forty - three percent of adults and 83% of students stay in a sitting position for more than 
 10 hours per day1 . sitting for long time affect musculoskeletal equilibrium , especially in the maintain posture case of asymmetric 
 posture3 . in an asymmetric posture , need 
 more power and energy and if posture maintained for a long time , would result in spinal 
 imbalance1 , 3 . genevieve et al.4 
 demonstrated that sitting for a long time may provoke crossed leg posture , leading to spinal 
 imbalances . an asymmetric posture may cause permanent spinal deformity such as kyphosis , scoliosis , 
 lordosis , and also result in chronic low back pain as well5 . in addition to lumbago , other 
 complications could occur such as fatigue , impaired cardiopulmonary function , neurotic and 
 psychiatric problems and matters of appearance7 . common asymmetric sitting positions are sitting with crossed legs , with the chin resting on 
 a hand , and with a purse in a hip pocket , and with lying prone on a desk8 . in sitting with crossed legs , asymmetric 
 usage of abdominal internal and external oblique muscles may cause spinal imbalances . moreover , as lumbar vertebrae are weak for flexing or twisting although they are well 
 tolerable with pressing , sitting with crossed legs may also provoke lumbago9 , 10 . it is known as 
 more than 80% of adolescents sit resting their chin on a hand when they study behind a 
 desk11 . as the spent with the chin 
 resting on a hand gets longer , it is more likely to cause permanent disparity of shoulder 
 height , placement of eyes , and position of hips11 , 
 12 . further , because resting the chin 
 on a hand inevitably leads prone position , it could cause musculoskeletal non - equilibrium 
 and spinal instability , and cause spinal injuries13 , 
 14 . asymmetric sitting such as sitting with the chin resting on a hand or with crossed legs , 
 which arise from poor habits , may affect spinal balance . this research was approved by ethics 
 committee of woosong university , and consent to participation was obtained from each subject 
 after they had received detailed explanations of the study . we fully explained whole 
 procedure of the experiment , and only included participants who agreed to participate . subjects who had experience of surgery or trauma within 6 months , difficulty with sitting in 
 the same position for more than 1 hour , limitation of spinal motion , or back pain , including 
 lumbago were excluded . thirty - seven subjects were enrolled , and randomly divided into two groups : the sitting with 
 the chin resting on a hand group and the sitting with legs crossed group ( table 1table 1.general characteristics of the subjectsmean  sdtotal ( n = 37)gender ( % ) male18 ( 47.6%)female19 ( 51.4%)age ( years)22.62 3.7height ( cm)166.2  9.6 weight ( kg)62.9  10.7sitting with the chin resting on a hand ( n = 20)gender ( % ) male9 ( 45.0%)female11 ( 55.0%)age ( years)21.8  4.7height ( cm)165.6  5.3 weight ( kg)62.3  10.4sitting with the legs crossed ( n = 17)gender ( % ) male9 ( 52.9%)female8 ( 47.1%)age ( years)23.6  1.6height ( cm)166.9  9.9 weight ( kg)63.6  11.3data are expressed as mean  sd ) . the sitting with the chin resting on a hand group sat on a hard chair with 
 their back straight at a table with a height of 110  cm from the ground . the elbow was firmly put on the 
 table , and flexed at angle of 100120 degrees , and the subjects used the palm of their hands 
 to support the chin . the subjects sat with the soles of their feet flat on the floor , their 
 most comfortable posture . the subjects crossed their legs in the way that they were habitually accustomed to , 
 and adopted the most comfortable posture . they sat on the chair with their legs crossed , 
 with both thighs fully crossed . data are expressed as mean  sd before the intervention , the spinal balances of the subjects were evaluated . sitting with the legs 
 crossed and sitting with the chin resting on a hand were performed by each group , and these 
 postures are commonly observed in real life . each position was maintained for 1 hour , and 
 during that time the subjects read books or watch videos . at the end of 1 hour the spinal 
 balances was immediately re - evaluated . then , the subject laid the supine position for 
 another 1 hour at the end of which spinal balance was evaluated again in order to 
 investigate the relationship between the time and effects of asymmetric sitting . the 
 formetric 4d ( diers , german ) device was used to analyze spinal balance . formetric 4d takes a 
 picture of the subjects from behind using light with a strip pattern , and then 
 three - dimensionally analyzes spinal balance based on contour of the back . it is 
 intrinsically safe because it does not emit radiation , and it can analyze sagittal 
 imbalance , coronal imbalance , pelvic obliquity , pelvic torsion , and angles of kyphosis and 
 lordosis15 , 16 . for statistical analysis , spss windows version 21.0 was used . in order to identify 
 differences between times points ( pre - intervention , directly after , 1 hour later ) , the data 
 of each position was analyzed by repeated measures of anova , with =0.05 as the level of 
 significance . bonferroni s method was used for post hoc analysis for matching analysis among 
 variables . after sitting for 1 hour with the chin resting on a hand , there were statistically 
 significant differences in sagittal imbalance , coronal imbalance , pelvic obliquity , and 
 lordosis angle . however there were no statistically significant differences in pelvic 
 torsion and kyphosis angle ( table 2table 2.spinal balance analysis of the different time points of the chin resting on a 
 hand grouppre intervention(meansd)directly after(meansd)1 hr later(meansd)sagittal imbalance(mm)26.39.737.511.928.58.4coronal imbalance(mm)6.04.910.54.27.64.9pelvic obliquity(mm)2.32.54.53.53.22.3pelvic torsion(angle)1.00.81.40.91.61.1kyphosis angle(angle)43.110.441.99.840.412.5lordosis angle(angle)34.87.132.87.834.07.3data are expressed as mean  sd . * p < 0.05 ) . these were compared those results with graphs and with the results of post 
 hoc analysis , and sagittal imbalance , coronal imbalance , pelvic obliquity and lordosis angle 
 there were statistically significant , and there were significant differences compared with 
  directly after ; however , no significant differences when compared with  1 hour later. data are expressed as mean  sd . * p < 0.05 after sitting for 1 hour with crossed legs , there were statistically significant in 
 sagittal imbalance , coronal imbalance , pelvic obliquity and lordosis angle . however , there 
 were no statistically significant differences in pelvic torsion and kyphosis angle ( table 3table 3.spinal balance analysis of the different time points of the sitting with legs 
 crossed grouppre intervention(meansd)directly after(meansd)1 hr later(meansd)sagittal imbalance ( mm)18.711.326.113.722.615.5coronal imbalance(mm)7.36.49.06.98.96.7pelvic obliquity(mm)2.82.23.42.93.43.1pelvic torsion(angle)1.81.32.81.51.91.2kyphosis angle(angle)38.713.338.511.938.410.7lordosis angle(angle)37.410.737.111.138.59.9data are expressed as mean  sd . * p < 0.05 ) . these were compared results with graphs and with the results of post hoc 
 analysis . sagittal imbalance , pelvic torsion were statistically significant , and there were 
 significant differences compared with  directly after ; however , no significant difference 
 when compared with  1 hour later. data are expressed as mean  sd . the effects of asymmetric sitting positions represented by resting the chin on a hand and 
 crossed legs , which are commonly observed in real life , on spinal balance were investigated 
 at two time points . therefore , it was our 
 assumption that asymmetric sitting position would affect pelvic balance and consequently 
 spinal balance as well . for sitting with the chin resting on a hand , directly after the intervention , sagittal 
 imbalance , coronal imbalance , pelvic obliquity and lordosis angle presented statistically 
 significant differences and they all out of normal ranges , so they could be a cause health 
 problems . in other words , cervical spine imbalances resulting from resting the chin on a 
 hand would have caused lordotic spinal imbalances . those unexpected contour changes were 
 presented laterally and frontally as well , increasing the lordosis angle to a degree that 
 could be regarded as illness . panjabi et al.17 also reported there was 
 asymmetric shortening or stiffness of the spinal erector muscles when the spine was 
 consistently imbalanced . this is similar to the results of our study and may indicate that 
 long term lateral spinal flexion could be a risk factor of spinal illness . these asymmetric 
 positions may lead to rotational deformity in the horizontal plane which would provoke 
 positional changes of the head , shoulder , and pelvis and deformation of the trunk and 
 thoracic cage as well . these changes could ultimately affect the spinal equilibrium18 . for sitting with crossed legs ,  directly after the intervention , different from the 
 resting the chin on a hand , sagittal imbalance , and pelvic torsion presented statistically 
 significant differences . both it appears results were close to abnormality of balance , and 
 since pelvic torsion increased , it appears that crossed legs generate pelvic torsion19.this could affect lumbar - pelvic rhythm , 
 and pelvic torsion increment resulting from asymmetric posture could accelerate pelvic 
 posterior tilting for a long time , and could also increase thoracic kyphosis exacerbating 
 abnormal posture9 , 18 . a positive aspect of this study was that , for both asymmetric sitting positions , 1 hour 
 after the intervention spinal balance and returned to the original position . however , when 
 an asymmetric position becomes habitual , a subject may consider it comfortable and stay in 
 the asymmetric posture consistently . then the muscles , ligaments , bone , vertebral discs , 
 pelvis would be under stress and could be permanently deformed20 . although spinal deformity needs some time to progress , secondary results 
 such as pain and neurotic complication could cause problems of appearance and psychiatric 
 trouble , and could shorten life expectancy21 . in this study , this device emits no radiation and it was 
 used to analyze the relationship between asymmetric position and spinal balance at different 
 time points . this study has demonstrated that a habitually maintained asymmetric position 
 could be a risk for spine disease . good posture could be an innate ability , however it would 
 mainly be made up of learning through life habits7 , 
 17 . so this study is meaningful from 
 the perspective of the importance of good posture . a limitation of the study was that we only checked changes at preset time points so small 
 temporal differences were not observed . another limitation was that we did not consider the 
 spinal imbalances subjects already had .
[ purpose ] to investigate the effects of two common asymmetric sitting positions on spinal 
 balance . 
 [ subjects and methods ] thirty - seven healthy subjects in their twenties were 
 enrolled and randomly divided into two groups . 
 asymmetric positions of resting the chin on 
 a hand and crossing the legs were performed by each group for 1 hour . 
 after 1 hour , the 
 subjects lay in the supine position again and spinal imbalance was measured using a 
 device . 
 [ results ] after 1 hour of resting with the chin on a hand , sagittal imbalance , 
 coronal imbalance , pelvic obliquity and lordosis angle presented spinal imbalance 
 worsening of 1 hour of crossing legs , sagittal imbalance , pelvic torsion showed in mainly 
 learned spinal imbalance living . 
 [ conclusion ] good posture could be an innate ability , 
 however it through habits . 
 so this study is meaningful from the perspective of the 
 importance of good posture .