Does an Increase in Supraspinatus Tendon Thickness After Swimming Increase the Likelihood of Future Shoulder Pain?

Background Increase in supraspinatus tendon thickness (STT) resulting from swimming practice has been observed in those with a history of shoulder pain. The magnitude of change in STT after a swimming session and its rate of recovery may be an indicator of future shoulder pain incidence. Hypothesis The supraspinatus tendons that demonstrate a greater increase in thickness as a result of swimming practice will have an increased likelihood of future shoulder pain in a cohort of competitive swimmers over a period of 6 months. Design Descriptive epidemiology study. Level of Evidence: Level 2b, individual cohort studies. Methods: A cohort of 50 nationally qualified swimmers aged between 14 and 22 years, from 3 open National Swimming Programs in Victoria, Australia, were recruited for this study. Ultrasonographic measurements of swimmers' STT was obtained of both shoulders, before, immediately after, and 6 hours after a single swimming practice session. Data were recorded of any significant interfering shoulder pain at 3 and 6 months after the initial testing session. Results Stepwise logistic regression models indicated that significant predictors of the likelihood of experiencing significant interfering pain were sex [significant at 6 months; odds ratio (OR) 4.2] and the extent of change in STT immediately (OR 2.3 and 1.3 per mm at 3 and 6 months, respectively) and 6 hours postpractice (OR 1.9 and 1.5 per mm at 3 and 6 months, respectively). Conclusion The current data suggest larger increases in tendon thickness after training are associated with an increased likelihood of future shoulder pain. Clinical Relevance These data may be valuable for monitoring training load and identifying athletes who may have an increased likelihood of shoulder pain.