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Shigehiko Ogoh - One of the best experts on this subject based on the ideXlab platform.
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skin blood flow influences cerebral oxygenation measured by near infrared spectroscopy during Dynamic Exercise
European Journal of Applied Physiology, 2013Co-Authors: Taiki Miyazawa, Masahiro Horiuchi, Hidehiko Komine, Jun Sugawara, Paul J Fadel, Shigehiko OgohAbstract:Purpose Near-infrared spectroscopy (NIRS) is widely used to investigate cerebral oxygenation and/or neural activation during physiological conditions such as Exercise. However, NIRS-determined cerebral oxygenated hemoglobin (O2Hb) may not necessarily correspond to intracranial blood flow during Dynamic Exercise. To determine the selectivity of NIRS to assess cerebral oxygenation and neural activation during Exercise, we examined the influence of changes in forehead skin blood flow (SkBFhead) on NIRS signals during Dynamic Exercise.
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skin blood flow influences cerebral oxygenation measured by near infrared spectroscopy during Dynamic Exercise
European Journal of Applied Physiology, 2013Co-Authors: Taiki Miyazawa, Masahiro Horiuchi, Hidehiko Komine, Jun Sugawara, Paul J Fadel, Shigehiko OgohAbstract:Near-infrared spectroscopy (NIRS) is widely used to investigate cerebral oxygenation and/or neural activation during physiological conditions such as Exercise. However, NIRS-determined cerebral oxygenated hemoglobin (O2Hb) may not necessarily correspond to intracranial blood flow during Dynamic Exercise. To determine the selectivity of NIRS to assess cerebral oxygenation and neural activation during Exercise, we examined the influence of changes in forehead skin blood flow (SkBFhead) on NIRS signals during Dynamic Exercise. In ten healthy men (age: 20 ± 1 years), middle cerebral artery blood flow velocity (MCA V mean, via transcranial Doppler ultrasonography), SkBFhead (via laser Doppler flowmetry), and cerebral O2Hb (via NIRS) were continuously measured. Each subject performed 60 % maximum heart rate moderate-intensity steady-state cycling Exercise. To manipulate SkBFhead, facial cooling using a mist of cold water (~4 °C) was applied for 3 min during steady-state cycling. MCA V mean significantly increased during Exercise and remained unchanged with facial cooling. O2Hb and SkBFhead were also significantly increased during Exercise; however, both of these signals were lowered with facial cooling and returned to pre-cooling values with the removal of facial cooling. The changes in O2Hb correlated significantly with the relative percent changes in SkBFhead in each individual (r = 0.71–0.99). These findings suggest that during Dynamic Exercise NIRS-derived O2Hb signal can be influenced by thermoregulatory changes in SkBFhead and therefore, may not be completely reflective of cerebral oxygenation or neural activation.
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the distribution of blood flow in the carotid and vertebral arteries during Dynamic Exercise in humans
The Journal of Physiology, 2011Co-Authors: Kohei Sato, Shigehiko Ogoh, Ai Hirasawa, Anna Oue, Tomoko SadamotoAbstract:The mechanism underlying the plateau or relative decrease in cerebral blood flow (CBF) during maximal incremental Dynamic Exercise remains unclear. We hypothesized that cerebral perfusion is limited during high-intensity Dynamic Exercise due to a redistribution of carotid artery blood flow. To identify the distribution of blood flow among the arteries supplying the head and brain, we evaluated common carotid artery (CCA), internal carotid artery (ICA), external carotid artery (ECA) and vertebral artery (VA) blood flow during Dynamic Exercise using Doppler ultrasound. Ten subjects performed graded cycling Exercise in a semi-supine position at 40, 60 and 80% of peak oxygen uptake (VO2 peak) for 5 min at each workload. The ICA blood flow increased by 23.0 ± 4.6% (mean ± SE) from rest to Exercise at 60% (VO2 peak). However, at 80% (VO2 peak), ICA blood flow returned towards near resting levels (9.6 ± 4.7% vs. rest). In contrast, ECA, CCA and VA blood flow increased proportionally with workload. The change in ICA blood flow during graded Exercise was correlated with end-tidal partial pressure of CO2 (r = 0.72). The change in ICA blood flow from 60% (VO2 peak) to 80% (VO2 peak) was negatively correlated with the change in ECA blood flow (r = −0.77). Moreover, there was a significant correlation between forehead cutaneous vascular conductance and ECA blood flow during Exercise (r = 0.79). These results suggest that during high-intensity Dynamic Exercise the plateau or decrease in ICA blood flow is partly due to a large increase in ECA blood flow, which is selectively increased to prioritize thermoregulation.
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middle cerebral artery flow velocity and pulse pressure during Dynamic Exercise in humans
American Journal of Physiology-heart and Circulatory Physiology, 2005Co-Authors: Shigehiko Ogoh, Paul J Fadel, Rong Zhang, Christian Selmer, Oivind Jans, Niels H Secher, Peter B RavenAbstract:Exercise challenges cerebral autoregulation (CA) by a large increase in pulse pressure (PP) that may make systolic pressure exceed what is normally considered the upper range of CA. This study exam...
Jens Bangsbo - One of the best experts on this subject based on the ideXlab platform.
