Investigating the association between supraspinatus tendon abnormality, shoulder pain and isokinetic strength in elite swimmers : a cross-sectional study

Abstract

Shoulder pain is common among elite swimmers due to the tre-mendous stress over shoulders during swimming. Supraspinatus muscle is one of the major prime movers and stabilizers of shoul-der and is highly susceptible to overloading and tendinopathy. An understanding of the relationship between supraspinatus tendon and pain; and between supraspinatus tendon and strength would assist health care practitioners for developing training regime. The objectives of this study are to evaluate 1) the association be-tween structural abnormality of supraspinatus tendon and shoul-der pain and 2) the association between structural abnormality of supraspinatus tendon and shoulder strength. We hypothesized that structural abnormality of supraspinatus tendons positively as-sociated with shoulder pain and negatively associated with shoul-der muscle strength among elite swimmers. 44 elite swimmers were recruited from the Hong Kong China Swimming Associa-tion. Supraspinatus tendon condition was evaluated using diag-nostic ultrasound imaging and shoulder internal and external ro-tation strength was evaluated by the isokinetic dynamometer. Pearson's R was used to study the correlation between shoulder pain and supraspinatus tendon condition and to evaluate the asso-ciation between isokinetic strength of shoulders and supraspina-tus tendon condition. 82 shoulders had supraspinatus tendinopa-thy or tendon tear (93.18%). However, there was no statistically significant association between structural abnormality of suprasp-inatus tendon and shoulder pain. The results showed that there was no association between supraspinatus tendon abnormality and shoulder pain and there was a significant correlation between left maximal supraspinatus tendon thickness (LMSTT) and left external rotation/ concentric (LER/Con) and left external rotation/ eccentric (LER/Ecc) shoulder strength (p < 0.05) while internal rotation/ external rotation (IR/ER) ratio can also be a significant predicator on LMSTT >6mm (R2 = 0.462, F = 7.016, df = 1, p = 0.038). Structural change of supraspinatus tendon was not associ-ated with shoulder pain, but could be a predictor on MSTT >6mm in elite swimmers.