Responses of lean and obese boys to repeated summer exercise in the heat bouts.
OBJECTIVE
To determine the degree of natural acclimatization and artificially induced acclimation-related changes during repeated exercise in the heat bouts in seven lean and seven obese 9- to 12-yr-old boys during summer months.


METHODS
Beginning at random times during the summer, subjects underwent a 70-min exercise (30% VO(2max)) in the heat exposure (38 degrees C, 50% relative humidity) on six separate days.


RESULTS
On day 1, obese children were less naturally acclimatized as indicated by significantly higher baseline core temperatures (T(c)) (obese = 37.62 +/- 0.06 vs lean = 37.41 +/- 0.06; P < 0.004). By day 6 versus day 1, significant reductions in baseline T(c) were evident in both groups (obese = 37.41 +/- 0.04 vs lean = 37.18 +/- 0.04; both P < 0.05). Baseline T(c) in obese subjects by day 6 was similar to that of lean subjects on day 1. Daily reductions in exercise T(c) were evident in both groups (final exercising T(c) day 1 vs day 6: obese = 38.15 +/- 0.05 vs 37.89 +/- 0.05; lean = 38.17 +/- 0.09 vs 37.72 +/- 0.06 degrees C; both P < 0.001), occurring at a significantly slower rate in obese subjects (final exercise T(c) day 6 - day 1: obese vs lean = -0.26 +/- 0.04 vs -0.45 +/- 0.08 degrees C; P < 0.05). Significant reductions in exercising heart rate (HR) occurred in the lean but not the obese subjects by day 6 (final exercising HR day 1 vs day 6: obese = 132 +/- 3 vs 131 +/- 3, P > 0.05; lean = 138 +/- 3 vs 127 +/- 3 bpm; P < 0.001).


CONCLUSIONS
During summer months, obese children are less naturally heat-acclimatized and subsequently acclimate at a slower rate.
Dougherty
Kelly A
KA
Noll Laboratory, Department of Kinesiology, The Pennsylvania State University, University Park, PA 16802-6900, USA. kellydoc35@aol.com
Chow
Mosuk
M
Kenney
W Larry
WL
D000064:Acclimatization / Q000502:physiology*; D001833:Body Temperature Regulation / Q000502:physiology*; D016022:Case-Control Studies; D002648:Child; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D009765:Obesity / Q000503:physiopathology*; D013546:Sweating / Q000502:physiology