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Paper text:
the generally known traction effect of traditional - style home neck traction devices has 
 been supported by scientific evidence . the most representative home traction device are 
 over - the - door traction devices , which are connected to sandbags or water bags with ropes . 

other types of home neck traction device are products that are 
 ergonomically designed in relation to traction position and traction angle , and their 
 sufficient traction effect has been proven2 .
this include air - inflatable neck traction devices , which are 
 economical , light , and easily wearable compared to other traction devices ; therefore , they 
 have attracted the attention clinicians and patients .
however , according to some 
 investigations , the traction effect of air - inflatable neck traction devices has not been 
 properly verified relative to other home traction devices .
previous studies have verified the traction effect by analyzing radiological images2 or evaluating the activity3 or thickness of the muscles4 around the vertebrae during traction .
. however , if muscular contraction increases 
 during traction , elongation between the vertebrae may be interrupted , and discomfort may be 
 triggered in the subjects , therby offsetting the traction effects6 .
this study aims to examine the effects of air - inflatable 
 neck traction devices , which have not yet been sufficiently verified . to this end , this 
 study investigated the use of different traction forces of an air - inflatable neck traction 
 device and the activity of the muscles around the neck was observed .
the subjects who participated in this study were 18 healthy adult males without orthopedic 
 disease of the neck or shoulders ( age , 22.31.8  years ; height , 175.54.2  cm ; weight , 
 71.36.2  kg ) . according to the ethical standards of the declaration of helsinki , the study 
 purpose , content , and procedure
were explained to all subjects in detail , and only those who 
 voluntarily signed an informed consent participated in the experiment .
moreover , the study 
 was approved by the institutional review board of the catholic university of pusan . for neck 
 traction , an air - inflatable neck traction device ( diskwell , eunsung inc .
, korea ) was used 
 and a mercury manometer ( ck-101 , sprit inc . ,
taiwan ) was connected to the traction device 
 for remodeling so that the traction force could be measured .
cervical traction was conducted 
 in a sitting position , as generally done in a hospital .
the height of the chair used was 
 adjustable , and it was an armchair with a back .
the height of the chair was adjusted so that 
 the ankle , knee , and hip joints reached 90 degrees and the trunk and the arms were supported 
 by the back and arm of the chair . through these measures ,
the contraction of the muscles 
 around the neck resulting from movement of the trunk and arms was controlled .
first , in a sitting position , the subjects put on a neck traction device and rested for 1 
 minute , looking straight and sitting comfortably .
the traction forces provided to the 
 subjects were 40 , 80 , and 120 mmhg , and each force was administered for 30 seconds .
the 
 pressure were employed in a random order . when air was injected , the neck traction device 
 inflated , with the neck posture in a natural state .
previous studies that evaluated the 
 effects of a traction device measured the activity of the muscles around the neck to verify 
 the traction effects and experimented on the appropriateness of ergonomic traction devices 
 using electromyography ( emg)3 . accordingly , this study measured the activity of the muscles around the neck while applying 
 traction with an air - inflatable neck traction device using an emg system ( lxm-3204 , laxtha 
 inc .
the sampling frequency was set at 1,000  hz and the obtained emg signals were 
 processed with a 60  hz notch filter and a 50500  hz bandpass filter .
the muscles used for 
 the muscle activity analysis were the splenius capitis and upper trapezius4 .
the subjects were placed in a prone 
 position at the corner of a bed , a 2  kg sandbag was placed behind their head , and the head 
 was extended .
emg signals were collected for 20 seconds , and signals for 10 seconds 
 excluding the first and last 5 seconds were collected and used as a reference for voluntary 
 contraction of the splenius capitis . in an anatomical position , the subjects grasped a 1  kg 
 dumbbell , abducted both arms by 90 degrees and contracted them for 20 seconds .
signals for 
 10 seconds excluding the first and the last 5 seconds were collected and used as a reference 
 for voluntary contraction of the upper trapezius . before and after neck traction with air 
 pressures of 40 , 80 , and 120 mmhg
, the emg signals of the splenius capitis and upper 
 trapezius were collected for 30 seconds .
signals for 20 seconds excluding the first and the 
 last 5 seconds were collected , and the % reference voluntary contraction ( rvc ) was derived 
 using each muscle s rvc value .
data obtained while conducting the experiment were expressed 
 as average and standard deviation . in order to compare the emg values before and during the 
 application of each traction force
, a wilcoxon signed - rank test was conducted , and the 
 significance level was set at 0.05 .
the muscle activity of the splenius capitis was 33.12.9 prior to the application of 
 traction force and 34.52.6 36.92.5 , and 40.94.3 with traction forces of 40 , 80 , and 120 
 mmhg , respectively . while each traction force was applied ,
the muscle activity of the upper trapezius was 
 7.00.9 before the traction force was applied and 7.00.9 , 7.00.8 , and 6.90.8 with 
 traction forces of 40 , 80 , and 120 mmhg , respectively ; no statistically difference was 
 observed .
the important mechanism of traction is an increase in the intervertebral space through 
 spinal elongation and muscle relaxation6 . 