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the effect of blood flow restricted interval training on lactate and h Dynamics during Dynamic Exercise in man
Acta Physiologica, 2021Co-Authors: Danny Christiansen, Kasper Eibye, Morten Hostrup, Jens BangsboAbstract:AIM To assess how blood-flow-restricted (BFR) interval-training affects the capacity of the leg muscles for pH regulation during Dynamic Exercise in physically trained men. METHODS Ten men (age: 25 ± 4y; V˙O2max : 50 ± 5 mL∙kg-1 ∙min-1 ) completed a 6-wk interval-cycling intervention (INT) with one leg under BFR (BFR-leg; ~180 mmHg) and the other without BFR (CON-leg). Before and after INT, thigh net H+ -release (lactate-dependent, lactate-independent and sum) and blood acid/base variables were measured during knee-extensor Exercise at 25% (Ex25) and 90% (Ex90) of incremental peak power output. A muscle biopsy was collected before and after Ex90 to determine pH, lactate and density of H+ -transport/buffering systems. RESULTS After INT, net H+ release (BFR-leg: 15 ± 2; CON-leg: 13 ± 3; mmol·min-1 ; Mean ± 95% CI), net lactate-independent H+ release (BFR-leg: 8 ± 1; CON-leg: 4 ± 1; mmol·min-1 ) and net lactate-dependent H+ release (BFR-leg: 9 ± 3; CON-leg: 10 ± 3; mmol·min-1 ) were similar between legs during Ex90 (P > .05), despite a ~142% lower muscle intracellular-to-interstitial lactate gradient in BFR-leg (-3 ± 4 vs 6 ± 6 mmol·L-1 ; P .05; BFR-leg: 48 ± 30; CON-leg: 44 ± 23; mmol·L-1 ). In BFR-leg, NHE1 density was higher than in CON-leg (~45%; P < .05) and correlated with total-net H+ -release (r = 0.71; P = .031) and lactate-independent H+ release (r = 0.74; P = .023) after INT, where arterial [ HCO3- ] and standard base excess in Ex25 were higher in BFR-leg than CON-leg. CONCLUSION Compared to a training control, BFR-interval training increases the capacity for pH regulation during Dynamic Exercise mainly via enhancement of muscle lactate-dependent H+ -transport function and blood H+ -buffering capacity.
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intense interval training enhances human skeletal muscle oxygen uptake in the initial phase of Dynamic Exercise at high but not at low intensities
The Journal of Physiology, 2004Co-Authors: Peter Krustrup, Ylva Hellsten, Jens BangsboAbstract:The present study tested the hypothesis that intense interval training enhances human skeletal muscle blood flow and oxygen uptake (VO2) at the onset of Dynamic Exercise. We also investigated whether possible training effects were dependent on Exercise intensity. Six habitually active males carried out 7 weeks of intermittent-Exercise one-legged knee-extensor training at an intensity corresponding to approximately 150% of peak thigh VO2 on three to five occasions per week. After the training period, cardiovascular and metabolic measurements were performed during knee-extensor Exercise with the trained leg (TL) and the control leg (CL) for 10 min at intensities of 10 and 30 W, and also for 4 min at 50 W. Femoral venous blood flow was higher (P < 0.05) in TL than CL from 75 to 180 s at 30 W ( approximately 75 s: 3.43 +/- 0.20 versus 2.99 +/- 0.18 l min(-1)) and from 40 to 210 s at 50 W ( approximately 75 s: 5.03 +/- 0.41 versus 4.13 +/- 0.33 l min(-1)). Mean arterial pressure was not different between legs. Thus, thigh vascular conductance was higher (P < 0.05) in TL than CL from 35 to 270 s at 30 W and from 150 to 240 s at 50 W. Femoral arterial-venous (a-v) O2 difference was higher (P < 0.05) in TL than CL from 20 to 70 s at 30 W, but not different between TL and CL at 50 W. Thigh VO2 was higher (P < 0.05) in TL than CL from 20 to 110 s at 30 W ( approximately 45 s: 0.38 +/- 0.04 versus 0.30 +/- 0.03 l min(-1)), and from 45 to 240 s at 50 W ( approximately 45 s: 0.64 +/- 0.06 versus 0.44 +/- 0.08 l min(-1)). No differences were observed between TL and CL during Exercise at 10 W. The present data demonstrate that intense interval training elevates muscle oxygen uptake, blood flow and vascular conductance in the initial phase of Exercise at high, but not at low, intensities.
