Influence of forward head posture on scapular upward rotators during isometric shoulder flexion
Jong-Hyuck Weon, Jae-Seop Oh, Heon-Seock Cynn, Yong-Wook Kim, Oh-Yun Kwon. Journal of Bodywork and Movement Therapies.
We assessed the effects of forward head posture in the sitting position on the activity of the scapular upward rotators during loaded isometric shoulder flexion in the sagittal plane.
Healthy volunteers (n = 21; 11 men, 10 women) with no history of pathology participated in the study. Subjects were instructed to perform isometric shoulder flexion with the right upper extremity in both the forward head posture (FHP) and neutral head posture (NHP) while sitting. Surface electromyography (EMG) was recorded from the upper trapezius, lower trapezius, and serratus anterior muscles. Dependent variables were examined by 2 (posture) × 3 (muscle) repeated measures analysis of variance. Significantly increased EMG activity in the upper trapezius and lower trapezius and significantly decreased EMG activity in the serratus anterior were found during loaded isometric shoulder flexion with FHP. Thus, FHP may contribute to work-related neck and shoulder pain during loaded shoulder flexion while sitting.
These results suggest that maintaining NHP is advantageous in reducing sustained upper and lower trapezius activity and enhancing serratus anterior activity as compared with FHP during loaded shoulder flexion.
Loaded isometric shoulder flexion at 90° shoulder flexion. (A) Neutral head position. (B) Forward head position.
A relationship between pectoralis minor muscle tightness and rounded shoulder posture (RSP) has been suggested, but evidence demonstrating that treatment aimed at the pectoralis minor affects posture or muscle function such as lower trapezius strength (LTS) remains lacking. In this randomized, blinded, controlled study of the 56 shoulders of 28 healthy participants, the experimental treatment consisting of pectoralis minor soft tissue mobilization (STM) and self-stretching significantly reduced RSP compared to the pre-treatment baseline (Friedman test, < .001) and the control treatment of placebo touch and pectoralis major self-stretching (Mann–Whitney U-test, <.01). RSP remained significantly reduced 2 weeks after the single treatment. Both control and experimental treatments resulted in increased LTS (Friedman test, p< .01) with no significant difference in LTS noted between treatments (p> .05). This study demonstrated that STM and self-stretching of the pectoralis minor can significantly reduce RSP.
Possible clinical relevance:
• Soft tissue mobilization and stretching of the pectoralis minor muscle can reduce rounded shoulder posture.
• Soft tissue mobilization and stretching of the pectoralis minor muscle is no more effective than passive touch and pectoralis major stretching in increasing lower trapezius muscle strength.
• The 2.5 cm threshold for the supine measure of rounded shoulder posture may not detect dysfunction.
The effects of manual treatment on rounded-shoulder posture, and associated muscle strength
Journal of Bodywork and Movement Therapies (In Press, Available online 26 June 2009). Christopher Kevin Wong, Denise Coleman, Vincent diPersia, Judi Song, Dennis Wright.