Recurrent Heat Exposure: Enzymatic Responses in Resting and Exercising Men.

摘要

Heat acclimatization was induced in a group of healthy male test subjects by walking on a treadmill (5.6 km/hr, 49 C/27 C dry/wet bulb, 90 min/day, 7 days), and confirmed by recording significantly reduced final rectal temperatures and heart rates on the seventh day of exercise in the heat. A second group of men, paired for maximal O(2) consumption and body weight, remained sedentary under identical environmental conditions. After correcting for subtle changes in hematocrit ratios, total plasma protein increased significantly after 45 (p<.05) and 90 (p<.025) minutes of exercise on the first day of heat exposure. Even after heat acclimatization was achieved (day 7), plasma levels of creatine phosphokinase increased during the 90 minute walk in the heat (time 0 vs 90, p<.025) as was also the case on day 1 (p<.05). Lactate dehydrogenase displayed similar trends on both days, but significance was not attained. Plasma glutamate-oxaloacetate transaminase and glutamate-pyruvate transaminase seemed to respond, although less consistently, to acute heat exposure as evidenced in several significant increases in the sedentary group. No correlations could be drawn between baseline levels of enzyme activity and state of physical conditioning. (Author)