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Adaptation of exercise ventilation during an actively-induced hyperthermia following passive heat acclimation

Beaudin, A. E., Clegg, M. E., Walsh, M. L. and White, M. D. (2009) Adaptation of exercise ventilation during an actively-induced hyperthermia following passive heat acclimation. American Journal of Physiology: Regulatory Integrative and Comparative Physiology, 297 (3). R605-R614. ISSN 0363-6119

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To link to this item DOI: 10.1152/ajpregu.90672.2008


Hyperthermia-induced hyperventilation has been proposed to be a human thermolytic thermoregulatory response and to contribute to the disproportionate increase in exercise ventilation (VE) relative to metabolic needs during high-intensity exercise. In this study it was hypothesized that VE would adapt similar to human eccrine sweating (E(SW)) following a passive heat acclimation (HA). All participants performed an incremental exercise test on a cycle ergometer from rest to exhaustion before and after a 10-day passive exposure for 2 h/day to either 50 degrees C and 20% relative humidity (RH) (n = 8, Acclimation group) or 24 degrees C and 32% RH (n = 4, Control group). Attainment of HA was confirmed by a significant decrease (P = 0.025) of the esophageal temperature (T(es)) threshold for the onset of E(SW) and a significantly elevated E(SW) (P < or = 0.040) during the post-HA exercise tests. HA also gave a significant decrease in resting T(es) (P = 0.006) and a significant increase in plasma volume (P = 0.005). Ventilatory adaptations during exercise tests following HA included significantly decreased T(es) thresholds (P < or = 0.005) for the onset of increases in the ventilatory equivalents for O(2) (VE/VO(2)) and CO(2) (VE/VCO(2)) and a significantly increased VE (P < or = 0.017) at all levels of T(es). Elevated VE was a function of a significantly greater tidal volume (P = 0.003) at lower T(es) and of breathing frequency (P < or = 0.005) at higher T(es). Following HA, the ventilatory threshold was uninfluenced and the relationships between VO(2) and either VE/VO(2) or VE/VCO(2) did not explain the resulting hyperventilation. In conclusion, the results support that exercise VE following passive HA responds similarly to E(SW), and the mechanism accounting for this adaptation is independent of changes of the ventilatory threshold or relationships between VO(2) with each of VE/VO(2) and VE/VCO(2).

Item Type:Article
Divisions:Life Sciences > School of Chemistry, Food and Pharmacy > Department of Food and Nutritional Sciences > Human Nutrition Research Group
ID Code:80415
Uncontrolled Keywords:Acclimatization Adult Anaerobic Threshold Bicycling Body Temperature Regulation Case-Control Studies *Exercise Fever/complications/*physiopathology *Hot Temperature Humans Humidity Hyperventilation/*etiology/physiopathology Male Muscle Fatigue Plasma Volume *Pulmonary Ventilation Respiratory Mechanics Sweating Tidal Volume Time Factors Young Adult
Publisher:American Physiological Society

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