Analysis of the ratios of medial-lateral and proximal-distal muscle activities surrounding the hip joint in the step-up and step-down positions.

Background: Many practitioners recommend step-up and step-down exercises to increase muscle strength in the lower extremities. However, decreased stability of the hip joint and imbalanced muscle activities can alter limb biomechanics during these movements.

Objective: This study investigated muscle imbalance between the medial and lateral muscle components and between the proximal and distal muscle components by expressing the proportions of muscle activation in the step-up and step-down positions.

Methods: Nineteen subjects participated in the study. Activity of the vastus medialis oblique, vastus lateralis, semitendinosus, biceps femoris, adductor, gluteus medius, and gluteus maximus was assessed.

Results: The semitendinosus-biceps femoris ratio was higher in the step-down position than in the step-up position. The adductor-gluteus medius, adductor-vastus lateralis, and adductor-biceps ratios were higher in the step-up position than in the step-down position. The gluteus maximus-biceps ratio was greater in the step-down position than in the step-up position. In the hip joint, internal rotation was significantly greater in the step-up position.

Conclusions: The transverse angle of the hip joint has a greater effect on the medial-lateral balance of the muscles surrounding the hip joint. Muscle activation in the medial hamstring is greater in the step-down position; in the adductor, muscle activation is greater in the step-up position. The step-down position is more appropriate for those with proximal weakness, as it can promote muscle activation in the gluteus maximus while maintaining biceps femoris activation.