Gender Differences in the Relationship between Quadriceps Work and Fatigue during High-Intensity Exercise

The purpose of this study was to examine gender differences in peak quadriceps torque, the rate of torque decline, and the relationship between these 2 variables during high-intensity isokinetic exercise. Subjects for this study included 16 healthy men and 16 healthy women. Following a dynamic warm-up period, subjects performed 30 reciprocal, concentric maximal knee extension and flexion contractions at a preset angular velocity of 180 deg·sec^-1 on the Biodex System II Isokinetic Dynamometer. Values for quadriceps work (N·m) were calculated for each repetition between a windowed range of motion of 10° and 60° of flexion. Values for quadriceps work were then converted to a ratio of individual body mass (N·m·kg^-1). The rate of quadriceps fatigue was calculated as the decline in work output by the linear slope (β) across the 30 repetitions. This value was then assessed for gender differences with an independent t-test. The relationship between peak quadriceps work and the associated slope was examined by regression analysis for men and women, separately, and differences in these relationships were calculated using Fisher's Z-transformation. The results demonstrated significantly higher peak quadriceps work and rate of fatigue (slope) in men as compared with women (p< 0.05). The relationship between peak quadriceps work and the rate of fatigue was demonstrated to be significant in both sexes (men: r = 0.86; women: r = 0.69), and was statistically higher in men than in women. The findings from this study suggest that the physiological characteristics of quadriceps in men may be more conducive for high-intensity, short-term work output.