630 FO60 – Plantarflexion weakness exists before calf muscle or Achilles tendon injuries in professional rugby union players

Background Plantarflexor weakness has been associated with calf muscle and Achilles tendon (CaAT) injuries however the temporal relationship remains unclear. Objective Primary aim – to investigate the relationship between plantarflexor strength and CaAT injuries in a cohort of professional rugby union players. Design Longitudinal, prospective cohort study across a single season. Plantarflexor strength and injury status was tested at early, mid and late season. Setting Male, full-time, Professional Rugby Union athletes from 6 teams competing in the English Premiership competition. Patients or Participants All players at involved teams were invited to participate. Only players deemed fit to complete testing by club medical staff were included at each point. Players currently injured due to CaAT symptoms were also excluded. 364 unique players were included (early season = 278, mid-season = 261 and end-season = 172). Interventions None. Main Outcome measures Primary independent variable was maximal Isometric Plantarflexion strength (IPF). The primary dependent variable was CaAT pain as reported via a symptom questionnaire. Results 76 unique CaAT injuries occurred during the study with a strength measure prior to onset of pain. Mean IPF (normalised to Body mass) of the asymptomatic group was 1.92 xBW (SD 0.33). Mean IPF of the asymptomatic limbs that went on to become symptomatic was 1.80 xBW (SD 0.36). Independent samples t-test to compare the means showed a significant difference (t (908) = 2.80, p = 0.004). The magnitude of difference (mean difference = 0.114, 95% CI: 0.034 to 0.195) xBW. Cohens d = 0.34 (CI95% 0.101–0.572) indicated a small-moderate effect size. Conclusions Rugby players who develop CaAT pain are significantly weaker than players who do not sustain injuries. Monitoring of IPF appears important for injury modification, further studies are needed to determine if improvements in IPF mitigate injury risk.