the results showed 
 that when a low traction force of 40 mmhg was provided with an air - inflatable home neck 
 traction device , the splenius capitis contracted significantly .
then , when traction forces 
 of a middle intensity of 80 mmhg and a high intensity of 120 mmhg were administered , a 
 greater contraction was observed .
muscle contraction , which occurs during cervical traction , 
 has an important significance . in general , when cervical radiculopathy is caused by a 
 herniated nucleus pulposus , the herniated disk compresses the nerve roots , resulting in an 
 entrapment of the intervertebral foramina . as a result ,
the nerves are irritated and the 
 reflex response of the cervical muscles may trigger muscle contraction and resulting neck 
 pain . the contracted muscles increase pressure on the intervertebral discs and compression 
 on the nerve roots , which may aid in creating a vicious cycle of aggravating pain7 , 8 . in 
 addition
, the splenius capitis , whose contraction increased in the present study , is known 
 as a muscle that triggers occipital neuralgia9 .
murphy3 noted that the simultaneous 
 realization of an increase in intervertebral space through spinal elongation and muscle 
 relaxation might interrupt the cycle of neck pain . from this perspective , it can be stated 
 that when a vertical traction force is provided , spinal elongation may naturally occur ; 
 however , the accompaniment of muscle contraction during this process may offset the traction 
 effect .
recently , katsushi4 proposed that a 
 traction force of a low intensity , such as 5  kg or 8  kg , did not significantly change the 
 thickness of the upper trapezius ; however he reported that a traction force of a high 
 intensity at 11  kg might significantly decrease muscle thickness .
in other words , when a 
 relatively high traction force is given , changes in the upper trapezius may be triggered . 
 however , this study showed no differences in the activity of the upper trapezius .
in 
 particular , the muscle activity did not differ at 40 , 80 , or 120 mmhg .
thus the 
 air - inflatable neck traction device is not considered to provide stimulation to the upper 
 trapezius .
katsushi4 administered intermittent 
 cervical traction in a reclining wheelchair composed of traction for 20 seconds and resting 
 for 10 seconds with the cervical flexion angle at 10 degrees ; meanwhile , we used the same 
 sitting posture as that in a hospital but traction device s cervical flexion angle was 
 uncontrollable .
therefore , the differences between the two studies s results are considered 
 to have emerged from differences in the traction positions , cervical flexion angles , or 
 types of traction devices . according to the results of increasing the air pressure of the 
 traction device and monitoring the subjects responses , as the volume of the traction device 
 increased with rising air pressure ,
this is considered to occur because of the structure of the 
 air - inflatable cervical traction device .
in general , it is known that cervical traction is 
 effective when performing traction in a posture of flexion of 20 to 30 degrees10 .
in contrast , the posture of neck 
 extension may fail to generate spinal elongation , and instead narrow the intervertebral 
 space5 ; when this is narrowed , 
 compression on the nerve roots may increase , triggering a contraction of the muscles around 
 the neck3 .
therefore , increased muscle 
 activity of the splenius capitis in this study is estimated to be the problem with the 
 structure of the air - inflatable home traction device , which extends the neck as the air 
 pressure rises .
the air - inflatable neck disk traction device is a traction unit used in a sitting posture , 
 and muscle activity is regarded as differing according to traction posture .
katsushi4 minimized the contraction of the muscles 
 around the neck during traction by positioning the head of the subject on the headrest in a 
 reclining wheelchair .
moreover , jette et al.11 had their subjects rest for 5 minutes prior to traction , thereby 
 reducing the influence of gravity on the muscles .
when traction is conducted in a sitting 
 posture , the subject is influenced by gravity and therefore muscle activity increases more 
 than when traction is performed in a lying position or supporting the head .
fater and 
 kernozek12 noted that the space between 
 intervertebral bodies increased more in a lying position than in a sitting position , while 
 murphy3 observed that muscle activity 
 around the neck increased more in a sitting position than in a lying posture .
according to 
 previous studies , it has been demonstrated that muscle activity is higher in a sitting 
 position than in a lying position . in the present study , the activity of the splenius 
 capitis increased as well , and this is explained in that the posture of traction conducted 
 in a sitting position is a major factor .
the results of this study show that the indiscriminate use of an air - inflatable home neck 
 traction device may aggravate symptoms .
the structure of the device , method of applying 
 traction , and the traction posture are all considered to have an effect . therefore , these 
 elements should be considered as independent variables in a more detailed analysis of the 
 appropriate structure , posture , and utilization method related to air - inflatable home neck 
 traction devices .
[ purpose ] the purpose of this study was to analyze cervical muscle activity at different 
 traction forces of an air - inflatable neck traction device . [ subjects ] eighteen males 
 participated in this study . 
 [ methods ] the subjects put on an air - inflatable neck traction 
 device and the traction forces administered were 40 , 80 , and 120 mmhg . 
 the 
 electromyography ( emg ) signals of the splenius capitis , and upper trapezius were measured 
 to assess the muscle activity . 
 [ results ] the muscle activity of the splenius capitis was 
 significantly higher at 80 , and 120 mmhg compared to 40 mmhg . 
 the muscle activity of the 
 upper trapezius did not show significant differences among the traction forces . 
 
 [ conclusion ] our research result showed that the air - inflatable home neck traction device 
 did not meet the condition of muscle relaxation .