Effectiveness of a Standardised Stabilisation Exercise Protocol in Volleyball Players With Non-traumatic Shoulder Instability

Plain-language summary

This randomized controlled clinical trial aims to evaluate the effectiveness of a standardized shoulder stabilization exercise program in amateur volleyball players diagnosed with atraumatic shoulder instability. Shoulder pain is one of the most prevalent musculoskeletal complaints, affecting up to two-thirds of the general population at some point in life and frequently leading to long-term symptoms, functional limitations, sleep disturbances, and high socio-economic costs. Atraumatic glenohumeral instability is particularly common among athletes performing overhead movements, such as volleyball players, who are repeatedly exposed to high-velocity external and internal rotation actions during serves and spikes. The Derby Shoulder Instability Rehabilitation Programme (DSIRP) is a structured, reproducible protocol integrating strengthening, proprioceptive, neuromuscular control, plyometric, and speed-oriented exercises. Although widely used in clinical practice, evidence supporting its superiority over the natural progression of the condition remains limited. More than 80% of physiotherapists in the United Kingdom do not use specific standardized protocols for atraumatic shoulder instability, highlighting the need for high-quality clinical trials that evaluate structured rehabilitation approaches. This study will recruit amateur volleyball players aged 20 to 30 years with a clinical diagnosis of atraumatic shoulder instability lasting more than 3 months. Participants will be randomized (1:1) into two parallel groups: an experimental group performing the DSIRP for 8 weeks (three 25-minute sessions per week), and a control group following a "wait-and-see" approach. Outcome measures will be assessed at baseline, 1 month, and 2 months (post-intervention). The primary outcomes include pain intensity measured with the Numeric Pain Rating Scale and shoulder disability measured with the Spanish version of the Shoulder Pain and Disability Index. Secondary outcomes include external rotation strength, grip strength, shoulder range of motion, and health-related quality of life assessed with the SF-12 questionnaire. All measurements use validated instruments with high reliability for clinical and research settings. Statistical analysis will follow an intention-to-treat approach using mixed-model repeated-measures ANOVA or non-parametric alternatives when appropriate. Effect sizes and Bonferroni correction for multiple comparisons will be applied. An independent biostatistician blinded to allocation will conduct the analysis. The study follows CONSORT and TIDieR guidelines for reporting and intervention description. This trial seeks to determine whether a structured, progressive stabilization protocol offers clinically meaningful improvements in pain, disability, strength, mobility, and quality of life compared with no intervention in young volleyball players with atraumatic shoulder instability. Results may support the implementation of standardized rehabilitation strategies in physiotherapy practice for this condition.

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