FOREARM TEMPERATURE PROFILE DURING THE TRANSIENT PHASE OF THERMAL-STRESS

The transient temperature response of the resting human forearm immersed in water at temperatures (T(w)) ranging from 15 to 36-degrees-C was investigated. Tissue temperature (T(t)) was continuously monitored by a calibrated multicouple probe during the 3-h immersions. T(t) was measured every 5 mm, from the longitudinal axis of the forearm to the skin surface. Skin temperature,. rectal temperature, and blood flow (Q) were also measured during the immersions. The maximum rate of change of the forearm mean tissue temperature (T(t,max)) occurred during the first 5 min of the immersion. T(t,max) was linearly dependent on T(w) (P < 0.001), with mean values (SEM) ranging from -0.8 (0.1)-degrees-C.min-1 at 15-degrees-C to 0.2 (0.1)-degrees-C.min-1 at 36-degrees-C. The maximum rate of change of compartment mean temperature was dependent (P < 0.001) on the radial distance from the longitudinal axis of the forearm. The half-time for thermal steady state of the forearm mean tissue temperature was linearly dependent on T(w) between 30 and 36-degrees-C (P < 0.001), with mean values (SEM) ranging from 15.6 (0.6) min at 30-degrees-C to 9.7 (1.2) min at 36-degrees-C and not different between 15 and 30-degrees-C, averaging 16.2 (0.6) min. There was a significant linear relationship between the half-time for thermal steady-state of the compartment mean temperature and the radial distance from the longitudinal axis of the forearm for each value of T(w) tested (P < 0.001). The data of the present study suggest that the forearm Q is an important determinant of the transient thermal response of the forearm tissue during thermal stress.