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Phys. Ther. Korea 2019; 26(2): 61-68

Published online May 31, 2019

https://doi.org/10.12674/ptk.2019.26.2.061

© Korean Research Society of Physical Therapy

Change of Head Position and Muscle Activities of Neck During Overhead Arm Lift Test in Subjects With Forward Head Posture

Tae-ho Kim, and Byoung-ha Hwang

Dept. of Physical Therapy, College of Rehabilitation Science, Daegu University

Correspondence to: Corresponding author: Byoung-ha Hwang hwang_b_h@naver.com

Received: April 3, 2019; Revised: April 3, 2019; Accepted: May 13, 2019

Background:

Forward head posture (FHP) is a postural alignment of the cervical vertebrae that leads to increased gravitational load on cervical segmental motions. The overhead arm lift test assesses the ability to actively dissociate and control low cervical flexion and move the shoulders through overhead flexion.

Objects:

The purpose of this study was to explore muscle activities in the upper trapezius (UT), serratus anterior (SA), sternocleidomastoid (SCM), and lower trapezius (LT) alongside changes in head position during the overhead arm lift test in individuals with FHP.

Methods:

Fifteen subjects with forward head posture and fifteen subjects with normal subjcects were enrolled in this study. The patients performed the overhead arm lift test, and muscle activities of the UT, SCM, SA, and LT were measured using surface electromyography and by evaluating changes in head position. Independent t-tests were used to detect significant differences between the two groups and Cohen’s d was calculated to measure the size of the mean difference between the groups.

Results:

The FHP group demonstrated significantly increased muscle activity of the UT (32.46±7.64), SCM (12.79±4.01), and LT (45.65±10.52) and significantly decreased activity in the SA (26.65±6.15) than the normal group. The change in head position was significantly higher in the FHP group (6.66±2.08) than the normal group. Effect sizes for all parameters assessed were large between the two groups.

Conclusion:

The subjects with excessive FHP displayed were unable to fix their heads in position during the overhead arm lift test. The overhead arm lift test can thus be used in clinical settings to confirm control of the neck in these subjects.

Keywords: Forward head posture, Head position, Neck stability, Overhead arm lift test

With advancements in information technology, computers have penetrated almost every part of our lives, including work and study, entertainment, and social activities; people now spend a great deal of time sitting in front of a computer (Kang et al, 2012). This increase in computer use forces individuals to maintain the same posture for long durations, and lower cervical flexion and upper cervical extension yields an abnormal posture in which the head is forced forward (Cagnie et al, 2007;,Viljanen et al, 2003). The resulting neck pain has become one of the most common musculoskeletal disorders seen in modern populations (Vernon, 2008).

Forward head posture (FHP) refers to a confirmation wherein the anterior muscles of the neck are extended in length, and the muscles at the back of the neck are shortened, combining flexion of the lower cervical vertebrae with the excessive extension of the upper cervical vertebrae (Hanten, 1991). This posture induces neck pain from a reduction in the stability of the cervical vertebrae and inhibition of deep cervical flexor muscle activity due to excessive activation of the sternocleidomastoid muscle and anterior scalene muscle (Falla et al, 2004;,Yip et al, 2008). FHP alignment places the center of gravity of the head anterior to the vertical axis, thereby increasing the load on the posterior neck. these postural alters scapular mechanics and muscular activity about the shoulder complex, causing altered force couples and scapular motions that result in tissue overuse, injury, and pain (Thigpen et al, 2010). therefore may thereby affect not only the neck but also the thoracic spine and scapulae, which can result in an overall imbalance in the musculoskeletal system (Griegel-Morris et al, 1992).

Studies have shown that certain postural orientations of the cervical spine including FHP result in heightened gravitational load on cervical motion segments (Harms-Ringdahl et al, 1986) and increased extensor muscle activity (Edmondston et al, 2011). Maintaining the head in a forward position for long periods of time may cause musculoskeletal disorders such as upper crossed syndrome, which involves reduced lordosis of the lower cervical verterbrae in conjunction with kyphosis of the upper thoracic vertebrae like round shoulder posture (RSP) (Moore, 2004). FHP or RSP subjects show that shortens the upper trapezius (UT) and sternocleidomastoid (SCM) and weakens the serratus anterior (SA) and decreased lower trapezius (LT) muscle activity during shoulder motions (Kendall et al, 2014;,Weon et al, 2010). The altered positions of the scapula in subjects displaying FHP and Round-shoulder might change the electromyographic (EMG) activity of the musculature surrounding the scapula and glenohumeral joint, leading to injury (Lewis et al, 2005).

Comerford and Mottram (2012) developed the overhead arm lift test to assess one’s ability to actively dissociate and control low cervical flexion and move the shoulders through overhead flexion. They suggested the patient should be able to keep the head neutral while actively flexing the shoulders and lifting the arms to 180-degree flexion. An ideal posture in the overhead arm lift test is possible if the neck is stable enough.

Only a handful of previous studies have investigated control and stability of the neck using the overhead arm lift test, and no studies have been located that apply this test to patients with FHP. The purpose of this study was to explore UT, SA, SCM and lower trapezius (LT) muscle activity and head position change during an overhead arm lift test in individuals with FHP.

Participants

This study was conducted with 30 participants, with 15 each in the normal and experimental groups. Subjects were recruited from Daegu University in Gyeongsan, Korea. Prior to participation, all subjects read and signed the university-approved, human subjects consent form. This study was approved by the Daegu University Institutional Review Board. Demographic and clinical characteristics of these patients are shown in Table 1.

Table 1 . General characteristics of subjects. (N=30).


Measurement of FHP

The subjects were asked to expose their neck, and two adhesive markers were attached on the spinous process of the C7 vertebra and tragus. Photography of the lateral view of the subject, a common method used for the assessment of FHP, was performed on each participant (Quek et al, 2013;,Salahzadeh et al, 2014). The base of the camera was set at the height of the subjects’ shoulder. We then measured the CVA, defined as the angle between a horizontal line passing through the C7 vertebra and a line extending from the tragus of the ear to the C7 vertebra. Before taking the photograph in a neutral position, each patient was asked to completely flex and extend his or her neck three times before coming to rest in their most comfortably balanced position (Fernandez-de-las-Penas et al, 2006). Subjects were then instructed to stand looking straight ahead in their natural resting posture (Figure 1). The CVA of less than 53˚ is generally considered to be FHP (Salahzadeh et al, 2014).

Figure 1.

Measurement of craniovertebral angle.


Surface electromyography (EMG)

Muscle activity data were measured during the overhead arm lift test condition via a wireless EMG system (TeleMyo DTS, Noraxon Inc., Scottsdale, AZ, USA) using silver-silver chloride dual surface electrodes. All subjects were asked to comfortly stand and look straight ahead then perform overhead arm lift test and keep the end range for five seconds. The positioning of surface electrodes for each muscle was selected in congruence with previous studies (Cram et al, 1998).

Electrodes for the UT were located on the dominant right side, 2 ㎝ lateral to a midline drawn between the C7 spinous process and the posterolateral acromion. For the LT, electrodes were placed at an oblique angle and centered at a point 10 ㎝ medial from the inferior angle of the scapula. For the SA, electrodes were placed vertically along the mid-axillary line at rib levels 6 through 8. For the SCM, electrodes were placed along a line leading from the sternal notch to the mastoid process, at one-third the length of the line from the mastoid process. Before attaching the electrodes, the skin was cleaned with alcohol to reduce impedance. EMG data were normalized using maximal voluntary isometric contractions (MVIC) of the UT, LT, SA, and SCM separately. EMG activities were recorded for each muscle as subjects performed the MVIC. The measurement positions for MVIC were selected according to the study by Kendall (Kendall et al, 2014). MVIC values reflected the average RMS of three trials. EMG data were used for the three seconds in end range of the overhead arm lift test and expressed as a percentage of MVIC (%MVIC).

Overhead arm lift test

Subjects looked straight ahead in their natural standing posture. The examiner took the first picture in a standing position sideways in front of a wall with a grid line, then instructed the subject to “lift your arms to the horizontal bar over your head comfortably” and took a second picture. Neutral forearm posture should be maintained. Ideally, the person should have the ability to keep the head neutral while independently flexing the shoulders, lifting the arms to a vertical overhead position (180˚ flexion), and lowering them back to the side (Comerford and Mottram, 2012). The subjects were asked to fix their trunk during the overhead arm lift test, and those with trunk sway were tested again.

In the pre- and post-photographs, the change in the distance between the vertical line passing through the marker attached to the ear and the vertical line at the forefront of a grid line was used to evaluate changes in head position. All operations were repeated three times, and the average value was used. ImageJ software was used for photographic analysis (Figure 2).

Figure 2.

Overhead arm lift test and measurement of head position (A: start position, B: end position, HP: head position).


Statistical analysis

The normality of data was evaluated with the Shapiro-Wilk test. Independent t-tests were used to analyze the difference in the activity of the UT, LT, SCM, and SA, and the change in head position between the FHP group and the normal group during the overhead arm lift test. Cohen’s d was calculated to measure the size of the mean difference between the experimental and normal groups (Cohen 1977). Statistical analyses were performed using SPSS ver. 17.0 (SPSS Inc., Chicago, IL, USA) for Windows, and a p-value of less than .05 was considered statistically significant.

Comparison of head position

The change of head position in the FHP group was significantly greater than that of the normal group during the overhead arm lift test (p<.05) (Table 2). Cohen’s d was -3.57, indicating a large effect size between the two groups.

Table 2 . A comparison of head position change between two groups when performing overhead arm lift test..


