This study aimed to investigate the effect of repeated local forearm tissue cooling on the metabolism in hypothermic skeletal muscle. It is hypothesized that repeated decrease of muscle temperature increases the oxygen consumption in hypothermic skeletal muscle. Eight healthy males participated in this study. Their right forearm tissues were locally cooled to 25℃ by cooling pads attached to the skin. This local cooling was repeated eight times on separate days. To evaluate adaptation in nonshivering thermogenesis in skeletal muscle, local cooling test was conducted at pre and post the repeated cooling period. The muscle oxygenation (oxy- and deoxyhemoglobin) during 25-second isometric handgrip (10% maximal voluntary construction) was measured by Near-infrared spectroscopy every 2℃ reduction in the forearm tissue temperature. The arterial blood flow was occluded for 15 seconds by upper arm cuff inflation during the isometric handgrip. The oxygen consumption in the flexor digitorum muscle was evaluated by a slope of the oxy- and deoxyhemoglobin difference during the arterial occlusion. In both test experiments the skeletal muscle oxygen consumption decreased significantly depending on the muscle temperature reduction (P<0.05). The oxygen consumption in hypothermic skeletal muscle was significantly higher at post local cooling test than pretest over the range of tissue temperature 35 to 31℃ (P<0.05). This result indicated that repeated local tissue hypothermia and suppression of muscle oxygen consumption might facilitate non-shivering thermogenesis in the skeletal muscle. In summary, non-shivering thermogenesis in hypothermic skeletal muscle in human was facilitated after repeated local tissue cooling.

DESCENTE SPORTS SCIENCE Vol.34/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE