Effect of core muscle fatigue on the performance, kinematics, and electromyography of horizontal hop in recreational runners with and without dynamic knee valgus

Abstract

Introduction: Runners experience fatigue during training and competition, and core endurance is crucial for maintaining trunk and lower limb stability during dynamic and functional tasks, such as the single-leg hop test for distance, which simulates the challenges of running. This study aimed to compare performance, kinematic, and electromyographic parameters between recreational runners with and without dynamic knee valgus during a single-leg hop test for distance before and after a core fatigue protocol.

Methods: Thirty-eight recreational runners were divided into groups with (valgus group: n = 17) and without dynamic knee valgus (non-valgus group: n = 21). During the single-leg hop test for distance, we measured performance, kinematics, and electromyographic activity.

Results: After fatigue, the runners showed lower performance, greater hip abduction, knee adduction, trunk displacement towards the supporting lower limb, and reduced biceps femoris EMG during the preparatory phase. The valgus group showed greater vastus lateralis and semitendinosus EMG in the preparatory phase than the non-valgus group.

Conclusion: Core fatigue affects the single-leg hop test for distance performance and influences the kinematic and electromyographic strategies adopted by recreational runners. Regardless of core fatigue, runners with dynamic knee valgus recruit more muscles that cross the knee, possibly contributing to the stability needed before the hop.

Keywords: Biomechanics; Core muscles; Functional tests; Knee valgus.