cerebral palsy is an abnormality related to mobility and postural development due to lack 
 of development progression in the brain of an unborn child in the developmental phase or a 
 baby .
it encompasses sensory , cognition , communication , behavior disorders including motor 
 disorder and spasticity1 .
motor disorders 
 with cerebral palsy characteristics limit physical activity leading to lack of experience 
 with motor activity which would delay concept formation about sensation and motor activity , 
 sociality etc , therefore it imposes many limitation on social activity and 
 participation2 .
cerebral palsy may involve problems in the neuromuscular system such as spasticity , 
 contracture , muscle weakness , and loss of selective movement3 .
the gastrocnemius is involved in weight bearing during gait , and 
 plays the main role in adjusting the angle of the ankle in the stance and swing phases4 .
the length of the gastrocnemius and the 
 ankle range of motion is lower in cerebral palsy subjects than in normally developing 
 infants , and this is known to adversely affect gait5 .
the quadriceps femoris is essential for functional activities 
 involving weight - support , such as moving from the sitting position to the standing posture , 
 climbing up and down the stairs , and adjusting against gravity in the stance phase during 
 gate6 .
children with cerebral palsy show weakened muscle due to lack of motor unit activation and 
 thickness of 50% of small muscles , compared to children with normal development7 .
cerebral palsy with capability of 
 independent ambulation also had limitation on muscle contraction in that its greatest 
 ability of muscle contraction only reached 52% of that of normally developed children8 , regular physical activity ameliorates , but 
 does not prevent age - related atrophy of lower extremity muscles9 .
the gross motor function measure ( gmfm ) and computerized 
 gait analysis are commonly used to assess patients with cerebral palsy ( cp ) .
primary weakness and secondary disuse of this muscle group , 
 coupled with abnormal movement patterns , may lead to muscle atrophy and rearrangement of the 
 internal muscle architecture , thus adversely affecting function11 .
but , few studies of the muscle structure and body 
 function of cerebral palsy subjects have been performed .
therefore , the purpose of this 
 study was to provide the information necessary for intervention by comparing the muscle 
 thicknesses , gross motor functions , activities of daily living of the main lower limb 
 muscles and functional levels of activity of daily living between cerebral palsy and mental 
 retardation subjects .
the subjects of this study were 38 cerebral palsy children ( 21 males and 17 females ) who 
 were diagnosed as having diplegic cerebral palsy ( gmfcs level i , n=10 ; level ii , n=6 ; level 
 iii , n=22 ) and were receiving physical therapy at the kyeung - ki - do g rehabilitation 
 hospital , 13 normally developing infants ( 8 males and 5 females ) , and 9 mental retardation 
 subjects ( 4 males and 5 females ) with no other underlying disease , a total of 60 subjects . 

the specific selection criteria were as follows : no orthopedic surgery within the last 6 
 months , and no botulin or bacropen treatments of the lower limbs during the previous 3 
 months .
the present study was approved by sahmyook university 
 institutional review board ( syuirb2012 - 030 ) .
a subject was explained the objective of the 
 study and its requirements , and all those who participated provided written parental 
 consent .
movable ultrasonic waves ( mysono u5 , medison korea , 2009 ) were used to measure the muscle 
 thicknesses of the rectus femoris and gastrocnemius .
subjects were made comfortable in the 
 prone position with knee extension , and the distance between the superior aponeurosis and 
 the inferior aponerosis of the gastrocnemius was measured as the thickness of the 
 gastrocnemius13 .
an intra - rater 
 reliability of r = 0.98:1.0 , and an inter - rater reliability of 
 r = 0.93:0.98 have been reported for ultrasonic waves imaging14 .
an manual muscle tester ( model 11001163 , lafayette instruments , usa , 2003 ) was used to 
 evaluate the muscle strength of the knee extensor and plantar flexor muscles .
subjects sat 
 on a chair with the trunk fixed , and the knees flexed at 90 degrees and performed maximum 
 isometric contraction for measurement of knee extensor strength . during this time , the 
 degree of contraction of the quadriceps femoris was measured using the manual muscle tester . 

subjects sat on the chair with the trunk fixed , and the knee and ankle joints at 90 degrees . 

the ankle was fixed in the central position by supporting the foot heel with a foot stand . 

an intra - rater reliability for the manual 
 muscle tester of r = 0.84:0.99 , and an inter - rater reliability for the 
 manual muscle tester of r = 0.84:0.94 have been reported16 .
the gross motor function measure ( gmfm ) was used to evaluate the gross motor function .
gmfm 
 is divided into 5 domains , which are a ( lying and rolling ) , b ( sitting ) , c ( quadruped and 
 kneeling ) , d ( standing ) , e ( walking , running , jumping ) , encompassing 88 items . inter - rater 
 reliability for gmfm of r = 0.77 , a test - retest reliability for gmfm of 
 r = 0.88 , and intra - rater reliability for gmfm of r = 
 0.68 have been reported17 , 18 .
the wee functional independence measure ( weefim ) was used to evaluate the health of the 
 subjects , their developmental condition , educational level conditions and degree of local 
 sociality .
items of the weefim are scored from 1 to score 7 which is a condition of complete 
 independent .
an inter - rater reliability of 0.92 , a 
 test - retest reliability of 0.99 , and an intra - rater reliability of 0.81 have been reported 
 for the weeflm20 .
the shapiro - wilk test was used for 
 determination of the general properties and variables of the subjects .
the independent t 
 test was used for the comparison of gmfm and weefim between cerebral palsy and mental 
 retardation subjects , and one - way anova was performed for comparison of the means of muscle 
 thickness and strength among the subjects groups . a post - hoc test using the scheffe method 

general characteristics of the participantsnormal development infant ( n=13)cerebral palsy ( n=38)mental retardation ( n=9)sex ( male / female)8/521/174/5age ( month)79.6 ( 24.0 ) 66.6 ( 15.7)53.8 ( 17.9)height ( cm)120.3 ( 16.7)107.6 ( 6.6)102.4 ( 9.2)weight ( kg)21.3 ( 5.6)18.3 ( 3.2)16.6 ( 3.0)values are   mean ( sd ) . ) .
differences in muscle thicknesses of the rectus femoris and gastrocnemius according to the 
 posture are presented in table 2table 2 .
comparison of muscle thickness and strengths among the groupsndi ( n=13)cp ( n=38)mr ( n=9)muscle thickness ( mm)rf in standing12.69 ( 1.97 ) 11.89 ( 2.05 ) 10.14 ( 2.51)rf lying16.13 ( 3.07)14.55 ( 2.33 ) 12.63 ( 1.85)gastrocnemius standing11.46 ( 1.55)11.90 ( 2.57)12.55 ( 3.06)gastrocnemius lying15.41 ( 2.42)14.72 ( 3.68)14.34 ( 3.78)muscle strength ( kg)knee extensor17.77 ( 5.45 ) 7.92 ( 4.82)11.19 ( 5.85 ) plantar flexor15.54 ( 7.51 ) 6.01 ( 4.11)7.82 ( 3.04 ) values are mean ( sd ) .
ndi : normally developing infants ; cp : cerebral palsy ; mr : 
 mental retardation ; rf : rectus femoris ; * p<0.05 from mean among the three groups ; 
 a , ndi is significantly greater than cp and mr ; b , cp is significantly greater than 
 mr ; c , ndi is significantly stronger than cp and mr ; d , mr is significantly stronger 
 than cp according to the post hoc test .. the average thickness of the rectus femoris in the standing position was 
 12.69  mm for normally developing infants , 11.89  mm for cerebral palsy subjects and 10.14  mm 
 for mental retardation subjects , with significant differences among the groups ( p<0.05 ) . 

