The goal of this clinical trial is to learn if Floss Band application works as effectively as mobilization with movement (MWM) to improve shoulder mobility in volleyball athletes. It will also explore whether these techniques affect athletes' perception of movement fluency and sport-specific performance.

The main questions it aims to answer are:

Does Floss Band application immediately improve shoulder range of motion in volleyball athletes? Does Floss Band application change the perception of movement fluency compared to MWM? Does Floss Band application impact sport-specific performance tests compared to MWM?

Participants will:

Be randomly assigned to receive either Floss Band or mobilization with movement Have their shoulder mobility, perception of movement, and sport performance tested before and immediately after the intervention

Overhead sports such as volleyball demand repetitive, high-velocity arm movements that predispose athletes to musculoskeletal adaptations, especially in the glenohumeral joint. Among these, glenohumeral internal rotation deficit (GIRD) is a frequent finding, typically associated with posterior capsular tightness and muscular adaptations. This condition has been linked to decreased shoulder performance and a greater risk of overuse injuries.

Conservative approaches are essential for preserving mobility and reducing injury risk in overhead athletes. Mobilization with movement (MWM) is a well-established manual therapy intervention, combining therapist-applied accessory glenohumeral mobilization with the athlete's active shoulder motion. Evidence supports its capacity to produce immediate improvements in range of motion and sensorimotor control.

In contrast, the use of compressive elastic bands, or Floss Bands, represents a more recent strategy in rehabilitation. Proposed mechanisms include transient ischemia followed by reperfusion, improved soft tissue gliding, neuromuscular activation, and increased proprioceptive input. Although Floss Band applications have gained popularity, robust evidence on their effects in overhead athletes is still limited.

The current randomized, controlled, double-blind equivalence trial aims to compare the immediate effects of Floss Band application with MWM on shoulder mobility in volleyball athletes. The equivalence design was selected because both interventions are hypothesized to provide similar clinical benefits, and the study seeks to determine whether the novel approach (Floss Band) is not inferior to the well-established MWM.

Intervention Procedures Participants will undergo two assessments: baseline and immediately post-intervention. Interventions will be delivered by researchers trained and standardized in both techniques.

Floss Band Group (FBG): The participant will be seated with the shoulder positioned at 90° abduction. The researcher will apply a compressive elastic band (100% polymer gel, 210 cm circumference, 5 cm width, 1.3 mm thickness). The first anchor will be placed two finger-widths medial to the acromion, and the band will be wrapped circumferentially around the shoulder until the material length is exhausted, securing the final anchor. During the two-minute application, the participant will perform sport-specific movements (e.g., spike and serve gestures). After the time limit, the band will be removed.

Mobilization with Movement Group (MWM): The participant will remain seated with back support and hips, knees, and ankles flexed at 90°. The therapist will stabilize the scapula with one hand, while the other hand will apply a posterolateral glide to the humeral head during active arm elevation in the scapular plane. The protocol will consist of three sets of 10 repetitions, with one-minute rest intervals between sets.

Data Management and Quality Assurance All assessors will undergo standardized training to ensure consistency across evaluations. Prior to trial initiation, pilot testing of procedures will be conducted. Data will be collected using predefined case report forms and transferred into a secure electronic database.

Quality assurance measures will include:

Data validation: Automated checks for range, completeness, and logical consistency between variables.

Source data verification: Cross-checks of electronic entries with original case report forms by an independent monitor.

Auditing: Periodic audits conducted by external staff not involved in data collection or intervention delivery.

Standard Operating Procedures (SOPs): Detailed instructions for participant recruitment, intervention delivery, data entry, adverse event reporting, and change management.

Data dictionary: Comprehensive description of variables, coding schemes, and reference values to maintain consistency and transparency.

Sample Size and Statistical Plan The trial is powered to detect equivalence between interventions in the primary outcome (shoulder ROM). A total of 36 athletes will be randomized equally across groups, stratified by sex and age. Analyses will follow the intention-to-treat principle. Between-group differences will be adjusted for baseline values, and 95% confidence intervals will be calculated to test equivalence margins. Missing data will be addressed with multiple imputation methods.

Expected Contribution By comparing an innovative compressive technique with an established manual therapy, this study is designed to provide high-quality evidence on immediate intervention effects in volleyball athletes. The results are expected to inform clinicians, coaches, and sports medicine professionals on effective strategies for optimizing shoulder function and preventing injury in overhead sports.

Inclusion Criteria:

• Age between 18 and 50 years.
• Male or female volleyball athletes (indoor or beach), at amateur or professional level.
• Regular training routine of at least two sessions per week.
• No shoulder pain at the time of testing or during the previous three months.

Exclusion Criteria:

• History of shoulder surgery, structural shoulder injuries (e.g., fractures, labrum tear), or recurrent glenohumeral dislocation.
• Skin disorders contraindicating the intervention, including active dermatitis, inflammatory-phase psoriasis, cutaneous infections (e.g., folliculitis), open wounds, burns, eczema, or hypersensitivity in the shoulder region.
• Vascular disorders contraindicating the intervention, including history or diagnosis of deep vein thrombosis, symptomatic varicose veins, peripheral arterial disease, lymphedema, or advanced chronic venous insufficiency.
• Other conditions contraindicating intervention: peripheral neuropathies with significant sensory loss, presence of a pacemaker in the region of band application, known allergy to elastic band material, or pain during shoulder movement at assessment.
• Development of shoulder or elbow injuries during the study, especially requiring surgical intervention.
• Participants who voluntarily withdraw from the study at any time.

Individual participant data (IPD) collected in this study, including de-identified measurements of shoulder range of motion, functional performance tests, and perceived movement fluency, will be made available to other researchers. Data dictionaries describing each variable, coding, and units will also be provided. Sharing will occur in accordance with participant consent, ethical approvals, and data privacy regulations, after the publication of the main study results.

IPD and supporting information will be made available starting 6 months after publication of the main study results and will remain accessible for 5 years.

Data will be shared with qualified researchers upon request. Researchers must submit a data access request and sign a data use agreement outlining the intended analyses and ensuring confidentiality. Requests will be reviewed by the principal investigator to ensure that proposed use aligns with the study objectives and ethical standards.