The relationship of maximal anaerobic power (Pmax) of the quadriceps muscle and corresponding optimal shortening velocity (vopt) with age, habitual physical activity (PA) and maximal oxygen consumption (VO2max) were assessed in 37 healthy older [71.1 (SD 3.8) years] men and compared to those of 16 young [22.7 (SD 3.4) years] men. The PA was evaluated using a questionnaire. The Pmax and vopt were measured on a friction loaded non-isokinetic cycle ergometer. The Pmax was expressed relative to body mass - Pmax x kg(-1), and relative to the mass of the two quadriceps muscles - Pmax x kgquad(-1). The decline of Pmax x kg(-1) from youth to advanced age (8.3% per decade) was greater than the decrease in quadriceps muscle mass (3.8% per decade), in Pmax x kgquad(-1) (5.9% per decade) and in vopt (4.3% per decade). In the older men, a negative relationship of Pmax x kg(-1) (r = -0.33) and Pmax x kgquad(-1) (r = -0.44) with age was found. Ergometer measurements were not correlated with PA activity indices or VO2max, while VO2max was positively associated with PA. In a multiple stepwise regression analysis age was the only variable that contributed significantly to Pmax x kg(-1) and Pmax x kgquad(-1) variances. Our findings indicated that in these healthy elderly men, unlike the fall in VO2max, habitual PA did not attenuate the decline in Pmax of the quadriceps muscle with age. This finding was different from a previously described relationship in older women and would suggest sex differences in determining Pmax in healthy older subjects.