the average thickness of the rectus femoris in the supine position was 16.13  mm for normally 
 developing infants , 14.55  mm for cerebral palsy subjects , and 12.63  mm for mental 
 retardation subjects , with significant differences among the groups ( p<0.05 ) .
the average 
 strength of the knee extensor was 17.77  kg for normally developing infants , 7.92  kg for 
 cerebral palsy subjects and 11.19  kg for mental retardation subjects , with significant 
 differences ( p<0.01 ) .
the average strength of the ankle plantar flexor was 15.54  kg for 
 normally developing infants , 6.01  kg for cerebral palsy subjects , and 7.82  kg for mental 
 retardation subjects , with significant differences among the groups(p<0.01 ) . normally 
 developing infants rectus femoris was thicker than that of cerebral palsy , and mental 
 retardation subjects , according to the post hoc test .
knee extensor and ankle plantar flexor 
 strengths were the strongest for normally developing infants , followed by mental retardation 
 and cerebral palsy subjects , according to the post hoc test .
ndi : normally developing infants ; cp : cerebral palsy ; mr : 
 mental retardation ; rf : rectus femoris ; * p<0.05 from mean among the three groups ; 
 a , ndi is significantly greater than cp and mr ; b , cp is significantly greater than 
 mr ; c , ndi is significantly stronger than cp and mr ; d , mr is significantly stronger 
 than cp according to the post hoc test .
the results of comparison of the gmfm , and weefim between cerebral palsy and mental 
 retardation are presented in table 3table 3 .
comparison of gmfm and weefim between cp and mrcp ( n=38)mr ( n=9)gmfm ( score)lying & rolling97.76 ( 8.42)100.00 ( 0.00)sitting95.00 ( 10.00)97.78 ( 3.93)crawling & kneeling80.42 ( 18.49)84.11 ( 24.01)standing53.95 ( 30.76)68.89 ( 34.03)walking , running & jumping39.47 ( 33.32)60.56 ( 39.22)total73.34 ( 17.71)82.33 ( 19.95)weefim ( score)self - care27.21 ( 11.89)28.00 ( 11.63)bladder & bowel control12.05 ( 3.67)12.33 ( 3.04)ambulation12.95 ( 6.81)15.33 ( 6.44)place transfer8.18 ( 4.69)9.11 ( 5.48)conversation11.16 ( 3.82)8.89 ( 3.51)social cognition16.68 ( 6.01)*11.56 ( 5.10)total88.24 ( 31.39)85.22 ( 21.73)values are mean ( sd ) . *
there was a significant difference in the average scores of social cognition 
 in the weefim : 16.68 for cerebral palsy subjects , and 11.56 for mental retardation subjects 
 ( p<0.05 ) .
cerebral palsy s problems due to motor disorder may lead to limitation of body activity and 
 lack of exercise ( motor ) experience that may delay development of sensation , conceptual 
 formation about motor control and sociality , etc2 .
these problems include spasticity , dystonia , contractures , 
 abnormal bone growth , poor balance , and loss of selective motor control3 .
a previous study of the muscle structure of cerebral palsy 
 subjects investigated the formation of the gastrocnemius and hamstrings using ultrasound and 
 reported the pennation angle of the gastrocnemius was 10 degrees , the pennation angle of the 
 plantar flexor was 10 degrees , and the pennation angle of the dorsi flexor was 10 
 degrees5 . compared to normally 
 developing infants , in cerebral palsy subjects , the pennation angle of the calf muscle and 
 the range of motion of the ankle were smaller , and this may be a cause of decrease in 
 physical activity . therefore , structural problems of the muscle are the main factor 
 affecting muscular function and decrease in activity21 .
the gastrocnemius , one of the lower extremity muscles , plays an 
 important role in supporting weight in gait , and in adjusting the angle of the ankle in the 
 stance and swing phases . when compared with normally developing infants , and there were significant differences in 
 cerebral palsy subjects gastrocnemius and rectus femoris thicknesses5 , 11 .
significant 
 differences between the thickness of the postural rectus femoris of children with cerebral 
 palsy and mental retardation were shown in this study ( p<0.05 ) , as well as significant 
 differences in knee extensor and plantar flexor strengths ( p<0.01 ) .
the 
 rectus femoris and gastrocnemius of childen with cerebral palsy were thicker than those of 
 childen with mental retardation ; however , knee extensor and plantar flexor strengths of 
 childen with mental retardation were stronger . generally , strength is proportional to the 
 diameter of the muscle . compared to children with mental retardation ,
the rectus femoris and 
 gastrocnemius of children with cerebral palsy were thicker , yet their strengths were less 
 strong .
this is because of spasticity in the muscle in cerebral palsy , which results in 
 pseudo atrophy . in the comparison of the gmfm and weefim between children with cerebral 
 palsy and mental retardation
however , cerebral palsy children showed limitations in basic ability of 
 movement which appeared as lower scored in the items of standing , walking , running in gmfm . 
 limitations of functional activity were shown by both groups of children in the weefim . 

children with mental disability showed a significant difference from children with cerebral 
 palsy in the item of social cognition showing a problems with reciprocal action that is 
 necessary for social activity .
it s difficult to assume that the sample of the study is representative of the population , 
 because of the small sample numbers , and the disparities in size between the different 
 groups of children .
in addition , this study only compared muscle thickness , strength and 
 function , standards of activity and participation using cross sectional design . therefore , 
 further correlation analysis of each of the items and further study into effective 
 intervention methods for improvement of function are needed .
   [ purpose ] the purpose of the study was to provide information for intervention by 
 comparing lower limb muscle thickness , gross motor function and functional level of 
 activity daily living between cerebral palsy ( cp ) and mental retardation ( mr ) . 
 [ subjects ] 
 sixty subjects participated : 38 cp and 9 mr subjects and 13 normally developing infants . 
 [ methods ] ultrasonography and a manual muscle tester were used for measuring the thickness 
 and strength of knee extensor and ankle plantar flexor muscles . the gross motor function 
 measure ( gmfm ) and wee functional independence measure ( weefim ) 
 were used to evaluate 
 level of gross motor and independence level . 
 [ results ] knee extensor thicknesses of cp and 
 mr subjects were thinner than those of normally developing infants . 
 strengths of knee 
 extensor and ankle plantar flexor showed differences being strongest in normally 
 developing infants , followed by mr , and cp . 
 subjects in the examination of gmfm , there 
 were no significant differences between cp and mr . a decline in social cognition of mr 
 subjects 
 was found in the examination of weefim . 
 [ conclusion ] cp and mr subjects had 
 smaller muscle thicknesses and strengths than those of normally developing infants , and 
 lower gross motor function and functional independent level . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION