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This Article Full Text Full Text (PDF) All Versions of this Article: 294/5/R1586    most recent 00717.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Jay, O. Articles by Kenny, G. P. PubMed PubMed Citation Articles by Jay, O. Articles by Kenny, G. P.

ENVIRONMENTAL, EXERCISE AND RESPIRATORY PHYSIOLOGY

Human heat balance during postexercise recovery: separating metabolic and nonthermal effects

¹Laboratory of Human Bioenergetics and Environmental Physiology, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada; ²Yellow Springs, Ohio; and ³Defence R&D Canada, Quebec City, Quebec, Canada

Submitted 4 October 2007 ; accepted in final form 10 March 2008

Previous studies report greater postexercise heat loss responses during active recovery relative to inactive recovery despite similar core temperatures between conditions. Differences have been ascribed to nonthermal factors influencing heat loss response control since elevations in metabolism during active recovery are assumed to be insufficient to change core temperature and modify heat loss responses. However, from a heat balance perspective, different rates of total heat loss with corresponding rates of metabolism are possible at any core temperature. Seven male volunteers cycled at 75% of O_2peak in the Snellen whole body air calorimeter regulated at 25.0°C, 30% relative humidity (RH), for 15 min followed by 30 min of active (AR) or inactive (IR) recovery. Relative to IR, a greater rate of metabolic heat production ( – ) during AR was paralleled by a greater rate of total heat loss (_L) and a greater local sweat rate, despite similar esophageal temperatures between conditions. At end-recovery, rate of body heat storage, that is, [( – ) – _L] approached zero similarly in both conditions, with – and _L elevated during AR by 91 ± 26 W and 93 ± 25 W, respectively. Despite a higher – during AR, change in body heat content from calorimetry was similar between conditions due to a slower relative decrease in _L during AR, suggesting an influence of nonthermal factors. In conclusion, different levels of heat loss are possible at similar core temperatures during recovery modes of different metabolic rates. Evidence for nonthermal influences upon heat loss responses must therefore be sought after accounting for differences in heat production.

body heat storage; calorimetry; heat production; heat stress; nonthermal factors; thermoregulation