Exposure to impacts across a competitive rugby season impairs balance and neuromuscular function in female rugby athletes

Abstract

Objectives We used objective assessment tools to detect subtle neurological deficits that accompany repetitive and mild head impacts in contact sport across a season. Methods Female participants (n=13, 21±1.8 years old; 167.6±6.7 cm; 72.8±6.1 kg) completed assessments pre and post the varsity rugby season. A commercial balance board was used to assess static balance and response to dynamic postural challenge. Spinal cord excitability via the soleus H-reflex was assessed in both legs. Video analysis was used to identify head impact exposures. Results A total of 172 potential concussive events were verified across 11 athletes (15.6±11; 95 CI: 6.5 to 19.8). Balance performance was worse at post-season for total centre of pressure which increased by 26 in the double stance on a stable surface (t(12)=-2.33; p=0.03; d=0.6) and by 140 in the tandem stance on a foam surface (t(12)=-3.43; p<0.01; d=0.9). Despite that, dynamic postural performance was improved after the season (p<0.01). Spinal cord excitability in rugby athletes did not change across the season but deviated from normative values at baseline. Conclusion Quantitative measures revealed that exposure to impacts across a competitive rugby season impair balance in two specific stances in female rugby athletes. Tandem-leg stance on an unstable surface and double-leg stance on firm surface are useful assessment conditions when performed over a low-cost balance board, even without clinically diagnosed concussion.