Heat Loss from the Upper Extremities and Clothing Thermal Comfort

Abstract

This mini-review aimed to examine a. The effects of different skin areas between extremities and torso covered by clothing on changes of body core temperature during exercise. b. To what extent hand vasodilation contributes to heat losses from the extremities and clothing thermal comfort during exercise. In experiment 1, seven subjects performed bicycle ergometer exercise at a Ta of 30˚C. Subjects wore two different types of clothing: A, designed to expose upper extremities and B, designed to expose the torso, covered identically 74% skin of body surface area. At the end of 60-min exercise, Tre increased to 37.88˚C in clothing A and to 38.14˚C in clothing B, respectively. The results clearly showed that the upper extremities are more efficient than the torso for heat dissipation from the body. In experiment 2, seven subjects performed 25-min exercise and 20-min recovery period after exercise at a Ta of 20.0˚C. In OCCL, both wrists were occluded to stop the hand blood flow with a cuff for 30min from the 15th min of exercise to the end of the experiment. In CONT, the wrists were not occluded throughout the experiment. In CONT, finger Tsk increased from 20.5˚C to 34.0˚C, and forearm Tsk increased concomitantly from 25.4˚C to 27.7˚C during and after exercise. In OCCL, however, Tsks in the finger and forearm did not increase at all during wrist occlusion. Despite of a compensatory increase in thermo-physiological responses, Tes was significantly higher in OCCL than in CONT. We have confirmed that hand vasodilation (mainly through AVAs) plays an important role for enhancing heat dissipation through the venous blood returning from the hands, consequently suppressing increase of body temperature and enhancing clothing thermal comfort during heat load