Association of clinical and biomechanical measures of postural stability for musculoskeletal injury risk assessment in ballet dancers

Abstract

Introduction: Ballet is a strenuous activity and requires an extreme demand for physical valences, which makes the dancer prone to musculoskeletal injuries. In this population, the high (re) incidence of lower limb injuries creates complications in their careers. Dynamic postural stability tests, such as the Star Excursion Balance Test (SEBT) or its short version, the Y-Balance Test (YBT), are often used to assess the risk of lower limb injury. However, dancers are known to have exceptional motor skills, especially with regard to postural control, which is a potential complicating factor for assessing the risk of injury in this population. Objective:  In order to determine the usefulness of such tests in assessing the risk of injury to dancers, the aim of the present study was to investigate the relationship between clinical and biomechanical measures of postural stability and the characteristics and occurrences of musculoskeletal injuries in this population. Methods: Two observational studies were conducted with a total sample of 41 dancers. The characteristics of the lesions were surveyed using a standardized questionnaire. Postural control was assessed by posturography under quasi-static conditions (orthostatic posture and ballet-specific demi-point posture) and dynamic (during YBT performance). Results: In general terms, measures of amplitude and velocity of postural displacement were useful for discriminating balarinos with or without a history of injuries (Welch's t test, P <0.005, d> 1.741); however, this effect was observed only at the demi-point position, specific to the ballet. When applying YBT to assess injury risk, most dancers (85%) were classified as low risk. The characteristics of postural control during YBT were different when comparing the directions of the test (ANT, anterior; PL, posterior-lateral; PM, posterior-medial) and the gender of the dancers: specifically, the postural displacements were larger, slower and in the PL and PM directions in women (ANOVA P <0.010). Conclusion: In conclusion, we can state that posturographic measurements taken at specific ballet positions are able to distinguish those with or without a history of musculoskeletal injuries. On the other hand, the performance of a dynamic stability test cannot identify those with high risk of musculoskeletal injury, determined from the history of injury. In addition, the posturographic characteristics of such a test vary significantly between directions and gender. The utility of dynamic stability tests for risk assessment in this population needs to be considered with caution, taking into account the specificity of ballet positions and gender of the dancers evaluated.