when driving ,  slumping  often happens ; drivers move their hips forward when they feel 
 uncomfortable mainly because of the inadequate design of car seats .
their intention is to 
 shift to a more comfortable position when the level of seat is too low , the cushion of the 
 seat is too firm , or the back of a seat is not properly reclined1 .
this phenomenon occurs when drivers adopt a comfortable 
 posture instead of a correct one , and it often results in a bent backbone and , consequently , 
 low back pain2 .
musculoskeletal disorders such as low back pain and shoulder discomfort often arise from 
 doing simple repetitive jobs and appear in the low back , neck , shoulders , arms , and 
 legs3 .
long hours of driving may yield 
 fatigue in the neck , shoulders , or low back .
pain might be the result of sitting posture , 
 vibration during driving , tension , or fatigue4 .
gyi and porter5 , 
 in their study of musculoskeletal disorders of policemen , reported that shoulder discomfort 
 was a significant problem for driving policemen .
porter and gyi6 also found that drivers are more likely to have low back 
 pain than people working either while sitting or standing .
kim et al.7reported that workers in the transport industry had a 2.14 
 subjective degree of fatigue on a 5-point scale , and the main locations of pain were the 
 shoulders ( 56.59% ) , neck ( 50.24% ) , and knees ( 43.90% ) .
judic et al.8 examined some previous 
 studies proposing an optimal driving posture based on comfortable posture , and measured mean 
 values of angles for each joint .
they made an alternative proposal of an optimal posture 
 that takes into consideration all the aspects of driving posture .
lee9 , in his study of uncomfortableness of elbow motion , applied 
 a magnitude estimation method to kinematic parameters of the elbow joint and made a 
 quantitative estimation of the degree of uncomfortableness of the steering motion .
his 
 analysis of uncomfortableness was based on the measurement of the radius and angle of the 
 steering wheel , and the distance between a driver 's shoulders and the steering wheel . 

andreoni et al.10 performed a 3d analysis 
 of the pressure between a driver 's joint angle and the seat in a sitting position .
kyung and 
 nussbaum11 offered three kinds of 
 subjective evaluation ( overall evaluation , discomfort , and comfort ) in assessing the design 
 and layout of seats based on body pressure distribution .
hostens and ramon4investigated the activation of the muscles 
 during driving , and active and passive motion using surface electromyography of the deltoid 
 muscle of both the shoulders and the trapezius muscle .
most analyses of driving postures have been conducted from the perspective of mechanical 
 engineering , technology , industry , and ergonometric engineering .
however , little research 
 has been reported in the literature that focuses on maximal torque and muscle strength 
 according to arm length and gender .
the goal of this study was to propose an optimal driving 
 posture based on the key factors of maximal torque and muscle strength .
twenty - seven college students in their 20 's who were attending a university located in 
 chonan , korea , participated in the present research .
they all voluntarily agreed to 
 participate in the experiment after an orientation session about the research .
the subjects 
 were healthy adults who had no congenital deformity in the upper body or neurologic 
 disorder .
table 1 shows the physical 
 characteristics of the subjects participating in the present research .
the ethics committee 
 of namseoul university in korea approved the study . the orientation session conducted with the subjects offered the subjects a detailed 
 explanation of the contents of the research .
a body composition analyzer ( inbody 720 , biospace , korea ) was used to 
 measure their basic physical characteristics .  
seat distance of 50% of arm length   seat distance of 90% of arm length   seat distance of 70% of arm length we measured the arm lengths of the subjects in a standing position with their shoulder 
 joints in 90 flexion . a tape measure ( fitting , apsun ,
korea ) was used to measure the arm 
 length from the acromion to the styloid process of the radius .
the arm lengths were used as 
 the basis for the three different driving seat positions . for the purpose of measuring maximal torque and muscle strength
subjects sat on the equipment and belts were 
 fastened around the trunk and thigh in order to prevent compensation movements that might 
 occur during driving .
the arm length from the acromion to the styloid process of the radius 
 was then measured12 .
the center of the 
 subject 's body and that of the steering wheel were aligned , and the distance between the 
 steering wheel and the seat was adjusted to create the three different driving seat 
 positions as illustrated in fig . 1 , 2 , and 3 . in 
 each position
( distance from the driving wheel of 50% , 70% , and 90% of subject arm length ) 
 subjects ' maximal torque and muscle strength were measured . a slightly revised version of 
 the definition of yoo et al .
of 50% , 70% , and 90% of arm length was used in this study13 .
maximal torque was measured in each of the three driving seat positions in three alternate 
 sessions of clockwise and counterclockwise turning .
we calculated the mean values of these 
 test - retest processes to enhance the reliability of our research . in cases
where the cov 
 ( coefficient of variation ) was found to be greater than 15% , the experiment was repeated . in 
 order to eliminate the possibility of higher momentary pressures , the subjects maintained 
 maximal pressure for five seconds .
they were also asked to sit straight up and use only 
 their arms and shoulders to turn the steering wheel , so that we could reduce the error 
 attributable to weight variations from hanging on the steering wheel .
after 3 rounds of clockwise and counterclockwise 
 sessions , another 30 seconds of rest was given before we measured muscle strength14.values of 50% of the measured maximal 
 torque were used as the 100% resistance level for muscle strength . for fatigue recovery ,
after the 
 experiment was performed at a seat distance of 50% arm length , the experiment was performed 
 at a seat distance of 70% arm length after 24 hours , and at 90% arm length after a further 
 24 hours15 .
spss version 18.0 was utilized for the analysis of the results , and the data were confirmed 
 to have a normal distribution by the kolmogorov - smirnov test . a descriptive statistical 
 survey to identify the general characteristics of the subjects participating in the research 

