the number of people who use imaging equipment in a fixed posture for long hours is 
 increasing in modern society .
fhp means that head is anterior 
 to an imaginary vertical line on a horizontal plane penetrating the body s center of 
 mass2 .
such posture is largely 
 associated with muscle length and changes in muscle strength as well as weakness of deep 
 cervical flexors , tightness of the suboccipital muscle , and abnormal sternocleidomastoid 
 ( scm ) and scalene muscle function3 .
increased kyphosis of 
 lumbar vertebrae correlates with fhp , and when lumbar vertebrae flex , extension of cervical 
 vertebrae increases4 .
scm and scalene neck 
 flexors play a role in neck posture function and also act as accessory inspiratory muscles . 
 during inspiratory respiration , they act on the chest wall to affect breathing movement , 
 causing cranial displacement5 .
thus , scm 
 and scalene muscles are associated with functional neck movement and respiration . because 
 respiration correlates with neck pain , preventing compensation is necessary to not cause 
 improper contraction and to exercise effectively6 .
neck pain occurs when fhp decreases neck muscle strength , and fhp 
 also decreases respiratory muscle strength .
if mckenzie exercises are conducted to recover function that was weakened by 
 neck postural changes , they will help relieve symptoms by correcting posture .
feedback 
 respiratory exercises can help inhibit use of accessory muscles by adding visual factors 
 that prevent compensation during breathing because fhp correlates with disability of 
 respiratory function .
therefore , this study aims to implement respiratory exercise in 
 patients suffering from fhp and to investigate the muscle activities of scm and scalene 
 muscles , which are agonists of neck and breathing accessory muscles .
this study also aimed 
 to suggest intervention methods to be used in the clinic by analyzing the neck disability 
 index ( ndi ) .
this study included 24 patients who visited a medical institution located in jeollanamdo , 
 south korea from september 2015 to january 2016 .
patients were between the ages of 25 and 
 40  years old , and they were diagnosed fhp anterior positioning over 5  cm from the vertical 
 line passing through the acromion and the external auditory meatus7 .
this study excluded patients who had congenial deformities 
 in the neck and thoracic cage , limited knee flexion , or pain during contraction of the 
 abdominal muscles ( table 1table 1.general subject characteristicsvariablesexperimental group ( n=13)m  sdcontrol group ( n=11)m  sdage ( years)34.3  4.832.2  3.9height ( cm)169.4  6.4168.1  5.8weight ( kg)65.8  5.867.1  6.9scm ( % ) 40.3  4.838.8 
5.1scalenus - a ( % ) 47.2  5.244.9  6.3cva ( )47.3  3.146.8  2.8ndi ( points)17.6  1.817.1  1.5shapiro - wilk .
scm : sternocleidomastoid muscle ; scalenus - a : scalenus anterior ; cva : 
 craniovertebral angle ; ndi : neck disability index ) .
scm : sternocleidomastoid muscle ; scalenus - a : scalenus anterior ; cva : 
 craniovertebral angle ; ndi : neck disability index this study was approved by the bioethics committee of sehan university center ( irb ) 
 ( approval number : 2015 - 13 ) .
study subjects understood the purpose of this study very well 
 and agreed to participate in this study voluntarily , and written informed consent was 
 obtained from each subject .
thirteen subjects were selected to undergo feedback respiratory exercise as the 
 experimental group , and 12 subjects were selected to undergo mckenzie exercises as the 
 control group . the intervention program was conducted for 30 minutes a session , once a day , 
 four times a week , and for two weeks .
the percent maximum voluntary isometric contraction 
 ( % mvic ) was measured by surface electromyogram ( semg ) , and neck disability index ( ndi ) was 
 measured using the ndi evaluation form prior to intervention .
the surface emg mp100 system ( biopac , usa ) was used to collect semg data to investigate scm 
 and scalene activities .
the sampling rate for semg signal collection was set to 1,000  hz , 
 and the frequency band pass filter was set to 20450  hz .
electrodes were attached to each 
 muscle , and before attaching electrodes , the skin of each subject was swabbed with 
 alcohol - soaked cotton to minimize resistance .
