Physical characteristics and decrement in muscular performance after whole body cooling

The dependence of cooling-induced decrement in muscular performance on several physical characteristics was studied. The characteristics were: the amount of subcutaneous fat, body weight, height and surface area, maximal aerobic capacity and maximal voluntary isometric contraction of the trunk flexors. Ten male subjects wearing shorts and jogging shoes were exposed to 27 degrees C and 10 degrees C for 60 min. The cooling resulted in a decrease of 6.8 +/- 0.3 degrees C (mean +/- SE) in mean skin temperature. The temperatures of m. triceps and m. deltoideus were decreased by 2.8 +/- 1.0 degree C and 5.1 +/- 0.4 degree C, respectively. Rectal temperature was virtually unaffected. A significant negative correlation (r = -0.785) was found between the amount of subcutaneous fat and decrease in mean skin temperature after cooling. After the exposures to 27 degrees C and 10 degrees C, the subjects performed an overhead ball throwing test to measure muscular performance. The test was performed in a standing position using both arms. Five balls weighing from 0.27 kg to 3.0kg were thrown. On the average, cooling decreased muscular performance 7.6%. The decrease correlated significantly only with the amount of subcutaneous fat r = -0.710). The results indicate that from the measured physical characteristics, varying within normal range, only subcutaneous fat had significant effect on thermal responses. Accordingly, the decrease in muscular performance correlated only with the amount of subcutaneous fat.