Tags

Type your tag names separated by a space and hit enter

Adaptation of exercise ventilation during an actively-induced hyperthermia following passive heat acclimation.
Am J Physiol Regul Integr Comp Physiol. 2009 Sep; 297(3):R605-14.AJ

Abstract

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).

Authors+Show Affiliations

Laboratory for Exercise and Environmental Physiology, Dept. of Biomedical Physiology and Kinesiology, Simon Fraser Univ., 8888 Univ. Dr., Burnaby, BC, Canada, V5A 1S6.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

19494169

Citation

Beaudin, Andrew E., et al. "Adaptation of Exercise Ventilation During an Actively-induced Hyperthermia Following Passive Heat Acclimation." American Journal of Physiology. Regulatory, Integrative and Comparative Physiology, vol. 297, no. 3, 2009, pp. R605-14.
Beaudin AE, Clegg ME, Walsh ML, et al. Adaptation of exercise ventilation during an actively-induced hyperthermia following passive heat acclimation. Am J Physiol Regul Integr Comp Physiol. 2009;297(3):R605-14.
Beaudin, A. E., Clegg, M. E., Walsh, M. L., & 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), R605-14. https://doi.org/10.1152/ajpregu.90672.2008
Beaudin AE, et al. Adaptation of Exercise Ventilation During an Actively-induced Hyperthermia Following Passive Heat Acclimation. Am J Physiol Regul Integr Comp Physiol. 2009;297(3):R605-14. PubMed PMID: 19494169.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Adaptation of exercise ventilation during an actively-induced hyperthermia following passive heat acclimation. AU - Beaudin,Andrew E, AU - Clegg,Miriam E, AU - Walsh,Michael L, AU - White,Matthew D, Y1 - 2009/06/03/ PY - 2009/6/5/entrez PY - 2009/6/6/pubmed PY - 2009/9/11/medline SP - R605 EP - 14 JF - American journal of physiology. Regulatory, integrative and comparative physiology JO - Am. J. Physiol. Regul. Integr. Comp. Physiol. VL - 297 IS - 3 N2 - 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). SN - 1522-1490 UR - https://www.unboundmedicine.com/medline/citation/19494169/Adaptation_of_exercise_ventilation_during_an_actively_induced_hyperthermia_following_passive_heat_acclimation_ L2 - http://www.physiology.org/doi/full/10.1152/ajpregu.90672.2008?url_ver=Z39.88-2003&amp;rfr_id=ori:rid:crossref.org&amp;rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -