Effects of forward head posture on forced vital capacity and respiratory muscles activity

Abstract

[Purpose] This study investigated the effects of forward head posture on forced vital capacity and deep breathing. [Subjects] Twenty-six subjects, divided into the two groups (normal and forward head posture groups), participated in this study. [Methods] Forced vital capacity and forced expiratory volume in 1 second were measured using respiratory function instrumentation that met the American Thoracic Society’s recommendation for diagnostic spirometry. Accessory respiratory muscle activity during deep breathing was measured by electromyography. A Mann-Whitney test was used to compare the measure variables between the normal and forward head posture group. [Results] Forced vital capacity and forced expiratory volume in 1 second were significantly lower in the forward head posture group than in the normal group. Accessory respiratory muscle activity was also lower in the forward head posture group than in the normal group. In particular, the sternocleidomastoid and pectoralis major activity of the forward head posture group was significantly lower than that of normal group. Activities of the other muscles were generally decreased with forward head posture, but were not significantly different between the two groups. [Conclusion] These results indicate that forward head posture could reduce vital capacity, possibly because of weakness or disharmony of the accessory respiratory muscles.

Association Between Forward Head, Rounded Shoulders, and Increased Thoracic Kyphosis: A Review of the Literature

“…1,2 The head constitutes 6% of the total body weight, which is linked to the cervical spine and all other joints through the kinematic chain 3 by various muscles.…”

Effects of stretching the scalene muscles on slow vital capacity

“…Therefore, if the SCM and scalene have a large volume, a large muscular contraction force per unit area, and a large change in muscle length per unit time, the thorax is lifted to a greater extent and the inhalation volume increases. In this regard, Han et al 17 ) also noted that forward head posture could reduce vital capacity, possibly because of weakness of the accessory respiratory muscles. This means that respiratory function is related to the functions of the SCM and scalene muscle.…”

“…Likewise, the EVC increased because the scalene was relaxed and the descent of the thorax during exhalation became larger, further increasing intrathoracic pressure. In addition, Han et al 17 ) also mentioned that forward head posture could reduce vital capacity, possibly because of weakness of the accessory respiratory muscles.…”

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