An electromyographic evaluation of subdividing active-assistive shoulder elevation exercises

Area of Science:

• Orthopedics
• Sports Medicine
• Rehabilitation

Background:

• Active-assistive range of motion exercises for shoulder elevation are categorized as gravity-minimized or upright-assisted.
• Previous research has not compared the muscular demands of these exercise types.

Purpose of the Study:

• To compare the electromyographic (EMG) activity of shoulder muscles during gravity-minimized versus upright-assisted exercises.
• To determine if upright active forward elevation generates more EMG activity than other active-assistive exercises.

Main Methods:

• A controlled laboratory study involving fifteen healthy individuals.
• Electromyographic (EMG) amplitude of the supraspinatus, infraspinatus, and anterior deltoid was measured.
• Eleven exercises were performed in random order, with EMG normalized to maximal voluntary isometric contraction (MVIC).

Main Results:

• Significant differences in EMG activity were observed across exercises for all evaluated muscles (P < .001).
• Upright active forward elevation yielded the highest EMG activity for all muscles (12%-50% MVIC).
• Upright-assisted exercises showed greater anterior deltoid EMG activity (23%-42% MVIC) than gravity-minimized exercises (9%-21% MVIC).

Conclusions:

• A clear distinction in muscular demand exists between gravity-minimized and upright-assisted exercises for the anterior deltoid.
• While trends suggest increased EMG activity from gravity-minimized to upright-assisted for the infraspinatus and supraspinatus, the distinction is not always significant.
• Subdividing active-assistive exercises to protect the supraspinatus and infraspinatus may not be essential as muscle activation increases with reduced support.