manova ( multivariate analysis of variance ) was employed to compare 
 the measured results of maximal torque and muscle strength between gender and among seat 
 distances . in cases where significant differences were found with manova ,
* significant difference p<0.05 * significant difference p<0.05 table 2 shows that there were significant 
 differences ( p<0.05 ) between males and females in both maximal torque and muscle 
 strength , whether they were turning the steering wheel clockwise or counterclockwise . 

further , male subjects showed greater values than female subjects for both parameters . a : 50% of arm length b : 70% of arm length c : 90% of arm length .
* significant 
 difference p<0.05 manova analysis of maximal torque and muscle strength showed that neither gender nor seat 
 distance relative to arm length closely interacted with maximal torque , in clockwise and 
 counterclockwise turning , or with muscle strength ( p>0.05 ) .
we did find significant 
 differences in maximal torque , both clockwise and counterclockwise , and in muscle strength 
 among the different seat positions ( p<0.05 ) ( table 
 3 ) .
table 4 is a summary of multiple comparisons of 
 maximal torque and muscle strength .
it shows that maximal torque in clockwise turning was 
 greater at a seat distance of 50% than 90% arm length , and greater at a seat distance of 70% 
 than 90% arm length .
the same result was obtained for counterclockwise turning and the 
 differences were statistically significant ( p<0.05 ) .
scheffe 's post hoc test showed muscle strength was greater at a seat distance of 70% than 
 at either 50% or 90% of arm length , and the differences were also statistically significant 
 ( p<0.05 ) .
the current research compared maximal torque and muscle strength between gender and among 
 seat distances relative to arm length when turning a steering wheel clockwise and 
 counterclockwise .
. 
 however , the greater the muscle strength or endurance is , the lesser the physical burden a 
 subject experiences when participating in physical activities14 .
thus , it might be safe to assume that greater maximal torque and 
 muscle strength reduce the physical stress of drivers , leading to a more desirable driving 
 posture .
we found no interaction between gender and seat distance relative to arm length with 
 maximal torque , either in clockwise or counterclockwise turning , and with muscle strength 
 ( p>0.05 ) .
thus , we can conclude that neither gender nor seat distance has an independent 
 effect on maximal torque or muscle strength .
park16 conducted a survey of body size , muscle strength , nutrition intake , 
 and nutritive conditions among a group of 245 students attending a college in taegu , korea . 

