there is 
 mounting evidence indicating that the static neck posture frequently assumed by computer 
 workers using a computer is a risk factor for work - related neck and upper - limb 
 disorders1 , 2 . during computer work , use of the cervical erector spinae ( ces ) 
 muscles is important for efficient muscle activation and support for the task being 
 performed , as well as for the upper trapezius1 .
a previous study reported that pain - related activation of the ces 
 muscles could not be relaxed , even after an arm task2 .
recent findings indicated that the flexion - relaxation ( fr ) ratio in 
 the ces muscles may be a significant criterion of neuromuscular impairment and function3 .
also , a previous study reported that the 
 cervical extension and flexion angles could be a predictive factor for changes in head and 
 neck posture after long - term visual display terminal work4 .
korean household internet and computer distribution rates have 
 rapidly increased since 2000 , and korea has now been identified as the country with the 
 highest distribution of internet and computers in the world , with the rates exceeding 80% .
a 
 review of the rates of use of the internet using computers by age indicated that teenagers 
 and people in their 20s use the internet the most frequently5 .
therefore , as of 2013 , korean males and females in their 20s are 
 thought to be exposed the most to diseases related to computers .
therefore , this study 
 compared the cervical range of motion and cervical frr between computer users in their early 
 and late 20s in korea .
eleven male and 7 female computer users in their early 20s ( 2024 years ) and 10 male and 6 
 female computer users in their late 20s ( 2529 years ) participated in this study .
the early 
 20s group s average age , weight , and height were 21.6  1.5 ( mean  sd ) years , 60.8  
 10.1  kg , and 168.3  8.5  cm , respectively .
the late 20s group s average age , weight , and 
 height were 27.8  2.1  years , 62.8  10.4  kg , and 169.5  6.8  cm , respectively .
the subjects 
 used computers for 5.01.5 hours / day ( meansd ) as full - time student workers in a university 
 office .
all subjects were right - dominant , and free of any neck or back pain for a minimum of 
 1  year prior to the study , and they did not have upper limb or cervical spine pathologies or 
 rheumatological or neurological conditions . each subject provided informed consent before 
 participating in the study .
this study was approved by the inje university faculty of health 
 sciences human ethics committee .
all cervical rom measurements were taken with a cervical 
 range of motion instrument ( crom ) ( performance attainment associates , st .
the intra - test reliability of the crom instrument was 0.89 , and the inter - test reliability 
 was 0.91 .
each participant 
 began this phase by sitting on a standard folding chair and being fitted with the crom . 

after measuring the cervical active rom , electromyographic ( emg ) data were obtained for 
 analyzing the fr ratio .
surface electrodes were placed on the right sides of the ces 
 muscles , 2  cm lateral to the c4 spinous process .
the neck flexion and re - extension task comprised 
 flexion , relaxation , and re - extension periods .
the 
 trunk flexion and re - extension task comprised relaxed standing , forward flexion , full 
 flexion , and re - extension periods .
each movement period lasted 3 seconds . the cervical 
 flexion - relaxation ratio ( frr )
was calculated by dividing the maximal muscle activation 
 during the 3-s re - extension period by the average activation during the 3-s relaxation 
 period .
the paired t - test was used for comparison of the cervical range of motion and 
 cervical frr between the early and late 20s computer users in korea .
the cervical extension , right and left lateral flexion , and right and left rotation 
 ( 72.512.7 , 39.66.5 and 42.66.6 , 63.77.8 and 64.711.3 ) in the late 20s computer 
 users were significantly lower compared with the cervical extension , right and left lateral 
 flexion , and right and left rotation ( 83.513.7 , 46.78.0 and 49.58.6 , 72.58.5 and 
 73.57.2 ) in the early 20s computer users .
cervical flexion showed no significant 
 difference between the early 20s computer users ( 65.411.9 ) and late 20s computer users 
 ( 598.3 ) .
the cervical frr in the late 20s computer users ( 1.24.8 ) was significantly lower 
 compared with the cervical frr in the early 20s computer users ( 2.21.0 ) .
reduced crom can result from inactivity and structural changes in the tissues in the 
 cervical spine , and the shortening of collagen tissue and muscle fibrosis results in an 
 increased connective - tissue density6 . 

there are many methods of evaluating the cervical region , including assessing crom , posture , 
 muscle tenderness , pressure pain , neck - muscle power , and the subjective experience of pain . 

the results of the present study showed that the cervical extension , right and left lateral 
 flexion , and right and left rotation in the computer users in their late 20s were 
 significantly lower compared with the cervical motions in the computer users in their early 
 20s .
the frr obtained by dividing the maximal muscle activation during the re - extension 
 phase by activation during the relaxation phase was most highly associated with the cervical 
 active rom , which was considered a major clinical feature of the anticipatory dysfunction 
 and neck posture in previous studies4 . 

this result showed that the cervical frr in the late 20s computer users ( 1.24.8 ) was 
 significantly lower compared with the cervical frr in the early 20s computer users 
 ( 2.21.0 ) . in a previous study ,
the cervical frr values were relatively lower in the 
 symptomatic population than in the controls3 .
the cervical frr , which is expressed as a numerical value , is a 
 sensitive marker for measuring neuromuscular changes associated with even mild discomfort . 
 in recent korea society ,
computer work is clearly the most threatening element that causes 
 neck and shoulder pain for young computer users .
although it is difficult to classify them 
 as chronic patients given their ages , they may show tendencies of being chronic in terms of 
 neck pain because they have been exposed to computers since childhood .
this study was 
 conducted to prepare for the possibility that young computer generations in korea could 
 easily develop chronic neck pain , and the results of this study are thought to be very 
 helpful clinically in determining neck pain in young computer users in their late 20s in 
 korea , who could easily develop chronic neck and shoulder pain .
   [ purpose ] this study compared the cervical range of motion and cervical frr between 
 computer users in their early and late 20s in korea . 
 [ subjects ] eleven male and 7 female 
 computer users in their early 20s and 10 male and 6 female computer users in their late 
 20s participated in this study . 
 [ methods ] all cervical rom measurements were taken with a 
 cervical range of motion instrument . 
 electromyographic ( emg ) data were obtained for 
 analyzing the fr ratio . [ results ] cervical extension , right and left lateral flexion , and 
 right and left rotation in the late 20s computer users were significantly lower compared 
 with the cervical motions in the early 20s computer users . 
 the cervical frr in the late 
 20s computer users was significantly lower compared with the cervical frr in the early 20s 
 computer users . 
 [ conclusion ] this study was conducted to be prepared that the possibility 
 for young computer generations in korea could easily develop chronic neck pain . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION