Relation of heart rate to percentV˙<scp>o</scp> <sub>2 peak</sub> during submaximal exercise in the heat

Arngrímsson, Sigurbjörn Á.; Stewart, D.J.; Borrani, Fabio; Skinner, Kristie A.; Cureton, Kirk J.

doi:10.1152/japplphysiol.00508.2002

Cited by 76 publications

(73 citation statements)

References 25 publications

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“…The latter has been shown to produce an increase in heart rate of 7-8 beats·min Ϫ1 ·°C Ϫ1 (14,16,21). Hence, with progressive increases in ambient and concomitantly core temperature, the increase in heart rate during exercise-heat stress may be more pronounced for a given increase in %V O 2peak than in cooler conditions (2). Thus the proportional relationship between heart rate and relative exercise intensity that exists in COOL conditions (12) does not appear to extend to prolonged exercise performed in the heat, especially self-paced exercise.…”

Section: Discussionmentioning

confidence: 99%

“…3). Accordingly, it has been suggested that the increase in heart rate during sustained constant-load exercise in the heat is only partly related to the reduction in V O 2peak , with the remainder of the increase associated with other factors (2). The greater increase in heart rate is proposed to occur as a result of an elevation in sympathetic nervous activity and vagal withdrawal, as well as via the direct effect of blood temperature on the sinoatrial node (i.e., pacemaker tissue located in the right atrium) (16,21,22).…”

Section: Discussionmentioning

confidence: 99%

“…Specifically, subjects were asked to maintain the highest sustainable effort during 15 min and then reach maximal effort during a 1.5-min end-spurt, in order for V O2peak to be measured. This was conducted to evaluate the time course and extent of decrease in V O2peak, which was assumed to be attained if heart rate rose to within 5 beats/min of that observed in the preexperimental V O2max assessment in the same condition (2,48). V O2peak and peak heart rate were taken as the highest averaged 30-s segment during the final 45 s of the progressive maximal end-spurt.…”

Section: Methodsmentioning

confidence: 99%

“…3D). Hence, relative to the V O 2peak recorded during each progressive maximal end-spurt, the %V O 2peak maintained in each time trial was slightly greater in COOL (86 Ϯ 7, 86 Ϯ 6, 85 Ϯ 5, and 86 Ϯ 5%) compared with HOT (84 Ϯ 5, 84 Ϯ 5, 80 Ϯ 4, and 80 Ϯ 8%, respectively, for time trials [1][2][3][4].…”

Section: Preexperimental V O 2max Assessment Responsesmentioning

confidence: 99%

“…The combination of an increase in cutaneous blood volume and a temperature-mediated rise in intrinsic heart rate decreases cardiac filling, which leads to reductions in stroke volume and maximal cardiac output when heart rate approaches maximum (6,13,15,36). During prolonged constant-load exercise to exhaustion, for example, this forces the cardiovascular system toward a functional limit at submaximal workloads (e.g., power output), ultimately reducing maximal oxygen uptake (V O 2max ) (2,24,29). This decrement in cardiovascular reserve is purported to be the primary determinant limiting aerobic exercise in the heat (5,36,37).…”

mentioning

confidence: 99%

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Self-paced exercise in hot and cool conditions is associated with the maintenance of %V̇o_2peak within a narrow range

Périard

Racinais

2015

Journal of Applied Physiology

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Périard JD, Racinais S. Self-paced exercise in hot and cool conditions is associated with the maintenance of %V O2peak within a narrow range. J Appl Physiol 118: 1258 -1265. First published March 26, 2015 doi:10.1152/japplphysiol.00084.2015.-This study examined the time course and extent of decrease in peak oxygen uptake (V O2peak) during self-paced exercise in HOT (35°C and 60% relative humidity) and COOL (18°C and 40% relative humidity) laboratory conditions. Ten well-trained cyclists completed four consecutive 16.5-min time trials (15-min self-paced effort with 1.5-min maximal end-spurt to determine V O2peak) interspersed by 5 min of recovery on a cycle ergometer in each condition. Rectal temperature increased significantly more in HOT (39.4 Ϯ 0.7°C) than COOL (38.6 Ϯ 0.3°C; P Ͻ 0.001). Power output was lower throughout HOT compared with COOL (P Ͻ 0.001). The decrease in power output from trial 1 to 4 was ϳ16% greater in HOT (P Ͻ 0.001). Oxygen uptake (V O2) was lower throughout HOT than COOL (P Ͻ 0.05), except at 5 min and during the end-spurt in trial 1. In HOT, V O2peak reached 97, 89, 85, and 85% of predetermined maximal V O2, whereas in COOL 97, 94, 93, and 92% were attained. Relative exercise intensity (%V O2peak) during trials 1 and 2 was lower in HOT (ϳ84%) than COOL (ϳ86%; P Ͻ 0.05), decreasing slightly during trials 3 and 4 (ϳ80 and ϳ85%, respectively; P Ͻ 0.05). However, heart rate was higher throughout HOT (P ϭ 0.002), and ratings of perceived exertion greater during trials 3 and 4 in HOT (P Ͻ 0.05). Consequently, the regulation of self-paced exercise appears to occur in conjunction with the maintenance of %V O2peak within a narrow range (80-85% V O2peak). This range widens under heat stress, however, when exercise becomes protracted and a disassociation develops between relative exercise intensity, heart rate, and ratings of perceived exertion. cardiovascular strain; cycling; fatigue; hyperthermia; pacing; thermoregulation; time trial; V O2max SELF-PACED (I.E., TIME TRIAL) exercise requires the completion of a known distance in the quickest possible time or the production of the greatest amount of work in a set duration (1, 11). When undertaken in the heat, prolonged self-paced exercise performance is significantly impaired relative to cool conditions (10,27,28,42,46). The impairment in performance is mediated by the complex interplay of multiple physiological systems (e.g., nervous, metabolic) (8,34,45), with the development of thermal strain potentially modulating a performance-limiting increase in cardiovascular strain (5,27,28,30). Indeed, a narrowing core-to-skin temperature gradient during exercise-heat stress increases the skin blood flow requirement for heat dissipation (5,35,36). The combination of an increase in cutaneous blood volume and a temperature-mediated rise in intrinsic heart rate decreases cardiac filling, which leads to reductions in stroke volume and maximal cardiac output when heart rate approaches maximum (6,13,15,36). During prolonged constant-load exercise to exhaustion...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Preexperimental V O 2max Assessment Responsesmentioning