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intense interval training enhances human skeletal muscle oxygen uptake in the initial phase of Dynamic Exercise at high but not at low intensities
The Journal of Physiology, 2004Co-Authors: Peter Krustrup, Ylva Hellsten, Jens BangsboAbstract:Krogh & Lindhard (1913) observed in a pioneering work that pulmonary oxygen (O2) uptake in the transition from rest to constant cycle Exercise ‘does not rise instantaneously though certainly very rapidly to a level corresponding to the amount of work performed’. Since then, the transient lag in O2 uptake and the temporal pattern of O2 uptake has been studied extensively by the use of pulmonary measurements (see Tschakovsky & Hughson, 1999). These studies have established that training status, Exercise intensity and previous intense Exercise all affect O2 uptake at the onset of Dynamic Exercise (Hagberg et al. 1978; Cerretelli et al. 1979; Phillips et al. 1995; Engelen et al. 1996; MacDonald et al. 1997; McKenna et al. 1997; Carter et al. 2002). Cross-sectional and longitudinal studies have shown that O2 uptake kinetics is faster for endurance-trained than untrained subjects during submaximal running and cycle Exercise (Hagberg et al. 1978; Hickson et al. 1978; Cerretelli et al. 1979; Overend et al. 1992; Phillips et al. 1995; Womack et al. 1995). Moreover, McKenna et al. (1997) observed that the pulmonary oxygen uptake during maximal 30 s cycle Exercise was higher after a period of intense intermittent training. However, it is uncertain to what extent these findings are applicable to the exercising muscles, since pulmonary measurements represent an integrated response of the whole body. Little knowledge has been obtained about training effects on transient O2 uptake at the muscular level. Shoemaker et al. (1996) showed that a short period of endurance training resulted in a faster femoral artery blood velocity at the onset of knee-extensor Exercise, but thigh arterial–venous (a-v) O2 difference was not determined. Over the last decade techniques have been developed to determine transient muscle O2 uptake, i.e. frequent measurements of muscle blood flow, arterio-venous O2 difference and assessment of transient time delays from the capillaries to the sampling sites (Grassi et al. 1996; Hughson et al. 1996; Bangsbo et al. 2001; Krustrup et al. 2001, 2003). A combined use of these techniques makes it is possible to examine the effect of Exercise training on transient O2 uptake at the muscular level. Furthermore, such measurements can elucidate whether any training-induced changes in muscle O2 uptake are caused by alterations in vascular resistance, blood perfusion and/or O2 extraction. Several studies have shown that pulmonary O2 uptake kinetics is slower at high compared to low Exercise intensities (Hagberg et al. 1978; Paterson & Whipp, 1991; Engelen et al. 1996; Carter et al. 2002). This finding may be explained by a gradually elevated fast-twitch (FT) fibre recruitment with increasing intensities (Gollnick et al. 1974; Vollestad & Blom, 1985; Krustrup et al. 2004), as in vitro studies and cross-sectional in vivo studies have provided evidence that O2 uptake kinetics are slower in FT than in slow-twitch (ST) fibres (Crow & Kushmerick, 1982; Barstow et al. 1996). Nevertheless, other studies report no differences in the time constants of the rapid phase of O2 uptake between Exercise intensities (Barstow & Mole, 1991; Ozyener et al. 2001; Rossiter et al. 2002) and it may be speculated that fibre type-specific differences in O2 uptake kinetics are related to training status. It is well known that muscular adaptations to training are dependent on the Exercise regime with continuous endurance training improving oxidative enzyme activity mainly in ST fibres and intense intermittent training predominantly affecting FT fibres (Saltin et al. 1976; Henriksson & Reitman, 1976). However, it has yet to be elucidated whether intense intermittent training specifically enhances muscular O2 uptake at Exercise intensities sufficiently high to involve FT fibre recruitment. Thus, the aim of the present study was to investigate the effect of intense interval one-legged knee-extensor training on muscle O2 uptake and cardiovascular response at the onset of low, moderate and high intensity submaximal Exercise.
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atp and heat production in human skeletal muscle during Dynamic Exercise higher efficiency of anaerobic than aerobic atp resynthesis
The Journal of Physiology, 2003Co-Authors: Peter Krustrup, Richard A Ferguson, Michael Kjaer, Jens BangsboAbstract:The aim of the present study was to simultaneously examine skeletal muscle heat production and ATP turnover in humans during Dynamic Exercise with marked differences in aerobic metabolism. This was done to test the hypothesis that efficiency is higher in anaerobic than aerobic ATP resynthesis. Six healthy male subjects performed 90 s of low intensity knee-extensor Exercise with (OCC) and without thigh occlusion (CON-LI) as well as 90 s of high intensity Exercise (CON-HI) that continued from the CON-LI bout. Muscle heat production was determined by continuous measurements of muscle heat accumulation and heat release to the blood. Muscle ATP production was quantified by repeated measurements of thigh oxygen uptake as well as blood and muscle metabolite changes. All temperatures of the thigh were equalized to ≈37 °C prior to Exercise by a water-perfused heating cuff. Oxygen uptake accounted for 80 ± 2 and 59 ± 4 %, respectively, of the total ATP resynthesis in CON-LI and CON-HI, whereas it was negligible in OCC. The rise in muscle temperature was lower (P < 0.05) in OCC than CON-LI (0.32 ± 0.04 vs. 0.37 ± 0.03 °C). The mean rate of heat production was also lower (P < 0.05) in OCC than CON-LI (36 ± 4 vs. 57 ± 4 J s−1). Mechanical efficiency was 52 ± 4 % after 15 s of OCC and remained constant, whereas it decreased (P < 0.05) from 56 ± 5 to 32 ± 3 % during CON-LI. During CON-HI, mechanical efficiency transiently increased (P < 0.05) to 47 ± 4 %, after which it decreased (P < 0.05) to 36 ± 3 % at the end of CON-HI. Assuming a fully coupled mitochondrial respiration, the ATP turnover per unit of work was calculated to be unaltered during OCC (≈20 mmol ATP kJ−1), whereas it increased (P < 0.05) from 21 ± 4 to 29 ± 3 mmol ATP kJ−1 during CON-LI and further (P < 0.05) to 37 ± 3 mmol ATP kJ−1 during CON-HI. The present data confirm the hypothesis that heat loss is lower in anaerobic ATP resynthesis than in oxidative phosphorylation and can in part explain the finding that efficiency declines markedly during Dynamic Exercise. In addition, the rate of ATP turnover apparently increases during constant load low intensity Exercise. Alternatively, mitochondrial efficiency is lowered as Exercise progresses, since ATP turnover was unaltered during the ischaemic Exercise bout.
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muscle heat production and anaerobic energy turnover during repeated intense Dynamic Exercise in humans
The Journal of Physiology, 2001Co-Authors: Peter Krustrup, Jose Gonzalezalonso, Bjorn Quistorff, Jens BangsboAbstract:1. The aim of the present study was to examine muscle heat production, oxygen uptake and anaerobic energy turnover throughout repeated intense Exercise to test the hypotheses that (i) energy turnover is reduced when intense Exercise is repeated and (ii) anaerobic energy production is diminished throughout repeated intense Exercise. 2. Five subjects performed three 3 min intense one-legged knee-extensor Exercise bouts (EX1, EX2 and EX3) at a power output of 65 +/- 5 W (mean +/- S.E.M.), separated by 6 min rest periods. Muscle, femoral arterial and venous temperatures were measured continuously during Exercise for the determination of muscle heat production. In addition, thigh blood flow was measured and femoral arterial and venous blood were sampled frequently during Exercise for the determination of muscle oxygen uptake. Anaerobic energy turnover was estimated as the difference between total energy turnover and aerobic energy turnover. 3. Prior to Exercise, the temperature of the quadriceps muscle was passively elevated to 37.02 +/- 0.12 degrees C and it increased 0.97 +/- 0.08 degrees C during EX1, which was higher (P < 0.05) than during EX2 (0.79 +/- 0.05 degrees C) and EX3 (0.77 +/- 0.06 degrees C). In EX1 the rate of muscle heat accumulation was higher (P < 0.05) during the first 120 s compared to EX2 and EX3, whereas the rate of heat release to the blood was greater (P < 0.05) throughout EX2 and EX3 compared to EX1. The rate of heat production, determined as the sum of heat accumulation and release, was the same in EX1, EX2 and EX3, and it increased (P < 0.05) from 86 +/- 8 during the first 15 s to 157 +/- 7 J s(-1) during the last 15 s of EX1. 4. Oxygen extraction was higher during the first 60 s of EX2 and EX3 than in EX 1 and thigh oxygen uptake was elevated (P < 0.05) during the first 120 s of EX2 and throughout EX3 compared to EX1. The anaerobic energy production during the first 105 s of EX2 and 150 s of EX3 was lower (P < 0.05) than in EX1. 5. The present study demonstrates that when intense Exercise is repeated muscle heat production is not changed, but muscle aerobic energy turnover is elevated and anaerobic energy production is reduced during the first minutes of Exercise.
Donal S Oleary - One of the best experts on this subject based on the ideXlab platform.
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neural control of circulation and Exercise a translational approach disclosing interactions between central command arterial baroreflex and muscle metaboreflex
American Journal of Physiology-heart and Circulatory Physiology, 2015Co-Authors: Lisete Compagno Michelini, Donal S Oleary, Peter B Raven, Antonio Claudio Lucas Da NobregaAbstract:The last 100 years witnessed a rapid and progressive development of the body of knowledge concerning the neural control of the cardiovascular system in health and disease. The understanding of the complexity and the relevance of the neuroregulatory system continues to evolve and as a result raises new questions. The purpose of this review is to articulate results from studies involving experimental models in animals as well as in humans concerning the interaction between the neural mechanisms mediating the hemoDynamic responses during Exercise. The review describes the arterial baroreflex, the pivotal mechanism controlling mean arterial blood pressure and its fluctuations along with the two main activation mechanisms to Exercise: central command (parallel activation of central somatomotor and autonomic descending pathways) and the muscle metaboreflex, the metabolic component of Exercise pressor reflex (feedback from ergoreceptors within contracting skeletal muscles). In addition, the role of the cardiopulmonary baroreceptors in modulating the resetting of arterial baroreflex is identified, and the mechanisms in the central nervous system involved with the resetting of baroreflex function during Dynamic Exercise are also described. Approaching a very relevant clinical condition, the review also presents the concept that the impaired arterial baroreflex function is an integral component of the metaboreflex-mediated exaggerated sympathetic tone in subjects with heart failure. This increased sympathetic activity has a major role in causing the depressed ventricular function observed during submaximal Dynamic Exercise in these patients. The potential contribution of a metaboreflex arising from respiratory muscles is also considered.
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neural regulation of cardiovascular response to Exercise role of central command and peripheral afferents
BioMed Research International, 2014Co-Authors: Antonio Claudio Lucas Da Nobrega, Donal S Oleary, Bruno M Silva, Elisabetta Marongiu, Massimo F Piepoli, Antonio CrisafulliAbstract:During Dynamic Exercise, mechanisms controlling the cardiovascular apparatus operate to provide adequate oxygen to fulfill metabolic demand of exercising muscles and to guarantee metabolic end-products washout. Moreover, arterial blood pressure is regulated to maintain adequate perfusion of the vital organs without excessive pressure variations. The autonomic nervous system adjustments are characterized by a parasympathetic withdrawal and a sympathetic activation. In this review, we briefly summarize neural reflexes operating during Dynamic Exercise. The main focus of the present review will be on the central command, the arterial baroreflex and chemoreflex, and the Exercise pressure reflex. The regulation and integration of these reflexes operating during Dynamic Exercise and their possible role in the pathophysiology of some cardiovascular diseases are also discussed.
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muscle metaboreflex induced coronary vasoconstriction limits ventricular contractility during Dynamic Exercise in heart failure
American Journal of Physiology-heart and Circulatory Physiology, 2013Co-Authors: Matthew Coutsos, Masashi Ichinose, Javier A Salamercado, Elizabeth J Dawe, Zhenhua Li, Donal S OlearyAbstract:Muscle metaboreflex activation (MMA) during Dynamic Exercise increases cardiac work and myocardial O2 demand via increases in heart rate, ventricular contractility, and afterload. This increase in cardiac work should lead to metabolic coronary vasodilation; however, no change in coronary vascular conductance occurs. This indicates that the MMA-induced increase in sympathetic activity to the heart, which raises heart rate, ventricular contractility, and cardiac output, also elicits coronary vasoconstriction. In heart failure, cardiac output does not increase with MMA presumably due to impaired ability to improve left ventricular contractility. In this setting actual coronary vasoconstriction is observed. We tested whether this coronary vasoconstriction could explain, in part, the reduced ability to increase cardiac performance during MMA. In conscious, chronically instrumented dogs before and after pacing-induced heart failure, MMA responses during mild Exercise were observed before and after α1-adrenergic blockade (prazosin 20–50 μg/kg). During MMA, the increases in coronary vascular conductance, coronary blood flow, maximal rate of left ventricular pressure change, and cardiac output were significantly greater after α1-adrenergic blockade. We conclude that in subjects with heart failure, coronary vasoconstriction during MMA limits the ability to increase left ventricular contractility.
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integration of cardiovascular control systems in Dynamic Exercise
Comprehensive Physiology, 2011Co-Authors: L B Rowell, Donal S Oleary, Dean L KelloggAbstract:The sections in this article are: 1 I. Intrinsic Properties of the Cardiovascular System: How They Permit the Rise in Cardiac Output 2 The Heart 2.1 Intrinsic Properties of the Heart 2.2 Pericardial Constraints 3 The Vascular System 3.1 Distribution of Resistance, Conductance, and Compliance 3.2 Dependency of CVP on Cardiac Output 3.3 Mechanical Effects on the Circulation—Auxiliary Pumps 3.4 Does Exercise Reduce Systemic Vascular Compliance? 3.5 Neural Control of the Vascular System during Exercise: How Important? 3.6 Balance between Mechanical and Neural Effects on Blood Flow and Blood Volume Distribution 4 II. Reflex Control of the Cardiovascular System During Dynamic Exercise: What Variables are Sensed and then Regulated by the Autonomic Nervous System During Dynamic Exercise? 4.1 Central Command 4.2 Reflexes from Active Muscles 5 Isometric Contractions: Testing Hypotheses 5.1 Isometric Contractions vs. Dynamic Exercise 5.2 Open-Loop vs. Closed-Loop Conditions 5.3 Does the Pressor Response to Voluntary Isometric Contraction have Chemoreflex or Mechanoreflex Origin? 6 Functional Importance of Muscle Chemoreflexes During Dynamic Exercise 6.1 Basic Concepts and Theory 6.2 Changes in MSNA as Evidence for Chemoreflex Activity in Dynamic Exercise 6.3 Does the Muscle Chemoreflex Initiate Increased SNA during Dynamic Exercise with Unimpaired Flow? 6.4 Does Activation of the Muscle Chemoreflex Correct Blood Flow Errors, and if so, How? 7 Baroreflex Regulation of Arterial Pressure (SAP) and Vascular Conductance in Dynamic Exercise 7.1 Does the Arterial Baroreflex Control SAP During Exercise? 7.2 Characterization and Analysis of Arterial Baroreflex Function 7.3 Baroreflex Sensitivity in Dynamic Exercise 7.4 Importance of Arterial Baroreflexes at the Onset of Exercise 7.5 Evidence Indicating “Resetting” of the Arterial Baroreflex 7.6 Central Command and Resetting of the Arterial Baroreflex—An Hypothesis 8 Role of Cardiopulmonary Baroreceptors in Dynamic Exercise 8.1 The Cardiopulmonary, or Low-Pressure, Baroreflex 8.2 Interaction between the Cardiopulmonary and Arterial Baroreflexes at Rest 8.3 Role of Cardiopulmonary Baroreflex during Dynamic Exercise 8.4 Interaction between Cardiopulmonary Baroreflex and Muscle Chemoreflex 8.5 Interaction between Cardiopulmonary and Arterial Baroreflexes in Exercise 8.6 Importance of Cardiopulmonary Baroreflexes during Dynamic Exercise 9 Control of the Circulation During Exercise and Heat Stress: Competing Reflexes 9.1 Cardiovascular Demands of Heat Stress 9.2 Overall Neural Control of the Cutaneous Circulation 9.3 Reflex Control of the Cutaneous Circulation during Exercise 9.4 Baroreflex v. Thermoregulatory Reflex Control of the Cutaneous Circulation during Exercise 10 How Does Physical Conditioning Alter Cardiovascular Function? 10.1 Range of Adjustment in Overall Cardiovascular Function 10.2 What Cardiovascular Adjustments Explain the Rise in ? 10.3 How does Maximal SV Increase with Physical Conditioning? 10.4 Does Physical Conditioning Change Autonomic Control of the Circulation? 11 Synthesis 11.1 What is the Autonomic Nervous System Controlling during Exercise? 11.2 What Errors Are Sensed and then Corrected by the Autonomic Nervous System during Exercise?
