Torque-angle curve of the knee flexors in athletes with a prior history of hamstring strain

Abstract Objectives To investigate the knee flexor torque-angle curve after hamstring strain injury using different muscle action types and angular velocities. Design Cross-sectional. Setting Controlled laboratory. Participants Thirteen collegiate athletes injured hamstring strain (21.0 ± 0.8 years; 173.9 ± 6.5 cm; 70.1 ± 10.5 kg). Main outcome measures Concentric and eccentric knee flexor torque was measured at 60 & 300°/sec. Peak torque and average torque every 10° were determined from torque-angle curve and injured side was compared with non-injured side. Results No significant differences were found in the concentric muscle actions. However, the eccentric peak torque was significantly lower on the injured side at 60°/sec (p = 0.048) and at 300°/sec (p = 0.002). The average eccentric torque was significantly lower on the injured side at 60°/sec from 10° to 20° of knee flexion (p = 0.012–0.018) and at 300°/sec from 10° to 60° of knee flexion (p = 0.005–0.049). Conclusion The knee flexor torque-angle curve changes with eccentric muscle action after hamstring injury. Eccentric torque declines were close to full knee extension at 60°/sec and a wide range of knee flexion at 300°/sec. The assessment and rehabilitation of eccentric hamstring strength may be important to consider the effect of the angular velocity after hamstring strain injury.