Sex differences in strength - some observations on their variability.

One hundred and twelve datasets, which allowed a direct comparison of the strengths of men and women, were located in the published literature. For each of these, three indices of sex difference were calculated: the ratio of the mean female strength to the mean male (F/M), the proportion of the total variance in strength attributable to sex (R(2)) and the "percentage of chance encounters between members of the opposite sex in which the female is stronger" (%CEFS). Sex difference was shown to be very variable, the values of these indices being both task and population specific. An experiment was conducted in which male and female subjects gripped and turned knurled cylindrical handles of 10, 30, 50 and 70 mm diameter. Maximum isometric torques were recorded. Sex differences became more pronounced as handle size increased. The optimal handle-size was 50 mm for both male and female subjects. Data concerning whole body exertion (Pheasant et al, 1982) were also analysed for sex differences. It was concluded that very similar tests of strength could exhibit very different levels of sex difference. The task or equipment designer should not make assumptions about sex differences in strength for a particular action, but should rely on empirical investigation.