The aim of the present study was to compare the influence of three rest intervals of 30, 60 and 180 seconds randomly applied between two sets of five isokinetic contractions of flexor-extensor knee muscles in a cohort composed of 14 men (32.5 ± 8 years). The comparison of the isokinetic values measured during the first set of each evaluation session showed no significant differences (0.55 < P < 0.80). The analysis of the time and rest interval interaction demonstrated no significant difference between the isokinetic measures obtained after the rest intervals for peak torque of the quadriceps and of the hamstrings and for the mean power of the quadriceps and the hamstrings. These findings raise questions about a strict energetic approach and a future research should analyze the interaction of force production and fatigue phenomena in relation to the rest interval.