Electromyographic recordings in shoulder muscles during eccentric movements

Area of Science:

• Biomechanics
• Musculoskeletal Research
• Orthopedics

Background:

• Joint laxity, particularly in the shoulder, can lead to instability.
• Understanding muscle activation patterns is crucial for managing shoulder instability.

Purpose of the Study:

• To investigate shoulder muscle activity during eccentric movements.
• To compare electromyograms (EMG) between individuals with joint laxity and normal subjects.

Main Methods:

• Electromyograms (EMG) were recorded from 8 shoulder muscles during eccentric movements.
• Both normal subjects and patients with generalized joint laxity were studied.
• Intramuscular and surface electrodes were used to capture muscle activity.

Main Results:

• A general trend of multi-muscle activation was observed during all movements.
• Patients with joint laxity exhibited higher supraspinatus and subscapularis muscle activation during flexion and adduction.
• Muscle activation magnitude was significantly lower during eccentric movements compared to concentric movements in both groups.

Conclusions:

• Increased supraspinatus and subscapularis activity in lax joints may enhance anterior shoulder stability.
• Eccentric muscle contractions demonstrate lower activation levels than concentric contractions.
• Findings provide insights into the neuromuscular control of shoulder stability in joint laxity.