The Effect of Head Posture on Myoelectric Activity of Some Scapular Muscles in Arm Abduction

The aim of this study was to assess the activity of scapular muscles in subjects with forward head posture. The statistical population consisted of female students living in University of Tehran dormitories. 14 healthy girls and 18 girls with forward head posture aged between 23 and 30 were selected. The electromyography activity of serratus anterior، upper trapezius and lower trapezius were recorded during arm abduction. To normalize the data، the mean square of level of electromyography of each muscle was divided by the mean square of level of isometric contraction. Independent t test was used to compare the results in the two groups. The results showed that the electric activity of upper trapezius (P=0. 002) in subjects with forward head posture was higher than the healthy group while lower trapezius and serratus anterior showed no difference between the groups. The results showed a difference in electromyography activity of upper trapezius during arm abduction between the healthy group and forward head group. Thus، it can be concluded that normal head posture during arm abduction can support the biomechanical head posture to reduce excessive activity of the upper trapezius.