Improvements in Hip Extensor Rate of Torque Development Influence Hip and Knee Extensor Feed-Forward Control

Abstract

Females have been reported to utilize a feedforward control strategy during landing in which they compensate for decreased rate of torque development (RTD) of the hip extensors through earlier pre-activation of the knee extensors. The purpose of this study was to determine the influence of a 4-week hip-focused training program on hip extensor RTD and feedforward control of the hip and knee extensors. Twenty-one females underwent hip extensor RTD evaluation and electromyographic assessment of the hip and knee extensors during a drop-jump task. Post-training, there was a significant improvement in hip extensor RTD (21.68 ± 5.44 to 23.33 ± 5.45 Nm/kg s, p = 0.009), and pre-activation of the hip extensors (87.1 ± 63.6 to 56.2 ± 60.9 ms, p < 0.001) and knee extensors (272.3 ± 113.8 to 124.0 ± 67.7 ms, p < 0.001) occurred closer to ground contact. A negative association was found between the change in hip extensor RTD and the change in knee extensor onset (r = −0.48, p = 0.03). We propose that the observed change in feedforward control is reflective of the decreased need for preparatory muscle activity owing to the improved capacity of the hip extensors to rapidly generate force.