most stroke survivors experience 
 changes in the level of consciousness , loss of motor and sensory functions , language 
 disorder , and loss of cognitive and perceptual abilities .
in addition , performance of 
 activities of daily living becomes limited and participation in social activities 
 decreases1 , 2 .
in particular , functional activities are limited by stroke - induced 
 impairment of movement , including balance , an important performance factor in functional 
 activities3 . in general , the stability of the body
is achieved by actively adjusting physical stability 
 and reacting to gravity , the support surface , visual perception , and the external 
 environment through the interaction of various sensory and motor neurons4 , 5 .
a 
 reduction in balance ability leads to a decrease in the weight - bearing ratio of the lower 
 limbs , or to paralysis , and acts as a factor in abnormal gait , affecting gait 
 characteristics such as gait velocity , stride length , and cadence6 , 7 .
hence , gait recovery is one of the most important goals in the 
 rehabilitation of stroke patients9 .
the trunk muscles play an important role in functional activities such as balance and 
 gait10 , 11 .
they participate in voluntary trunk movement as agonists and 
 synergists12 , automatically responding 
 to unpredictable perturbations13 , and 
 preparing for instability induced by upper and lower limb movements .
they also play a role 
 in adapting the trunk in space so that proper movement can be achieved14 . however , stroke patients are unable to keep their weight 
 on both feet evenly , owing to loss of trunk muscle strength and trunk control ability15 , and have difficulties in performing 
 functional activities because of a decrease in balance ability11 . therefore , improvement of trunk control ability can 
 result in balance and functional recovery of the extremities , and predict functional 
 improvement in activities of daily living . training in a sitting position was reported to be 
 effective at improving trunk control ability16 , 17 . in the study by encheff et al . ,
10 weeks 
 horseback riding therapy was performed by 11 children whose mobility was decreased due to 
 nerve damage . following the therapy , the position of the hip joint in the sagittal plane was 
 greatly improved during the early stance and pre - swing phases . moreover ,
the trunk became 
 more upright , and in consequence , postural adjustment in walking improved18 . in the study by silkwood - sherer , 15 
 multiple sclerosis patients performed horseback riding therapy once a week for 14 weeks , and 
 the outcome was assessed using the berg balance scale ( bbs ) and performance - oriented 
 mobility assessment ( poma ) .
the efficacy of horseback riding therapy for the improvement of 
 balance ability was confirmed , with increases in the bbs and poma scores of 9.15 and 10.38 
 points , respectively19 .
in addition , 20 
 stroke patients performed a 16-week horseback riding therapy , and improvements in their 
 fugl - meyer assessment scale  lower limbs and bbs scores were observed20 .
however , it is a fact that horseback riding therapy is 
 difficult for many people to perform and its outcomes are impossible to generalize because 
 of the high costs and difficulty of creating an environment for horseback riding therapy , 
 issues which outweigh its benefits .
the horseback riding simulator accurately reproduces the movements of a horse , has the same 
 physiological effect as horseback riding therapy , and activates muscles for postural 
 maintenance ; it also eliminates many of the disadvantages of the horseback riding 
 therapy21 , 22 .
present study aimed to examine the impact of horseback riding 
 therapy program on the trunk balance and gait of chronic stroke patients , using a horseback 
 riding simulator .
the subjects of this study were 20 patients hospitalized for the treatment of stroke in 2 
 hospitals located in south korea ( table 
 1table 1 .
general characteristics of subjectsgenderage ( years)post - stroke duration ( month)height ( cm)weight ( kg)male : 10 , female : 763.9  8.723 . 6  2.8165.7  2.964.0  4.3 ) .
all the subjects and their guardians voluntarily agreed to participate in the 
 study after receiving explanations regarding the purpose and procedures of the experiment , 
 and signed an informed consent statement before its start .
the criteria for selecting the 
 subjects were as follows : more than 6 months since the onset of non - traumatic and unilateral 
 stroke , a brunnstrom stage higher than 4 , a functional ambulation category ( fac ) higher than 
 stage 3 , no visual or hearing loss , and a mini - mental state examination - k score of 21 or 
 higher .
patients with cardiovascular diseases , uncontrolled diabetes , psychiatric problems , 
 and bilateral stroke were excluded from the experiment . to assess the static and dynamic balance abilities in a sitting position and trunk 
 coordination ability , we made assessments of the trunk impairment scale ( tis ) in 3 
 replicates and recorded the highest score28 .
the tis score has a maximum of 23 points , and higher scores are 
 given for better trunk performance . a balance assessment device ( biorescue , rm ingenierie , 
 france ) , consisting of a force plate equipped with sensors , was used for static balance 
 assessment in a standing position .
the subjects stood with their feet set apart at 
 approximately 30 degrees on the force plate , and a description was provided by an image on 
 the monitor installed in front of the subjects .
distance ( cm ) , and velocity ( cm / s ) of 
 body sway were measured while maintaining standing with the eyes open and closed for 30 
 seconds each .
the mean value of the measurements from 3 replicates was calculated . to assess gait ability
, we used the functional gait assessment ( fga)24 and a gait analyzer ( gaitrite , cir systems inc . ,
the functional gait assessment , 10 items 
 were measured on walkway , which was 6  m long and 30  cm wide and marked every 1.5  m. each 
 item was scored from 0 to 4 , with overall scores ranging from 0 to 30 . in the gait analysis , 
 velocity ,
cadence , stride length , and double limb support were measured when he subjects 
 walked at a comfortable speed on the sensor - equipped electronic gait plate , which was 5  m 
 long , 60  cm wide , and 0.6  cm high .
the collected information was processed using the 
 gaitrite gold version 3.2b software . to exclude acceleration and deceleration artifacts , 

data were collected 2  m from the start until 2  m from the end of the gait plate27 . in the gait measurement , the mean
value 
 was calculated of the measurements obtained when subjects walked over gait plate 3 
 times .
the simulated horseback riding therapy was performed for 30 minutes , 5 times a week for 6 
 weeks .
the horseback riding simulator used for this experiment exactly reproduces the 
 movement of the saddle and has speeds adjustable to 9 levels , ranging from 1.4 to 3.6 
 seconds / cycle ( joba eu6414 , national , ltd . , japan ) . for the safety of the subjects ,
a frame 
 was set to install a safety belt , and a physical therapist observed the patients while 
 standing by their affected side .
the 30-minute intervention consisted of a 5-minute warm - up , 
 20-minute horseback riding simulation training , and 5-minute cool - down . in the warm - up , the 
 patients were asked to load their lower limbs in a sitting position and perform a turn task , 
 looking back .
the levels of load and turn were gradually increased . in the cool - down ,
these exercises were 
 performed at levels ranging from  fairly light ( 11 )  to  somewhat hard ( 13 )  on ratings of 
 perceived exertion23 .
the 
 kolmogorov - smirnov test was used to test the data normality , and the paired t - test was used 
 to compare outcome measures between before and after the training .
the changes in trunk balance ability were determined based on the tis scores and pre- and 
 post - experimental values of the sway area , distance , and velocity , with the eyes open and 
 closed ( table 2table 2 .
changes in trunk balance measured by the tis and balance measuring 
 deviceparameterpre - testpost - testtis10.82  2.2114.17  2.48*biorescue- eosway area ( cm)129.16  8.50126.37  7.25*sway length ( mm)51.03  4.7446.55  8.13*sway speed ( cm / s)1.77  0.581.51  0.54*biorescue- ecsway area ( cm)214.05  5.83211.17  5.79*sway length ( mm)79.68  2.8076.56  2.74*sway speed ( cm / s)2.84  0.272.50  0.33*tis : trunk impairment scale , eo : eyes open , ec : eyes close , * p - value < 0.05 , 
 paired t - test ) .
significant the differences in the tis scores were observed between before 
 and after training : 10.82  2.21 points and 14.17  2.48 points ( p < 0.05 ) . moreover , 
 with the eyes open , significant differences in sway area , distance , and velocity were found 
 between before and after training , 129.16  8.50 mm and 126.37  7.25 
 mm , 51.03  4.74  cm and 46.55  8.13  cm , and 1.77  0.58  cm / s and 1.51  
 0.54  cm / s , respectively ( p < 0.05 ) ; whereas with eyes closed , significant differences 
 were observed between before and after training of 214.05  5.83 mm and 211.17  
 5.79 mm , 79.68  2.80  cm and 76.56  2.74  cm , and 2.84  0.27  cm / s and 2.50  
 0.33  cm / s , respectively ( p < 0.05 ) .
tis : trunk impairment scale , eo : eyes open , ec : eyes close , * p - value < 0.05 , 
 paired t - test gait ability was examined by measuring changes in fga score , gait velocity , cadence , stride 
 length of the affected and unaffected sides , and double limb support of the affected and 
 unaffected sides between before and after training .
significant differences were found in 
 fga score , 16.35  2.17 points and 19.94  2.27 points ( p < 0.05 ) ; gait velocity , 39.80  
 14.75  cm / s and 49.73  18.69  cm / s ; cadence , 77.90  12.97 steps / min and 82.25  13.68 
 steps / min ; stride lengths of the affected and unaffected sides , 60.32  17.19  cm and 66.12  
 16.23  cm , and 59.15  17.06  cm and 64.06  17.39  cm ; and double limb support of the affected 
 and unaffected sides , 55.27  13.81% and 47.84  11.36% , and 54.00  13.07% and 49.95  
 13.19% ( p
changes in gait measured by the fga and gait analyzerparameterpre - testpost - testfga16.35  2.1719.94  2.27*gaitritevelocity ( cm / s)39.80  14.7549.73  18.69*cadence ( steps / min)77.90  12.9782.25  13.68*stride ( affected ) ( cm)60.32  17.1966.12  16.23*stride ( non - affected ) ( cm)59.15  17.0664.06  17.39*double support ( % ) 55.27  13.8147.84  11.36*double support ( non ) ( % ) 54.00  13.0749.95 13.19*fga : functional gait assessment , * p - value < 0.05 , paired t - test ) .
fga : functional gait assessment , * p - value < 0.05 , paired t - test
a decrease in trunk function due to stroke affects balance adjustment and gait , and leads 
 to functional changes that are constraints on social participation .
therefore , various 
 approaches to the assessment and treatment of trunk control performance have been developed 
 for stroke patients , because both are regarded as important elements in the rehabilitation 
 of stroke patients14,16,17 .
the present study investigated the effects of a 6-week horseback riding simulation training 
 on trunk balance of stroke patients . as a result of the training ,
the trunk control ability 
 in a sitting position improved , as determined by the tis . in a study by silva et al .
, not 
 only the postural control ability in a seated position but also the motor function of 
 children with cerebral palsy was improved after horseback riding simulation training . 
 furthermore , the subjects reported in a quality - of - life assessment that they were more 
 satisfied because the training was more interesting and fun than their previous 
 treatment21 . in another study , herrero 
 et al . conducted horseback riding simulation training , once a week for 10 weeks , for 38 
 children with cerebral palsy , and reported their sitting balance improved ( effect size , 
 0.36 ; 95% confidence interval [ ci ] , 0.010.71 ) .
in particular , the training had a major 
 impact on the group with severe disabilities ( effect size , 0.80 ; 95% ci , 0.131.47 ) . in the 
 evaluation of their balance ability in a standing position ,
decreases were observed in sway 
 area , distance , and velocity of the center of pressure with the eyes open and closed29 .
yasuhiro et al . also conducted horseback 
 riding simulation training , twice a week for 12 weeks , for 23 elderly people aged 65  years 
 and older , and reported their performance of the subjects in the one - leg standing with eyes 
 open task of the functional reach test improved28 . in the functional gait assessment of our present study , changes in gait ability and 
 improvements in gait velocity , cadence , stride length , and double limb support were 
 observed .
studied the effects of horseback riding in 20 stroke patients who 
 performed horseback riding therapy once a week for 16 weeks in addition to ordinary physical 
 therapy .
their fugl - meyer assessment scale  lower limbs , bbs , and fac scores improved from 
 14.7 to 18.5 points , 46.1 to 49.0 points , and 3.6 to 3.8 points , respectively . compared with 
 the control group , the scores in the assessment items for the lower limbs of the fugl - meyer 
 assessment scale and bbs were improved by the horseback riding therapy . their results 
 demonstrate that performing the horseback riding therapy in addition to the ordinary 
 physical therapy has a positive effect on gait training20 . moreover , when elderly people who experienced a fall performed 
 horseback riding simulation training , an improvement was observed in the 5-m walking test at 
 a comfortable speed , number of steps in the 5-m gait at a fast speed , flexion angle of the 
 lumbar spine , and the tilt angle of the sacral vertebrae .
the training was found to improve 
 the balance ability necessary for gait and contributed to gait improvement28 .
in addition , uchiyama et al . performed a 
 comparative 3-dimensional analysis of gait using 50 healthy adults and 11 horses .
furthermore , only slight 
 differences in heart rate , respiratory rate , and blood pressure were observed after 127 
 adults performed gait and horseback riding at a speed with similar acceleration patterns . 

therefore , the optimal therapeutic effect of horseback riding therapy has been demonstrated 
 for patients with gait disorders , because it provides a similar stimulus to that generated 
 by human gait28 .
the trunk control ability of stroke patients is an index which is used to indicate the 
 recovery of performance in activities of daily living , and it is closely related to balance 
 and gait17
. horseback riding therapy 
 improves trunk balance and postural adjustment by utilizing the repeated stimuli of a 
 horse s movement to enhance the muscles around the pelvis , abdomen , and waist which are used 
 to maintain posture30 .
however , horseback 
 riding therapy is not feasible for many patients because of practical difficulties such as 
 economic burden , lack of facilities for horseback riding therapy , shortage of professional 
 therapists , fear of horses , and allergy
. therefore , horseback riding simulation training was 
 developed to reproduce its advantages and address the disadvantages .
its efficacy for 
 children with cerebral palsy and elderly people who have experienced a fall has been 
 studied21 , 28 .
the present study provides information on the efficacy of horseback 
 riding simulation training for chronic stroke patients , and demonstrated that it improved 
 their trunk balance and gait .
however , our study was limited in terms of generalization , 
 because we enrolled only a small number of subjects , and we could not completely control 
 their activities of daily living . regardless of these limitations , our study was able to 
 demonstrate that horseback riding simulation training has potential as a therapeutic method 
 for improving the trunk balance and gait of stroke patients .
however , future research 
 studies with a larger number of subjects , longer application period , and assessment of 
 functional levels of patients are required to validate our results .
 [ purpose ] the purpose of this study was to assess the effect of horseback 
 riding simulation machine training on trunk balance and gait of patients with chronic 
 stroke . 
 [ subjects and methods ] the subjects were 20 patients hospitalized for treatment 
 after being diagnosed with stroke . 
 horseback riding simulation training was provided for 
 30 minutes , 5 times a week , for 6 weeks . 
 trunk balance was assessed using the trunk 
 impairment scale ( tis ) and a balance measuring device ( biorescue , rm ingenierie , france ) , 
 and gait ability was measured using the functional gait assessment ( fga ) and a gait 
 analyzer ( gaitrite , cir system inc . 
 , usa ) . 
 [ results ] there were significant changes in 
 movement area , distance and velocity of body sway as measured by the tis and the balance 
 measuring device , and in gait velocity , cadence , stride length and double limb support as 
 measured by the fga and gait analyzer . 
 [ conclusion ] horseback riding simulation training 
 improved the trunk balance and gait of chronic stroke patients . 
 this present study 
 provides preliminary objective data for future research , and useful clinical information 
 for physical therapists using horseback riding simulation machines as a treatment modality 
 for patients with chronic stroke . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION