaction Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan.,Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki, Japan
| | - Marina Fukuie
- Human Informatics and Interaction Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan.,Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki, Japan
| | - David C Zhu
- Department of Radiology and Cognitive Imaging Research Center, Michigan State University, East Lansing, Michigan, USA
| | - Rong Zhang
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Texas, USA.,Department of Neurology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.,Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Shigehiko Ogoh
- Department of Biomedical Engineering, Toyo University, Kawagoe-shi, Saitama, Japan
| | - Jun Sugawara
- Human Informatics and Interaction Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan.,Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki, Japan
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4
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Abstract
People undertaking prolonged vigorous exercise experience substantial bodily fluid losses due to thermoregulatory sweating. If these fluid losses are not replaced, endurance capacity may be impaired in association with a myriad of alterations in physiological function, including hyperthermia, hyperventilation, cardiovascular strain with reductions in brain, skeletal muscle and skin blood perfusion, greater reliance on muscle glycogen and cellular metabolism, alterations in neural activity and, in some conditions, compromised muscle metabolism and aerobic capacity. The physiological strain accompanying progressive exercise-induced dehydration to a level of ~ 4% of body mass loss can be attenuated or even prevented by: (1) ingesting fluids during exercise, (2) exercising in cold environments, and/or (3) working at intensities that require a small fraction of the overall body functional capacity. The impact of dehydration upon physiological function therefore depends on the functional demand evoked by exercise and environmental stress, as cardiac output, limb blood perfusion and muscle metabolism are stable or increase during small muscle mass exercise or resting conditions, but are impaired during whole-body moderate to intense exercise. Progressive dehydration is also associated with an accelerated drop in perfusion and oxygen supply to the human brain during submaximal and maximal endurance exercise. Yet their consequences on aerobic metabolism are greater in the exercising muscles because of the much smaller functional oxygen extraction reserve. This review describes how dehydration differentially impacts physiological function during exercise requiring low compared to high functional demand, with an emphasis on the responses of the human brain, heart and skeletal muscles.
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Katayama K, Saito M. Muscle sympathetic nerve activity during exercise. J Physiol Sci 2019; 69:589-598. [PMID: 31054082 PMCID: PMC10717921 DOI: 10.1007/s12576-019-00669-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Accepted: 02/22/2019] [Indexed: 11/25/2022]
Abstract
Appropriate cardiovascular adjustment is necessary to meet the metabolic demands of working skeletal muscle during exercise. The sympathetic nervous system plays a crucial role in the regulation of arterial blood pressure and blood flow during exercise, and several important neural mechanisms are responsible for changes in sympathetic vasomotor outflow. Changes in sympathetic vasomotor outflow (i.e., muscle sympathetic nerve activity: MSNA) in inactive muscles during exercise differ depending on the exercise mode (static or dynamic), intensity, duration, and various environmental conditions (e.g., hot and cold environments or hypoxic). In 1991, Seals and Victor [6] reviewed MSNA responses to static and dynamic exercise with small muscle mass. This review provides an updated comprehensive overview on the MSNA response to exercise including large-muscle, dynamic leg exercise, e.g., two-legged cycling, and its regulatory mechanisms in healthy humans.
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Affiliation(s)
- Keisho Katayama
- Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, 464-8601, Japan.
- Graduate School of Medicine, Nagoya University, Nagoya, Japan.
| | - Mitsuru Saito
- Applied Physiology Laboratory, Toyota Technological Institute, Nagoya, Japan
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6
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Ogoh S, Sato K, Hirasawa A, Sadamoto T. The effect of muscle metaboreflex on the distribution of blood flow in cerebral arteries during isometric exercise. J Physiol Sci 2019; 69:375-385. [PMID: 30604287 PMCID: PMC10717543 DOI: 10.1007/s12576-018-0653-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2018] [Accepted: 12/11/2018] [Indexed: 12/20/2022]
Abstract
The present study examined the effect of muscle metaboreflex on blood flow in different cerebral arteries. Eleven healthy participants performed isometric, one-leg knee extension at 30% maximal voluntary contraction for 2 min. Activated muscle metaboreflex was isolated for 2 min by post-exercise muscle ischemia (PEMI). The contralateral internal carotid (ICA), vertebral (VA), and ipsilateral external carotid arteries (ECA) blood flows were evaluated using Doppler ultrasound. The ICA blood flow increased at the beginning of exercise (P = 0.004) but returned to the baseline level at the end of exercise (P = 0.055). In contrast, the VA blood flow increased and it was maintained until the end of the exercise (P = 0.011), while the ECA blood flow gradually increased throughout the exercise (P = 0.001). These findings indicate that isometric exercise causes a heterogeneous cerebral blood flow response in different cerebral arteries. During PEMI, the conductance of the VA as well as that of the ICA was significantly lower compared with the baseline value (P = 0.020 and P = 0.032, at PEMI90), while the conductance of the ECA was not different from the baseline (P = 0.587), suggesting that the posterior and anterior cerebral vasculature were similarly affected during exercise by activation of muscle metaboreceptors, but not in the non-cerebral artery. Since ECA branches from ICA, the balance in the different influence of muscle metaboreflex on ECA (vasodilation via exercise-induced hypertension) and ICA (vasoconstriction) may contribute to the decrease in ICA blood flow at the end of isometric exercise.
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Affiliation(s)
- Shigehiko Ogoh
- Department of Biomedical Engineering, Toyo University, 2100 Kujirai, Kawagoe-shi, Saitama, 350-8585, Japan.
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7
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Ozturk ED, Tan CO. Human cerebrovascular function in health and disease: insights from integrative approaches. J Physiol Anthropol 2018; 37:4. [PMID: 29454381 PMCID: PMC5816507 DOI: 10.1186/s40101-018-0164-z] [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: 12/22/2017] [Accepted: 02/02/2018] [Indexed: 11/21/2022] Open
Abstract
Background The marked increase in the size of the brain, and consequently, in neural processing capability, throughout human evolution is the basis of the higher cognitive function in humans. However, greater neural, and thus information processing capability, comes at a significant metabolic cost; despite its relatively small size, the modern human brain consumes almost a quarter of the glucose and oxygen supply in the human body. Fortunately, several vascular mechanisms ensure sufficient delivery of glucose and oxygen to the active neural tissue (neurovascular coupling), prompt removal of neural metabolic by-products (cerebral vasoreactivity), and constant global blood supply despite daily variations in perfusion pressure (cerebral autoregulation). The aim of this review is to provide an integrated overview of the available data on these vascular mechanisms and their underlying physiology. We also briefly review modern experimental approaches to assess these mechanisms in humans, and further highlight the importance of these mechanisms for humans’ evolutionary success by providing examples of their healthy adaptations as well as pathophysiological alterations. Conclusions Data reviewed in this paper demonstrate the importance of the cerebrovascular function to support humans’ unique ability to form new and different interactions with each other and their surroundings. This highlights that there is much insight into the neural and cognitive functions that could be gleaned from interrogating the cerebrovascular function.
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Affiliation(s)
- Erin D Ozturk
- Cerebrovascular Research Laboratory, Spaulding Rehabilitation Hospital, Boston, MA, USA.,Department of Psychology, Harvard University, Cambridge, MA, USA
| | - Can Ozan Tan
- Cerebrovascular Research Laboratory, Spaulding Rehabilitation Hospital, Boston, MA, USA. .,Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA, USA.
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8
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A Patient-Specific Three-Dimensional Hemodynamic Model of the Circle of Willis. Cardiovasc Eng Technol 2017; 8:495-504. [PMID: 28913763 DOI: 10.1007/s13239-017-0330-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Accepted: 09/04/2017] [Indexed: 10/18/2022]
Abstract
Circle of Willis (CoW) is one of the most important cerebral arteries in the human body and various attempts have been made to study the hemodynamic of blood flow in this vital part of the brain. In the present study, blood flow in a patient specific CoW is numerically modeled to predict disease-prone regions of the CoW. Medical images and computer aided design software are used to construct a realistic three-dimensional model of the CoW for this particular case. The arteries are considered as elastic conduits and the interactions between arterial walls and the blood flow are taken into account. Mooney-Rivlin hyperelastic model is used to describe the behavior of arterial walls and blood is considered as a non-Newtonian fluid obeying the Carreau model. An available experimental-based pulsatile velocity profile is used at the entrance of the CoW. The finite element-based commercial software, ADINA, is used to solve the governing equations. Blood pressure and velocity and arterial wall shear stress are calculated in different regions of the CoW. A simplified form of the model is also compared with the available published data. Results affirmed that the proposed computational model has the potential to capture the hemodynamic characteristics of the CoW. The computational results can be used to determine disease-prone locations for a given CoW.
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9
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Verbree J, Bronzwaer A, van Buchem MA, Daemen M, van Lieshout JJ, van Osch M. Middle cerebral artery diameter changes during rhythmic handgrip exercise in humans. J Cereb Blood Flow Metab 2017; 37:2921-2927. [PMID: 27837189 PMCID: PMC5536799 DOI: 10.1177/0271678x16679419] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Transcranial Doppler (TCD) sonography is a frequently employed technique for quantifying cerebral blood flow by assuming a constant arterial diameter. Given that exercise increases arterial pressure by sympathetic activation, we hypothesized that exercise might induce a change in the diameter of large cerebral arteries. Middle cerebral artery (MCA) cross-sectional area was assessed in response to handgrip exercise by direct magnetic resonance imaging (MRI) observations. Twenty healthy subjects (11 female) performed three 5 min bouts of rhythmic handgrip exercise at 60% maximum voluntary contraction, alternated with 5 min of rest. High-resolution 7 T MRI scans were acquired perpendicular to the MCA. Two blinded observers manually determined the MCA cross-sectional area. Sufficient image quality was obtained in 101 MCA-scans of 19 subjects (age-range 20-59 years). Mixed effects modelling showed that the MCA cross-sectional area decreased by 2.1 ± 0.8% (p = 0.01) during handgrip, while the heart rate increased by 11 ± 2% (p < 0.001) at constant end-tidal CO2 (p = 0.10). In conclusion, the present study showed a 2% decrease in MCA cross-sectional area during rhythmic handgrip exercise. This further strengthens the current concept of sympathetic control of large cerebral arteries, showing in vivo vasoconstriction during exercise-induced sympathetic activation. Moreover, care must be taken when interpreting TCD exercise studies as diameter constancy cannot be assumed.
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Affiliation(s)
- J Verbree
- 1 Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Agt Bronzwaer
- 2 Department of Internal Medicine, Academic Medical Center, Amsterdam, The Netherlands.,3 Laboratory for Clinical Cardiovascular Physiology, Academic Medical Center, Amsterdam, The Netherlands
| | - M A van Buchem
- 1 Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Mjap Daemen
- 4 Department of Pathology, Academic Medical Center, Amsterdam, The Netherlands
| | - J J van Lieshout
- 2 Department of Internal Medicine, Academic Medical Center, Amsterdam, The Netherlands.,3 Laboratory for Clinical Cardiovascular Physiology, Academic Medical Center, Amsterdam, The Netherlands.,5 MRC/Arthritis Research UK Centre for Musculoskeletal Ageing Research, School of Life Sciences, University of Nottingham Medical School, Nottingham, UK
| | - Mjp van Osch
- 1 Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
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10
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Abstract
Temporal changes in cerebral blood flow induced by jaw movement have yet to be investigated. To assess the influence of pattern and intensity of muscle contraction during jaw movement on task-induced change in cerebral blood flow, we performed bilateral transcranial Doppler ultrasound examination during clenching, gum chewing, and tooth tapping in healthy volunteers. A random-effects model analysis revealed a significant increase in middle cerebral artery blood flow velocity during clenching (high muscle activity) and gum chewing (moderate muscle activity), compared with the preceding rest period; however, such an increase was not detected during tooth tapping (low muscle activity). Cerebral blood flow was greater on the working side during the intensive isometric contraction of the masseter muscle in clenching. These results suggest that task-induced change in cerebral blood flow during jaw movement is influenced by the change in peripheral circulation evoked by muscle contraction.
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Affiliation(s)
- Y Hasegawa
- Division of Oromaxillofacial Regeneration, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita City, Osaka, 565-0871, Japan
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11
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Prodel E, Fisher JP, Barbosa TC, Fernandes IA, Nobrega AC, Vianna LC. Relationship between aortic augmentation index and blood pressure during metaboreflex activation in healthy young men. Blood Press Monit 2016; 21:288-94. [DOI: 10.1097/mbp.0000000000000202] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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12
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Prodel E, Balanos GM, Braz ID, Nobrega ACL, Vianna LC, Fisher JP. Muscle metaboreflex and cerebral blood flow regulation in humans: implications for exercise with blood flow restriction. Am J Physiol Heart Circ Physiol 2016; 310:H1201-9. [DOI: 10.1152/ajpheart.00894.2015] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Accepted: 02/11/2016] [Indexed: 12/31/2022]
Abstract
We investigated the effect of activating metabolically sensitive skeletal muscle afferents (muscle metaboreflex) on cerebral blood flow and the potentially confounding influence of concomitant changes in the partial pressure of arterial carbon dioxide. Eleven healthy males (25 ± 4 yr) performed submaximal leg cycling exercise on a semirecumbent cycle ergometer (heart rate: ∼120 beats/min), and assessments were made of the partial pressure of end-tidal carbon dioxide (PetCO2), internal carotid artery blood flow (ICAQ) and conductance (ICACVC), and middle cerebral artery mean blood velocity (MCAvm) and conductance index (MCACVCi).The muscle metaboreflex was activated during cycling with leg blood flow restriction (BFR) or isolated with postexercise ischemia (PEI). In separate trials, PetCO2was either permitted to fluctuate spontaneously (control trial) or was clamped at 1 mmHg above resting levels (PetCO2clamp trial). In the control trial, leg cycling with BFR decreased PetCO2(Δ−4.8 ± 0.9 mmHg vs. leg cycling exercise) secondary to hyperventilation, while ICAQ, ICACVC, and MCAvmwere unchanged and MCACVCidecreased. However, in the PetCO2clamp trial, leg cycling with BFR increased both MCAvm(Δ5.9 ± 1.4 cm/s) and ICAQ(Δ20.0 ± 7.8 ml/min) and attenuated the decrease in MCACVCi, while ICACVCwas unchanged. In the control trial, PEI decreased PetCO2(Δ−7.0 ± 1.3 mmHg vs. rest), MCAvmand MCACVCi, whereas ICAQand ICACVCwere unchanged. In contrast, in the PetCO2clamp trial both ICAQ(Δ18.5 ± 11.9 ml/min) and MCAvm(Δ8.8 ± 2.0 cm/s) were elevated, while ICACVCand MCACVCiwere unchanged. In conclusion, when hyperventilation-related decreases in PetCO2are prevented the activation of metabolically sensitive skeletal muscle afferent fibers increases cerebral blood flow.
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Affiliation(s)
- Eliza Prodel
- School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Birmingham, United Kingdom
- Department of Physiology and Pharmacology, Fluminense Federal University, Niterói, Brazil; and
| | - George M. Balanos
- School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Igor D. Braz
- School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Antonio C. L. Nobrega
- Department of Physiology and Pharmacology, Fluminense Federal University, Niterói, Brazil; and
| | - Lauro C. Vianna
- Faculty of Physical Education, University of Brasília, Brasília, Distrito Federal, Brazil
| | - James P. Fisher
- School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Birmingham, United Kingdom
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Cerebral Blood Flow During Treadmill Exercise Is a Marker of Physiological Postconcussion Syndrome in Female Athletes. J Head Trauma Rehabil 2016; 31:215-24. [DOI: 10.1097/htr.0000000000000145] [Citation(s) in RCA: 90] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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14
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Correlation between baseline blood pressure and the brainstem FMRI response to isometric forearm contraction in human volunteers: a pilot study. J Hum Hypertens 2014; 29:449-55. [PMID: 25391759 DOI: 10.1038/jhh.2014.103] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Revised: 09/20/2014] [Accepted: 10/08/2014] [Indexed: 02/07/2023]
Abstract
It has been shown previously that changes in brainstem neural activity correlate with changes in both mean arterial pressure (MAP) and muscle sympathetic nerve activity (MSNA) during static handgrip (SHG). However, the relationship between baseline MAP and brainstem neural activity is unclear. We investigated changes in blood oxygen level-dependent (BOLD) signal induced by SHG in 12 young adults using BOLD functional magnetic resonance imaging (FMRI). An estimation of the blood pressure response to SHG was obtained in seven subjects during a session outside the MRI scanner and was used to model the blood pressure response to SHG inside the scanner. SHG at 40% of maximum grip increased MAP (mean ± s.d.) at the end of the 180-s squeeze from 85 ± 6 mm Hg to 108 ± 15 mm Hg, P = 0.0001. The brainstem BOLD signal change associated with SHG was localised to the ventrolateral medulla. This regional BOLD signal change negatively correlated with baseline MAP, r = -0.61, P = 0.01. This relationship between baseline MAP and brainstem FMRI responses to forearm contraction is suggestive of a possible role for brainstem activity in the control of MAP and may provide mechanistic insights into neurogenic hypertension.
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15
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Braz ID, Scott C, Simpson LL, Springham EL, Tan BWL, Balanos GM, Fisher JP. Influence of muscle metaboreceptor stimulation on middle cerebral artery blood velocity in humans. Exp Physiol 2014; 99:1478-87. [PMID: 25217497 DOI: 10.1113/expphysiol.2014.081687] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Regional anaesthesia to attenuate skeletal muscle afferent feedback abolishes the exercise-induced increase in middle cerebral artery mean blood velocity (MCA Vmean). However, such exercise-related increases in cerebral perfusion are not preserved during post exercise muscle ischaemia (PEMI) where the activation of metabolically sensitive muscle afferents is isolated. We tested the hypothesis that a hyperventilation-mediated decrease in the arterial partial pressure of CO2, hence cerebral vasoconstriction, masks the influence of muscle metaboreceptor stimulation on MCA Vmean during PEMI. Ten healthy men (20 ± 1 years old) performed two trials of fatiguing isometric hand-grip exercise followed by PEMI, in control conditions and with end-tidal CO2 (P ET ,CO2) clamped at ∼1 mmHg above the resting partial pressure. In the control trial, P ET ,CO2 decreased from rest during hand-grip exercise and PEMI, while MCA Vmean was unchanged from rest. By design, P ET ,CO2 remained unchanged from rest throughout the clamp trial, while MCA Vmean increased during hand-grip (+10.6 ±1.8 cm s(-1)) and PEMI (+9.2 ± 1.6 cm s(-1); P < 0.05 versus rest and control trial). Increases in minute ventilation and mean arterial pressure during hand-grip and PEMI were not different in the control and P ET ,CO2 clamp trials (P > 0.05). These findings indicate that metabolically sensitive skeletal muscle afferents play an important role in the regional increase in cerebral perfusion observed in exercise, but that influence can be masked by a decrease in P ET ,CO2 when they are activated in isolation during PEMI.
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Affiliation(s)
- Igor D Braz
- School of Sport, Exercise & Rehabilitation Sciences, College of Life & Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UK
| | - Clare Scott
- School of Sport, Exercise & Rehabilitation Sciences, College of Life & Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UK
| | - Lydia L Simpson
- School of Sport, Exercise & Rehabilitation Sciences, College of Life & Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UK
| | - Emma L Springham
- School of Sport, Exercise & Rehabilitation Sciences, College of Life & Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UK
| | - Beverly W L Tan
- School of Sport, Exercise & Rehabilitation Sciences, College of Life & Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UK
| | - George M Balanos
- School of Sport, Exercise & Rehabilitation Sciences, College of Life & Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UK
| | - James P Fisher
- School of Sport, Exercise & Rehabilitation Sciences, College of Life & Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UK
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Yamaguchi Y, Kashima H, Fukuba Y, Hayashi N. Cerebral blood flow and neurovascular coupling during static exercise. J Physiol Sci 2014; 64:195-201. [PMID: 24682807 PMCID: PMC10717924 DOI: 10.1007/s12576-014-0311-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Accepted: 03/13/2014] [Indexed: 12/30/2022]
Abstract
The effect of static exercise on neurovascular coupling (NVC) was investigated by measuring the blood flow velocity in the posterior cerebral artery (PCAv) during 2-min static handgrip exercises (HG) at 30 % of the maximum voluntary contraction in 17 healthy males. NVC was estimated as the relative change in PCAv from eye closing to a peak response to looking at a reversed checkerboard. The conductance index (CI) was calculated by dividing PCAv by the mean arterial pressure (MAP). HG significantly increased PCAv from the resting baseline, with an increase in MAP and a reduction in CI, whereas NVC did not differ significantly between the resting and HG. Compared to the resting baseline, HG significantly increased the pressor response to visual stimulation by 5.6 ± 1.1 (mean ± SE) mmHg, while the CI response was significantly inhibited by -7.0 ± 1.5 %. These results indicate that NVC was maintained during HG via contributions from both the pressor response and vasodilatation.
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Affiliation(s)
- Yuji Yamaguchi
- Graduate School of Human-Environment Studies, Kyushu University, Kasuga, Fukuoka 816-8580 Japan
| | - Hideaki Kashima
- Department of Exercise Science and Physiology, School of Health and Nutritional Sciences, Prefectural University of Hiroshima, Hiroshima, 734-8558 Japan
| | - Yoshiyuki Fukuba
- Department of Exercise Science and Physiology, School of Health and Nutritional Sciences, Prefectural University of Hiroshima, Hiroshima, 734-8558 Japan
| | - Naoyuki Hayashi
- Graduate School of Decision Science and Technology, Tokyo Insitute of Technology, Meguro, Tokyo, 152-8852 Japan
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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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Purkayastha S, Saxena A, Eubank WL, Hoxha B, Raven PB. α1-Adrenergic receptor control of the cerebral vasculature in humans at rest and during exercise. Exp Physiol 2012; 98:451-61. [DOI: 10.1113/expphysiol.2012.066118] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Rasmussen P, Kim Y, Krogh‐Madsen R, Lundby C, Olsen NV, Secher NH, Lieshout JJ. Both acute and prolonged administration of EPO reduce cerebral and systemic vascular conductance in humans. FASEB J 2011; 26:1343-8. [DOI: 10.1096/fj.11-193508] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Peter Rasmussen
- Copenhagen Muscle Research CenterUniversity of CopenhagenCopenhagenDenmark
- Department of AnesthesiaUniversity of CopenhagenCopenhagenDenmark
- Zurich Center for Integrative Human PhysiologyUniversity of ZurichZurichSwitzerland
| | - Yu‐Sok Kim
- Department of Internal MedicineAMC Center for Heart Failure Research, Academic Medical CenterUniversity of AmsterdamAmsterdamThe Netherlands
- Laboratory for Cardiovascular PhysiologyAMC Center for Heart Failure Research, Academic Medical CenterUniversity of AmsterdamAmsterdamThe Netherlands
| | - Rikke Krogh‐Madsen
- Copenhagen Muscle Research CenterUniversity of CopenhagenCopenhagenDenmark
- Department of Infectious DiseasesCenter of Inflammation and Metabolism, RigshospitaletUniversity of CopenhagenCopenhagenDenmark
| | - Carsten Lundby
- Copenhagen Muscle Research CenterUniversity of CopenhagenCopenhagenDenmark
- Zurich Center for Integrative Human PhysiologyUniversity of ZurichZurichSwitzerland
| | - Niels V. Olsen
- Department of AnesthesiaUniversity of CopenhagenCopenhagenDenmark
- Department of Neuroscience and PharmacologyUniversity of CopenhagenCopenhagenDenmark
| | - Niels H. Secher
- Copenhagen Muscle Research CenterUniversity of CopenhagenCopenhagenDenmark
- Department of AnesthesiaUniversity of CopenhagenCopenhagenDenmark
| | - Johannes J. Lieshout
- Department of Internal MedicineAMC Center for Heart Failure Research, Academic Medical CenterUniversity of AmsterdamAmsterdamThe Netherlands
- Laboratory for Cardiovascular PhysiologyAMC Center for Heart Failure Research, Academic Medical CenterUniversity of AmsterdamAmsterdamThe Netherlands
- School of Biomedical SciencesUniversity of Nottingham Medical SchoolQueen's Medical CentreNottinghamUK
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Vianna LC, Sales ARK, da Nóbrega ACL. Cerebrovascular responses to cold pressor test during static exercise in humans. Clin Physiol Funct Imaging 2011; 32:59-64. [DOI: 10.1111/j.1475-097x.2011.01055.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Seifert T, Secher NH. Sympathetic influence on cerebral blood flow and metabolism during exercise in humans. Prog Neurobiol 2011; 95:406-26. [PMID: 21963551 DOI: 10.1016/j.pneurobio.2011.09.008] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Revised: 09/13/2011] [Accepted: 09/19/2011] [Indexed: 11/26/2022]
Abstract
This review focuses on the possibility that autonomic activity influences cerebral blood flow (CBF) and metabolism during exercise in humans. Apart from cerebral autoregulation, the arterial carbon dioxide tension, and neuronal activation, it may be that the autonomic nervous system influences CBF as evidenced by pharmacological manipulation of adrenergic and cholinergic receptors. Cholinergic blockade by glycopyrrolate blocks the exercise-induced increase in the transcranial Doppler determined mean flow velocity (MCA Vmean). Conversely, alpha-adrenergic activation increases that expression of cerebral perfusion and reduces the near-infrared determined cerebral oxygenation at rest, but not during exercise associated with an increased cerebral metabolic rate for oxygen (CMRO(2)), suggesting competition between CMRO(2) and sympathetic control of CBF. CMRO(2) does not change during even intense handgrip, but increases during cycling exercise. The increase in CMRO(2) is unaffected by beta-adrenergic blockade even though CBF is reduced suggesting that cerebral oxygenation becomes critical and a limited cerebral mitochondrial oxygen tension may induce fatigue. Also, sympathetic activity may drive cerebral non-oxidative carbohydrate uptake during exercise. Adrenaline appears to accelerate cerebral glycolysis through a beta2-adrenergic receptor mechanism since noradrenaline is without such an effect. In addition, the exercise-induced cerebral non-oxidative carbohydrate uptake is blocked by combined beta 1/2-adrenergic blockade, but not by beta1-adrenergic blockade. Furthermore, endurance training appears to lower the cerebral non-oxidative carbohydrate uptake and preserve cerebral oxygenation during submaximal exercise. This is possibly related to an attenuated catecholamine response. Finally, exercise promotes brain health as evidenced by increased release of brain-derived neurotrophic factor (BDNF) from the brain.
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Affiliation(s)
- Thomas Seifert
- Department of Anaesthesia and The Copenhagen Muscle Research Centre, Rigshospitalet 2041, University of Copenhagen, Blegdamsvej 9, DK-2100 Copenhagen Ø, Denmark.
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Hartwich D, Fowler KL, Wynn LJ, Fisher JP. Differential responses to sympathetic stimulation in the cerebral and brachial circulations during rhythmic handgrip exercise in humans. Exp Physiol 2011; 95:1089-97. [PMID: 20851860 DOI: 10.1113/expphysiol.2010.054387] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The sympathetic neural regulation of the cerebral circulation remains controversial. The purpose of the present study was to determine how exercise modulates the simultaneous responsiveness of the cerebral and brachial circulations to 'endogenous' sympathetic activation (cold pressor test). In nine healthy subjects, heart rate (HR) and mean arterial blood pressure (MAP) were continuously measured during cold pressor tests (4°C water) conducted at rest and during randomized bouts of rhythmic handgrip of 10, 25 and 40% of maximal voluntary contraction. Doppler ultrasound was used to examine brachial artery blood flow (FBF) and middle cerebral artery (MCA) mean blood velocity (V mean), and indices of vascular conductance were calculated for the brachial artery (forearm vascular conductance, FVC) and MCA (cerebral vascular conductance index, CVCi). End-tidal PCO2 (P ET.CO2) was evaluated on a breath-by-breath basis. Handgrip evoked increases in HR, FBF, FVC and MCA V mean (P < 0.05 versus rest), while MAP and CVCi were unchanged and P ET.CO2 fell slightly (P < 0.05 versus rest). Increases in MAP and HR during the cold pressor test were similar at rest and during all handgrip trials. Forearm vascular conductance was markedly reduced with the cold pressor test at rest (-45 ± 8%), but this vasoconstrictor effect was progressively attenuated with increasing exercise intensity (FVC -17 ± 3% during exercise at 40% of maximal voluntary contraction; P < 0.05). In contrast, the small reduction in CVCi with cold pressor test was similar at rest and during handgrip (approximately -5%). Our data indicate that while the marked vasoconstrictor responses to sympathetic activation in the skeletal muscle vasculature are blunted by handgrip exercise, the modest cerebrovascular responses to a cold pressor test remain unchanged.
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Affiliation(s)
- Doreen Hartwich
- School of Sport and Exercise Sciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
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Sakagami J, Ono T, Hasegawa Y, Hori K, Zhang M, Maeda Y. Transfer Function Analysis of Cerebral Autoregulation Dynamics during Jaw Movements. J Dent Res 2010; 90:71-6. [DOI: 10.1177/0022034510383692] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Mastication as a mild but life-long exercise has been examined as a possibility for maintaining brain function in the elderly. Little is known, however, about the cerebral circulatory response during masticatory movement. The aim of this study was to develop a monitoring system for circulation dynamics during masticatory movement and to apply this system to the study of cerebral autoregulation. Cerebral blood flow, heart rate, and arterial blood pressure were simultaneously recorded, and changes in these circulatory systems were quantitatively evaluated in 38 young healthy volunteers. Transfer function analysis was also performed on blood pressure and cerebral blood flow for investigation of cerebral autoregulation during gum chewing. Although increases in cerebral blood flow, mean blood pressure, and heart rate suggested the activation of cerebral and systemic circulation during gum chewing, increased cerebral circulation was independent of systemic circulation. Our results suggest that cerebral autoregulation is well maintained during jaw movements.
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Affiliation(s)
- J. Sakagami
- Department of Prosthodontics and Oral Rehabilitation, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan
| | - T. Ono
- Department of Prosthodontics and Oral Rehabilitation, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan
| | - Y. Hasegawa
- Department of Dentistry and Oral Surgery, Hyogo College of Medicine, Nishinomiya, Hyogo, Japan
| | - K. Hori
- Division of Dysphagia Rehabilitation, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - M. Zhang
- Department of General Dentistry & Emergency, School of Stomatology, Fourth Military Medical University, Xi’an, China
| | - Y. Maeda
- Department of Prosthodontics and Oral Rehabilitation, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan
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Seifert T, Fisher JP, Young CN, Hartwich D, Ogoh S, Raven PB, Fadel PJ, Secher NH. Experimental Physiology -Research Paper: Glycopyrrolate abolishes the exercise-induced increase in cerebral perfusion in humans. Exp Physiol 2010; 95:1016-25. [DOI: 10.1113/expphysiol.2010.054346] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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25
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Ogoh S, Brothers RM, Jeschke M, Secher NH, Raven PB. Estimation of cerebral vascular tone during exercise; evaluation by critical closing pressure in humans. Exp Physiol 2010; 95:678-85. [DOI: 10.1113/expphysiol.2010.052340] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Ogoh S, Sato K, Akimoto T, Oue A, Hirasawa A, Sadamoto T. Dynamic cerebral autoregulation during and after handgrip exercise in humans. J Appl Physiol (1985) 2010; 108:1701-5. [PMID: 20378708 DOI: 10.1152/japplphysiol.01031.2009] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The purpose of the present study was to examine the effect of static exercise on dynamic cerebral autoregulation (CA). In nine healthy subjects at rest before, during, and after static handgrip exercise at 30% maximum voluntary contraction, the response to an acute drop in mean arterial blood pressure and middle cerebral artery mean blood velocity was examined. Acute hypotension was induced nonpharmacologically via rapid release of bilateral thigh occlusion cuffs. Subjects were instructed to avoid executing a Valsalva maneuver during handgrip. To quantify dynamic CA, the rate of regulation (RoR) was calculated from the change in cerebral vascular conductance index during the transient fall in blood pressure. There was no significant difference in RoR between rest (mean+/-SE; 0.278+/-0.052/s), exercise (0.333+/-0.053/s), and recovery (0.305+/-0.059/s) conditions (P=0.747). In addition, there was no significant difference in the rate of absolute cerebral vasodilatory response to acute hypotension between three conditions (P=0.737). This finding indicates that static exercise and related elevations in blood pressure do not alter dynamic CA.
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Affiliation(s)
- Shigehiko Ogoh
- Department of Biomedical Engineering, Toyo University, 2100 Kujirai, Kawagoe-shi, Saitama 350-8585, Japan.
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Lykidis CK, Kumar P, Vianna LC, White MJ, Balanos GM. A respiratory response to the activation of the muscle metaboreflex during concurrent hypercapnia in man. Exp Physiol 2009; 95:194-201. [DOI: 10.1113/expphysiol.2009.049999] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Vianna LC, Araújo CGS, Fisher JP. Influence of central command and muscle afferent activation on anterior cerebral artery blood velocity responses to calf exercise in humans. J Appl Physiol (1985) 2009; 107:1113-20. [DOI: 10.1152/japplphysiol.00480.2009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The purpose of the present study was to determine the relative importance of peripheral feedback from mechanically (mechanoreflex) and metabolically (metaboreflex) sensitive muscle afferents and central signals arising from higher centers (central command) to the exercise-induced increases in regional cerebral perfusion. To accomplish this, anterior cerebral artery (ACA) mean blood velocity ( Vmean) responses were assessed during sustained and rhythmic passive calf muscle stretch (mechanoreflex), volitional calf exercise (mechanoreflex, metaboreflex, and central command), and electrically stimulated calf exercise (mechanoreflex and metaboreflex but no central command) at 35% of maximum voluntary contraction ( n = 16). In addition, a period of postexercise muscle ischemia (PEMI) was used to isolate the metaboreflex. Blood pressure, cardiac output, and the end-tidal partial pressure of carbon dioxide (PetCO2) were also measured. ACA Vmean was unchanged from rest during either sustained or rhythmic calf muscle stretch ( P > 0.05). However, ACA Vmean was increased from rest during both isometric (+15 ± 1%) and rhythmic (+15 ± 2%, voluntary exercise P < 0.05) but remained unchanged during stimulated exercise ( P > 0.05). Isometric and rhythmic exercise-induced increases in blood pressure and cardiac output were similar during voluntary and stimulated exercise ( P > 0.05 between conditions). Blood pressure remained elevated during PEMI after all exercise conditions ( P < 0.05 vs. rest), whereas cardiac output and ACA Vmean were not different from rest ( P > 0.05). PetCO2 was unchanged from rest throughout. These data suggest that selective activation of skeletal muscle afferents (i.e., stretch, PEMI, or stimulated exercise) does not increase ACA Vmean and that increases in ACA Vmean during volitional contractions of an exercising calf muscle are dependent on the presence of central command.
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Affiliation(s)
- Lauro C. Vianna
- School of Sport and Exercise Sciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom; and
- Graduate Program in Physical Education, Gama Filho University, Rio de Janeiro, Brazil
| | - Claudio Gil S. Araújo
- Graduate Program in Physical Education, Gama Filho University, Rio de Janeiro, Brazil
| | - James P. Fisher
- School of Sport and Exercise Sciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom; and
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Abstract
Sickle cell disease (SCD) is associated with a high incidence of ischemic stroke. SCD is characterized by hemolytic anemia, resulting in reduced nitric oxide-bioavailability, and by impaired cerebrovascular hemodynamics. Cerebrovascular CO2 responsiveness is nitric oxide dependent and has been related to an increased stroke risk in microvascular diseases. We questioned whether cerebrovascular CO2 responsiveness is impaired in SCD and related to hemolytic anemia. Transcranial Doppler-determined mean cerebral blood flow velocity (V(mean)), near-infrared spectroscopy-determined cerebral oxygenation, and end-tidal CO2 tension were monitored during normocapnia and hypercapnia in 23 patients and 16 control subjects. Cerebrovascular CO2 responsiveness was quantified as Delta% V(mean) and Deltamicromol/L cerebral oxyhemoglobin, deoxyhemoglobin, and total hemoglobin per mm Hg change in end-tidal CO2 tension. Both ways of measurements revealed lower cerebrovascular CO2 responsiveness in SCD patients versus controls (V(mean), 3.7, 3.1-4.7 vs 5.9, 4.6-6.7 Delta% V(mean) per mm Hg, P < .001; oxyhemoglobin, 0.36, 0.14-0.82 vs 0.78, 0.61-1.22 Deltamicromol/L per mm Hg, P = .025; deoxyhemoglobin, 0.35, 0.14-0.67 vs 0.58, 0.41-0.86 Deltamicromol/L per mm Hg, P = .033; total-hemoglobin, 0.13, 0.02-0.18 vs 0.23, 0.13-0.38 Deltamicromol/L per mm Hg, P = .038). Cerebrovascular CO2 responsiveness was not related to markers of hemolytic anemia. In SCD patients, impaired cerebrovascular CO2 responsiveness reflects reduced cerebrovascular reserve capacity, which may play a role in pathophysiology of stroke.
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Lykidis CK, Kumar P, Balanos GM. The respiratory responses to the combined activation of the muscle metaboreflex and the ventilatory chemoreflex. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2009; 648:281-7. [PMID: 19536491 DOI: 10.1007/978-90-481-2259-2_32] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The excessive hyperventilation seen during exercise in chronic heart failure (CHF) contributes to the limited exercise capacity in this condition. The hyperactivation of reflexes originating, independently, from muscle (ergoreflex) and from chemoreceptors (chemoreflex) has been suggested to play an important part in the mediation of the CHF ventilatory abnormalities. In this study we aimed to assess the ventilatory responses to the combined activation of the muscle ergoreflex and the ventilatory chemoreflex, achieved by post-exercise circulatory occlusion (PECO) and euoxic hypercapnia (end-tidal PCO(2) = 7 mmHg above normal), respectively.Three healthy women and three healthy men (29.33 +/- 1.28 yrs; mean +/- SD) undertook four trials, in random order, separated from each other by 30 min of rest: 2 min of isometric handgrip exercise followed by 2 min of PECO with hypercapnia, 2 min of isometric handgrip exercise followed by 2 min of PECO while breathing room air, 4 min of rest with hypercapnia and 4 min of rest while breathing room air.Ventilation (V(E)) was significantly elevated by the ventilatory chemoreflex and it was further elevated by 5.13+/-0.83 L/min (P<0.05) when the muscle ergoreflex was superimposed upon it. The response to the combination of these stimuli was significantly greater than the sum of the responses to the two stimuli when given independently (P<0.05).The results indicate that the interaction between the two reflexes has an additional stimulatory effect on ventilation and consequently could be involved in the limited exercise capacity in CHF.
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Affiliation(s)
- C K Lykidis
- School of Sport and Exercise Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.
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31
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Secher NH, Seifert T, Van Lieshout JJ. Cerebral blood flow and metabolism during exercise: implications for fatigue. J Appl Physiol (1985) 2008; 104:306-14. [PMID: 17962575 DOI: 10.1152/japplphysiol.00853.2007] [Citation(s) in RCA: 251] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
During exercise: the Kety-Schmidt-determined cerebral blood flow (CBF) does not change because the jugular vein is collapsed in the upright position. In contrast, when CBF is evaluated by 133Xe clearance, by flow in the internal carotid artery, or by flow velocity in basal cerebral arteries, a ∼25% increase is detected with a parallel increase in metabolism. During activation, an increase in cerebral O2 supply is required because there is no capillary recruitment within the brain and increased metabolism becomes dependent on an enhanced gradient for oxygen diffusion. During maximal whole body exercise, however, cerebral oxygenation decreases because of eventual arterial desaturation and marked hyperventilation-related hypocapnia of consequence for CBF. Reduced cerebral oxygenation affects recruitment of motor units, and supplemental O2 enhances cerebral oxygenation and work capacity without effects on muscle oxygenation. Also, the work of breathing and the increasing temperature of the brain during exercise are of importance for the development of so-called central fatigue. During prolonged exercise, the perceived exertion is related to accumulation of ammonia in the brain, and data support the theory that glycogen depletion in astrocytes limits the ability of the brain to accelerate its metabolism during activation. The release of interleukin-6 from the brain when exercise is prolonged may represent a signaling pathway in matching the metabolic response of the brain. Preliminary data suggest a coupling between the circulatory and metabolic perturbations in the brain during strenuous exercise and the ability of the brain to access slow-twitch muscle fiber populations.
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Ogoh S, Dalsgaard MK, Secher NH, Raven PB. Dynamic blood pressure control and middle cerebral artery mean blood velocity variability at rest and during exercise in humans. Acta Physiol (Oxf) 2007; 191:3-14. [PMID: 17506866 DOI: 10.1111/j.1748-1716.2007.01708.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
AIMS Cardiac failure and ischaemic heart disease patients receive standard of care cardiac beta(1)-adrenergic blockade medication. Such medication reduces cardiac output and cerebral blood flow. It is unknown whether the beta(1)-adrenergic blockade-induced reduction of cardiac output in the presence of an exercise-induced reduction in cardiac-arterial baroreflex gain affects cerebral blood flow variability. This study evaluated the influence of cardiac output variability on beat-to-beat middle cerebral artery mean blood velocity (MCA V(mean)) during exercise with and without cardiac beta(1)-adrenergic blockade. METHODS Eight men (22 +/- 1 years; mean +/- SE) performed 15 min bouts of moderate (105 +/- 11 W) and heavy (162 +/- 8 W) intensity cycling before and after cardio-selective beta(1)-adrenergic blockade (0.15 mg kg(-1) metoprolol). The relationship between changes in cardiac output or mean arterial pressure (MAP) and MCA V(mean) as well as cardiac-arterial baroreflex gain were evaluated using transfer function analysis. RESULTS Both exercise intensities decreased the low frequency (LF) transfer function gain between cardiac output and MCA V(mean) (P < 0.05) with no significant influence of beta(1)-blockade. In contrast, the LF transfer function gain between MAP and MCA V(mean) remained stable also with no significant influence of metoprolol (P > 0.05). The LF transfer function gain between MAP and HR, an index of cardiac-arterial baroreflex gain, decreased from rest to heavy exercise with and without beta(1)-blockade (P < 0.05). CONCLUSION These findings suggest that the exercise intensity related reduction in cardiac-arterial baroreflex function at its operating point does not influence the dynamic control of MCA V(mean), even when the ability of exercise-induced increase in cardiac output is reduced by cardiac beta(1)-adrenergic blockade.
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Affiliation(s)
- S Ogoh
- Department of Integrative Physiology, University of North Texas Health Science Center, Fort Worth, TX 76107, USA.
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Nybo L, Rasmussen P. Inadequate Cerebral Oxygen Delivery and Central Fatigue during Strenuous Exercise. Exerc Sport Sci Rev 2007; 35:110-8. [PMID: 17620929 DOI: 10.1097/jes.0b013e3180a031ec] [Citation(s) in RCA: 130] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Under resting conditions, the brain is protected against hypoxia because cerebral blood flow increases when the arterial oxygen tension becomes low. However, during strenuous exercise, hyperventilation lowers the arterial carbon dioxide tension and blunts the increase in cerebral blood flow, which can lead to an inadequate oxygen delivery to the brain and contribute to the development of fatigue.
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Affiliation(s)
- Lars Nybo
- Institute of Exercise and Sport Sciences and Department of Anaesthesia, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
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Kim YS, Krogh-Madsen R, Rasmussen P, Plomgaard P, Ogoh S, Secher NH, van Lieshout JJ. Effects of hyperglycemia on the cerebrovascular response to rhythmic handgrip exercise. Am J Physiol Heart Circ Physiol 2007; 293:H467-73. [PMID: 17369470 DOI: 10.1152/ajpheart.00045.2007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Dynamic cerebral autoregulation (CA) is challenged by exercise and may become less effective when exercise is exhaustive. Exercise may increase arterial glucose concentration, and we evaluated whether the cerebrovascular response to exercise is affected by hyperglycemia. The effects of a hyperinsulinemic euglycemic clamp (EU) and hyperglycemic clamp (HY) on the cerebrovascular (CVRI) and systemic vascular resistance index (SVRI) responses were evaluated in seven healthy subjects at rest and during rhythmic handgrip exercise. Transfer function analysis of the dynamic relationship between beat-to-beat changes in mean arterial pressure and middle cerebral artery (MCA) mean blood flow velocity ( Vmean) was used to assess dynamic CA. At rest, SVRI decreased with HY and EU ( P < 0.01). CVRI was maintained with EU but became reduced with HY [11% (SD 3); P < 0.01], and MCA Vmean increased ( P < 0.05), whereas brain catecholamine uptake and arterial Pco2 did not change significantly. HY did not affect the normalized low-frequency gain between mean arterial pressure and MCA Vmean or the phase shift, indicating maintained dynamic CA. With HY, the increase in CVRI associated with exercise was enhanced (19 ± 7% vs. 9 ± 7%; P < 0.05), concomitant with a larger increase in heart rate and cardiac output and a larger reduction in SVRI (22 ± 4% vs. 14 ± 2%; P < 0.05). Thus hyperglycemia lowered cerebral vascular tone independently of CA capacity at rest, whereas dynamic CA remained able to modulate cerebral blood flow around the exercise-induced increase in MCA Vmean. These findings suggest that elevated blood glucose does not explain that dynamic CA is affected during intense exercise.
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Affiliation(s)
- Yu-Sok Kim
- Medium Care Unit, Department of Internal Medicine, F7-205 Academic Medical Center, University of Amsterdam, 1100 DE Amsterdam, The Netherlands
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Abstract
Constant cerebral blood flow (CBF) is vital to human survival. Originally thought to receive steady blood flow, the brain has shown to experience increases in blood flow during exercise. Although increases have not consistently been documented, the overwhelming evidence supporting an increase may be a result of an increase in brain metabolism. While an increase in metabolism may be the underlying causative factor for the increase in CBF during exercise, there are many modulating variables. Arterial blood gas tensions, most specifically the partial pressure of carbon dioxide, strongly regulate CBF by affecting cerebral vessel diameter through changes in pH, while carbon dioxide reactivity increases from rest to exercise. Muscle mechanoreceptors may contribute to the initial increase in CBF at the onset of exercise, after which exercise-induced hyperventilation tends to decrease flow by pial vessel vasoconstriction. Although elite athletes may benefit from hyperoxia during intense exercise, cerebral tissue is well protected during exercise, and cerebral oxygenation does not appear to pose a limiting factor to exercise performance. The role of arterial blood pressure is important to the increase in CBF during exercise; however, during times of acute hypotension such as during diastole at high-intensity exercise or post-exercise hypotension, cerebral autoregulation may be impaired. The impairment of an increase in cardiac output during exercise with a large muscle mass similarly impairs the increase in CBF velocity, suggesting that cardiac output may play a key role in the CBF response to exercise. Glucose uptake and CBF do not appear to be related; however, there is growing evidence to suggest that lactate is used as a substrate when glucose levels are low. Traditionally thought to have no influence, neural innervation appears to be a protective mechanism to large increases in cardiac output. Changes in middle cerebral arterial velocity are independent of changes in muscle sympathetic nerve activity, suggesting that sympathetic activity does not alter medium-sized arteries (middle cerebral artery).CBF does not remain steady, as seen by apparent increases during exercise, which is accomplished by a multi-factorial system, operating in a way that does not pose any clear danger to cerebral tissue during exercise under normal circumstances.
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Affiliation(s)
- Jordan S Querido
- Health and Integrative Physiology Laboratory, School of Human Kinetics, The University of British Columbia, Vancouver, British Columbia, Canada
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36
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Abstract
The metabolic response to brain activation in exercise might be expressed as the cerebral metabolic ratio (MR; uptake O2/glucose + 1/2 lactate). At rest, brain energy is provided by a balanced oxidation of glucose as MR is close to 6, but activation provokes a 'surplus' uptake of glucose relative to that of O2. Whereas MR remains stable during light exercise, it is reduced by 30% to 40% when exercise becomes demanding. The MR integrates metabolism in brain areas stimulated by sensory input from skeletal muscle, the mental effort to exercise and control of exercising limbs. The MR decreases during prolonged exhaustive exercise where blood lactate remains low, but when vigorous exercise raises blood lactate, the brain takes up lactate in an amount similar to that of glucose. This lactate taken up by the brain is oxidised as it does not accumulate within the brain and such pronounced brain uptake of substrate occurs independently of plasma hormones. The 'surplus' of glucose equivalents taken up by the activated brain may reach approximately 10 mmol, that is, an amount compatible with the global glycogen level. It is suggested that a low MR predicts shortage of energy that ultimately limits motor activation and reflects a biologic background for 'central fatigue'.
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Affiliation(s)
- Mads K Dalsgaard
- Department of Anaesthesia and The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
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37
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Abstract
We investigated whether dynamic cerebral autoregulation is affected by exhaustive exercise using transfer-function gain and phase shift between oscillations in mean arterial pressure (MAP) and middle cerebral artery (MCA) mean blood flow velocity (V(mean)). Seven subjects were instrumented with a brachial artery catheter for measurement of MAP and determination of arterial Pco(2) (Pa(CO(2))) while jugular venous oxygen saturation (Sv(O(2))) was determined to assess changes in whole brain blood flow. After a 10-min resting period, the subjects performed dynamic leg-cycle ergometry at 168 +/- 5 W (mean +/- SE) that was continued to exhaustion with a group average time of 26.8 +/- 5.8 min. Despite no significant change in MAP during exercise, MCA V(mean) decreased from 70.2 +/- 3.6 to 57.4 +/- 5.4 cm/s, Sv(O(2)) decreased from 68 +/- 1 to 58 +/- 2% at exhaustion, and both correlated to Pa(CO(2)) (5.5 +/- 0.2 to 3.9 +/- 0.2 kPa; r = 0.47; P = 0.04 and r = 0.74; P < 0.001, respectively). An effect on brain metabolism was indicated by a decrease in the cerebral metabolic ratio of O(2) to [glucose + one-half lactate] from 5.6 to 3.8 (P < 0.05). At the same time, the normalized low-frequency gain between MAP and MCA V(mean) was increased (P < 0.05), whereas the phase shift tended to decrease. These findings suggest that dynamic cerebral autoregulation was impaired by exhaustive exercise despite a hyperventilation-induced reduction in Pa(CO(2)).
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Kimmerly DS, Tutungi E, Wilson TD, Serrador JM, Gelb AW, Hughson RL, Shoemaker JK. Circulating norepinephrine and cerebrovascular control in conscious humans. Clin Physiol Funct Imaging 2004; 23:314-9. [PMID: 14617260 DOI: 10.1046/j.1475-0961.2003.00507.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Cerebral vasoconstriction without concurrent changes in systemic arterial blood pressure has been observed in both normal individuals and those with idiopathic orthostatic intolerance following several minutes of postural stress when circulating catecholamines are elevated. Therefore, we tested the hypothesis that alpha-adrenergic activation with and without elevated circulating norepinephrine (NE) directly affects cerebrovascular tone in healthy individuals. METHODS Mean arterial pressure (MAP; tonometry) and cerebral blood flow velocity (MFV) in the middle cerebral artery (transcranial Doppler) were measured in seven healthy individuals during 15 min periods of saline and of 50 (low NE) and 100 (high NE) ng kg(-1) min(-1) infusions of NE. Following this, phentolamine (PHO) was administered to return MAP back to baseline while high NE infusion continued (high NE+PHO). Finally, NE infusion was stopped allowing the persistent effects of PHO to dominate. RESULTS Circulating NE caused a dose-dependent increase in MAP (P<0.05). During combined high NE+PHO, blood pressure was initially reduced to baseline levels but then increased a second time (P<0.05) during the final approximately 5 min of this phase. MFV remained constant during both low NE and high NE. In contrast, the secondary increase in BP during the late high NE+PHO phase was associated with elevated MFV. Cerebral vascular resistance (CVR) increased during high NE but was reduced to baseline during both early and late portions of the combined high NE+PHO phase (i.e. despite the late-phase increase in blood pressure). CONCLUSIONS The increase in CVR during NE infusion was explained by an autoregulatory response to the increased blood pressure and not an alpha-mediated constriction. However, PHO appeared to interfere with the normal autoregulatory response to increasing blood pressure.
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Affiliation(s)
- D S Kimmerly
- Neurovascular Research Lab, University of Western Ontario, London, Ontario, Canada
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Bruder N, Pellissier D, Grillot P, Gouin F. Cerebral hyperemia during recovery from general anesthesia in neurosurgical patients. Anesth Analg 2002; 94:650-4; table of contents. [PMID: 11867391 DOI: 10.1097/00000539-200203000-00031] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
UNLABELLED Changes in the cerebral circulation during recovery from neurosurgical anesthesia are poorly understood. We used transcranial Doppler to compare cerebral blood flow velocity changes (Vmca) during recovery after anesthesia. In the first part of the study, 30 patients were randomized to propofol- or isoflurane-based anesthesia. Vmca, mean arterial pressure (MAP), and CO(2) partial pressure (PaCO(2)) were measured before anesthesia, at tracheal extubation, at 5 to 60 min after extubation, and at 24 h after anesthesia. There was a 60% increase in Vmca above the awake value at extubation. The increase in Vmca was significant at least for 30 min after extubation. There was no difference between the Propofol and Isoflurane anesthesia groups. There was no correlation between Vmca and MAP or PaCO(2) at any time. In the second part of the study, Vmca, MAP, and jugular venous bulb saturation in oxygen (SjvO(2)) were measured after isoflurane anesthesia. SjvO(2) increased significantly at extubation, consistent with cerebral hyperemia. In conclusion, cerebral hyperemia occurs during recovery from general anesthesia independently of the anesthetic technique or hemodynamic or ventilatory changes. It is speculated that cerebral hyperemia is a nonspecific response to stress during emergence from anesthesia. IMPLICATIONS Cerebral hyperemia occurs during emergence from general anesthesia. It might be one mechanism of cerebral complications in the early postoperative period.
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Affiliation(s)
- Nicolas Bruder
- Département d'Anesthésie-Réanimation, CHU Timone, 13385 Marseille Cedex, France.
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40
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Abstract
During exercise regional cerebral blood flow (rCBF), as blood velocity in major cerebral arteries and also blood flow in the internal carotid artery increase, suggesting an increase in blood flow to a large part of the brain. Such an increase in CBF is independent of the concomitant increase in blood pressure but is modified by the alteration in arterial carbon dioxide tension (PaCO(2)). Also, the increase in middle cerebral artery mean blood velocity (MCA V(mean)) reported with exercise appears to depend on the ability to increase cardiac output (CO), as demonstrated in response to beta-1 blockade and in patients with cardiac insufficiency or atrial fibrillation.Near-infrared spectroscopy (NIRS) determined cerebral oxygenation supports the alterations in MCA V(mean) during exercise. Equally, the observation that the cerebrovascular CO(2)-reactivity appears to be smaller in the standing than in the sitting and especially in the supine position could relate to the progressively smaller CO. In contrast, during exercise "global" cerebral blood flow (gCBF), as determined by the Kety-Schmidt technique is regarded as being constant. One limitation of the Kety-Schmidt method for measuring CBF is that blood flow in the two internal jugular veins depends on the origin of drainage and it has not been defined which internal jugular venous flow is evaluated. Such a consideration is equally relevant for an evaluation of cerebral metabolism during exercise. While the regional cerebral uptake of oxygen (O(2)) increases during exercise, the global value is regarded as being constant. Yet, during high intensity exercise lactate is taken up by the brain and its O(2) uptake also increases. Furthermore, in the initial minutes of recovery immediately following exercise, brain glucose and O(2) uptake are elevated and lactate uptake remains high.A maintained substrate uptake by the brain after exercise suggests a role for brain glycogen in cerebral activation, but the fate of brain substrate uptake has not yet been determined.
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Affiliation(s)
- K Ide
- The Copenhagen Muscle Research Centre, Department of Anaesthesia, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, DK-2100, Copenhagen, Denmark.
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Serrador JM, Picot PA, Rutt BK, Shoemaker JK, Bondar RL. MRI measures of middle cerebral artery diameter in conscious humans during simulated orthostasis. Stroke 2000; 31:1672-8. [PMID: 10884472 DOI: 10.1161/01.str.31.7.1672] [Citation(s) in RCA: 551] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
BACKGROUND AND PURPOSE The relationship between middle cerebral artery (MCA) flow velocity (CFV) and cerebral blood flow (CBF) is uncertain because of unknown vessel diameter response to physiological stimuli. The purpose of this study was to directly examine the effect of a simulated orthostatic stress (lower body negative pressure [LBNP]) as well as increased or decreased end-tidal carbon dioxide partial pressure (P(ET)CO(2)) on MCA diameter and CFV. METHODS Twelve subjects participated in a CO(2) manipulation protocol and/or an LBNP protocol. In the CO(2) manipulation protocol, subjects breathed room air (normocapnia) or 6% inspired CO(2) (hypercapnia), or they hyperventilated to approximately 25 mm Hg P(ET)CO(2) (hypocapnia). In the LBNP protocol, subjects experienced 10 minutes each of -20 and -40 mm Hg lower body suction. CFV and diameter of the MCA were measured by transcranial Doppler and MRI, respectively, during the experimental protocols. RESULTS Compared with normocapnia, hypercapnia produced increases in both P(ET)CO(2) (from 36+/-3 to 40+/-4 mm Hg, P<0.05) and CFV (from 63+/-4 to 80+/-6 cm/s, P<0.001) but did not change MCA diameters (from 2.9+/-0.3 to 2.8+/-0.3 mm). Hypocapnia produced decreases in both P(ET)CO(2) (24+/-2 mm Hg, P<0.005) and CFV (43+/-7 cm/s, P<0.001) compared with normocapnia, with no change in MCA diameters (from 2.9+/-0.3 to 2.9+/-0.4 mm). During -40 mm Hg LBNP, P(ET)CO(2) was not changed, but CFV (55+/-4 cm/s) was reduced from baseline (58+/-4 cm/s, P<0.05), with no change in MCA diameter. CONCLUSIONS Under the conditions of this study, changes in MCA diameter were not detected. Therefore, we conclude that relative changes in CFV were representative of changes in CBF during the physiological stimuli of moderate LBNP or changes in P(ET)CO(2).
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Affiliation(s)
- J M Serrador
- Neurovascular Research Laboratory, School of Kinesiology, and the Robarts Research Institute, The University of Western Ontario, London, Ontario, Canada
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Giller CA, Giller AM, Cooper CR, Hatab MR. Evaluation of the cerebral hemodynamic response to rhythmic handgrip. J Appl Physiol (1985) 2000; 88:2205-13. [PMID: 10846037 DOI: 10.1152/jappl.2000.88.6.2205] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The response of the cerebral circulation to exercise has been studied with transcranial Doppler ultrasound (TCD) because this modality provides continuous measurements of blood velocity and is well suited for the exercise environment. The use of TCD as an index of cerebral blood flow, however, requires the assumption that the diameter of the insonated vessel is constant. Here, we examine this assumption for rhythmic handgrip using a spectral index designed to measure trends in vessel flow. Nineteen normal subjects were studied during 5 min of volitional maximum rhythmic right handgrip at 1 Hz. TCD velocities from both middle arteries (left and right), blood pressure, and end-tidal PCO(2) were recorded every 10 s. A spectral weighted sum was also calculated as a flow index (FI). Averages were computed from the last 2 min of handgrip. Relative changes in velocity, FI, and pressure were calculated. The validity of FI was tested by comparing the change in diameter derived from equations relating flow and diameter. Mean blood pressure increased 23.8 +/- 17.8% (SD), and velocity increased 13.3 +/- 9.8% (left) and 9.6 +/- 8.3% (right). Although the mean change in FI was small [2.0 +/- 18. 2% (left) and 4.7 +/- 29.7% (right)], the variation was high: some subjects showed a significant increase in FI and others a significant decrease. Diameter estimates from two equations relating flow and luminal area were not significantly different. Decreases in FI were associated with estimated diameter decreases of 10%. Our data suggest that the cerebral blood flow (CBF) response to rhythmic handgrip is heterogeneous and that middle cerebral artery flow can decrease in some subjects, in agreement with prior studies using the Kety-Schmidt technique. We speculate that the velocity increase is due to sympathetically mediated vasoconstriction rather than a ubiquitous flow increase. Our data suggest that the use of ordinary TCD velocities to interpret the CBF response during exercise may be invalid.
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Affiliation(s)
- C A Giller
- Department of Neurological Surgery and Radiology, University of Texas Southwestern Medical Center, Dallas 75235-8855, USA
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Pott F, van Lieshout JJ, Ide K, Madsen P, Secher NH. Middle cerebral artery blood velocity during a valsalva maneuver in the standing position. J Appl Physiol (1985) 2000; 88:1545-50. [PMID: 10797110 DOI: 10.1152/jappl.2000.88.5.1545] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Occasionally, lifting of a heavy weight leads to dizziness and even to fainting, suggesting that, especially in the standing position, expiratory straining compromises cerebral perfusion. In 10 subjects, the middle cerebral artery mean blood velocity (V(mean)) was evaluated during a Valsalva maneuver (mouth pressure 40 mmHg for 15 s) both in the supine and in the standing position. During standing, cardiac output decreased by 16 +/- 4 (SE) % (P < 0.05), and at the level of the brain mean arterial pressure (MAP) decreased from 89 +/- 2 to 78 +/- 3 mmHg (P < 0.05), as did V(mean) from 73 +/- 4 to 62 +/- 5 cm/s (P < 0.05). In both postures, the Valsalva maneuver increased central venous pressure by approximately 40 mmHg with a nadir in MAP and cardiac output that was most pronounced during standing (MAP: 65 +/- 6 vs. 87 +/- 3 mmHg; cardiac output: 37 +/- 3 vs. 57 +/- 4% of the resting value; P < 0.05). Also, V(mean) was lowest during the standing Valsalva maneuver (39 +/- 5 vs. 47 +/- 4 cm/s; P < 0.05). In healthy individuals, orthostasis induces an approximately 15% reduction in middle cerebral artery V(mean) that is exaggerated by a Valsalva maneuver performed with 40-mmHg mouth pressure to approximately 50% of supine rest.
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Affiliation(s)
- F Pott
- The Copenhagen Muscle Research Center, Rigshospitalet, University of Copenhagen, DK-2100 Copenhagen, Denmark.
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Ide K, Gulløv AL, Pott F, Van Lieshout JJ, Koefoed BG, Petersen P, Secher NH. Middle cerebral artery blood velocity during exercise in patients with atrial fibrillation. CLINICAL PHYSIOLOGY (OXFORD, ENGLAND) 1999; 19:284-9. [PMID: 10451787 DOI: 10.1046/j.1365-2281.1999.00178.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Atrial fibrillation limits the ability to increase cardiac output during exercise and may, in turn, affect the exercise-associated elevation in cerebral perfusion. In nine patients with atrial fibrillation (AF) and in five age-matched healthy subjects, middle cerebral artery blood velocity (MCA Vmean) was measured during incremental exercise using the transcranial Doppler. The AF patient group exhibited a lower aerobic capacity than the control group [peak work rate: 106 W (71-153 W; median and range) vs. 129 W (118-1.9 W) and maximal oxygen uptake: 1.4 l min-1 (1.0-1.9 l min-1) vs. 1.7 l min-1 (1.4-2.2 l min-1); P = 0.05]. At rest, MCA Vmean was not significantly different between the two groups [43 cm s-1 (39-56 cm s-1) vs. 52 cm s-1 (40-68 cm s-1)]. During intense cycling, the increase in MCA Vmean was to 51 cm s-1 (40-78 cm s-1) (9%) in the AF group and lower than in the healthy subjects [to 62 cm s-1 (50-81 cm s-1) 23%; P < 0.05], which corresponded with the smaller than expected increase in cardiac output [156% (130-169%) vs. 180%]. Thus, there was a correlation between the increase in MCA Vmean and the ability to increase cardiac output (r2 = 0.55, P < 0.01). We suggest that, during exercise with a large muscle mass, atrial fibrillation affects the ability to elevate cerebral perfusion, and this results from an impaired ability to increase cardiac output.
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Affiliation(s)
- K Ide
- Copenhagen Muscle Research Centre, Department of Anaesthesia, Rigshospitalet, University of Copenhagen, Denmark
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Roatta S, Micieli G, Bosone D, Losano G, Bini R, Cavallini A, Passatore M. Effect of generalised sympathetic activation by cold pressor test on cerebral haemodynamics in healthy humans. JOURNAL OF THE AUTONOMIC NERVOUS SYSTEM 1998; 71:159-66. [PMID: 9760052 DOI: 10.1016/s0165-1838(98)00075-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
There is no general agreement regarding several aspects of the role of the sympathetic system on cerebral haemodynamics such as extent of effectiveness, operational range and site of action. This study was planned to identify the effect of a generalised sympathetic activation on the cerebral haemodynamics in healthy humans before it is masked by secondary corrections, metabolic or myogenic in nature. A total of 35 healthy volunteers aged 20-35 underwent a 5 min lasting cold pressor test (CPT) performed on their left hand. The cerebral blood flow (CBF) velocity in the middle cerebral arteries and arterial blood pressure were recorded with transcranial Doppler sonography and with a non-invasive finger-cuff method, respectively. The ratio of arterial blood pressure to mean blood velocity (ABP/Vm) and Pulsatility Index (PI) were calculated throughout each trial. CPT induced an increase in mean ABP (range 2-54 mmHg depending on the subject) and only a slight, though significant, increase in blood velocity in the middle cerebral artery (+2.4 and +4.4% on ipsi- and contralateral side, respectively). During CPT, the ratio ABP/Vm increased and PI decreased in all subjects on both sides. These changes began simultaneously with the increase in blood pressure. The increase in ABP/Vm ratio is attributed to an increase in the cerebrovascular resistance, while the concomitant reduction in PI is interpreted as due to the reduction in the compliance of the middle cerebral artery. The results suggest that generalised increases in the sympathetic discharge, causing increases in ABP, can prevent concomitant increases in CBF by acting on both small resistance and large compliant vessels. This effect is also present when a slight increase in blood pressure occurs, which suggests a moderate increase in the sympathetic discharge, i.e. when ABP remains far below the upper limit of CBF autoregulation.
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Affiliation(s)
- S Roatta
- Department of Neuroscience, Centro Interuniversitario per la Neurofisiologia del Dolore, University of Torino Medical School, Italy
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46
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Ide K, Pott F, Van Lieshout JJ, Secher NH. Middle cerebral artery blood velocity depends on cardiac output during exercise with a large muscle mass. ACTA PHYSIOLOGICA SCANDINAVICA 1998; 162:13-20. [PMID: 9492897 DOI: 10.1046/j.1365-201x.1998.0280f.x] [Citation(s) in RCA: 120] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
We tested the hypothesis that pharmacological reduction of the increase in cardiac output during dynamic exercise with a large muscle mass would influence the cerebral blood velocity/perfusion. We studied the relationship between changes in cerebral blood velocity (transcranial Doppler), rectus femoris blood oxygenation (near-infrared spectroscopy) and systemic blood flow (cardiac output from model flow analysis of the arterial pressure wave) as induced by dynamic exercise of large (cycling) vs. small muscle groups (rhythmic handgrip) before and after cardioselective beta 1 adrenergic blockade (0.15 mg kg-1 metoprolol i.v.). During rhythmic handgrip, the increments in systemic haemodynamic variables as in middle cerebral artery mean blood velocity were not influenced significantly by metoprolol. In contrast, during cycling (e.g. 113 W), metoprolol reduced the increase in cardiac output (222 +/- 13 vs. 260 +/- 16%), heart rate (114 +/- 3 vs. 135 +/- 7 beats min-1) and mean arterial pressure (103 +/- 3 vs. 112 +/- 4 mmHg), and the increase in cerebral artery mean blood velocity also became lower (from 59 +/- 3 to 66 +/- 3 vs. 60 +/- 2 to 72 +/- 3 cm s-1; P < 0.05). Likewise, during cycling with metoprolol, oxyhaemoglobin in the rectus femoris muscle became reduced (compared to rest: -4.8 +/- 1.8 vs. 1.2 +/- 1.7 mumol L-1, P < 0.05). Neither during rhythmic handgrip nor during cycling was the arterial carbon dioxide tension affected significantly by metoprolol. The results suggest that as for the muscle blood flow, the cerebral circulation is also affected by a reduced cardiac output during exercise with a large muscle mass.
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Affiliation(s)
- K Ide
- Copenhagen Muscle Research Centre, Department of Anaesthesia, Rigshospitalet, University of Copenhagen, Denmark
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