The Effect of Augmented Feedback on Lower Limb Kinematics and Jumping Performance of Male Athletes With Dynamic Knee Valgus During a Double-leg Drop Vertical Jump Task

Background and Aims The immediate impact of augmented feedback on biomechanical risk factors has been well established, but its effect on the jumping performance of athletes is still unknown. Therefore, this study aims to evaluate the effect of augmented feedback on lower limb kinematics and jumping performance of male athletes with dynamic knee valgus (DKV) during a double-leg drop vertical jump (DLDVJ) task.
Methods In this quasi-experimental study, 21 male recreational athletes with DKV aged 1-25 years participated. Three-dimensional kinematic and kinetic data were collected simultaneously before and after augmented feedback during the DLDVJ task at the eccentric and concentric phases. The jumping performance was calculated by using the reactive strength index-modified (RSImod). 
Results The results showed a significant decrease in the hip adduction angle in the eccentric (P=0.001) and concentric (P=0.001) phases in the maximum knee flexion position (P=0.001) after the intervention compared to the pre-intervention stage. Also, there was a decrease in external tibiofemoral rotation in the eccentric (P=0.031) and concentric (P=0.019) phases in the maximum knee flexion position (P=0.037). In addition, a significant increase in knee flexion in the eccentric phase (P=0.007) and maximum knee flexion position (P=0.017) was reported after the intervention compared to the pre-intervention stage. Regarding jumping performance, the intervention was associated with an increase in the take-off time (P=0.039) and a subsequent decrease in the RSImod value (P=0.011).
Conclusion The augmented feedback can immediately improve the DKV without reducing the jump height during a DLDVJ task in male athletes, but it reduces the take-off time and, subsequently, the jumping performance (The RSImod value). As an evidence-based sports injury prevention program, the effects of improving DKV on athletes’ jumping performance in the long term should be investigated in future studies.