18 young men (24.22 ± 2.58 yrs) and 20 older men (66.85 ± 4.02 yrs) performed 3 sets of 10 unilateral isokinetic knee extension repetitions at 60°/s. The rest intervals between sets were 1 and 2 minutes and were counterbalanced across 2 testing days, separated by a minimum of 48 hours. The work-to-rest ratio was 1:3 and 1:6. All subjects were not involved in exercise programs that included resistance exercises within the last 6 months. Statistical evaluation of the data was performed using a 2x 2 x 3 mixed factor repeated measures ANOVA [age (younger and older) x rest interval (1 and 2 min) x set (1st, 2nd, and 3rd)]. Statistical significance was set at p < 0.05 for all comparisons.