she found significant differences in both back muscle strength and grip strength , with male 
 students showing higher values than female students .
the results of our present study are 
 similar in that muscular strength and endurance showed differences that were statistically 
 significant .
askew et al.17 also found that males 
 possess greater flexion and extension strength of the elbow joint , and maximal torque of 
 forearm pronation and supination .
these differences in muscular strength between males and 
 females arise from the actions of sex hormones . during the period of adolescence ,
a female 's 
 secondary sexual characteristics lead to an accumulation of internal body fat leading to 
 less accumulation of muscle than in males18 , 19 .
their study conducted a descriptive 
 statistical analysis of the subjects ' physical characteristics in order to examine the 
 differences in the amount of muscle and body fat .
the data for males and females were as 
 follows : 31.820  3.264 vs 19.667  3.120 for skeletal muscle , and 12.973  6.460 vs 20.008 
  7.583 for body fat , respectively .
these figures support the widely accepted conclusion of 
 past research that females ' weaker muscle strength results from less skeletal muscle due to 
 greater volume of body fat .
an et al.20 report in their study of the 
 biceps brachii , brachialis , brachioradialis , and torque , that the greatest torque was 
 generated at elbow angles between 75100. neumann21 found that the supination torque when the elbow joint is flexed at 
 90 is twice as much as when it is flexed at was 30 , since the biceps brachii plays an 
 important role as a supination muscle .
we found that maximal torque was greater when the 
 steering wheel was nearer the body .
maximal torque was greater when the seat distance was 
 50% and 70% of arm length than when it was 90% .
we conclude that maximal torque is greatest 
 when the seat distance is between 50% and 70% arm length .
park et al.22 analyzed fatigue from long 
 driving and discovered that an open driving posture less fatigue than a closed one .
the open driving posture is 
 close to the seat distance of 70% arm length , while the closed one is very similar to the 
 seat distance of 50% arm length .
judic et al.8 suggested in their research of driving postures that the optimal one 
 features an elbow angle of 124139. their proposed posture is very similar to the seat 
 distance of 70% arm length .
these past proposals might support our conclusion that less 
 fatigue and improved muscle endurance can be achieved at a seat distance from the steering 
 wheel of 70% of arm length . in conclusion , male subjects exhibited greater maximal torque and muscle strength turning a 
 steering wheel both clockwise and counterclockwise .
a shorter distance between the steering 
 wheel and the driving seat leads to greater maximal torque .
muscle strength , in contrast , is 
 greatest when the seat distance from the steering wheel is 70% arm length . we conclude that 
 a proper driving posture exerts a positive influence on muscle strength and , as a 
 consequence , helps drivers feel less tired .
   [ purpose ] this research analyzed how seat distance and gender affect maximal torque and 
 muscle strength when driving to present base data for the optimal driving posture . 
 
 [ subjects and methods ] the subjects were 27 college students in their 20 's , 15 males and 
 12 females . 
 after had been measured , the subjects sat in front of a steering wheel with 
 the distance between the steering wheel and the seat set in turns . at 50 , 70 , and 90% 
 their arm length , and the maximal torque and muscle strength were measured . 
 [ results ] both 
 the maximal torque and muscle strength were found to be greater in male subjects than 
 female subjects whether they turned the steering wheel clockwise or counterclockwise . 
 the 
 difference was big enough to be statistically significant . 
 maximal torque was greatest 
 when the seat distance was 50% of arm length , whether turning the steering wheel clockwise 
 or counterclockwise . 
 there were statistically significant differences in maximal torque 
 between seat distances of 50 and 70% and 90% of the arm length . 
 muscle strength , in 
 contrast , was found to be the greatest at a seat distance of 70% of arm length . 
 
 [ conclusion ] we conclude that greater torque can be obtained when the steering wheel is 
 nearer the seat while greater muscle strength can be obtained when the seat distance from 
 the steering wheel is 70% of the arm length . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION