Finger skin cooling on contact with cold materials: an investigation of male and female responses during short-term exposures with a view on hand and finger size.

This study investigated the independent effects of hand anthropometry and gender upon contact cooling responses. Subjects were selected for matching hand/finger size between genders, with equal variation between individuals of each group. Fourteen volunteers (7 male, 7 female) participated, touching blocks of aluminium and stainless steel using the first phalanx of the index finger with a contact force of 1.0 N and 9.8 N, at surface temperatures of -2 degrees C and -10 degrees C. Conditions were selected in order to elicit varying rates of skin cooling upon contact. Contact temperature ( T(C)) of the finger-pad was measured over time using a T-type thermocouple. Overall, no significant difference was found between the cooling responses of males and females. In order to investigate whether differences in hand anthropometry correlated with contact cooling response, a multiple regression approach was used. Analyses of the residual variance in contact cooling data, after the effects of material type, surface temperature and finger contact force had been accounted for, showed that, under slow cooling conditions (>45 s to reach T(C)=1 degrees C), hand size correlated significantly with contact cooling response only when represented by index finger volume ( P<0.05), but gender did not. Whilst under fast cooling conditions (<25 s to reach T(C)=1 degrees C), hand size did not correlate significantly with contact cooling response at all, but gender had a significant effect ( P<0.001). Under slow cooling conditions, a larger finger (and in most cases hands) provides a higher heat content, thus giving a slower skin cooling speed. Under fast cooling conditions, the significantly longer time required for males to reach a T(C) of 1 degrees C, despite matching hand and finger size, is attributed to higher epidermal insulation provided by the thicker stratum corneum, combined with the higher starting skin temperature observed in the "slightly cool" environment.