Sex differences in the rate of torque development and torque-velocity relationship are due to maximal strength only

Purpose: This study aimed to analyse the sex differences in the rate of torque development (RTD) and torque-velocity parameters with and without normalisation for maximal voluntary torque (MVT). Methods: Right-leg knee extensors were tested in 64 healthy and active participants (31 F and 33 M). MVT and RTD were obtained under isometric conditions. Individual torque-velocity relationships were obtained using a curvilinear model on averaged torque and velocity over 80°-to-140° knee angle. Dynamic data were acquired through an incremental protocol on a leg extension machine, going from the lightest to the unmovable load despite maximal effort. Results: Independent samples t test revealed (p < 0.001) that males possess greater RTD measured at 50 ms (d = -1.2), 100ms (d = -2.1) and 150ms (d = -2.3), peak RTD (d = -1.3) and MVT (d = 2.1). When normalised by MVT, the sex differences in RTD disappeared. Curvilinear hyperbolic TV relationship well-fitted (R2 = 0.99). In FV parameters, maximal theoretical torque (d = -1.7), maximal power (Pmax) (d = -2.0), and torque at Pmax (d = -1.7) were greater in males (p < .05), while maximal theoretical velocity (V0) and velocity at Pmax did not differ. Conclusions: The sex differences in explosiveness (i.e., rapid isometric and dynamic force production) were mainly due to greater maximal strength in males than in females. These findings suggest that, in non-sedentary people, males do not present higher contraction velocity capacities, i.e. higher maximal velocity until which muscles can produce force, than females in knee extension.