Peroration: Hip Width and Metabolic Energy Expenditure of Abductor Muscles

We recently reported that functional pelvic width is not a statistically significant predictor of the metabolic energy expenditure of the hip abductor muscles during walking when mass, stature, and progression velocity were controlled. Others revised this analysis, suggesting that a different statistical approach would yield statistical significance. In order to address this suggestion, herein we refine our original analysis and increase our sample size.

Using a musculoskeletal model of the human body that estimates the metabolic energy expenditure of muscle activation for 66 people (33 females), 1093 trials were evaluated. Metabolic energy consumption for the abductor muscles was summed over a stride to create total abductor energy expenditure. A mixed effects model allowing the coefficient and slope of velocity to be a random effect was fit to the data.

We confirm our original analysis: functional pelvic width is not a statistically significant predictor of muscle metabolic energy expenditure of the hip abductors during walking.

We take as an initial assumption that a constraint on pelvic width exists and seek to establish if evidence for an energetic constraint is present in estimates of hip abductor muscle metabolic energy expenditure in humans. We find no such evidence in a sample of 66 people. Our results do not address whether or not a constraint on pelvic width exists, and we suggest that simulation of pelvic widths substantially wider or narrower than those observed in laboratory settings is necessary to assess this idea.