RELATIONSHIP BETWEEN PHYSIQUE AND RECTAL TEMPERATURE COOLING RATE

Despite many attempts to relate components of physique to core tempera ture cooling rate, no consistent relationship has emerged. The inconsi stencies among the reported findings may arise from unaccounted thermo regulatory responses or incomplete physique assessment or both. A stud y was designed to examine this relationship in the range of rectal tem peratures (T(re)) within which shivering and sweating are absent, defi ned as the null zone, thus minimizing the contribution of these effect or responses. Twenty healthy subjects (10 male and 10 female), represe nting a variety of physiques, participated in the study. The anthropom etric protocol included 5 heights, body mass, 8 skinfolds, 10 girths, and 4 breadths. This permitted derivation of a body surface-area-to-ma ss ratio and estimates of adipose and muscle tissue masses using a cad aver-validated mass fractionation model. Subjects were heated in a 40- degrees-C bath followed immediately by cooling in a 30.6-degrees-C bat h. During the cooling, forehead sweating rate and oxygen uptake were m onitored to establish the boundaries of the T(re) null zone. In additi on, on-line recordings were made of T(re), skin temperature, and surfa ce heat flux at six sites. The rate of cooling of T(re) (T(re)), in th e range of temperatures between thresholds for sweating and shivering, was correlated to the components of physique. Estimates of adipose an d skeletal muscle tissue masses did not correlate to T(re) in the rang e of core temperatures investigated. However, total mass exhibited a s ignificant correlation (r = 0.5, P less-than-or-equal-to 0.05) with T( re), but gender seemed to distort this relationship, possibly due to d ifferences in adipose tissue distribution.