desktop computer and laptop use is becoming common , and computing - related musculoskeletal 
 symptoms are considered important health problems in university students and office 
 workers1,2,3,4 . previous studies have indicated that improper sitting posture 
 during visual display terminal ( vdt ) work ( e.g. , desktop computer or laptop use ) can induce 
 musculoskeletal disorders , especially low - back pain3 , 
 4 ) . carter and banister3 
 suggested that increased tension in ligaments and discs during a slumped sitting posture may 
 lead to low - back pain . cross - legged sitting , a commonly adopted posture during daily living and vdt work , has been 
 reported to induce a slumped sitting posture5 , 6 . lee et al.5 showed that the cross - legged sitting 
 position leads to a greater slumped posture compared with an upright sitting posture during 
 vdt work . to prevent the unwanted slumped posture , it is crucial to identify factors that 
 contribute to slumped posture during cross - legged sitting . limited hip flexion range of 
 motion ( rom ) could be one possible risk factor for excessive lumbar flexion . because the 
 lumbar spine and hip joint are connected via the pelvis , limited hip flexion can cause 
 greater lumbar flexion through pelvic posterior tilt during the trunk flexion - related 
 posture7 . although it seems reasonable that limited hip flexion rom leads to greater lumbar flexion 
 during the cross - legged sitting posture , no study has investigated how hip flexion rom 
 influences the kinematics of the lumbar spine in the cross - legged posture during vdt work . furthermore , previous studies have not determined whether greater lumbar flexion during vdt 
 work with a cross - legged sitting posture changes trunk muscle activities as measured by 
 electromyography ( emg ) . only one emg study revealed decreased emg activity in the internal 
 oblique ( io ) muscles during the static cross - legged sitting posture compared with the static 
 normal sitting posture8 . thus , the aim of 
 the present study was to compare the lumbar flexion angle and trunk muscle activity in 
 individuals with and without limited hip flexion rom during vdt work with a cross - legged 
 sitting position . all subjects showed 
 right - leg dominance and performed computer work more than 20 hours per week . measurements of 
 the right hip flexion rom were used to classify subjects into the experimental or control 
 groups . according to previous findings9 , 
 sufficient hip flexion rom was defined as more than 120 of hip flexion , and limited hip 
 flexion rom was defined as 110 in this study . subjects with more than 120 of right hip 
 flexion rom ( one female , six males ) were classified into the control group , and subjects 
 with no more than 110 of right hip flexion rom ( eight males ) were classified into the 
 experimental group . subjects were excluded if they had acute low - back pain , orthopedic 
 damage , or lower extremity injury during the last 6 months . in addition , individuals with 
 hip flexion rom between 110 and 120 were also excluded in this study . the inje university 
 faculty of health science human ethics committee approved this study , and each subject 
 signed an informed consent form before participation . to measure hip flexion rom , subjects were placed in the supine position on a table , and an 
 examiner passively flexed the right hip of subjects until further hip flexion was limited by 
 firm end feel9 . the fulcrum of a 
 goniometer was placed on the greater trochanter , and the proximal and distal arms were 
 aligned with the lateral midlines of the pelvis and femur , respectively . the lumbar flexion angle was measured using eight vicon mx - t10 motion capture systems 
 ( vicon motion systems ltd . , three reflective 
 markers were placed on the bilateral anterior superior iliac spines and on the midpoint 
 between the bilateral posterior superior iliac spines for the pelvic segment . additionally , 
 four reflective markers were attached to the first and second lumbar spinous processes and 
 3  cm bilaterally from the second lumbar spinous process for the lumbar segment . the lumbar 
 flexion angle was calculated by assessing the anterior rotation of the lumbar segment with 
 respect to the pelvic segment using the cardan angle10 . the trunk muscle activity of the bilateral rectus abdominis ( ra ) , 
 external oblique ( eo ) , and io muscles was recorded using a synchronized surface emg system 
 ( delsys inc . , prior to attachment of the electrodes , skin preparation was 
 performed by shaving the hair and cleansing with an alcohol swab . each electrode was 
 attached along the direction of the muscle fiber based on placements suggested by 
 criswell11 . emg signals were acquired 
 at a sampling rate of 1,000  hz with a bandwidth of 20450  hz and converted into 
 root - mean - square ( rms ) data . to normalize emg data of the trunk muscles , reference voluntary 
 contraction ( rvc ) data of trunk muscles were collected when subjects were seated on a chair 
 in a comfortable sitting posture with 90 of hip and knee flexion for 40 s. the rvc maneuver 
 was repeated three times , and the mean value of the average muscle activity for the middle 
 30  s of the three trials was used to normalize trunk muscle activity . prior to vdt work , a laptop ( xnote r400 , lg , seoul , korea ) was placed on a 73-cm - high desk , 
 and subjects sat on a height - adjustable chair without a backrest with 90 of hip and knee 
 flexion . the examiner confirmed the 90 hip and knee flexion position using a goniometer . 
 for vdt work with a cross - legged sitting posture , subjects were instructed to cross the 
 right leg over the left by putting the right knee on the left knee5 , 8 . following 
 cross - legged sitting , subjected performed typing work in which they copied some text 
 provided on the monitor by the korean version of hansoft . the subjects typed for 1  min for 
 each trial , and three test trials were conducted with 30-s rest periods between trials . the 
 average values of the lumbar flexion angle and emg activity of the trunk muscles for the 
 middle 40  s of each trial were collected , and the mean values of three test trials were used 
 for data analysis . the subjects characteristics ( age , height , weight , hip flexion rom ) , lumbar flexion angle 
 and trunk muscle activity during vdt work with cross - legged sitting in the experimental and 
 control groups were compared using independent t - tests . , chicago , il , usa ) was used , and the statistical significance level 
 was set at p = 0.05 . the general characteristics of the subjects in the control group ( mean age 25.1  
 1.5  years ; mean weight 62.6  5.7  kg ; mean height 171.9  6.9  cm ) and the experimental group 
 ( mean age 23.6  1.5  years ; mean weight 67.4  4.1  kg ; mean height 175.1  4.5  cm ) were not 
 significantly different ( p > 0.05 ) , except for the hip flexion rom ( 123.6  2.4 
 versus 102.5  3.8 ; p < 0.001 ) . the lumbar flexion angle was significantly greater in the experimental group compared with 
 the control group during vdt work with cross - legged sitting ( p = 0.017 ) ( table 1table 1 . comparison of the lumbar flexion angle and trunk muscle activity between the two 
 groups during visual display terminal work with cross - legged sittingvariablemean  sdcontrol groupexperimental grouplumbar flexion ( )15.2  7.023.3  4.3*right ra activity ( % rvc)101.2  5.9100.5  8.2right eo activity ( % rvc)98.7  6.2113.3  30.4right io activity ( % rvc)91.4  7.9109.4  22.3left ra activity ( % rvc)101.3  7.1101.7  8.2left eo activity ( % rvc)98.3  5.0115.3  35.0left io activity ( % rvc)99.8  10.897.2  11.3rvc , reference voluntary contraction ; ra , rectus abdominis ; eo , external oblique ; io , 
 internal oblique . * however , there were no significant differences in emg measures of trunk 
 muscle activity between the control and experimental groups ( p > 0.05 ) . rvc , reference voluntary contraction ; ra , rectus abdominis ; eo , external oblique ; io , 
 internal oblique . * in the present study , the subjects with limited hip flexion rom showed greater lumbar 
 flexion compared with subjects with sufficient hip flexion rom during vdt work with 
 cross - legged sitting ; however , these differences in hip flexion rom did not influence emg 
 activity in trunk muscles . the lumbo - pelvic - hip complex is connected via a kinematic link termed the lumbo - pelvic 
 rhythm7 , 12 . during forward bending , the lumbar spine is flexed anteriorly with 
 respect to the pelvis , while the pelvis is flexed anteriorly on the femur12 . when lumbar flexion is limited , greater 
 hip flexion is required with pelvic anterior tilt throughout the lumbo - pelvic rhythm7 . in other words , greater lumbar flexion is 
 caused throughout the pelvic posterior tilt when hip flexion is limited . the results of our 
 study imply that greater lumbar flexion compensated for insufficient hip flexion in subjects 
 in the experimental group during vdt work with cross - legged sitting . despite significant differences in lumbar flexion between the experimental and control 
 groups , emg activity in the trunk muscles was not significantly different between the two 
 groups . snijders et al.8 
 reported that the cross - legged sitting position decreased emg activity in io muscles due to 
 increased stability in the sacroiliac joint . the cross - legged sitting posture is performed 
 by the combined motion of hip flexion and adduction . increased tension in the biceps 
 femoris , gluteus maximus and piriformis by hip flexion and abduction influences sacroiliac 
 joint compression and tension in the sacrotuberous ligament , which can contribute to 
 increased stability in the sacroiliac joint13,14,15 . although the hip flexion angle may have been influenced by differences in hip flexion rom in 
 subjects in this study , sufficient hip adduction may have been possible for all subjects 
 during vdt work with cross - legged sitting . we suggest that the sacroiliac joint compression 
 by hip adduction during cross - legged sitting may not differ between subjects with and 
 without limited hip flexion rom , resulting in the absence of significant differences in emg 
 activity in trunk muscles between the two groups . first , our study included a small sample size ; 
 therefore , it is difficult to generalize our results . however , a previous study by lee et al.5 showed that trunk kinematics were immediately changed after assuming 
 a cross - legged sitting posture during vdt work , and the trunk flexion angle then did not 
 significantly change for 30  min . based on previous findings , we consider that the kinematic 
 data of the lumbar spine and emg data of the trunk muscles during vdt work with cross - legged 
 sitting for short periods may provide meaningful information for individuals who prefer 
 cross - legged sitting .
[ purpose ] the purpose of this study was to compare the lumbar flexion angle and 
 electromyography ( emg ) measurements of trunk muscle activity in individuals with and 
 without limited hip flexion range of motion ( rom ) during visual display terminal ( vdt ) 
 work with cross - legged sitting . 
 [ subjects ] the 15 participants included a control group 
 with sufficient hip flexion rom ( n = 7 ) and an experimental group with limited hip flexion 
 rom ( n = 8) . [ methods ] all subjects performed vdt work with cross - legged sitting . 
 the 
 lumbar flexion angle was measured using a three - dimensional motion capture system , and the 
 trunk muscle activity was recorded using a surface emg system during vdt work with 
 cross - legged sitting . 
 the differences in trunk flexion angle and trunk muscle activity 
 between the two groups were analyzed using independent t - tests . 
 [ results ] the lumbar 
 flexion angle was significantly greater in the experimental group than the control group , 
 although trunk muscle activity did not differ between the two groups . 
 [ conclusion ] these 
 findings suggest that limited hip flexion leads to greater lumbar flexion during 
 cross - legged sitting .