The explosive power output of both legs during extension movement was assessed in 271 male (aged 16-84 yr) and 248 female (aged 16-82 yr) subjects, and the table of evaluation for the value obtained was prepared with the function of sex and age. From a sitting position on a seat, leg extension movement was performed toward the foot plate in the forward, to which the body mass of each subject was applied as a resistance. The reliability of the power measurement was ascertained from the result that the coefficients of variation were under 5 x 10^-2 when the power output of 6 subjects was measured once a day for 10 days. On both sexes, the power output per body mass declined linearly with age. The regression equations between age (x) and the power output per body mass (y) were as follows.
male: y=-0.22 x+28.38 (r=.659, n=271; p<0.001)
female: y=-0.13 x+18.36 (r=.583, n=248; p<0.001)
For all groups classified by 10 years, the male indicated greater value than the female in corresponding groups. The ratio of the value for the female relative to that for the male was between 64.8% and 72, 0%. These results suggested that the power output for the male decreased at a higher rate, and the sex difference of it decreased as the age increased.