Shoulder girdle muscle activity at rest and during jaw and shoulder movements in participants with and without temporomandibular disorders: A cross-sectional observational study

Background

Previous studies have shown the effects of temporomandibular joint (TMJ) alignment on the shoulder girdle muscles. No previous research has investigated the difference in activity of these muscles in those with and without temporomandibular disorders (TMD).

Objective

The study aimed to compare the activity of the shoulder girdle muscles in participants with and without TMD. Furthermore, to determine if there was a relationship between pain and disability of the TMJ and shoulder girdle.

Methods

A cross-sectional observational study was performed on participants with and without TMD. An assessment of pain, disability, range of the TMJ, scapulohumeral rhythm and muscle activity of the biceps, medial deltoid, infraspinatus, inferior trapezius and serratus anterior bilaterally was done. Statistical analysis was performed using IBM SPSS Statistics Version 28 and Microsoft Excel.

Results

Compared to those without TMD, participants with TMD had lower activity of all shoulder muscles during shoulder movements with significant differences of the right biceps during shoulder abduction (d = 0.33, p = 0.049), left infraspinatus (d = 0.38, p = 0.022) and right infraspinatus during shoulder flexion (d = 0.48, p = 0.004) and abduction (d = 0.33, p = 0.049). Lower shoulder muscle activity in participants with TMD was also seen during jaw movements, except for the right inferior trapezius, medial deltoid and serratus anterior, which had higher activity in participants with TMD.

Conclusion

The majority of the shoulder muscles had lower activity at rest, during jaw and shoulder movements in participants with TMD.