M-mode ultrasound imaging of the hip abductors
Of all hip abductors, gluteus minimus contains the highest percentage of slow twitch fibers and muscle spindles, rendering the muscle most appropriate for finely adjusted, low force, long-lasting activities.
This study hypothesed that there is a difference in activation of the gluteus minimus and gluteus medius during abduction in side lying exercises and weight bearing exercises.
The hip abductor complex comprises, at the deepest level, the gluteus minimus; at the intermediate level, the gluteus medius and piriformis; and at the superficial level, the upper portion of the gluteus maximus and the tensor fasciae lata.
The gluteus minimus has a shorter lever to produce abduction in comparison to the gluteus medius. It’s specific function is to pull, adjust and hold the acetabulum over the femoral head.
This article suggests that the M-mode ultrasound imaging revealed different patterns of the onset activity-related hip muscle motion between hip exercises. Compared to hip abduction in side-lying, the weight bearing exercises, weight shift to one-legged stance and ‘hip hitch’ showed a higher differentiation between gluteus minimus and deep gluteus medius activity onsets revealed by larger individual variability of onset differences. Larger differentiation of muscle motion onsets in weight bearing exercises were also observed between the deep and the superficial gluteus medius regions. The active straight leg lengthening exercise showed only a non-significant trend towards a higher differentiation of activity of hip abductor muscles. The time span between gluteus minimus and deep gluteus medius onset was highly variable with onset differences up to 200ms.
> From: Dieterich et al., Man Ther (2015) 715-722. All rights reserved to Elsevier Ltd. . Click here for the Pubmed summary.