The effect of external feedback on the lower extremity kinematics and the reactive strength of people with dynamic knee valgus during jump landing task

Background and aims: The effectiveness of the immediate augmented feedback on biomechanical risk factors is well established, but its relationship to athletes' jumping performance remains unknown synchronously. Therefore, the purpose of this investigation was to evaluate of the effect of external feedback on the lower extremity kinematics and the reactive strength of people with dynamic knee valgus (DKV) during double leg-jump landing task (DLDVJ).

Materials and Methods: In the present quasi-experimental study, twenty-one male recreational athletes with DKV and the age range of the 18 to 25 years participated in this investigation. Three-dimensional kinematics, kinetic data were synchronously collected 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 of the present study indicate a significant decrease in the hip adduction angle in the eccentric phase (P=0.001), concentric phase (P=0.001), and the maximum knee flexion position (P=0.001) at the post-intervention than pre-intervention. Also, there was a decrease in tibiofemoral external rotation in the eccentric phase (P=0.031), concentric (P=0.019), and 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) at the post-intervention than pre-intervention were shown. In relation to jumping performance, providing intervention was associated with an increase in take-off time (P=0.039) and subsequently a decrease in jumping performance based on the RSImod index (P=0.011).

Conclusion: The results of the present study show that the intervention of external feedback instantly improves the DVK movement fault without disturbing the jump height of the athletes during the DLDVJ, but by reducing the take-off time and subsequently by reducing the jumping performance based on the RSImod index. Nevertheless, as an evidence-based sports injury prevention program, the effectiveness of improving DVK movement deficits on athletes' jumping performance should be investigated in the long term as a new movement pattern.