ABSTRACT.The role of body weight, leg volume, and leg weight as determiners of the ability to produce work output during constant load (97 rpm at 34 kpm/rev) cycling of short duration (2 min) was studied. Body weight, leg volume, and leg weight accounted for approximately 41, 36, and 26 percent common variance in total work output, rsepectively. In combination (R= .68) the three variables predicted 46 percent of the variance in performance. Body weight, leg volume, and leg weight were shown to be of little importance during the initial seconds of performance, becoming increasingly more important as consistent decrement in work output occurred. The performance test resulted in substantial and consistent individual differences as revealed by the test‐retest reliability ofr= .92.