Background Adaptational changes (gleno-humeral internal rotation deficit – GIRD, SICK scapula signs and muscular imbalances) develop in the dominant shoulder of overhead athletes.

Objective To evaluate the incidence and the correlation between different adaptational changes and injury in the dominant shoulder. To evaluate the effect of (a)symmetrical hand-use on the development of adaptational changes and shoulder injury.

Design Observational cross-sectional correlational study.

Setting and participants 36 highly competitive female overhead athletes (21 handball players, 15 volleyball players), competing in Middle European volleyball league, EHF women's champions league and Slovene National leagues and National cups. Players were divided into two groups by the symmetry of hand-use.

Interventions Participants completed a self-reported shoulder history questionnaire. Complete clinical examination of the shoulders was performed, including passive internal (IR) and external rotation (ER), SICK scapula and GIRD evaluation. Isokinetic testing of IR and ER was performed in concentric (c) and eccentric (e) modes at two testing speeds (60°/s, 150°/s). Fatiguability of IR and ER was measured. Stability spiking (eER/cIR) and cocking ratios (eIR/cER) were calculated.

Results All participants had decreased IR and increased ER ROM in dominant shoulders (p>0.001). Average GIRD was 20.6°, greater GIRD correlated with higher cIR peak torques (p=0.008). Dominant hand eER peak torques were lower, hence the spiking ratios were lower (p=0.015 and p=0.002). Players with previous injury showed more scapular abduction, increased ER and lower cocking ratios (p=0.04, p=0.036, p=0.06). Players with asymmetrical hand-use showed higher fatiguability of IR and ER (p=0.019, p=0.01).

Conclusions Static and dynamic adaptational changes are found in the dominant shoulder and are positively correlated to each other and to history of injury. Hitters and throwers fatigue more. Preventive shoulder training is crucial for injury prevention of highly competitive overhead athletes with existing adaptational changes.