GENDER SPECIFIC RESPONSE OF KNEE EXTENSOR AND FLEXOR TORQUE AND FATIGUE DURING MAXIMAL CONTRACTIONS

Abstract

OBJECTIVES: The purpose of this study was to examine gender differences in knee extensor (KE) and knee flexor (KF) peak torque (PT), work (W), power (P), and fatigue during maximal effort contractions. METHODS: Subjects for this study included 19 healthy male and 20 healthy female volunters. Following a dynamic warm-up period, subjects performed 30 reciprocal, concentric maximal knee extension and flexion contractions at a pre-set angular velocity of 180 deg/s on the Biodex Isokinetic Dynamometer. Values for knee extensor PT, W, and P were calculated for each repetition between an angular displacement of 60 deg over the middle of each repetition. The single highest repetition value for knee extensor and flexor PT, W and P was then converted to relative (Nm/kg, Watts/kg) and allometric-scaled (Nm/kgn, Watts/kgn) units. The rate of quadriceps fatigue was calculated as the decline in each isokinetic variable by the linear slope (b) from the single highest repetition value through the 30th repetition, and by a fatigue index (% decrease = 100 - [(work last 5 repetitions/work first 5 repetitions) x 100]). RESULTS: The results demonstrated significantly higher (p < 0.05) knee extension and flexion PT, W and P in absolute, relative and allometric-scaled units in males than females. Males exhibited higher rates of fatigue for both muscle groups of each isokinetic variable than females, as described by the slope and the fatigue index. The fatigue index was not found to be significantly different between the knee extensor and knee flexors. CONCLUSIONS: The findings from this study suggest that during maximal effort muscle contractions, males exhibit a higher susceptibility to muscle fatigue than females, which may be related to a greater ability to generate knee extensor and flexor torque.