| Abstract [eng] |
Background: It is well known that cold exposure experienced during occupational or recreational activities may adversely affect motor, cognitive performance, and health. Most research has used prolonged passive external rewarming modalities and focused on the direct effects on the kinetics of physiological and psychological responses in hypothermic subjects. However, the brief whole body rewarming effects on physiological and psychological responses in parallel with functional consequences on cognitive and neurophysiological functions have not been investigated. This study explores these effects in 12 healthy young men. Methods: Subjects (20 +/- 1 years) participated in 4 randomized trials, which were designed to compare the effects of whole-body brief (5-min) rewarming in 37 degrees C water with rewarming for the same duration in 24 degrees C (air) thermoneutral environment in mildly hypothermic subjects. After each rewarming, indicators of neuromuscular function (reflexes, central activation ratio, electromyography of exercising muscle, and contractile properties of calf muscles) and cognitive function (attention, simple motor speed, and information processing speed) were assessed. Results: Compared to rewarming in thermoneutral environment, after brief rewarming in 37 degrees C water, significantly lower metabolic heat production (MHP) (206 +/- 33.4 vs. 121.9 +/- 24.3 W.m(2), P < 0.01), heart rate (76 +/- 16 vs. 60 +/- 12 b.min(-1), P < 0.01), cold strain (6.4 +/- 3.1 vs. 5.3 +/- 2.7, P < 0.01), improved thermal comfort and induced cessation of shivering were found. Electrically induced maximum torque amplitudes increased (P100, 102.8 +/- 21.3 vs. 109.2 +/- 17.5 Nm and PTT100, 83.1 +/- 17.1 vs. 92.7 +/- 16.0 Nm, P < 0.05), contraction half-relaxation time decreased (599.0 +/- 53.8 vs. 589.0 +/- 56.3 ms, P < 0.05), and Wax-wave latency shortened (17.5 +/- 2.2 vs. 15.6 +/- 2.0 ms, P < 0.05) after 37 degrees C water [...]. |
