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Thermal and cardiovascular strain from hypohydration: influence of exercise intensity.
Int J Sports Med. 1998 Feb; 19(2):87-91.IJ

Abstract

This study determined the effects of exercise intensity on the physiologic (thermal and cardiovascular) strain induced from hypohydration during heat stress. We hypothesized that the added thermal and cardiovascular strain induced by hypohydration would be greater during high intensity than low intensity exercise. Nine heat-acclimated men completed a matrix of nine trials: three exercise intensities, 25%, 45% and 65% VO2 max; and three hydration levels, euhydration and hypohydration at 3% and 5% body weight loss (BWL). During each trial, subjects attempted 50 min of treadmill exercise in a hot room (30 degrees C db, 50% rh) while body temperatures and cardiac output were measured. Hypohydration was achieved by exercise and fluid restriction the day preceding the trials. Core temperature increased (P<0.05) 0.12 degrees C per%BWL at each hypohydration level and was not affected by exercise intensity. Cardiac output was reduced (P<0.05) compared to euhydration levels and was reduced more during high compared to low intensity exercise after 5% BWL. It was concluded that: a) the thermal penalty (core temperature increase) accompanying hypohydration is not altered by exercise intensity; and b) at severe hypohydration levels, the cardiovascular penalty (cardiac output reduction) increases with exercise intensity.

Authors+Show Affiliations

Thermal & Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, MA 01760, USA. smontain@natick-ccmail.army.milNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Comparative Study
Journal Article

Language

eng

PubMed ID

9562215

Citation

Montain, S J., et al. "Thermal and Cardiovascular Strain From Hypohydration: Influence of Exercise Intensity." International Journal of Sports Medicine, vol. 19, no. 2, 1998, pp. 87-91.
Montain SJ, Sawka MN, Latzka WA, et al. Thermal and cardiovascular strain from hypohydration: influence of exercise intensity. Int J Sports Med. 1998;19(2):87-91.
Montain, S. J., Sawka, M. N., Latzka, W. A., & Valeri, C. R. (1998). Thermal and cardiovascular strain from hypohydration: influence of exercise intensity. International Journal of Sports Medicine, 19(2), 87-91.
Montain SJ, et al. Thermal and Cardiovascular Strain From Hypohydration: Influence of Exercise Intensity. Int J Sports Med. 1998;19(2):87-91. PubMed PMID: 9562215.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Thermal and cardiovascular strain from hypohydration: influence of exercise intensity. AU - Montain,S J, AU - Sawka,M N, AU - Latzka,W A, AU - Valeri,C R, PY - 1998/4/30/pubmed PY - 1998/4/30/medline PY - 1998/4/30/entrez SP - 87 EP - 91 JF - International journal of sports medicine JO - Int J Sports Med VL - 19 IS - 2 N2 - This study determined the effects of exercise intensity on the physiologic (thermal and cardiovascular) strain induced from hypohydration during heat stress. We hypothesized that the added thermal and cardiovascular strain induced by hypohydration would be greater during high intensity than low intensity exercise. Nine heat-acclimated men completed a matrix of nine trials: three exercise intensities, 25%, 45% and 65% VO2 max; and three hydration levels, euhydration and hypohydration at 3% and 5% body weight loss (BWL). During each trial, subjects attempted 50 min of treadmill exercise in a hot room (30 degrees C db, 50% rh) while body temperatures and cardiac output were measured. Hypohydration was achieved by exercise and fluid restriction the day preceding the trials. Core temperature increased (P<0.05) 0.12 degrees C per%BWL at each hypohydration level and was not affected by exercise intensity. Cardiac output was reduced (P<0.05) compared to euhydration levels and was reduced more during high compared to low intensity exercise after 5% BWL. It was concluded that: a) the thermal penalty (core temperature increase) accompanying hypohydration is not altered by exercise intensity; and b) at severe hypohydration levels, the cardiovascular penalty (cardiac output reduction) increases with exercise intensity. SN - 0172-4622 UR - https://www.unboundmedicine.com/medline/citation/9562215/Thermal_and_cardiovascular_strain_from_hypohydration:_influence_of_exercise_intensity_ L2 - http://www.thieme-connect.com/DOI/DOI?10.1055/s-2007-971887 DB - PRIME DP - Unbound Medicine ER -