inversion traction ( it ) is a form of spinal traction in which the body is maintained in an 
 inverted position so that back problems can be prevented and cured1 .
specifically , it provides the spinal column with traction 
 force using the body s weight .
the force of the body s weight in the it position is usually 
 calculated as approximately 40% of the body s overall weight2 ; this depends on the user s body weight and the traction angle . 
 unlike automated mechanical traction
, it is difficult in the case of it to adjust the 
 traction force because the traction angle is set by the users themselves .
thus , it places 
 excessive traction force on the spinal column . in the it process
the muscle spindles arranged parallel to the muscle fibers are then stretched , 
 and -motor neurons are stimulated by the stretch stimulus signal from the muscle spindles 
 through the ia and ii sensory nerves .
although muscle tension works as a muscle guard to protect the muscles , persistent 
 muscle guarding restricts blood flow and causes muscle fatigue3 .
recently , wang et al.5 reported that it 
 causes muscle fatigue in the lumbar erector spinae .
it can be deduced from this finding that 
 it prevents the lumbar erector spinae from relaxing .
however , the study of wang et al.5 did not provide any information on it in the 
 case of inversion above 30 , mainly because it was performed at an inverted angle below 30 
 in the study
. moreover , previous studies insisting that it helps to relax the lumbar erector 
 spinae are controversial6 , 7
. however , there is no doubt that it can prevent relaxation 
 of the lumbar erector spinae . in a study by vernon et al.6 on it , 19 subjects showed increased paraspinal electromyographic 
 activity .
accordingly , the current study analyzed the electromyographic activities of the lumbar 
 erector spinae resulting from the application of an it traction angle of over 30. based on 
 the results , we investigated whether it can help in the relaxation of the lumbar erector 
 spinae .
in this study , the subjects comprised 60 healthy male adults with no history of 
 musculoskeletal or neurological system disorders . the mean age , weight , and height of the 
 subjects
were 23.022.10  years old , 70.7710.14  kg , and 174.285.95  cm , respectively .
all 
 subjects were equally and randomly assigned to a 3030 group , a 3060 group , and a 6060 
 group depending on the angle of it applied .
all the subjects listened to a detailed 
 explanation about the study s methodology , safety matters concerning the progression of the 
 study , and bio - information protection before voluntarily consenting to participate in the 
 study .
this study was approved by the bioethics committee of the catholic university of 
 pusan ( cupirb-2015 - 027 ) .
the subjects were positioned horizontally on a table - form it 
 device ( tb2015-h1 , the ban , namyangju , republic of korea ) and remained resting in a supine 
 position for 10 minutes . after resting ,
for example , in 
 the case of the 3060 group , it was first performed at 30 of inversion for three minutes , 
 followed by a further three minutes at 60of inversion .
inversion was performed on the 
 3030 group and the 6060 group in the same way . to evaluate the muscle activities of the 
 lumbar erector spinae ,
electromyographic signals were collected at a sampling rate of 
 1,000  hz using an electromyography system ( lxm3204 , laxtha inc .
the root mean square ( rms ) values were calculated using the telescan software 
 ( laxtha inc . , daejeon , republic of korea ) after being processed with a 60  hz notch filter 
 and a 50500  hz band - pass filter .
the muscles were the lumbar erector spinae on both sides 
 of the lumbar spine ( l2 , l4)8 .
the paired 
 t - test was used to compare the significance of the differences in rms values between the 
 pre - it and post - it values .
one - way anova and scheff s post hoc test were used to compare 
 the significance of the differences in rms values between the groups .
the rms at the l2 and l4 levels on both sides were statistically significantly higher after 
 it compared with before it ( p<0.01 ) .
after it , the rms values at the l2 and l4 levels on 
 both sides in the 3060 group and 6060 group were significantly higher than those in the 
 3030 group ( p<0.01 ) . before it
, there were no significant differences between the 
 groups in terms of rms values at the l2 and l4 levels on both sides ( table 1table 1.changes in rms values after itgroupbefore itafter itl2 left ( v)30305.312.087.853.5030605.651.8412.704.1560605.502.0212.175.79l2 right ( v)30306.873.058.993.6630606.441.2113.053.6360606.611.7112.464.73l4 left ( v)30304.181.667.043.5930604.380.7811.783.8560605.062.4211.495.44l4 right ( v)30306.132.158.363.5330605.951.1012.143.5360606.201.7011.243.80*p<0.01 , values with different letters in a column are significantly different by 
 scheffe s test ) .
