Activation of the gluteus maximus, gluteus medius and tensor fascia lata muscles during hip internal and external rotation exercises at three hip flexion postures.

Background: Hip internal and external rotation exercises are usually performed in clinical practice. However, given the synergies required to stabilize the hip in the frontal plane, it is not clear how the activation of target muscles will differ between the two exercise directions.

Objective: I) Compare the activation of the upper and lower fibers of gluteus maximus (GMax), gluteus medius (GMed) and tensor fascia lata muscles between the hip internal and external rotation exercises; ii) Compare the maximal isometric force between hip internal and external rotation exercises and; iii) Assess the effect of varying hip flexion angles on muscle activation and maximal isometric force.