Heat exposure-induced changes in motor outflow component of reaction time

Conduction velocity, absolute refractory period, and subnormal conduction period measures of the right ulnar motor nerve were obtained during a simple reaction time task. 6 young, healthy, right-arm dominant male subjects were tested following 30 min. exposure in ambient (20 degrees C) and hot (36 degrees C) room air conditions. Motor and premotor components of fractionated reaction time were tested on the same arm. Oral, right forearm skin and a four-site mean skin temperature were monitored. During heat exposure, forearm skin temperature increased 4.7 degrees C and mean skin temperature 2.9 degrees C. Oral temperature did not alter. Conduction velocity increased 11.4%, absolute refractory period decreased 22.7%, and subnormal conduction period decreased 14.1% in the hot condition. Concomitantly, a 5.2% increase in premotor reaction time and 12.2% decrease in motor reaction time were observed. Total RT did not alter significantly. It was concluded that different component parts of reaction time were differentially influenced by exposure to heat.