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modulation of cardiac output alters the mechanisms of the muscle metaboreflex pressor response
American Journal of Physiology-heart and Circulatory Physiology, 2010Co-Authors: Masashi Ichinose, Javier A Salamercado, Matthew Coutsos, Tomoko Ichinose, Elizabeth J Dawe, Donal S OlearyAbstract:Muscle metaboreflex activation during submaximal Dynamic Exercise in normal subjects elicits a pressor response primarily due to increased cardiac output (CO). However, when the ability to increase CO is limited, such as in heart failure or during maximal Exercise, the muscle metaboreflex-induced increases in arterial pressure occur via peripheral vasoconstriction. How the mechanisms of this pressor response are altered is unknown. We tested the hypothesis that this change in metaboreflex function is dependent on the level of CO. The muscle metaboreflex was activated in dogs during mild Dynamic Exercise (3.2 km/h) via a partial reduction of hindlimb blood flow. Muscle metaboreflex activation increased CO and arterial pressure, whereas vascular conductance of all areas other than the hindlimbs did not change. CO was then reduced to the same level observed during Exercise before the muscle metaboreflex activation via partial occlusion of the inferior and superior vena cavae. Arterial pressure dropped rapidly with the reduction in CO but, subsequently, nearly completely recovered. With the removal of the muscle metaboreflex-induced rise in CO, substantial peripheral vasoconstriction occurred that maintained arterial pressure at the same levels as before CO reduction. Therefore, the muscle metaboreflex function is nearly instantaneously shifted from increased CO to increased vasoconstriction when the muscle metaboreflex-induced rise in CO is removed. We conclude that whether vasoconstriction occurs with muscle metaboreflex depends on whether CO rises.
Peter Krustrup - One of the best experts on this subject based on the ideXlab platform.
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intense interval training enhances human skeletal muscle oxygen uptake in the initial phase of Dynamic Exercise at high but not at low intensities
The Journal of Physiology, 2004Co-Authors: Peter Krustrup, Ylva Hellsten, Jens BangsboAbstract:The present study tested the hypothesis that intense interval training enhances human skeletal muscle blood flow and oxygen uptake (VO2) at the onset of Dynamic Exercise. We also investigated whether possible training effects were dependent on Exercise intensity. Six habitually active males carried out 7 weeks of intermittent-Exercise one-legged knee-extensor training at an intensity corresponding to approximately 150% of peak thigh VO2 on three to five occasions per week. After the training period, cardiovascular and metabolic measurements were performed during knee-extensor Exercise with the trained leg (TL) and the control leg (CL) for 10 min at intensities of 10 and 30 W, and also for 4 min at 50 W. Femoral venous blood flow was higher (P < 0.05) in TL than CL from 75 to 180 s at 30 W ( approximately 75 s: 3.43 +/- 0.20 versus 2.99 +/- 0.18 l min(-1)) and from 40 to 210 s at 50 W ( approximately 75 s: 5.03 +/- 0.41 versus 4.13 +/- 0.33 l min(-1)). Mean arterial pressure was not different between legs. Thus, thigh vascular conductance was higher (P < 0.05) in TL than CL from 35 to 270 s at 30 W and from 150 to 240 s at 50 W. Femoral arterial-venous (a-v) O2 difference was higher (P < 0.05) in TL than CL from 20 to 70 s at 30 W, but not different between TL and CL at 50 W. Thigh VO2 was higher (P < 0.05) in TL than CL from 20 to 110 s at 30 W ( approximately 45 s: 0.38 +/- 0.04 versus 0.30 +/- 0.03 l min(-1)), and from 45 to 240 s at 50 W ( approximately 45 s: 0.64 +/- 0.06 versus 0.44 +/- 0.08 l min(-1)). No differences were observed between TL and CL during Exercise at 10 W. The present data demonstrate that intense interval training elevates muscle oxygen uptake, blood flow and vascular conductance in the initial phase of Exercise at high, but not at low, intensities.
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intense interval training enhances human skeletal muscle oxygen uptake in the initial phase of Dynamic Exercise at high but not at low intensities
The Journal of Physiology, 2004Co-Authors: Peter Krustrup, Ylva Hellsten, Jens BangsboAbstract:Krogh & Lindhard (1913) observed in a pioneering work that pulmonary oxygen (O2) uptake in the transition from rest to constant cycle Exercise ‘does not rise instantaneously though certainly very rapidly to a level corresponding to the amount of work performed’. Since then, the transient lag in O2 uptake and the temporal pattern of O2 uptake has been studied extensively by the use of pulmonary measurements (see Tschakovsky & Hughson, 1999). These studies have established that training status, Exercise intensity and previous intense Exercise all affect O2 uptake at the onset of Dynamic Exercise (Hagberg et al. 1978; Cerretelli et al. 1979; Phillips et al. 1995; Engelen et al. 1996; MacDonald et al. 1997; McKenna et al. 1997; Carter et al. 2002). Cross-sectional and longitudinal studies have shown that O2 uptake kinetics is faster for endurance-trained than untrained subjects during submaximal running and cycle Exercise (Hagberg et al. 1978; Hickson et al. 1978; Cerretelli et al. 1979; Overend et al. 1992; Phillips et al. 1995; Womack et al. 1995). Moreover, McKenna et al. (1997) observed that the pulmonary oxygen uptake during maximal 30 s cycle Exercise was higher after a period of intense intermittent training. However, it is uncertain to what extent these findings are applicable to the exercising muscles, since pulmonary measurements represent an integrated response of the whole body. Little knowledge has been obtained about training effects on transient O2 uptake at the muscular level. Shoemaker et al. (1996) showed that a short period of endurance training resulted in a faster femoral artery blood velocity at the onset of knee-extensor Exercise, but thigh arterial–venous (a-v) O2 difference was not determined. Over the last decade techniques have been developed to determine transient muscle O2 uptake, i.e. frequent measurements of muscle blood flow, arterio-venous O2 difference and assessment of transient time delays from the capillaries to the sampling sites (Grassi et al. 1996; Hughson et al. 1996; Bangsbo et al. 2001; Krustrup et al. 2001, 2003). A combined use of these techniques makes it is possible to examine the effect of Exercise training on transient O2 uptake at the muscular level. Furthermore, such measurements can elucidate whether any training-induced changes in muscle O2 uptake are caused by alterations in vascular resistance, blood perfusion and/or O2 extraction. Several studies have shown that pulmonary O2 uptake kinetics is slower at high compared to low Exercise intensities (Hagberg et al. 1978; Paterson & Whipp, 1991; Engelen et al. 1996; Carter et al. 2002). This finding may be explained by a gradually elevated fast-twitch (FT) fibre recruitment with increasing intensities (Gollnick et al. 1974; Vollestad & Blom, 1985; Krustrup et al. 2004), as in vitro studies and cross-sectional in vivo studies have provided evidence that O2 uptake kinetics are slower in FT than in slow-twitch (ST) fibres (Crow & Kushmerick, 1982; Barstow et al. 1996). Nevertheless, other studies report no differences in the time constants of the rapid phase of O2 uptake between Exercise intensities (Barstow & Mole, 1991; Ozyener et al. 2001; Rossiter et al. 2002) and it may be speculated that fibre type-specific differences in O2 uptake kinetics are related to training status. It is well known that muscular adaptations to training are dependent on the Exercise regime with continuous endurance training improving oxidative enzyme activity mainly in ST fibres and intense intermittent training predominantly affecting FT fibres (Saltin et al. 1976; Henriksson & Reitman, 1976). However, it has yet to be elucidated whether intense intermittent training specifically enhances muscular O2 uptake at Exercise intensities sufficiently high to involve FT fibre recruitment. Thus, the aim of the present study was to investigate the effect of intense interval one-legged knee-extensor training on muscle O2 uptake and cardiovascular response at the onset of low, moderate and high intensity submaximal Exercise.
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atp and heat production in human skeletal muscle during Dynamic Exercise higher efficiency of anaerobic than aerobic atp resynthesis
The Journal of Physiology, 2003Co-Authors: Peter Krustrup, Richard A Ferguson, Michael Kjaer, Jens BangsboAbstract:The aim of the present study was to simultaneously examine skeletal muscle heat production and ATP turnover in humans during Dynamic Exercise with marked differences in aerobic metabolism. This was done to test the hypothesis that efficiency is higher in anaerobic than aerobic ATP resynthesis. Six healthy male subjects performed 90 s of low intensity knee-extensor Exercise with (OCC) and without thigh occlusion (CON-LI) as well as 90 s of high intensity Exercise (CON-HI) that continued from the CON-LI bout. Muscle heat production was determined by continuous measurements of muscle heat accumulation and heat release to the blood. Muscle ATP production was quantified by repeated measurements of thigh oxygen uptake as well as blood and muscle metabolite changes. All temperatures of the thigh were equalized to ≈37 °C prior to Exercise by a water-perfused heating cuff. Oxygen uptake accounted for 80 ± 2 and 59 ± 4 %, respectively, of the total ATP resynthesis in CON-LI and CON-HI, whereas it was negligible in OCC. The rise in muscle temperature was lower (P < 0.05) in OCC than CON-LI (0.32 ± 0.04 vs. 0.37 ± 0.03 °C). The mean rate of heat production was also lower (P < 0.05) in OCC than CON-LI (36 ± 4 vs. 57 ± 4 J s−1). Mechanical efficiency was 52 ± 4 % after 15 s of OCC and remained constant, whereas it decreased (P < 0.05) from 56 ± 5 to 32 ± 3 % during CON-LI. During CON-HI, mechanical efficiency transiently increased (P < 0.05) to 47 ± 4 %, after which it decreased (P < 0.05) to 36 ± 3 % at the end of CON-HI. Assuming a fully coupled mitochondrial respiration, the ATP turnover per unit of work was calculated to be unaltered during OCC (≈20 mmol ATP kJ−1), whereas it increased (P < 0.05) from 21 ± 4 to 29 ± 3 mmol ATP kJ−1 during CON-LI and further (P < 0.05) to 37 ± 3 mmol ATP kJ−1 during CON-HI. The present data confirm the hypothesis that heat loss is lower in anaerobic ATP resynthesis than in oxidative phosphorylation and can in part explain the finding that efficiency declines markedly during Dynamic Exercise. In addition, the rate of ATP turnover apparently increases during constant load low intensity Exercise. Alternatively, mitochondrial efficiency is lowered as Exercise progresses, since ATP turnover was unaltered during the ischaemic Exercise bout.
