despite advancements in modern medical science and the health management industry , the 
 incidence of cerebral palsy ( cp ) continues to rise1 .
the most common features of cp are decreased muscle strength and 
 abnormal muscle tone2 .
cp sufferers lack 
 theability to generate enough force to maintain antigravity postural control , which result 
 in abnormal postures3 .
the development of movement and posture may be altered by 
 non - progressive damage to the brain and subsequent neurological impairments ( spasticity , 
 muscle weakness , co - contractions and visual impairment)5 .
studies indicate that children and adults with both mild and severe 
 forms of cp have postural impairments6,7,8 . 

the emergence of sitting postural control 
 in early infancy changes the way infants interact with the world . from the sitting position , 
 looking , reaching , and interacting become functional and allow exploration that supports 
 learning and further development of motor skills .
therefore , independent sitting , defined as 
 not needing support from a caregiver or pillow while sitting , is one of the first 
 developmental goals for every child .
individual differences are present between children , 
 and characteristic signs of developmental disorders during infancy are relatively 
 unspecific . therefore , why a specific child is not able to achieve sitting postural control 
 is not always clear .
one method of examining postural control in adults and children is to measure the center of 
 pressure ( cop ) at the base of support using a force platform during the task of remaining 
 upright .
cop has frequently been used to investigate postural control during standing by 
 young children who are healthy or have cp9 , 10 .
the purpose of this study was to 
 investigate the differences of the pressure distributions of the sitting postures of typical 
 developmental ( td ) children and children with cp .
twelve cp childrens were recruited from an outpatient rehabilitation clinic . they were 
 hemiparetic , had an mmse - k score above 2411 , could maintain an independent sitting posture without support . 

two of the cp children were 
 subsequently excluded because they refused to participate in this experiment .
all parents of the enrolled participants provided 
 their written informed consent to their children s participation prior to this experiment , 
 in accordance with the ethical principles established in the declaration of helsinki . as a 
 result of the exclusion ,
this study used two 
 school chairs mounted on a force platform to assess the quiet - sitting pressure distribution 
 of the subjects . fsa seating assessment ( canada )
the acquisition frequency was set at 5  hz . the stated working range of the 
 device is 0200 mmhg , with a resolution of 1 mmhg .
the system was also calibrated to assign 
 absolute pressure values to the digital output from an a / d converter connected to the 
 sensing pad .
this was done by applying a pressure distribution as similar to actual 
 conditions as possible .
then thus subjects sat on one of two school 
 chairs according to their height .
the chairs were those generally used in school . for 
 research purposes , this study used two basic school chair because students spend a long time 
 of day - to - day sitting on them .
one chair had a 40  cm floor to seat height , a 35  cm seat 
 depth , and a 32  cm seat width and is designed for 122.4133.5  cm height of subjects .
the 
 another had a 35  cm floor to seat height , a 38  cm seat depth , and a 35  cm seat width , and is 
 designed for 133.6152.7  cm height of subjects .
it has been used for the 
 posture symmetry in other study13 statistical analyses were performed using pasw 18.0 .
descriptive statistics were calculated 
 ( frequency , mean , standard deviation , range ) .
the mann - whitney u - tests and wilcoxon s signed 
 rank tests were used to analyze differences between the groups and differences in lesion 
 side , respectively .
the si of the age matched td group was employed as the normal 
 criteria .
table 1table 1.general characteristics of the subjectscerebral palsygroup ( n=10)typicaldevelopmentalgroup ( n=10)age ( years)8.040.827.840.94gender ( male / female)5/54/6lesion side ( right / left)4/6symmetry index ( meansd)5.041.342.302.76 shows the general characteristics of the participants .
the si of the td group 
 was significantly closer to zero than that of the cp group of children .
cp and right hemiparetic cp were respectively 4.96 ( 2.24 ) and 5.12 ( 0.83 ) with 
 no significant difference between the hemiparetic sides .
the purpose of the present study was to investigate the differences in sitting posture of 
 children with cp while they sat on school chairs .
it is known that dynamic postural control 
 during sitting can be reliably assessed using cop data of infants who are developing 
 typically or infants with or at risk of cp14 .
the principal finding of this study is that cp children s sitting posture is asymmetrical , 
 leaning to the less - paretic side .
we thought that infants who are developing typically 
 develop the ability to sit by exhibiting an optimal range of movement variability , whereas 
 cp may present either too much or too little variability leading to a very rigid and narrow 
 or unpredictable set of movement solutions to achieve independent sitting .
the finding of 
 this study is agreement with previous studies that have the dissimilarities of the cop 
 patterns of infants with cp and td have been obviously demonstrated14 .
the results can not be generalized to all cp 
 children because the sample was limited to ten children and they were at the one stage of 
 the developmental process .
future studies should assess the relationship between symmetry of 
 sitting posture and functional activities .
 [ purpose ] the purpose of this study was to investigate the differences in symmetry of 
 sitting posture between typical developmental ( td ) children and hemi - cerebral palsy ( cp ) 
 children . 
 [ subjects and methods ] a school chair mounted on a force platform was used to 
 assess the quiet - sitting pressure distribution of 10 td and 10 cp children . 
 [ results ] the 
 symmetry index of the td children was significantly closer to zero than that of the cp 
 children irrespective of the latter group s hemiparetic side . [ conclusions ] sitting 
 posture on school chairs of cp children was more asymmetrical than that of td 
 children . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION