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Muscle activities in the region of neck, shoulder and back during isometric horizontal jaw exercises in various postures.

1990; Volume: 34; Issue: 1 Linguagem: Inglês

10.2186/jjps.34.157

1883-177X

Tadashi Yoshimatsu,

Ergonomics and Musculoskeletal Disorders

Eleven healthy participants were made to perform isometric horizontal jaw movements with maximum volantary efforts in various postures. Surface EMGs from the laterocervical, nucha, shoulder and back regions were bilaterally picked up, and simultaneously recorded with jaw force.The results obtained were as follows:1. Electromyographic power value in these regions depended on the directions of the jaw exercises (posteriorly pull> posterolaterally pull> anteriorly push anterolaterally push, P<0.0001).2. The directional effects mentioned above were significantly obvious in the inferior laterocervical (Electrode No.2) and back Electrode No.5) regions (P<0.0001).3. The postural effects on the power value were varied with the directions of the jaw exercises (P≈0.03); i.e., the highest value during jaw pull was observed in an upright position, while that during jaw push was found in a supine position.4. From above results, it would be considered that occlusal habits with sustained isometric jaw retrusion might have higher probability to provoke the discomfortableness in the neck, shoulder and back regions than those with protrusion, and that the habits with the retrusion might be more injurious in a supine than in an upright position, while those with the protrusion more injurious in an upright position.