Comparative Analysis of Lower Limb Muscle Activity in Generalised Joint Hypermobility, Non-Hypermobile and hEDS Dancers During releves / Bonnie Southgate (2024)

The prevalence of joint hypermobility (JH) in dancers has garnered increasing attention in clinical and research settings. However, existing studies often fail to distinguish between dancers with generalised joint hypermobility (GJH) and those with underlying connective tissue disorders such as hypermobility spectrum disorder (HSD) or hypermobile Ehlers-Danlos syndrome (hEDS). This lack of differentiation may contribute to the mixed and sometimes contradictory outcomes observed in current research. The potential for dance training to enhance flexibility, as demonstrated by studies examining the lumbar flexion component of the Beighton scoring system, further complicates the interpretation of hypermobility in dancers. This study posits that separating dancers with diagnosed hypermobility syndromes from those with non-symptomatic hypermobility may provide a more accurate representation of the hypermobility spectrum in dance and its effects. Considering the potential for altered tissue properties in dancers with connective tissue disorders, this study aimed to examine differences in muscle activation patterns among dancers with a known connective tissue disorder, those who met the criteria for GJH, and those who did not. This exploratory study utilized surface electromyography (EMG) to investigate muscle activation patterns in non-hypermobile, GJH, and hEDS dancers during relevés under four conditions: hyperextended knee with and without intrinsic foot activation, and straight knee with and without intrinsic foot activation. Thirteen dancers (3 males and 10 females; mean age: 23.9 ± 4.3 years) participated in the study. Results showed significantly lower peak muscle activation in hEDS dancers (mean: 78.3 ± 15.2% MVC) compared to both the GJH (mean: 146.0 ± 22.5% MVC, p < 0.001) and non-hypermobile dancers (mean: 124.0 ± 18.7% MVC, p < 0.001) across all muscles studied. No significant difference was found between GJH and non-hypermobile dancers (p = 0.725). The soleus muscle demonstrated the highest activation across all groups. Dancers with hEDS showed a faster return to baseline activation (mean time: 1.16 ± 0.09 s) compared to the GJH (1.27 ± 0.11 s, p = 0.029) and non-hypermobile dancers (1.21 ± 0.10 s, p = 0.245). These findings suggest altered neuromuscular control strategies in dancers with hEDS and highlight the need for individualised training approaches for dancers with different degrees and types of hypermobility.