Identification of an apprehension effect on physiological indices of thermal strain.

A laboratory assessment of the thermal strain produced by wearing a protective clothing assembly, in addition to a normal flying clothing assembly, in a hot environment is described. In addition to the demonstration of an increase in thermal strain when wearing the protective clothing, two points of importance emerged. First, condition replication revealed a significant apprehension effect which confounded the physiological variables used to evaluate the thermal strain, leading to an over-estimation of the severity of that strain. Second, there was a large between-subject variation amongst the eight subjects used, which made the arithmetic mean a potentially misleading statistic for evaluating the increased physiological strain caused by the additional clothing assembly during the heat exposure. The practical implications of these observations are discussed....