Influence of adiposity on cooling efficiency in hyperthermic individuals.
This study evaluated the effect of body adiposity on core cooling rates, as measured by decreases in rectal (T (re)), esophageal (T (es)) and aural canal (T (ac)) temperatures, of individuals rendered hyperthermic by dynamic exercise in the heat. Seventeen male participants were divided into two groups; low body fat (LF, 12.9 +/- 1.9%) and high body fat (HF, 22.3 +/- 4.3%). Participants exercised at 65% of their maximal oxygen uptake at an ambient air temperature of 40 degrees C until T (re) increased to 40 degrees C or until volitional fatigue. Following exercise, participants were immersed up to the clavicles in an 8 degrees C circulated water bath until T (re) returned to 37.5 degrees C. No significant differences were found between the LF and HF in the time to reach a T (re) of 39.5 degrees C (P = 0.205), 38.5 degrees C (P = 0.343) and 37.5 degrees C (P = 0.923) during the immersion. Overall cooling rate for T (re) was also similar between groups (0.23 +/- 0.09 degrees C/min (LF) vs. 0.20 +/- 0.09 degrees C/min (HF), P = 0.647) as well as those for T (es) (P = 0.502) and T (ac) (P = 0.940). Furthermore, mean rate of non-evaporative heat loss (702 +/- 217 W/m(2) (LF) vs. 612 +/- 141 W/m(2) (HF), P = 0.239) was not different between groups. These results suggest that a difference of approximately 10% of body adiposity does not affect core cooling rates in active individuals under 25% body fat rendered hyperthermic by exercise.
Laboratory of Human Bioenergetics and Environmental Physiology, School of Human Kinetics, Faculty of Health Sciences, University of Ottawa, 125 University, Ottawa, Ontario, Canada.
Bruno
B
Lemire
Daniel
D
Gagnon
Ollie
O
Jay
Lucy
L
Dorman
Michel B
MB
DuCharme
Glen P
GP
Kenny
D050154:Adiposity; D000328:Adult; D001833:Body Temperature Regulation; D003080:Cold Temperature; D015444:Exercise; D005334:Fever / Q000503:physiopathology*; D018882:Heat Stress Disorders / Q000503:physiopathology*; D006801:Humans; D007101:Immersion; D008297:Male; D009119:Muscle Contraction; D018763:Muscle Fatigue; D018482:Muscle, Skeletal / Q000503:physiopathology; D010101:Oxygen Consumption