Extended Abstract
1. Introduction
The head makes up 6% of the total body weight; the spine, neck, and other joints connect to the muscles through the kinematic chain. Keeping the cervical spine in a fixed position for a long time could alter head posture. It could eventually lead to a weakening of the body, i.e.  a Forward Head Posture (FHP), which is a deviation from the neutral or normal position [2 ,1]. Normal position is defined as a line of gravity that passes through the external auditory canal of the spine and neck and from the front to the thoracic vertebrae [3]. This condition must be morphologically acceptable. Besides, one must be able to maintain a state of discomfort and painlessness.
The FHP is among the most frequent abnormalities in patients with cervical disorders [4]. Studies have estimated its prevalence to be 66%-80% (5). The FHP refers to the anterior position of the head relative to the trunk concerning a vertical reference line [7 ,6]. However, the pattern of muscle activity measurement in people with anatomical abnormalities, especially in those with FHP complications during running, has rarely been studied.
The present study aimed to evaluate the measurement pattern of selective trunk and cervical muscles activity in high school students with anatomical abnormalities, compared to their healthy peers. The measurements were conducted during the onset and time of activity and muscle activity decline in running. Evaluating muscle activity based on the measurement variables of the mentioned cases can provide useful information for rehabilitation in these individuals.
2. Participants and Methods
This was a cross-sectional study. It was conducted using information from previous studies to estimate the sample size of ≥24 people to obtain statistical power of 0.8 at a significant level of P<0.05 [21]. The study subjects included 16 healthy boys and 12 boys with FHP. The study participants’ head angle was measured by goniometer.
Using a 16-channel Wireless Electromyography (EMG) (BTS FREEEMG300, BTS Bioengineering, Italy) with bipolar disposable surface electrodes, erector spinae (cervical part), sternocleidomastoid, upper trapezoid, anterior indentation, and upper and lower trapezius (right and left) were recorded while running. The center-to-center electrodes distance was equal to 2 cm [23].
The electrical signals were recorded at a sampling frequency of 1200 Hz. Low-pass filter 500 Hz and the high-pass filter 10 Hz and 60 Hz non-pass filter (to remove AC power noise) were used to filter raw Electromyography (EMG) data [26] . The machine’s gain was set at 1000.
3. Results
The obtained findings suggested no statistically significant difference between the two groups in the onset of the muscle activity (erector spinae, sternocleidomastoid, upper and lower trapezius, left and right anterior indentation) (P<0.05). The effect size values were in all cases, from small to medium (Table 1).

Furthermore, there was no statistically significant difference between the two groups in terms of the ending phase of muscle activity (erector spinae, sternocleidomastoid, upper and lower trapezoid, left and right anterior indentation) (P<0.05). The effect size values were small to medium in all cases.
4. Discussion
The present study evaluated the timing pattern of trunk and neck muscles in male students with FHP disorder, compared to their healthy peers during running. Besides, there was no statistically significant difference between the two groups at the beginning and end of the selected muscle activity.
A study compared shoulder muscle memory in patients with idiopathic neck pain and a healthy group. The relevant data indicated that the anterior indentation muscle delayed the onset and duration of shorter activity during dynamic movements [27].  They also found no significant difference in the onset and duration of trapezius muscle activity between patients with idiopathic neck pain and the healthy group [27]. Cools et al. reported no significant difference in the time of activity in the upper trapezius muscle between the controls and the group with shoulder pain syndrome during running [19]. Some researchers argued that people with musculoskeletal disorders have more muscle activity than healthy individuals, especially in the trapezius muscles [92 ,82]. These changes in neck posture can lead to abnormal movement patterns in this area [12]. Some studies have documented that changes in muscle activity were associated with changes in muscle frequency [30].
5. Conclusion
The onset and end of the selective trunk and neck muscle activity in the running phase demonstrated no statistically significant difference between the healthy individuals and those with FHP disorder. However, the activity duration of the erector spinae muscles of the right side and sternocleidomastoid of the left side were greater in the healthy group, compared to the FHP group. Additionally, more activity in these muscles was attributed to their weaker muscles. These findings could be used in the rehabilitation of people with FHP in therapeutic settings.
Ethical Considerations
Compliance with ethical guidelines
All ethical principles were considered in this article. The participants were informed about the purpose of the research and its implementation stages; they were also assured about the confidentiality of their information; Moreover, They were allowed to leave the study whenever they wish, and if desired, the results of the research would be available to them.

Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Authors' contributions
All authors contributed equally in preparing all parts of the research.
Conflicts of interest
The authors declared no conflict of interest.