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

Atraumatic shoulder instability is a prevalent condition among athletes who perform repetitive overhead movements, particularly volleyball players. The biomechanical demands of serving, spiking, and blocking expose the glenohumeral joint to repeated high-velocity rotational forces, which may contribute to impaired neuromuscular control, altered proprioception, and insufficient dynamic stabilization. These factors can lead to recurrent symptoms of pain, weakness, and functional limitation, often persisting for extended periods and interfering with sports performance and daily activities.

Although physiotherapy is widely recognized as a first-line approach for managing atraumatic shoulder instability, clinical practice frequently lacks standardized and reproducible rehabilitation protocols. Existing programs vary significantly in content, dosage, and progression criteria, limiting consistency across clinicians and settings. The Derby Shoulder Instability Rehabilitation Programme (DSIRP) is one of the few structured intervention models specifically designed for this condition. It integrates strengthening, proprioception, plyometric exercises, and motor control tasks, with progression based on clearly defined functional milestones. However, despite its clinical use, robust comparative evidence supporting its effectiveness remains limited.

This randomized controlled trial aims to evaluate the clinical impact of an eight-week DSIRP-based intervention compared with no active treatment in amateur volleyball players aged 20 to 30 years with at least three months of atraumatic shoulder instability. The study follows CONSORT and TIDieR recommendations to ensure transparent reporting and comprehensive intervention description. Participants are randomly allocated in a 1:1 ratio to either the experimental group, which performs the structured exercise program three times per week, or the control group, which receives no intervention ("wait-and-see"). The analytical team remains blinded to group assignment.

The intervention is designed to address multiple dimensions of shoulder stability, including rotator-cuff strength, scapular control, reactive stability, and proprioceptive acuity. It progresses through phases that incorporate isometric and isotonic strengthening, closed-chain stability tasks, rhythmic stabilization, plyometric drills, and functional movement patterns relevant to overhead athletes. Session duration and frequency are standardized, but progression criteria ensure individualized advancement according to each participant's ability to meet predefined performance targets.

Outcome assessments are conducted at baseline, one month, and after the completion of the eight-week intervention. Measures span several domains relevant to shoulder instability, including pain intensity, self-reported disability, shoulder mobility, isometric strength, and overall health-related quality of life. All clinical instruments used in the study have demonstrated strong reliability and validity in previous research. The measurement protocol ensures standardized positioning and examiner consistency to reduce variability.

The statistical analysis incorporates repeated-measures models to evaluate changes over time and between groups. Parametric or non-parametric methods are selected based on data distribution, and effect sizes are calculated to quantify the magnitude of observed changes. A blinded biostatistician performs all analyses to minimize bias.

This study is designed to generate high-quality evidence on the usefulness of a structured, pathology-specific rehabilitation program for atraumatic shoulder instability in young overhead athletes. By comparing the DSIRP-based intervention with a no-treatment control condition, the trial aims to clarify whether a well-defined and reproducible exercise protocol leads to meaningful improvements in pain, function, strength, and mobility. Findings may inform clinical practice, support the adoption of standardized rehabilitation pathways, and contribute to reducing the variability that currently characterizes conservative management of this condition.