confidence: 99%

mentioning

confidence: 99%

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Self-paced exercise in hot and cool conditions is associated with the maintenance of %V̇o_2peak within a narrow range

Périard

Racinais

2015

Journal of Applied Physiology

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Integrated Physiological Mechanisms of Exercise Performance, Adaptation, and Maladaptation to Heat Stress

Sawka

Leon

Montain

et al. 2011

Comprehensive Physiology

406

444

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This article emphasizes significant recent advances regarding heat stress and its impact on exercise performance, adaptations, fluid electrolyte imbalances, and pathophysiology. During exercise-heat stress, the physiological burden of supporting high skin blood flow and high sweating rates can impose considerable cardiovascular strain and initiate a cascade of pathophysiological events leading to heat stroke. We examine the association between heat stress, particularly high skin temperature, on diminishing cardiovascular/aerobic reserves as well as increasing relative intensity and perceptual cues that degrade aerobic exercise performance. We discuss novel systemic (heat acclimation) and cellular (acquired thermal tolerance) adaptations that improve performance in hot and temperate environments and protect organs from heat stroke as well as other dissimilar stresses. We delineate how heat stroke evolves from gut underperfusion/ischemia causing endotoxin release or the release of mitochondrial DNA fragments in response to cell necrosis, to mediate a systemic inflammatory syndrome inducing coagulopathies, immune dysfunction, cytokine modulation, and multiorgan damage and failure. We discuss how an inflammatory response that induces simultaneous fever and/or prior exposure to a pathogen (e.g., viral infection) that deactivates molecular protective mechanisms interacts synergistically with the hyperthermia of exercise to perhaps explain heat stroke cases reported in low-risk populations performing routine activities. Importantly, we question the "traditional" notion that high core temperature is the critical mediator of exercise performance degradation and heat stroke. Published 2011. This article is a U.S. Government work and is in the public domain in the USA.

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Performance in the Heat—Physiological Factors of Importance for Hyperthermia‐Induced Fatigue

Nybo

Rasmussen

Sawka

2014

Comprehensive Physiology

271

299

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This article presents a historical overview and an up-to-date review of hyperthermia-induced fatigue during exercise in the heat. Exercise in the heat is associated with a thermoregulatory burden which mediates cardiovascular challenges and influence the cerebral function, increase the pulmonary ventilation, and alter muscle metabolism; which all potentially may contribute to fatigue and impair the ability to sustain power output during aerobic exercise. For maximal intensity exercise, the performance impairment is clearly influenced by cardiovascular limitations to simultaneously support thermoregulation and oxygen delivery to the active skeletal muscle. In contrast, during submaximal intensity exercise at a fixed intensity, muscle blood flow and oxygen consumption remain unchanged and the potential influence from cardiovascular stressing and/or high skin temperature is not related to decreased oxygen delivery to the skeletal muscles. Regardless, performance is markedly deteriorated and exercise-induced hyperthermia is associated with central fatigue as indicated by impaired ability to sustain maximal muscle activation during sustained contractions. The central fatigue appears to be influenced by neurotransmitter activity of the dopaminergic system, but inhibitory signals from thermoreceptors arising secondary to the elevated core, muscle and skin temperatures and augmented afferent feedback from the increased ventilation and the cardiovascular stressing (perhaps baroreceptor sensing of blood pressure stability) and metabolic alterations within the skeletal muscles are likely all factors of importance for afferent feedback to mediate hyperthermia-induced fatigue during submaximal intensity exercise. Taking all the potential factors into account, we propose an integrative model that may help understanding the interplay among factors, but also acknowledging that the influence from a given factor depends on the exercise hyperthermia situation.

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Relation of heart rate to percentV˙o _2 peak during submaximal exercise in the heat

Cited by 76 publications

References 25 publications

Self-paced exercise in hot and cool conditions is associated with the maintenance of %V̇o_2peak within a narrow range

Self-paced exercise in hot and cool conditions is associated with the maintenance of %V̇o_2peak within a narrow range

Integrated Physiological Mechanisms of Exercise Performance, Adaptation, and Maladaptation to Heat Stress

Performance in the Heat—Physiological Factors of Importance for Hyperthermia‐Induced Fatigue

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Relation of heart rate to percentV˙o 2 peak during submaximal exercise in the heat

Cited by 76 publications

References 25 publications

Self-paced exercise in hot and cool conditions is associated with the maintenance of %V̇o2peak within a narrow range

Self-paced exercise in hot and cool conditions is associated with the maintenance of %V̇o2peak within a narrow range

Integrated Physiological Mechanisms of Exercise Performance, Adaptation, and Maladaptation to Heat Stress

Performance in the Heat—Physiological Factors of Importance for Hyperthermia‐Induced Fatigue

Contact Info

Product

Resources

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Relation of heart rate to percentV˙o _2 peak during submaximal exercise in the heat

Self-paced exercise in hot and cool conditions is associated with the maintenance of %V̇o_2peak within a narrow range

Self-paced exercise in hot and cool conditions is associated with the maintenance of %V̇o_2peak within a narrow range