in modern society , more people spend long periods working at computers , and experience 
 increased work - related neck and back discomfort1 . remaining seated for long periods can cause problems for the spine , 
 circulation , muscles , and joints2 . 
 prolonged sitting is a risk factor for low back pain ( lbp)2 .
osullivan et al.2 showed that decreased trunk muscle endurance is associated with 
 habitually adopting a passive sitting posture and reduced activity levels .
according to recent findings , the form of resting and the 
 work configuration are important to muscle activation and recovery of the circulation4 , 5 . 

the purpose of this study was to examine 
 the effects of a relaxation chair and resting with simple range of motion ( rom ) exercises 
 during computer work , and low back muscle strengthening exercises after computer work on 
 pain and the flexion - relaxation ( fr ) ratio of one computer worker with lbp .
the subject of this study was a 37-year - old male who complained of severe lbp pain at the 
 l4 level .
ethics approval was obtained from the yonsei university faculty of health science 
 human ethics committee .
he did not have back pain in the 
 morning but did have it in the evening after working on a computer all day .
when he 
 performed forward flexion in the standing position with his knees fully extended , he 
 experienced pain in his lower back with a visual analogue scale ( vas ) score of 7 .
, he rested three times 
 for approximately 10  min each at irregular intervals .
the rest of the time , he was 
 performing internet searches or shopping on a computer . in the study
, he worked on a 
 computer for 5  h each day for 3 days and followed a different program each day . the first 
 day ( session 1 )
, he spent 10  min in a relaxation chair resting after each hour of computer 
 work . the second day ( session 2 ) , he spent 10  min performing simple trunk rom exercises 
 ( trunk flexion , extension , lateral bending , and rotation ) while standing after each hour of 
 computer work . the third day ( session 3 ) , he performed low back muscle strengthening 
 exercises for 20  min after 5  h of using the computer .
the exercises consisted of a bridging 
 exercise in the supine position ( three sets of ten repetitions ) and hip extension exercises 
 in the quadruped position with knee extension ( left and right leg , five sets each of ten 
 repetitions ) .
this study measured the 
 fr ratio and vas score when he performed forward flexion in the standing position with his 
 knees fully extended , before and after each 5-h work session .
electromyography ( emg ) signals 
 were preamplified by a preamplifier placed close to the electrodes , and sent to the data 
 acquisition unit of an mp150 system ( biopac systems , santa barbara , ca , usa ) , which 
 amplified and sampled the emg input at 1000  hz .
the emg signals were band - stop filtered at 
 60  hz , and the root mean square ( rms ) values were calculated .
the subject was required to stand 
 comfortably , bend forward slowly with his arms dangling freely ( bending period ) , and then 
 hold this position for 3  s ( hanging period ) .
the fr ratio ( % ) was calculated as the ratio of 
 the rms activity in the hanging period to that in the bending period .
in session 1 , the fr ratios before and after work were 19% and 38% ( + 19% ) , respectively . 

the respective vas scores before and after work were 5 and 8 ( + 3 ) . in session 2 ,
the fr 
 ratios before and after work were 18% and 21% ( + 3% ) , respectively .
the respective vas scores 
 were 5 and 6 ( + 1 ) . in session 3 ,
the fr ratios before and after work were 22% and 29% ( + 7% ) , 
 respectively , and the vas scores were 5 and 6 ( + 1 ) .
the fr response is reported to occur in the lumbar region of more than 90% of healthy 
 people who do not have lbp8 . in 
 individuals with lbp
, the trunk muscle activation pattern is altered , and the lower back 
 muscles are strongly activated over a long period8 . it is necessary to evaluate the fr response for lbp .
mathieu and 
 forin9 suggested that if the erector 
 spinae ( es ) muscle activity during the hanging period is less than 10% of the muscle 
 activity during the bending period , it indicates the presence of fr . in session 1 ,
the fr 
 ratio ( + 19% ) and vas score ( + 3 ) increased to the greatest degree .
therefore , the relaxation 
 chair was not effective for muscle activation and recovery of the circulation . in session 2 , 
 the fr ratio increased by 3% and the vas score increased by + 1 . in session 3 ,
the fr ratio 
 was increased by 7% and the vas score increased by + 1 .
therefore , after computer work , the 
 back muscles require exercises to prevent lbp . there was no difference in pain between 
 sessions 2 and 3 .
however , difference in fr ratio was the lower in session 2 than session 3 . 

the fr ratio is known to be the more sensitive indicator for prediction of lbp8 , 9 . 
 also , session 3 required additional time after work , and it also required exercise with a 
 high load when compared with session 2 .
so , this study suggests that session 2 ( regular 
 trunk rom exercises after each hour of computer work ) was more effective than session 3 
 ( strengthening exercises after work ) .
however , this report has a limitation . the carryover 
 effects could have an influence on the results .
this study suggests that it is more 
 effective to perform regular , passive exercises to prevent lbp in computer users .
it also 
 suggests that poor resting is a risk factor for a change in the muscle pattern .
   [ purpose ] this study examined the effects of a relaxation chair and resting with simple 
 range of motion exercises during computer work and low back muscle strengthening exercises 
 after computer work on pain and the flexion - relaxation ( fr ) ratio of one computer worker 
 with lbp . [ subjects ] the subject of this study was a 37  year - old male who complained of 
 severe lbp pain at the l4 level . 
 [ methods ] in the study , the subject worked on a computer 
 for 5  h each day for 3 days and followed a different program each day . 
 [ results ] in 
 session 1 , the fr ratios before and after work were 19% and 38% ( + 19% ) , respectively . 
 the 
 respective vas scores before and after work were 5 and 8 ( + 3 ) . in session 2 , 
 the fr ratios 
 before and after work were 18% and 21% ( + 3% ) , respectively . 
 the respective vas scores were 
 5 and 6 ( + 1 ) . in session 3 , the fr ratios before and work were 22% and 29% ( + 7% ) , 
 respectively , and the vas scores were 5 and 6 ( + 1 ) . 
 [ conclusion ] this study suggests that 
 it is more effective to perform regular , passive exercises to prevent lbp in computer 
 users . 