most hemiplegic patients who suffer from stroke experience restrictions on mobility at home 
 and in the community , and they especially have difficulty with independent walking1 . turnbull et al.2 suggested that the recovery of gait ability is an important 
 goal of physical therapy for a stroke patient , because gait is an important element of 
 functional independence . with regard to this , mumman3 suggest that the biggest loss after stroke is gait ability , and 
 hemiplegic patients show disorders in the selective ability of regulated and coordinated 
 movements , which results in a slow gait velocity and compensatory movements by the lower 
 extremity of the unaffected side .
perry4 
 also suggested that hemiplegic patients show a short stride length and slow gait velocity 
 for result of damage to the joint and to the regulatory function of the muscles that are 
 necessary for normal gait .
furthermore , gait is closely connected with the environment , 
 since gait adapts and is modified to overcome obstacles and the varied geography that are 
 faced during walking5 .
due to central 
 nervous system damage , stroke patients show muscle weakness , abnormal muscle tone , and 
 disorders of balance and posture control , which result in difficulty in the control of 
 movement6 . for these reasons ,
problems 
 occur with the quality and adaptation of the gait pattern , resulting from imbalance in the 
 low extremity stance phase of the affected side and of the low extremity stance phase of the 
 unaffected side , a decline in cadence and gait velocity , asymmetrical weight distribution , 
 and a difference between step length and stride length7 , 8 .
in particular , gait 
 disorder after stroke reduces the functional independence level and results in a negative 
 prognosis , which is a reason why regaining gait ability is a critical element directly 
 connected with patients independence and is one of the goals of rehabilitation9 .
neurotherapy methods , which include bobath 
 therapy and proprioceptive neuromuscular facilitation , mainly focus on the control of 
 abnormal muscle tone and of the asymmetrical movement which leads to gait disorder10 .
these methods require many therapists and 
 time , because they mainly consist of muscle strengthening movements in a static position 
 through manual handling by a therapist .
however , studies on the effects of 
 neurophysiotherapy performed by therapist handling are inconclusive .
therefore , we 
 hypothesized that gait function would improve with pelvic control following a hip extensor 
 strengthening exercise ( hese ) program for the paretic lower extremity .
we examined whether 
 the hese program promotes functional improvement of the paretic lower extremity of stroke 
 patients .
the participants in this study were fifteen hemiplegic patients who had been diagnosed with 
 stroke ( table 1table 1.clinical characteristics of the hemiplegic stroke patientsage ( yr)gender ( % ) height ( cm)weight ( kg)cause of disease ( % ) as ( % ) k - mmse ( score)time post- stroke ( mo)44.2  3.9 m 10 ( 66.7)f 5 ( 33.3)168.5  2.168.5  3.5 in 12 ( 80.0)he 3 ( 20.0)rt 7 ( 46.7)lt 8 ( 53.3)26.5  2.520.5
m : male ; f : female ; in : infarction ; he : hemorrhage ; 
 as : affected side ; rt and lt : right and left side ; k - mmse : korean version of mini 
 mental status examination ) who were receiving inpatient or outpatient treatment at hospital p 
 rehabilitation center .
all the subjects participated in a 
 four - week six - method hip extensor strengthening exercise ( hese ) program .
this program was 
 performed by a therapist manipulating the subjects for about half an hour a day in the 
 supine position , side - lying position , and prone position on a treatment table .
the hese 
 program comprised six steps : data are presented as means  se .
m : male ; f : female ; in : infarction ; he : hemorrhage ; 
 as : affected side ; rt and lt : right and left side ; k - mmse : korean version of mini 
 mental status examination 1 . hip extension and posterior tilt movement ; 2 .
hip joint and pelvis movement using a therapeutic ball ; 4 . hip joint and pelvis movement
hip joint extension muscle strengthening movement in the side - lying position ; and 6 .
each session consisted of 
 three sets of 15 performances of the 6-step program lasting about half an hour , with 30 
 seconds of relaxation time between the sets11 .
each participant was assessed by a physical therapist before and 
 after the intervention in order to examine its effects on gait performance and stability . 

the 10-m walking velocity test and the berg balance scale ( bbs ) were used to evaluate the 
 changes in gait performance and stability .
bbs is a widely used clinical test which was 
 developed to evaluate both the static and kinetic balance abilities of stroke patients .
it 
 consists of 14 assessment items : sitting to standing , standing without support , sitting 
 without support , standing to sitting , transfers , standing with eyes closed , performing the 
 romberg test with eyes open , reaching , turning and looking over the shoulder , making 360 
 turn to the right and left , and standing on one leg .
it has 
 been shown that subjects with bbs scores > 41 have a low risk of fall , medium risk of fall 
 for bbs scores of 2140 , and high risk of fall for bbs scores of less than 20 .
bbs can be 
 used to evaluate the balance ability of patients with hemiplegia caused either by senile 
 disorder or stroke12 .
a gaitrite ( gait 
 trainer 2 analysis system , usa ) was used to measure the spatiotemporal variables of gait 
 ( walking speed , walking cycle , affected side stance phase , stride length ) and the symmetry 
 index ( stance phase , stride length ) .
subjects performed three trials for both pre- and 
 post - test measurements . when gaitrite was used in the study
, it helped the participants 
 observe in real time their feet touching the ground on a monitor .
gaitrite can compare gait 
 velocity ( meter / sec ) , gait cycle ( cycle / sec ) , and the symmetry index ( % ) of the stance phase 
 and the swing phase , with normal category values on a histogram13 .
statistical analyses were performed using spss version 
 20.0 . the shapiro - wilks test was used to verify the general and medical characteristics and 
 the measured variables displayed a normal distribution .
the chi - square 
 was used to compare the general and medical characteristics of the participants and the 
 paired t - test was conducted to compare the results of before and after the treatment .
the formulas for the symmetry indexes 
 of the stance phase and stride length used in the study were : symmetric index of length ( % ) 
 = non - affected side low extremity length ( cm)/affected side low extremity length ( cm )  
 100% ; and symmetric index of the stance phase ( % ) = affected side low extremity stance phase 
 ( sec)/non - affected side low extremity stance phase ( sec )  100% .
the protocol of this study 
 was approved by the committee of ethics in research of the university of yongin , in 
 accordance with the terms of resolution 5 - 1 - 20 , december 2006 .
furthermore , all subjects 
 provided their informed consent to participation in the present study .
table 1 summarizes the clinical characteristics 
 of the subjects . walking speed , stance phase and stride length of the affected side , and the 
 symmetry index of the stance phase
significantly improved after the hese program ( p<0.05 ) 
 ( table 2table 2.effects of hip extensor strengthening exercise program on the hemiplegic stroke 
 patientsvariableshemiplegic stroke patientspre - hesepost - hesewalking speed ( m / sec)0.5  0.00.6  0.0walking cycle ( c / sec)0.6  0.00.6  0.0as stance phase ( sec/%)47.0  1.248.5  1.1as stride length ( cm)38.1  3.041.8  2.8si of stance phase ( % ) 90.0  4.294.0  4.0si of stride length ( % ) 90.6  6.493.1  5.710wvt ( m / sec)29.8  11.829.2  11.6bbs ( score)37.1  2.537.3  2.8data are presented as means  se .
hese : hip extensor strengthening exercise ; as : 
 affected side ; si : symmetry index ; 10wvt : 10  m walking velocity test ; bbs : berg 
 balance scale . * : significantly different from pre - hese , p<0.05 ) .
hese : hip extensor strengthening exercise ; as : 
 affected side ; si : symmetry index ; 10wvt : 10  m walking velocity test ; bbs : berg 
 balance scale . * : significantly different from pre - hese , p<0.05
the distinctive gait patterns of hemiplegic patients include a slow gait cycle and 
 velocity , differences between the affected side and unaffected side step length , a short 
 stance phase , and a relatively long swing phase on the affected side14 , 15 .
restoration of 
 the ability to gait is a very important goal for stroke patients , and therefore , evaluating 
 gait patterns of hemiplegic patients and analyzing the related elements is meaningful16 , 17 . to contribute to the treatment of problems with gait ,
this study 
 aimed to discover the effects of hip extension muscle strengthening on gait ability and 
 stable gait . in the study , the experimental group showed significant improvements in walking 
 speed , the affected side stance phase , stride length , and the stance phase symmetry index 
 after the training . the hese program conducted for the hemiplegic patients contributed to 
 improvements in walking speed , stance phase , stride length , and the stance phase symmetry 
 index .
the treatment with respect to 
 movement after the acute phase improved hemiplegic patients gait and function , similar to 
 the results of a previous study18 . in 
 addition , in order to discover effective movement methods for hemiplegic patients besides 
 general movement treatment , a muscle strengthening movement program using manipulations by a 
 therapist was performed11 .
in that study 
 of the effects of leg muscle improvement movement and an aerobic movement program on muscle 
 weakness and stiffness , thirteen stroke patients at least nine months after stroke onset 
 were the subjects of a ten - week program11 .
for about half an hour , the experimental group carried out 
 resistance movements using a sand pocket , and therabands of eight different elasticities , 
 and also received a therapist s handling for the hip flexor and extensor , knee flexor and 
 extensor , and ankle flexor and extensor muscles .
there was an increase in strength of about 42.3% in the leg muscles , and gait velocity also 
 increased11 .
moreover , in a study of 
 the effects of gradual resistance movement on the leg muscle , involving twenty chronic 
 stroke patients , gradual resistance movement by centripetal and centrifugal movement was 
 conducted for eight weeks19 . as measured 
 by computed tomography
, there was a decline in hypoderm and the amount of body fat and an 
 increase in midthigh muscle area of the femoral region19 .
there was also an increase of the femoral muscles of about 
 9.04.5% , and of gait velocity of about 48%19 .
considering the results of previous studies of movement programs 
 using gradual muscle movement and therapist handling , it seems that a treatment program 
 using hip joint muscle strengthening movements and therapist handling provides an 
 appropriate environment for improvement of gait ability and for motivation of patients .
wade 
 et al.20 reported that the 10-m walking 
 velocity test for hemiplegic patients is a simple , objective measurement for evaluating 
 functional recovery
. however , sharp and brouwer21 reported that after a six - week intervention of knee joint 
 isokinetic resistance movement involving fifteen chronic stroke patients , muscle power and 
 gait velocity improved , whereas walking up and down stairs and tug times showed no 
 significant differences with respect to functional performance ability .
page22 reported that the effect of movement 
 treatment on stroke patients depends on the treatment time , the movement form , and the 
 patient s positive participation .
hendricks et al.23 suggested that the degree of recovery from stroke weakens as time 
 passes and that the recovery of movement regulation ability occurs no later than three 
 months after a stroke .
a limitation of their study was that the disease period of the 
 participants ranged from 6 months to 91 months , and no improvement of movement regulation 
 function resulted .
the reason why there was no significant improvement in all test items 
 after four weeks of movement therapy was the order of movement and other factors during the 
 intervention . to elicit an improvement in hemiplegic patients stable gait ,
a much longer 
 treatment period is required , and the stage and duration of stroke and a variety of forms of 
 movement also need to be considered . from this
it can be understood that for hip joint 
 muscle power strengthening movements to influence hemiplegic patients stable gait , several 
 things are required at the same time : a long enough treatment period , a variety of movements 
 and muscle power strengthening movements of the hip joint , knee joint , and ankle joint . 
 despite positive changes ,
the ability to generalize the present study s results to every 
 hemiplegic patient is limited .
further study of more methods for improving stable gait 
 through hip flexor muscle power strengthening movements is required , with larger numbers of 
 participants , a longer treatment period , and a follow - up after the treatment .
furthermore , 
 scientific multi - dimensional investigations on the effects of neurophysiotherapy related to 
 gait and muscle function should be conducted for stroke patients24,25,26,27,28,29,30 .
 [ purpose ] the purpose of this study was to investigate the effects of strengthening 
 exercises for the hip extensors on the gait performance and stability of patients with 
 hemiplegia . 
 [ subjects and methods ] the subjects were fifteen stroke patients ( ten males , 
 five females ) . 
 the experimental subjects performed a hip extensor strengthening exercise 
 ( hese ) program for a total of four weeks . 
 [ results ] the experimental subjects showed 
 significant improvements after the hese program . especially , walking speed and the 
 affected side stance phase time significantly increased after the hese program . 
 
 furthermore , the affected side stride length and symmetry index in the stance phase 
 significantly increased after hese program . 
 [ conclusion ] these results suggest that the 
 hese program may , in part , help to improve gait performance ability and stabilize physical 
 disability after stroke . 