* p<0.01 , values with different letters in a column are significantly different by 
 scheffe s test
inversion traction is a widely used conservative treatment for low back pain conditions 
 ( e.g. , degenerative or herniated discs , spinal stenosis , or other spinal conditions ) .
it 
 provides pain relief , muscle relaxation , and distraction of vertebral column1 , 6
. 
 however , the paraspinal muscles generally provided resistance against spinal traction . a 
 traction force of at least 25% of the body s weight is necessary to achieve distraction of 
 the lumbar vertebrae against muscular resistance9 .
the force of it applied is usually approximately 40% of the overall 
 body weight2 .
the applied traction force 
 places a direct stretching load on the paraspinal muscles , and this load elicits increasing 
 muscle tension .
our study also produced a similar result , and we verified increased muscle 
 activities of the lumbar erector spinae after it .
these results 
 concur with those of a study by wang et al.5 showing that it causes muscle fatigue .
although the study by wang et 
 al.5 only examined an it angle of less 
 than 30 , it was clear from our study that it can not help to achieve relaxation of the 
 lumbar erector spinae in our study .
however , previous studies have clearly stated that it 
 can help with relaxation of the lumbar erector spinae6 , 7 .
in addition , these studies 
 noted that it decreases electromyographic activities of the lumbar erector spinae , but this 
 was not found in our study .
moreover , the previous studies measured electromyographic 
 activities during it , and this was the reason why the electromyographic activities were 
 considered to have decreased . during the process of it ,
the induced accommodation , in turn , affects the response of the stretching 
 load , and electromyographic activities decrease as time passes . for these reasons
, we compared the rms values after it with the rms values before it in order 
 to examine changes in muscle tension .
this method was used in a study by acedo et al.11 , and like that study , we were able to 
 obtain results showing changes in muscle tension .
after it , the rms values of the lumbar erector spinae in the 3060 group and 6060 
 group were higher than those in the 3030 group , and there was no difference between the 
 3060 group and the 6060 group .
in other words , muscle tension increased by it was 
 affected by the size of the traction angle rather than the process of traction angle 
 application . in a study by cholewicki
et al.12 , there was no difference between the electromyographic activities 
 of the lumbar erector spinae during several types of traction , when the same peak torque was 
 applied by spinal traction .
in the case of it , the traction force depended on the user s body weight and on the traction 
 angle .
accordingly , it was affected by the size of the traction angle rather than the 
 process of traction angle application .
therefore , the size of the traction angle should be 
 fully taken into account and applied very carefully in prescribing it . in this study ,
the subject was comprised of healthy male adults , so the results of this 
 study were limited to a healthy population .
however , muscle tension will be increased by it 
 in any other population , as it also lengthens paraspinal muscles in any other population . 

the aspects of the change in muscle tension will be different depending on the pathological 
 symptoms or conditions of the subject .
therefore , we suggest that it need not be applied if 
 it does not aid in the relaxation of the lumbar elector spinae .
 [ purpose ] the purpose of this study was to analyze changes in the electromyographic 
 activities of the lumbar erector spinae caused by inversion traction in order to verify 
 the relaxation effect . 
 [ subjects and methods ] the subjects included 60 healthy male adults 
 who were equally and randomly assigned to a 3030 group , a 3060 group , and a 6060 
 group . 
 inversion traction was performed for six minutes , and the electromyographic 
 activities of the lumbar erector spinae ( l2 , l4 ) were measured before and after inversion 
 traction . [ results ] the root mean square values at the l2 and l4 levels on both sides 
 were 
 statistically significantly higher after inversion traction compared with before inversion 
 traction . before inversion traction , 
 the root mean square values at the l2 and l4 levels 
 on both sides in the 3060 group and 6060 group were significantly higher than those in 
 the 3030 group , while the root mean square values at the l2 and l4 levels on both sides 
 showed no significant differences between the groups before inversion traction . 
 
 [ conclusion ] the findings of this study indicated that it is more likely to elicits an 
 increase in muscle tension and prevent relaxation of the lumbar erector spinae . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION