Effects of Adding Respiratory Exercises to the Therapeutic Routine in Smartphone Users With Forward Head Posture and Non-Specic Chronic Neck Pain: A Randomised Controlled Trial

Background: Neck pain and forward head posture are common in prolonged smartphone users and need to be targeted for treatment. We aimed to compare the effect of adding respiratory exercises to the therapeutic routine in smartphone users with forward-head posture and non-specic chronic neck pain. Mehods: Sixty patients (aged 24.7±2.1 years), were randomly assigned to the therapeutic routine (n=20), combined respiratory-exercises with therapeutic routine (n=20), or control groups (n=20). Each programme was implemented three times a week for 8 weeks. Forward head angle, pain, electromyographic activity, and respiratory patterns were measured at baseline and at 8-weeks’ post-treatment. Results: There were signicant improvements in the combined group compared with the therapeutic routine group (p=0.03) for diaphragm muscle activation, (p=0.03), neck erector spinae activity (p=0.04), respiratory balance (p=0.04), and number of breaths (p=0.02). There were signicant within-group changes from baseline to post-treatment in the combined group for all outcomes above, but no changes in the therapeutic exercise routine group. Outcomes for the combined group were superior to the control group in every variable. Conclusion: Combination treatment is more effective than the standard therapeutic routine. These results could be strengthened by more studies with longer follow-up assessments. Trial registration: Current Controlled Trials using the IRCT website with ID number of, “Prospectively registered” at 2020/03/04. non-specic neck pain. As with therapeutic routine exercises with or without breathing exercises, the results showed that the amount of pain and the FHP improved signicantly after an 8-week relevant training intervention. However, no signicant difference was observed between the two groups.


Background
The use of electronic tools is increasing worldwide [1]. Varieties and the attractiveness of these tools have led to various groups of people, especially teenagers, using them for prolong periods and this has increased some related musculoskeletal problems [1]. It is commonly thought that in addition to psychological problems, like anxiety, headaches, insomnia, depression, poor sleep quality, and fatigue, long-term use of smartphones leads to inactivity and abnormal posture, such as the forward head posture (FHP) and rounded shoulders [2]. This can necessarily affect muscular activity, and place more pressure on the cervical spine where chronic pain originates [3,4].
Individuals with FHP and chronic neck pain often suffer from weakness of the deep neck exor muscles, which is to be compensated by excessive activity of other muscles such as sternocleidomastoid, and scalene [5]. This compensation leads to muscle imbalance and changes in the stress-strain diagram, by which cervical spine overload occurs [5,6]. This may also be observed in the thoracic spine as some involved muscles are connected to both areas. Also, disorders or impairments occur in the neck and respiratory system because of the joint activity of the above-mentioned muscles operated on the neck movements and respiratory function [5,6].
Maximal inspiratory and expiratory pressure (MIP & MEP) decrease in individuals with chronic neck pain and FHP [6].
This situation causes the respiratory pattern to change from nasal breathing to mouth breathing. As compared to the normal posture, both scalene and sternocleidomastoid muscles show a higher activity amount in FHP [5]. Such long-term activation can create poor respiratory habits to facilitate activities in auxiliary respiratory muscles [5]. Furthermore, the respiratory function is affected by changed muscle activity due to pain and disability, affecting the neck in a vicious circle. To improve such problems, various therapeutic and rehabilitative methods have been used such as the McKenzie exercise, Kinesio taping, and myofascial release [7]. Each method has demonstrated positive results in improving impairments and disorders in this area [7]. In this regard, some researchers have reported better consequences obtained from combinations of some of their therapeutic methods [7]. But previous research has not compared the effect of adding breathing exercises to therapeutic exercises; also respiratory exercises have shown bene ts for respiration and balancing the main and auxiliary muscles [5]. Respiratory exercises are low cost and are also easily used in different situations [5]. In this regard, the present research aimed to compare the effect of adding respiratory exercises to the therapeutic routine on pain, electromyography (EMG), posture, and respiratory patterns in smartphone users with FHP and non-speci c chronic neck pain. We hypothesised that adding respiratory exercise would enhance treatment effects on neck pain, respiratory pattern, electromyography, and posture in smartphone users with moderate chronic neck pain and FHP.

Study Design and Participants
The study was a randomised assessor-blind controlled trial (RCT ID: IRCT20200212046469N1). Patients (age 24.7±2.1 years) with chronic neck pain were recruited by orthopaedic physicians via yers displayed at the hospitals over 3-months from April to June 2020.
Insert gure 1 here Inclusion criteria were males and females who using a smartphone for more than 4 hours a day who rated their 'worst pain over the last 24-hours' as moderate using the visual analogue scale (VAS), with neck disability index (NDI) scores between 28% and 45%, and pain lasting longer than 3 months [8][9][10][11]. Forward head posture was de ned as a cervical angle <50° [12][13][14]. A lateral-view photograph was taken to identify cervical angle in standing position [12][13][14].
The exclusion criteria were, previous history of neck or back surgery, neurological signs, rheumatoid arthritis, and currently using muscle relaxation medication. The local ethics committee at Kharazmi University approved the study protocol. This study complied with the ethical standards of the Declaration of Helsinki and all subjects signed informed consent.
Participants were randomised into two experimental groups and one control group, by drawing a number, from 1 to 63, placed in sealed envelopes in a box prepared in advance by the trainer. The randomisation sequence was not disclosed until participants had completed their baseline assessments. The assessor was blinded to group allocation. Participants were not blinded to exercise study, however they were not aware which treatment was considered to be therapeutic. The same physiotherapist and trainer supervised both active treatment groups.

Outcome Assessments
The outcomes were measured at baseline and post-treatment two days after the 8-week intervention. The primary outcome measure was pain, and secondary outcome measures were EMG, respiratory pattern, and posture.
All participants completed a baseline questionnaire (Table 1). A physical therapy evaluation was performed by a Ph.D.
trained physiotherapist with 25 years of clinical experience who was unaware of the type of treatments given and the group randomisation. All participants were instructed to limit their weekly exercise to the study treatment [3,15,16].

Pain intensity
Pain was evaluated using VAS choosing a number from 0 (no pain at all) to 10 (unbearable pain), which was displayed along a horizontal line. This scale is widely used in clinical settings [17,18] and is a valid and reliable tool [16]. The minimum clinically important difference for within-group on the pain scale has been reported to be 2.5-points in people with chronic neck pain with a baseline score greater than 6.0 [19].

Electromyography
An EMG device with eight channels (made by data Log Biometrics company, Canada) was used to measure the activity of upper trapezius muscles, sternocleidomastoid, scalene, neck erector spine, and diaphragm muscles. Based on the recommendations of SENIAM, the skin surface was shaved of hair and cleaned with alcohol swabs before wireless EMG electrodes were applied. EMG electrodes were placed in ve areas as follows: upper trapezius, as positioned from the lateral to the midpoint, as an imaginary line was formed by the posterior aspect of the acromion and the spinous process of C7, and the electrode was placed on the muscle bulk [20]. For the sternocleidomastoid, the electrode was placed at the lower one-third of the line connecting the sternal notch and mastoid process [20]. Forward head posture was de ned as a cervical angle<50° [12][13][14]. A lateral-view photograph was taken to identify cervical angles in a standing position [12][13][14].
For scalene muscles, the electrode was placed on the posterior triangle of the scalene muscle, above the clavicle, more inclined to the sternocleidomastoid (just posterior to and at a slightly oblique angle relative to the sternocleidomastoid [SCM], just above the clavicle and in the hollow triangle anterior of the upper trapezius) [21]. For neck erector spine, the electrode was attached to the muscles around the C4 vertebra [22]. The diaphragm, lower edge of the rib cage on a vertical line that passes through the nipple centre was selected for electrode placement [23].
The EMG information was collected using an EMG device with a sampling frequency of 1000 hertz, and in this study the EMG signal data were sampled at 1000 hertz. These signals were ltered in the bandpass between 20 and 500 hertz [20]. The full shoulder exion task was used to obtain data on the activity of the selected muscles. In this regard, each exion movement and return to the initial state was performed by the subjects at a 5-second time, in 3 consecutive times [20,21,24].
Additionally, to estimate a maximum voluntary contraction (MVC) for the upper trapezius, subjects placed their hand at 90 0 abduction, sitting down on a chair, and were asked to apply pressure against the exposed resistance at the top [25].
To obtain the MVC for sternocleidomastoid and scalene muscles, subjects were placed in the supine position, and their hands were put on their own heads. Then, the head was anterolaterally placed and pressurised against the hand resistance [21]. To obtain the MVC for the erector spinae muscle, the subjects were asked to be in a prone posture and put both hands behind their head as moving the overhand against the resistance in the extension direction [25]. To achieve MVC for the diaphragm muscle in the sitting position subjects took deep breaths [26]. Each position of the maximal voluntary contraction was used two times for 5-second duration to normalise the data [25].
The EMG signal was processed by the Root Mean Square (RMS) algorithm in the MATLAB program. The resulting number represented the average power of a signal that indicated the muscle activity. To compare the subjects and normalise the data, the obtained values from the RMS were divided by those obtained from the MVC of each muscle, and the amount of muscle activity was considered as a percentage of the MVC [20,21,24].

Respiratory Pattern Assessment
To assess the breathing pattern using Manual Assessment of Respiratory Motion (MARM), as the subject sitting on the bed, with natural breathing, the tester recorded and interpreted different aspects of respiration, including the number of breaths and the balance of respiration between the upper and lower parts of the rib cage and abdomen, by touching the lower back and lateral rib cage with both hands and without putting pressure on these parts [15].

Forward head posture assessment
The forward head and shoulder angles were measured using photogrammetry of the sagittal plane. This method favoured reliability, and it has been used in various research [3]. To measure the angles, three anatomical signs, including left tragus, acromion, and the spinous process of C7 vertebra were determined and marked. Then, the subjects were asked to stand at the designated area beside a wall (at a 23-cm distance) so that their left side was placed toward the wall. The photographic tripod supporting the digital camera was placed at a distance of 265 cm, and its height was set based on the subject's right shoulder level. In such circumstances, the subjects were asked to lean forward three times and raise their hand over their head three times. They were then asked to stand in a completely relaxed and natural posture, and to look at an imaginary point on the opposite wall (eyes in line with horizon). The tester took images of the body pro le view after a ve-second pause. Finally, these images were transferred to a computer, and the angle of the line connecting tragus to C7 vertebrae, and that of the line connecting C7 and the acromion process were respectively measured with the vertical line (forward head and shoulder angles) using Kenova software (Kinova-0.8.27-64-bit, Kinova company, Canada) [27,28].

Training Protocol
As intended in this study, training included two parts: therapeutic routine and respiratory exercises. The therapeutic exercises contained resistance and stretching exercises (in the three stretching exercises, we used the static stretching with a 30-second hold for 2 sets) for 45 to 60 minutes per session, speci cally one session a day for 3 sessions a week; totally all held in 8 weeks [29,30]. The rest interval between movements in these exercises was 45 and 30 seconds for resistance and stretching exercises respectively. In the combined group respiratory exercises were added to the therapeutic routine above which consisted of balloon breathing exercises performed in sessions of 4 sets, and as each set had 4 complete breathing breaks, these exercises were conducted for 2 sessions a day and 3 days a week for 8 weeks [31]. All exercise was done under supervision of a physical therapist at the pain clinic. All participants received documentation including information on postural corrections and improving general health.

Control Group
The control group (n=20) received a pamphlet including information on postural corrections and improving general health during the 8-week study period. No other physical therapy modalities or treatments were performed [32].

Statistical analysis
The necessary sample size was estimated using G*Power 3.1.7 for Windows (G*Power©, University of Dusseldorf, Germany). The sample size calculation was considered a power calculation to detect between-group differences in the primary outcome measure (neck pain). To obtain 80% statistical power (1-β error probability) with an α error level probability of 0.05, we used repeated-measure analysis of variance (ANOVA), within-between interaction, and a medium effect size of 0.25 to consider two groups and two measurements for the primary outcome, generating a sample size about of 18 participants per group (total sample size of 54 subjects). The sample was increased to 63 (21 in each group) to allow for a 15% dropout rate. A total of 63 subjects met study criteria and participated in the study.
One-way ANOVA was used to compare the group demographics and post hoc independent t-tests were performed in the case of a signi cant omnibus test. The dependent variables of interest were pain, function, strength, and kinematics. For each variable, the 3-trial mean was calculated for each participant. One-way analysis of covariance (ANCOVA), with a between-factor of the group (control, therapeutic routine, combined exercises) and participants' baseline scores included as a covariate, was used to determine if there were group differences in the dependent variables of interest at posttesting.
This analysis approach (i.e. post-test performance as the outcome with baseline performance as a covariate) allowed us to compare post-testing outcomes while accounting for potential baseline group differences [33]. In the case of a signi cant omnibus test, pairwise comparisons were performed to examine potential between-group differences. These pairwise comparisons were based on the adjusted group means. In addition, 95% con dence intervals (CI95%) were calculated based on the adjusted group mean differences, and Cohen's d effect size (ES) statistics were calculated by dividing the adjusted group mean differences by the larger of the group standard deviations. The Bryant-Paulson procedure was used when conducting the pairwise comparisons and calculating the con dence intervals [34]. An alpha of .05 was used for all signi cance tests. Effect sizes of 0.2, 0.5, and 0.8 were considered 'small', 'moderate', and 'large' respectively [35]. SPSS software was used for statistical analysis (IBM Corp., Armonk, NY, USA).

Results
100 participants were recruited, 37 did not qualify based on the exclusion and inclusion criteria of the study, and 63 were randomised to 3 groups. Intention to treat protocol was followed for post-treatment analysis. See the CONSORT diagram for details ( gure 1).
There was a high degree of adherence to all three interventions. Of the possible 24 sessions, the therapeutic routine group, the combined group, and the control group attended 20 ± 2 sessions, 20 ± 1 sessions, and 19 ± 2 sessions, respectively.
Our cohort comprised male and female subjects, mean age 24.

Discussion
The present study aimed to compare the effect of adding respiratory exercises to therapeutic routine on pain, electromyography, posture, and breathing pattern in smartphone users with FHP and chronic non-speci c neck pain. As with therapeutic routine exercises with or without breathing exercises, the results showed that the amount of pain and the FHP improved signi cantly after an 8-week relevant training intervention. However, no signi cant difference was observed between the two groups.
Moreover, the amount of activity in the upper trapezius, sternocleidomastoid, scalene, and cervical erector spineae muscles revealed a signi cant decrease in both experimental groups, although no signi cant differences were found between these two groups. Having conducted the training interventions, the amount of activity in the diaphragm muscle indicated a remarkable increase in the combined group as compared with the two other groups, including the therapeutic and control ones. As for the respiratory pattern, a signi cant improvement and superiority were observed in the number of breaths and respiratory balance for the group of combined exercises compared to the therapeutic routine and control groups. In the control group, there were no signi cant differences over time.
Having performed the intended exercises, a decrease in activity could be found in the upper trapezius, sternocleidomastoid, scalene, and cervical erector spineae muscles in both exercise groups. However, changes in the diaphragm muscle activity were only observed in the combined group. Having performed all the exercises in both experimental groups in the present study, the probable effect mechanism can be implied as activation in the collaborative muscles in the cervical area, correcting FHP, and decreasing the activity amount in muscles, including the upper trapezius, sternocleidomastoid, scalene, and cervical erector spineae [37]. In fact, adding the respiratory exercises to the therapeutic ones did not create a remarkable change in the activity of the upper trapezius, sternocleidomastoid, scalene, and cervical erector spineae muscles. However, a signi cant increase in diaphragm muscle activity was revealed due to the respiratory exercises in the combined group compared with the two other groups.
As for the FHP, the experimental groups indicated a considerable improvement as compared with the controls, but no signi cant difference was observed between the experimental groups. In this regard, the results obtained in this research were consistent with those found by Kong et al. [38]. According to the previous research, the chin-tuck exercise merely is not of enough durability [39]. Hence, researchers have tried to combine this exercise with some other endurance and strength exercises, aimed to strengthen the movement domain and increase the endurance of the cervical muscles. Kong et al. [38] reported that performing a course of modi ed cervical exercises has revealed a remarkable positive effect on the FHP of smartphone users who suffered from such an abnormal disorder. Therefore, the probable mechanism to improve the FHP in both experimental groups has been assumed to reduce the activity of upper trapezius, sternocleidomastoid, scalene, and cervical erector spinae muscles, strengthen cervical deep exor muscles, and use collaborative muscles in this very area [38].
Before and after performance of the training interventions in the three involved groups, the number of pain changes were measured and evaluated using VAS. Although the controls experienced no signi cant reduction in pain, both experimental groups' subjects showed an observable decrease in pain following the interventions. Having reviewed the obtained results, no signi cant difference was found based on the effectiveness of pain between the two experimental groups.
As for the pain variable, the research results were consistent with those obtained from Chung et al.'s study [29] in which two exercise methods of 'craniocervical exion and isometric neck exercise' were compared in patients with chronic neck pain in terms of the effect on pain. Their comparative results indicated that both mentioned exercise methods have had a remarkable effect in improving pain [29]. The present research aimed to compare the effect caused by adding respiratory exercises to the therapeutic routine by applying mere therapeutic exercises using a different method. Having conducted all the exercises, consequently, both experimental groups bene ted from a remarkable improvement in their amount of pain while no signi cant difference was observed between both groups in this regard. As inferred from these ndings, the addition of respiratory exercises did not increase the effect of the therapeutic ones on decreasing pain. Therefore, the positive effect of performed therapeutic exercises on balancing cervical muscle activity and improving posture in this area can be simply deemed the main cause to decrease pain.
On the other hand, the respiratory pattern was evaluated using the MARM method in this research, and the obtained results revealed that only the combined group experienced positive changes in this pattern as compared with the therapeutic routine. Generally, these results were consistent with those observed in Lee et al.'s study [40] Having examined whether and how a course of exercises affects the cervical angle and respiratory function in smartphone users, Lee et al.
[40] reported that the participants conducted the related exercises, experienced positive and remarkable results in the cervical angle and multiple respiratory factors as compared with the controls [40]. As aimed in this research preface, the breath number and respiratory balance were compared to be affected by the respiratory-therapeutic and therapeutic exercises. The possible mechanism of effects caused by the respiratory-therapeutic exercises, which focused on correcting the FHP, seemed to strengthen respiratory muscles such as the diaphragm, increase lung volume, extend vital capacity and inform people with their body and breath position. Accordingly, the respiratory pattern was associated with positive changes in the respiratory-therapeutic exercise group [40, 41].

Limitations
Our study limitation was that no long-term follow-up assessment was considered in the current study, so a similar study with a follow-up stage is highly recommended. It is also recommended that future research use advanced respiratory assessment and respiratory exercise tools such as spirometry and power breath to assess other respiratory factors.

Conclusions
As compared with the therapeutic routine alone, performing 8-week respiratory-therapeutic exercises has positive effects on pain, FHP, and activity balance of the upper trapezius, sternocleidomastoid, scalene, and cervical erector spineae muscles, and also it can improve respiratory patterns. Moreover, diaphragm muscle activity is thereby enhanced to enable more complete breathing. Therefore, these exercises are recommended to correct upper quarter disorders.   Abbreviations: Visual analogue scale (VAS); forward head posture (FHP). ¥, Signi cant between therapeutic exercise alone and control groups. §, Percent change (↓decrease, ↑ increase). ‡, Denotes signi cant within group improvement between the baseline and 8-weeks treatment period.
€, Signi cant between combined respiratory-therapeutic exercise and therapeutic exercise alone groups.
Ω, Signi cant group × time interaction. €, Signi cant between combined respiratory-therapeutic exercise and therapeutic exercise alone groups. §, Percent change (↓decrease, ↑ increase). ‡, Denotes signi cant within group improvement between the baseline and 8-weeks treatment period.
Ω, Signi cant group × time interaction. Figure 1 Flow Diagram of the study

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