electrodes were also attached to the midpoint between the mastoid process and 
 clavicle along the scm muscle .
the anterior scalene electrode was attached parallel to the 
 direction of the muscle fiber of the anterior upper trapezius away from the scm muscle5 . to normalize the signal for muscle 
 contraction , the root mean square ( rms )
was collected while subjects lifted their heads 
 maximally and maintained the position for 5 seconds .
while resistance was applied to the 
 head in a sitting position for 5 seconds , the rms of maximum voluntary isometric contraction 
 was collected .
is the angle formed by the line connecting the seventh 
 cervical vertebra and tragus and a horizontal line
. subjects with fhp have a smaller cva and 
 show increased flexion of lower cervical vertebrae8 .
subjects answered one of 
 six questions related to 10 items , including pain intensity , daily life , lifting , reading , 
 headache , concentration level , work , driving , sleep , and leisure life , that were scored 05 
 points .
subjects sat down with stretched bodies and held a mouthpiece in their mouth . 
 when the therapist pressed the start button of the coupling device , subjects inhaled when 
 the orange gradation faced the  in  side , and they exhaled when it faced the  out  side . 

feedback respiratory exercises were performed for 30 minutes and were composed of warming up 
 and main exercises .
warming up was performed for 2 minutes by breathing 2627 times a minute 
 and then resting for 2 minutes .
the main exercise consisted of 7 total sets of 2930 breaths 
 per minute for two minutes . after performing 1 set , subjects rested for 2 minutes10 .
mckenzie exercises consist of seven exercise motions performed for 10 seconds at static 
 maximum muscle strength and repeated 1520 times .
enough explanation and demonstration were 
 given for subjects to perform the exact exercises , and they were supervised by a 
 researcher11 .
this study used spss 18.0 to analyze data , and the shapiro - wilk test was used to test the 
 normality of general subject characteristics . paired t - tests were used to analyze changes 
 within groups , and the covariance was set using examination before performing the experiment 
 to control for examination values when comparing changes between groups .
there were significant differences in scm muscle and scalenus muscle activities , cva , and 
 ndi within both the experimental group and control group after intervention ( p<0.05 , 
 p<0.01 , and p<0.001 , respectively ) .
there were also significant differences in changes 
 in scm and ndi between groups after intervention ( p<0.05 and p<0.01 , respectively ; 
 table 2table 2.comparison of muscle activity changes , cva , and ndi within group and between 
 groupsvariablesgrouppre - testm  sdpost - testm  sdscm ( % ) experimental group40.3  4.859.8  4.1control group38.8  5.149.2
 4.4scalenus - a ( % ) experimental group47.2  5.256.2  5.3control group44.9  6.351.3  4.8cva ( )experimental group47.3  3.155.1  2.5control group46.8  2.852.5  3.4ndi ( points)experimental group17.6  1.812.3  1.1control group17.1  1.514.9  1.1paired
scm : sternocleidomastoid muscle ; scalenus - a : scalenus anterior 
 muscle ; cva : craniovertebral angle ; ndi : neck disability index . * p<0.05 , 
 * * p<0.01 , * * * p<0.001 ) .
scm : sternocleidomastoid muscle ; scalenus - a : scalenus anterior 
 muscle ; cva : craniovertebral angle ; ndi : neck disability index . * p<0.05 , 
 * * p<0.01 , * * * p<0.001
terret et al.13 reported excessive scm activation in their study , and koh and 
 jung14 investigated % mvic of scm and 
 scalene muscles in fhp and neutral position in their study .
both muscles showed higher 
 muscle activities when subjects were in fhp than when they were in the neutral position . 

such long - term activation can elicit poor respiratory habits by facilitating the action of 
 accessory respiratory muscles .
borisut et al.15 reported that scm , anterior scalene , and erector spine muscle 
 activities increased in all groups except for the control group as a consequence of 
 mediating extensional movement and endurance exercise for 12 weeks for 25 patients with 
 chronic neck pain .
they showed that conducting neck exercises is useful to improve the 
 activities of muscles around the neck .
jang16 suggested that running while performing breathing exercises is 
 effective in improving function for patients with fhp .
this study suggested that scm and 
 anterior scalene activities increased in both groups when comparing the changes within 
 groups .
however , feedback respiratory exercises more effectively induced activity changes in 
 the scm when comparing changes between 1groups
. excessive tension and contraction of neck 
 muscles happens by compensation for patients with fhp .
this leads to decreased frequency of 
 contraction and relaxation of muscles as muscle activities due to stiffness of neck flexors 
 increase . however , inhibition of compensation is effective if a proper load is applied 
 during inhalation and exhalation using feedback respiratory exercises .
fhp causes twisting of 
 the alignment from the head to the trunk by increasing kyphosis of the thoracic vertebrae as 
 well as the neck bone .
neck posture alignment to maintain balance of the neck muscles is 
 important to prevent musculoskeletal disorders1 .
jung11 analyzed 
 cva by mediating mckenzie exercises 4 days a week for 4 weeks in patients with chronic neck 
 pain , and cva increased in those patients .
kim et al.17 mediated sling exercises for 4 weeks for patients with fhp to 
 reveal a meaningful difference in cva , and there was a correlation with neck muscle 
 activity .
this study supported the results of the previous research within groups , but there 
 was no significant result between groups .
cho18 reported that cva increased meaningfully when applying orthotherapy 
 along with accessory muscle breathing exercises in 18 patients with fhp .
kang19 mediated flexion exercises for deep neck 
 flexor muscles using feedback equipment for 10 minutes a day , three times a week , for 6 
 weeks . as a result , the range of motion and cva increased .
this could be because advanced research targeted selective 
 respiratory accessory muscles , and the period of mediation was longer than that of this 
 study by over 6 weeks .
gong20 reported 
 that cva positively correlates with ndi as a consequence of performing correlation analysis 
 between cva , the range of motion of deep neck flexors , and ndi using data from 24 normal 
 people .
iqbal9 showed improvement of ndi 
 after mediating neck flexion exercises using biofeedback equipment for 4 weeks for 30 
 teachers complaining of neck pain .
katayama et al.21 
 reported that proper breathing can release the body by stimulating activity of the 
 sympathetic nervous system , and kim et al.22 reported that neck pain and ndi improved after mediating active 
 release techniques for 3 weeks for 24 patients with chronic neck pain . based on these 
 studies , when breathing exercises are mediated , they are effective in releasing the body . 

exercises are thought to effectively improve the ndi , which is a subjective functional 
 scale .
this study suggests that is more efficient in scm activity , neck flexor , and ndi by 
 mediating feedback respiratory exercise than those in control group .
such results can affect 
 inefficient breathing imbalances of patients with fhp , as neck flexors are accessory 
 respiratory muscles .
active intervention methods should be studied continually in order to 
 not affect upper chest breathing patterns by preventing such phenomenon in future .
therefore , 
 the ability to generalize about all patients with fhp is limited , and other variables may 
 exist due to the difficulty of controlling drugs and daily life habits .
 [ purpose ] this study aimed to simultaneously investigate the activities of the 
 sternocleidomastoid muscle and scalenus anterior muscle , which are agonists of neck and 
 breathing accessory muscles , by implementing breathing exercises . 
 [ subjects and methods ] 
 thirteen subjects were selected for the experimental group , which performed feedback 
 respiratory exercises with mckenzie exercises , and 12 subjects were selected for the 
 control group , which performed mckenzie exercises alone . 
 the intervention program was 
 performed for 30 minutes a session , once a day , four times a week , and for 2 weeks before 
 conducting the experiment . before intervention 
 , muscle activity was measured using surface 
 electromyogram , and the neck disability index was evaluated . 
 [ results ] there were 
 meaningful differences in activities of the sternocleidomastoid muscle and the scalenus 
 anterior muscle , craniovertebral angle , and neck disability index within both the 
 experimental group and control group after intervention . 
 there also were meaningful 
 differences in sternocleidomastoid muscle and neck disability index changes between 
 groups . 
 [ conclusion ] neck flexors as accessory respiratory muscle can affect inefficient 
 respiratory imbalance of forward head posture patients . 
 multimodal intervention method 
 should be studied continually and not be exposed to upper chest breathing patterns by 
 preventing such phenomenon . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION