Heat acclimatization and hydration status of American football players during initial summer workouts

Document Type

Journal Article


National Strength and Conditioning Association


Faculty of Computing, Health and Science


School of Exercise, Biomedical and Health Science / Centre for Sustainable Regional Futures




Yeargin, S.W., D.J. Casa, L.E. Armstrong, G. Watson, Judelson, D. A., Psathas, E., & Sparrow, S. L. (2006). Heat acclimatization and hydration status of American football players during initial summer workouts. Journal of strength and conditioning research, 20(3), 463-470.


This investigation evaluated the new National Collegiate Athletic heat acclimatization for football players using physiological, psychological, fluid balance, anthropometric, and nutritional variables. Eleven football players (20 ± 1 year, 1.88 ± 0.05 m, and 115.36 ± 18.85 kg) from a Division I football team were observed for the first 8 days of preseason practices. Measurements such as heart rate and gastrointestinal temperature (TGI) via telemetric sensor were taken before, 3 times during, and after practice daily. An average 1.39- kg (1.2%) decrease of body mass occurred from prepractice to postpractice (p < 0.01). Consistent with mild body mass losses, urinary indices of hydration status (i.e., color, specific gravity, and osmolality) indicated mild fluid deficits. A significant in- crease (p < 0.05) from pre to postpractice was observed in urine color and urine specific gravity, but chronic hypohydration over the 8 days was not noted. The Environmental Symptoms Ques- tionnaire (ESQ) postpractice score was significantly higher (p < 0.05) than the prepractice score was, but averages did not differ across practice days. There was no difference in postpractice TGI measurements across days (p < 0.05). Heart rate, TGI, and ESQ measurements indicated that football players experienced gradual heat acclimatization and enhanced heat tolerance, despite progressive increases of exercise variables, clothing, and environmental stressors.

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