Quality assessment of shoulder plyometric exercises: Examining the relationship to scapular muscle activity

Objectives The purpose of the study was to evaluate performance quality of shoulder plyometric exercises, and examine the relationship to scapular muscle activation during an intense exercise bout. Design Observational study. Setting University laboratory. Participants 32 healthy university students (male/female: 14/18) volunteers. Main outcome measures Subjects performed 10 plyometric exercises. Surface EMG of upper (UT), middle (MT) and lower (LT) trapezius and serratus anterior (SA) was registered. A quality assessment questionnaire was administered at the beginning and end of the exercise bout. Muscle activation at the beginning and end was evaluated by t-test. Mixed repeated measures ANOVA was conducted to test the effects of criterion-quality, time, muscles, exercises, and their interactions. Results Increased EMG activation was noted in 34/40 cases, (21/40 significant (p < 0.05) changes). Quality assessment revealed a decline in the ability to maintain initial position (43% of subjects), failure to keep a consistent and symmetrical arc of motion (62% of subjects), and performance with trick movements (48% of subjects). Inability to keep a consistent arc of motion was significant in 4 exercises. Conclusions The novel questionnaire may aid quality assessment during plyometric exercises. Ability to keep a consistent arc of motion was the most sensitive marker of decline of performance quality.