Training Induces Scapular Dyskinesis in Pain-Free Competitive Swimmers: A Reliability and Observational Study

OBJECTIVE: Scapular dyskinesis is a major etiological factor in overhead athletes' shoulder problems. Our hypotheses were to evaluate if (1) visual observation of scapular dyskinesis during scaption has substantial interobserver reliability, and (2) scapular dyskinesis may be induced by swim training in pain-free swimmers. DESIGN: A reliability and observational study. SETTING: Bachelor project at a college institution and at a private sports orthopedic hospital. PARTICIPANTS: Seventy-eight competitive swimmers with no history of shoulder pain were included in the study. Fourteen swimmers were evaluated regarding reliability. Inclusion criteria were competitive swimmers with high training volume who previously had no shoulder pain. INTERVENTIONS: Observations of scapular dyskinesis (yes/no) during simple scaption. The interobserver reliability of scaption and wall push-up was evaluated in 14 swimmers using kappa analysis. MAIN OUTCOME MEASURES: Prevalence of scapular dyskinesis at 4 time intervals during a swim training session. RESULTS: The scaption test resulted in a weighted kappa value of 0.75. Scapular dyskinesis was seen in 29 shoulders (37%) after the first time interval, in another 24 (cumulated prevalence 68%) after one-half of the training session, and in an additional 4 swimmers (cumulated prevalence 73%) after three-quarters of the training session. During the last quarter of the training session, another 7 swimmers had dyskinesis, resulting in a cumulated prevalence of 82%. CONCLUSIONS: The prevalence of abnormal scapular kinesis during a normal training session is high in previously pain-free swimmers. The prevalence increases with more training and occurs early during the training session.