The Addition of Real-time Ultrasound Visual Feedback to Manual Facilitation Increases Serratus Anterior Activation in Adults With Painful Shoulders: A Randomized Crossover Trial

Abstract Objective Serratus anterior (SA) muscle activation may be decreased with subacromial pain syndrome. The purpose of this study was to determine whether the addition of real-time ultrasound (RTUS) visual feedback increased activation of SA in adults with painful shoulders in comparison to manual facilitation alone. Methods This assessor-blinded, 2-period, randomized cross-over trial was conducted in a university medical imaging laboratory. Adults with mild-moderate unilateral subacromial pain received both interventions in random order with at least 1-week washout between interventions. Fourteen participants were randomized to receive manual facilitation with RTUS first, and 13 were randomized to receive manual facilitation alone first. Fifteen repetitions of a supine ``serratus punch'' were facilitated by RTUS visual feedback with manual facilitation or by manual facilitation alone. Levels of SA activation via surface electromyography were normalized to a maximum voluntary isometric contraction. Results A total of 25 participants completed the full trial of both interventions. Data from 25 participant periods for RTUS with manual facilitation and data from 26 participant periods for manual facilitation only were analyzed. The predicted marginal mean difference between interventions was 55.5% (95% CI = 13.9% to 97.1%) in favor of the addition of RTUS feedback. No adverse effects occurred. Conclusion RTUS visual feedback increases SA activation in adults with painful shoulders compared with manual facilitation alone. Impact Determining if RTUS can improve SA muscle activation may help clinicians improve physical therapist interventions for subacromial pain syndrome.