Gluteal Muscle Size and Quality in Professional Ballet Dancers Compared to Non-Dancing Athletes.

INTRODUCTION: Professional ballet dancers load their hips in extreme ranges of motion and commonly report hip pain. Evaluating gluteal muscle size and quality may help guide exercise programs. Objectives of this study were to compare gluteal muscle size and quality (fatty infiltration) in ballet dancers compared to athletes; and to investigate the relationship between gluteal muscle size and quality, and reports of hip-related pain.

METHODS: This study was a case-control design. Professional ballet dancers (current and retired, n = 49, mean age 35 years, range 19-63) and age and sex-matched athletes (current and retired, n = 49) underwent magnetic resonance imaging of both hips. Muscle cross-sectional areas (CSA) were obtained at standardized landmarks for gluteus maximus (GMax) and gluteus medius (GMed). Full muscle volume was calculated for gluteus minimus (GMin). Fatty infiltration was rated using the Goutallier classification system. Muscle size was compared between groups using linear mixed models. Fatty infiltration was compared using a mixed model binary logistic regression. Hip-related pain, participation status, limb side and sex were included as covariates.

RESULTS: Ballet dancers had significantly larger GMax (upper P  < .01, middle P  < .01, lower P  = .01) and GMed (level of anterior inferior iliac spine P  < .01, greater sciatic foramen P  < .01) CSA and larger GMin volume ( P  < .01), when normalized to weight. There was no difference in fatty infiltration ratings between dancers and non-dancing athletes. Retired dancers and athletes reporting hip-related pain were more likely to have fatty infiltration in GMax lower ( P  = .04).

CONCLUSION: Gluteal muscles are larger in ballet dancers compared to athletes suggesting high-level loading of these muscles. There is no relationship between hip-related pain and gluteal muscle size. Dancers and athletes have comparable muscle quality.