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 .