Effects of gluteus medius and biceps femoris stimulation on reduction of knee abduction moment during a landing task

Anterior cruciate ligament (ACL) injury prevention should focus primarily on reduction of the knee abduction moment (KAM) in landing tasks. Gluteus medius and hamstring forces are considered to decrease KAM during landing. The effects of different muscle stimulations on KAM reduction were compared using two electrode sizes (standard 38 cm² and half-size 19 cm²) during a landing task. Twelve young healthy female adults (22.3 ± 3.6 yrs, 1.62 ± 0.02 m, 50.2 ± 4.7 kg) were recruited. KAM was calculated under three conditions of muscle stimulation (gluteus medius, biceps femoris, and both gluteus medius and biceps femoris) using two electrode sizes, respectively, versus no stimulation during a landing task. A repeated measures ANOVA determined that KAM differed significantly among stimulation conditions and post hoc analysis revealed that KAM was significantly decreased in conditions of stimulating either the gluteus medius (p < 0.001) or the biceps femoris (p < 0.001) with the standard electrode size, and condition of stimulating both gluteus medius and biceps femoris with half-size electrode (p = 0.012) when compared to the control condition. Therefore, stimulation on the gluteus medius, the biceps femoris, or both muscles could be implemented for the examination of ACL injury potential.