Stretching-Positioned Extracorporeal Shock Wave Therapy Yields Superior Short-Term Efficacy for Post-Stroke Upper-Limb Spasticity: A Retrospective Comparative Study

Background Extracorporeal shock wave therapy (ESWT) reduces post-stroke spasticity, but the optimal muscle position during application is unclear. We hypothesized that ESWT applied under muscle stretch would yield superior anti-spastic effects. This study aimed to compare the short-term efficacy of ESWT on the biceps brachii under stretching versus relaxation postures. Material/Methods This retrospective comparative study analyzed data from 96 stroke patients categorized into Group A (ESWT under stretching, n=48) or Group B (ESWT under relaxation, n=48). Outcome measures included the Modified Ashworth Scale (MAS), Fugl-Meyer Assessment (FMA) for upper extremity, surface electromyography (average electromyography [AEMG]; root mean square [RMS]), and passive range of motion (PROM). Assessments occurred at baseline, immediately after treatment and at 6 h, 12 h, and 48 h. Results A significant Group×Time interaction was found for all outcomes (P<0.01). While both groups improved, post hoc tests revealed superior efficacy in Group A. At 12 h, Group B demonstrated higher spasticity (MAS score: 1.39±0.38 vs 0.97±0.25, P<0.001) and lower motor function (FMA-UE: 31.06±4.01 vs 33.01±2.87, P=0.007) versus Group A. By 48 h, outcomes regressed, but the rebound in MAS was significantly smaller in Group A (1.80±0.30 vs 2.15±0.41, P<0.001). Conclusions This exploratory study suggests that applying ESWT with the muscle under stretch provides a greater short-term reduction of spasticity and numerical improvement in motor function compared to relaxation positioning over 48 h. Treatment posture may be a factor influencing the immediate effects of ESWT, but the clinical implications remain uncertain.