Objective To compare the efficacy and underlying mechanisms of scapular dyskinesis-based exercise therapy (SDBET) and multimodal physical therapy (MPT) in young male overhead athletes with subacromial impingement syndrome (SIS) and scapular dyskinesis (SD). Methods This single-center, single-blind, parallel-group superiority randomized controlled trial was designed to compare two interventions in athletes clinically diagnosed with SIS and SD. Outcome assessors were blinded to group allocation. Sample size was determined a priori using G*Power (f = 0.25, a = 0.05, power = 0.80), yielding a required sample of 28; 32 participants were planned to account for potential dropout. Inclusion criteria were: male overhead athletes aged 18-25 years with clinically diagnosed SIS and SD. Exclusion criteria included prior surgery or other contraindications. Participants were randomized to either SDBET or MPT groups. Both groups received 8 weeks of intervention (3 sessions/week) and a 4-week follow-up. The primary variable was disability, measured using the Shoulder Pain and Disability Index (SPADI). The secondary variables were pain (measured using the Visual Analog Scale [VAS]), shoulder active range of motion (AROM, measured using goniometry), strength (measured using Isometric Strength Tests [IST] of scapular stabilizers and external rotators), and scapular kinematics (measured using the Scapular Dyskinesis Test [SDT]). Assessments were conducted at baseline, week 8, and week 12. Result A total of 32 participants were analyzed (SDBET group: n = 16; MPT group: n = 16). Mixed-design ANOVA revealed significant main effects of time for all outcomes (all p < 0.001, n² = 0.71-0.92), and significant group effects for SPADI and IST (p < 0.01). Significant Time × Group interactions were also observed for all variables (p < 0.05, n² = 0.15-0.76), prompting further simple effects analysis. Disability (SPADI) decreased significantly in both groups by week 8 (p < 0.001, n² = 0.03), with no between-group difference. However, only the SDBET group maintained improvements at week 12 (p < 0.001, n² = 0.59). Pain (VAS) decreased more in the MPT group at week 8 (p = 0.018, n² = 0.17), but rebounded by week 12, eliminating group differences (p = 0.268, n² = 0.04). Active range of motion (AROM) improved in both groups by week 8 (p < 0.001), with only the SDBET group sustaining these gains at week 12 (p < 0.001, n² = 0.37). Strength (IST of scapular stabilizers and external rotators) improved exclusively in the SDBET group at both week 8 and 12 (all p < 0.001), with significant between-group differences (n² = 0.57-0.74). Scapular kinematics (SDT) improved in 43.8% of SDBET participants, while no change was observed in the MPT group (p = 0.001-0.004). Conclusion Both SDBET and MPT improved shoulder disability, pain and AROM in SIS patients with SD, but only SDBET showed lasting effects. Targeted therapy has more comprehensive and sustained effects. Trial registration This study was retrospectively registered in the Chinese Clinical Trial Registry on 03/04/2025 (Registration Number: ChiCTR2500100213), after the completion of participant enrolment due to administrative oversight. Although registration occurred post-enrolment, the study protocol was finalized and ethically approved prior to participant recruitment. The authors acknowledge the importance of prospective trial registration and are committed to adhering to this standard in all future trials.
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