Effects of percussion massage therapy and instrument-assisted soft tissue mobilization on proprioception, pain, disability, and quality of life in individuals with subacromial impingement syndrome: a randomized controlled trial

Background: This assessor-blinded randomized trial compared percussion massage therapy (PMT) and instrument-assisted soft tissue mobilization (IASTM) as adjuncts to conventional physiotherapy (CP) for subacromial impingement syndrome. Methods: Forty-two participants were randomized equally to PMT, IASTM, or time-matched active CP. All received CP five days weekly for four weeks; adjunct groups received 12-minute sessions thrice weekly. Primary outcomes were shoulder joint position sense (JPS) errors at 60° flexion and abduction; secondary outcomes included range of motion (ROM), pain, disability, and rotator cuff-related quality of life. Baseline-adjusted ANCOVA and Holm correction were used. Results: All participants completed treatment. Flexion JPS differed between groups (F(2,38)=5.76; Holm-adjusted p=0.013), favoring IASTM over CP (p=0.005), but not PMT over CP. Conventional abduction JPS analysis was nonsignificant (p=0.169), whereas exploratory robust analysis suggested significance (p=0.014). ROM differed across groups (all p<0.001), favoring PMT in conventional ANCOVA. Both adjuncts showed favorable pain and disability outcomes relative to CP, and PMT favored quality of life over IASTM; however, significant group-by-baseline interactions limited interpretability of several outcomes, including ROM, pain, disability, and quality-of-life. Conclusions: IASTM reduced flexion JPS error relative to CP, whereas PMT showed favorable ROM estimates. Baseline interactions and model sensitivity warrant cautious interpretation and larger confirmatory trials.