Pre- or co-activation of leg muscles is associated with risk of non-contact knee injury during a single-leg landing in badminton

Objectives: The present study evaluated if lower limb muscle pre- and co-activation was associated with the biomechanics of knee joint control during backward step single-leg landings following a badminton overhead stroke. Methods: Three-dimensional biomechanics data of the knee joint and electromyographic data of lower limb muscles were collected from 34 badminton players. Linear regression analysis of gluteus maximus, quadriceps, hamstrings, gastrocnemius pre-and muscle co-activation in relation to peak knee flexion angle, knee valgus angle and moment, peak extension moment, and tibial anterior shear force in participants 100 ms before initial touchdown were analyzed. Results: Increased quadriceps pre-activation predicts increased knee valgus angle (R² = 0.48, P < 0.001). Greater Lateral Hamstring/Quadriceps co-contraction predicts increased peak knee extension moment (R² = 0.39, P < 0.001). Greater lateral gastrocnemius/quadriceps co-contraction predicts an increased peak knee valgus moment (R² = 0.20, P = 0.0073). No EMG pre-activity parameters were predictors (P > 0.05) for knee flexion angle and anterior tibial shear force. Conclusion: These findings suggested that pre-activation of the quadriceps or co-contraction ratio of the lateral hamstrings to the quadriceps or lateral gastrocnemius to the quadriceps would be positively associated with the risk of non-contact anterior cruciate ligament (ACL) injuries during a single-leg landing following a badminton backward step overhead stroke.