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muscle heat production and anaerobic energy turnover during repeated intense Dynamic Exercise in humans
The Journal of Physiology, 2001Co-Authors: Peter Krustrup, Jose Gonzalezalonso, Bjorn Quistorff, Jens BangsboAbstract:1. The aim of the present study was to examine muscle heat production, oxygen uptake and anaerobic energy turnover throughout repeated intense Exercise to test the hypotheses that (i) energy turnover is reduced when intense Exercise is repeated and (ii) anaerobic energy production is diminished throughout repeated intense Exercise. 2. Five subjects performed three 3 min intense one-legged knee-extensor Exercise bouts (EX1, EX2 and EX3) at a power output of 65 +/- 5 W (mean +/- S.E.M.), separated by 6 min rest periods. Muscle, femoral arterial and venous temperatures were measured continuously during Exercise for the determination of muscle heat production. In addition, thigh blood flow was measured and femoral arterial and venous blood were sampled frequently during Exercise for the determination of muscle oxygen uptake. Anaerobic energy turnover was estimated as the difference between total energy turnover and aerobic energy turnover. 3. Prior to Exercise, the temperature of the quadriceps muscle was passively elevated to 37.02 +/- 0.12 degrees C and it increased 0.97 +/- 0.08 degrees C during EX1, which was higher (P < 0.05) than during EX2 (0.79 +/- 0.05 degrees C) and EX3 (0.77 +/- 0.06 degrees C). In EX1 the rate of muscle heat accumulation was higher (P < 0.05) during the first 120 s compared to EX2 and EX3, whereas the rate of heat release to the blood was greater (P < 0.05) throughout EX2 and EX3 compared to EX1. The rate of heat production, determined as the sum of heat accumulation and release, was the same in EX1, EX2 and EX3, and it increased (P < 0.05) from 86 +/- 8 during the first 15 s to 157 +/- 7 J s(-1) during the last 15 s of EX1. 4. Oxygen extraction was higher during the first 60 s of EX2 and EX3 than in EX 1 and thigh oxygen uptake was elevated (P < 0.05) during the first 120 s of EX2 and throughout EX3 compared to EX1. The anaerobic energy production during the first 105 s of EX2 and 150 s of EX3 was lower (P < 0.05) than in EX1. 5. The present study demonstrates that when intense Exercise is repeated muscle heat production is not changed, but muscle aerobic energy turnover is elevated and anaerobic energy production is reduced during the first minutes of Exercise.
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muscle oxygen kinetics at onset of intense Dynamic Exercise in humans
American Journal of Physiology-regulatory Integrative and Comparative Physiology, 2000Co-Authors: Jens Bangsbo, Peter Krustrup, Jose Gonzalezalonso, Robert Boushel, Bengt SaltinAbstract:The present study examined the onset and the rate of rise of muscle oxidation during intense Exercise in humans and whether oxygen availability limits muscle oxygen uptake in the initial phase of i...
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muscle oxygen kinetics at onset of intense Dynamic Exercise in humans
American Journal of Physiology-regulatory Integrative and Comparative Physiology, 2000Co-Authors: Jens Bangsbo, Peter Krustrup, Jose Gonzalezalonso, Robert Boushel, Bengt SaltinAbstract:The present study examined the onset and the rate of rise of muscle oxidation during intense Exercise in humans and whether oxygen availability limits muscle oxygen uptake in the initial phase of i...
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heat production in human skeletal muscle at the onset of intense Dynamic Exercise
The Journal of Physiology, 2000Co-Authors: Jose Gonzalezalonso, Jens Bangsbo, Peter Krustrup, Bjorn Quistorff, Bengt SaltinAbstract:1. We hypothesised that heat production of human skeletal muscle at a given high power output would gradually increase as heat liberation per mole of ATP produced rises when energy is derived from oxidation compared to phosphocreatine (PCr) breakdown and glycogenolysis. 2. Five young volunteers performed 180 s of intense Dynamic knee-extensor Exercise ( approximately 80 W) while estimates of muscle heat production, power output, oxygen uptake, lactate release, lactate accumulation and ATP and PCr hydrolysis were made. Heat production was determined continuously by (i) measuring heat storage in the contracting muscles, (ii) measuring heat removal to the body core by the circulation, and (iii) estimating heat transfer to the skin by convection and conductance as well as to the body core by lymph drainage. 3. The rate of heat storage in knee-extensor muscles was highest during the first 45 s of Exercise (70-80 J s-1) and declined gradually to 14 +/- 10 J s-1 at 180 s. 4. The rate of heat removal by blood was negligible during the first 10 s of Exercise, rising gradually to 112 +/- 14 J s-1 at 180 s. The estimated rate of heat release to skin and heat removal via lymph flow was < 2 J s-1 during the first 5 s and increased progressively to 24 +/- 1 J s-1 at 180 s. The rate of heat production increased significantly throughout Exercise, being 107 % higher at 180 s compared to the initial 5 s, with half of the increase occurring during the first 38 s, while power output remained essentially constant. 5. The contribution of muscle oxygen uptake and net lactate release to total energy turnover increased curvilinearly from 32 % and 2 %, respectively, during the first 30 s to 86 % and 8 %, respectively, during the last 30 s of Exercise. The combined energy contribution from net ATP hydrolysis, net PCr hydrolysis and muscle lactate accumulation is estimated to decline from 37 % to 3 % comparing the same time intervals. 6. The magnitude and rate of elevation in heat production by human skeletal muscle during Exercise in vivo could be the result of the enhanced heat liberation during ATP production when aerobic metabolism gradually becomes dominant after PCr and glycogenolysis have initially provided most of the energy.
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muscle blood f low at onset of Dynamic Exercise in humans
American Journal of Physiology-heart and Circulatory Physiology, 1998Co-Authors: G Radegran, Bengt SaltinAbstract:To evaluate the temporal relationship between blood flow, blood pressure, and muscle contractions, we continuously measured femoral arterial inflow with ultrasound Doppler at onset of passive exerc...