Comparison of the muscle activities

The activities of the UT, SCM, and LT muscles in the FHP group were significantly higher than in normal group during the overhead arm lift test (p<.05). Conversely, SA muscle involvement in the normal group was significantly higher than in the FHP group (p<.05) (Table 3). Effect sizes for all four muscles assessed were large between the two groups.

Table 3 . A comparison of muscle activities for UT, SA, SCM, and LT between two groups when performing overhead arm lift test..


The purpose of this study was to investigate changes in neck stability and muscle activity during the overhead arm lift test in subjects with FHP as compared to normal subjects. This study used the overhead arm lift test to determine head instability. Comerford and Mottram (2012) found the overhead arm lift test to be a reliable method for evaluating head instability. This study measured both FHP subjects and normal subjects to identify differences in muscle activity between the two groups when performing overhead arm lift test.

Results of this study revealed that during the overhead arm lift test, muscle activity of the UT was higher than that of the normal group, while muscle activity of the SA was significantly lower than that of the normal group. These abnormal scapulohumeral rhythm or decreases in upward rotation of the scapula during overhead arm lift test have been linked to imbalances in force production of the upper and lower trapezius muscle and the serratus anterior muscle.

A study by Lau et al (2010) found that UT muscle activity was increased in FHP patients, and another by Ludewig and Cook (2000) demonstrated that SA muscle activity was reduced during the arm lift in these patients, perhaps due to excessive activation of the UT, as a compensatory, upward rotation motion of the scapula. These results support the findings of this study. In Park et al (2010) study, SA muscle activity was highly correlated with the rounded shoulders associated with FHP; he suggests that strengthening the SA may reduce the activity of the UT, thereby stabilizing the shoulder and correcting FHP abnormality. Kim and Park (2018) suggested that rotation relies on the synergist muscles of the UT and SA, contending that excessive activation of the UT muscle explains abnormal scapular motion.

The results of these previous studies are in alignment with the results of this study. Based on these results, FHP subjects displayed overuse of the UT due to the improper alignment, leading to in the functional failure of the SA that prevented the upward rotation of the scapula while lifting the arm.

A study by McLean (2005) surprising finding was that muscle activity levels and postural changes had the largest impact on the masseter muscle, which demonstrated activation levels in the order of 20% MVIC. therefore showed more SCM muscle activity when patients presented with FHP or various other habitual postures compared to a healthy posture. The results of this study also showed that SCM muscle activity was as high as 12% of MVIC.

Therefore in ideal posture, the muscles of the neck maintain an optimal balance via a craniocervical guy-wire system. FHP breaks down the stability of the neck, and the SCM pulls the head forward as a result of this rearrangement (Neumann, 2002). When the relative activity of other surface muscles such as the SCM is reduced, results include improved cervical pain and function (Lee et al, 2015).

It has been suggested that by reducing the activity of the SCM and UT and increasing the activity of the deep neck muscles, pain and function are improved due to a reduction in compression force on the neck (Sahrmann, 2010). In this way, when theoverhead arm lift test is performed in FHP, the head position changes due to insufficient stability of the head following high activation resulting from SCM malfunction.

In another study, relaxation and reinforcement of LT were required to correct abnormal neck posture and rounding of the shoulders in FHP patients (Smith et al, 2002), in this study, LT muscle activity was greater in the experimental group during the lifting of the arms. This due to excessive engagement by the UT wherein the upper arm of the shoulder bone rotates upward during the lifting of the arm. McLean (2005) reported that levator scapula muscle tensions in FHP enhance the upward rotation of the scapula, further increasing LT activity.

In the overhead arm lift test, FHP group showed head position changes averaging 5.24 ㎝ more than the normal group. These results suggest that head position change is increased as a result of excessive muscle activity of the UT, LT, and SCM that follows misalignment of the neck by the FHP. In FHP, the moment the arm is lifted, the bending torque in the middle to lower neck bone is almost doubled (Vasavada et al, 1998;,Weon et al, 2010). Therefore, the bending torque of the lower neck bone caused by FHP may increase muscle activity and subsequently the movement of the head as tension in the UT, LT, and SCM increases during the overhead arm lift test.

Some limitations of this study must be acknowledged. First, our study was performed on a very small number of subjects within a limited age range. Second, the distance change for head position was only measured during the overhead arm lift test. Future studies should seek out interventions that can reduce head movement during the overhead arm lift test by performing three-dimensional measurements of head angles.

The purpose of this study was to determine whether neck instability in patients with FHP could be confirmed by the overhead arm lift test. FHP patients did demonstrate greater muscle activity in the UT, SCM, and LT, and less in the SA, than the normal group, and we confirmed that the change in head position was increased by this muscle activity. We thereby affirm that the arm lifting test can be used to more easily identify the patients with FHP in the clinical setting. We also recommend further studies to improve FHP through interventions rather than evaluations.

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