impaired sitting balance is a common problem for stroke patients1 , yet a sitting position is essential for safe execution of a 
 variety of movements2 .
several interventions have been devised to improve balance , including task - oriented 
 training4 and treadmill training5 .
dean and shepherd demonstrated that 
 task - oriented training was effective at improving reach while sitting6 .
recently , whole - body vibration ( wbv ) exercise has been 
 developed as a new modality for physical therapy7 .
previous studies have suggested that wbv exercise increases muscle 
 strength and improves muscular performance and balance8 , 9 , and the positive effects 
 of wbv on muscle performance should help to improve balance10 , 11 .
wbv acts through 
 repetitive sensorimotor stimulation and therapies with wbv have been conducted for elderly 
 patients as well as patients with cerebral palsy , multiple sclerosis , and stroke12,13,14,15 . 

some authors have reported wbv training combined with other physical therapies improves 
 balance16,17,18 , and wbv was shown to 
 positively influence the postural control and mobility of chronic hemiparetic stroke 
 patients11 .
recently , studies have emphasized the importance of sitting balance for stroke patients and 
 have recommended various balance training methods for its improvement .
however , physical 
 therapies for improved sitting balance are underpinned by little empirical evidence19 . some studies
have focused on the use of 
 wbv , but no study has been conducted to verify the effects of wbv for stroke patients in the 
 sitting position .
therefore , we investigated the effects of task - oriented training with wbv 
 on the sitting balance of stroke patients .
we hypothesized that a group of stroke patients 
 performing task - oriented training with wbv would show greater improvement of sitting balance 
 than a control group that performing task - oriented training alone .
the inclusion 
 criteria were history and clinical presentation ( hemiparesis ) of stroke ( > 6 month 
 post - event ) ; ability to sit independently for at least 10 minutes ; no participation in any 
 balance training program during the previous six months ; no orthopedic problems , such as a 
 fracture , deformity , or severe osteoarthritis ; and sufficient cognitive ability to 
 participate in the training : korean version of mini - mental state examination ( mmse - k ) scores 
 of 21 or higher .
the exclusion criteria were comorbidity or disability other than stroke , 
 and an uncontrolled health condition for which vibration is contraindicated .
participation 
 in the study was voluntary and the subjects fully understood the contents of this study . 

after providing an explanation of the study purpose , as well as the experimental method and 
 processes , written informed consent to participation in the study was obtained from all the 
 subjects .
subjects 
 sat , with their feet unsupported , on a wii balance board ( nintendo , kyoto , japan ) and were 
 asked to keep their arms folded across their chests .
their thighs were kept parallel , with 
 75% of their length supported on the wii balance board .
data were acquired at 100  hz , and 
 the mean value of three measurements collected over 30 seconds was used .
cop total path 
 length and average velocity were the outcome measures used in this study .
this 
 was performed using a level yardstick mounted on a wall at the height of each subject s 
 acromion of the nonparetic side , while sitting on a chair with no back or arm rests .
the 
 subjects were seated with their hips , knees , and ankles positioned at 90 of flexion , with 
 their feet positioned flat on the floor .
three measurements were made under each of the 
 following conditions : ( 1 ) sitting with the nonparetic side near the wall and leaning 
 forward , ( 2 ) sitting with the back to the wall and leaning toward the nonparetic side , and 
 ( 3 ) sitting with the back to the wall and leaning toward the paretic side .
the subjects were 
 instructed to lean as far as possible in each direction without rotating or touching the 
 wall .
if the patient 
 could not raise the paretic arm , the distance covered by the acromion during leaning was 
 used .
thirty people fulfilled the inclusion criteria and voluntarily agreed to participate in 
 this study .
the participants were randomly assigned to the experimental group ( n1 
 = 15 ) or the control group ( n2 = 15 ) .
both groups performed one session 
 ( 15 minutes ) a day ( 5 days / week ) of task - oriented training in the sitting position .
the 
 experimental group received wbv during task - oriented training ( galileo pro ; novotec medical 
 gmbh , germany ) .
the control group performed only task - oriented training . the wbv frequency 
 ( 1522  hz ) and amplitude ( 05.8 mm ) were adjusted relative to subjects physical 
 abilities10 .
the four exercise tasks were ( 1 ) 
 sitting alone at a table and correcting body alignment ; ( 2 ) reaching in different directions 
 for objects located beyond arm s length using the nonparetic side ; ( 3 ) reaching in different 
 directions for objects located beyond arm s length using the paretic side ; and ( 4 ) a 
 bilateral reaching task , such as throwing a ball , lifting a box , and inserting a ring .
each 
 exercise session was 15 minutes in duration , and subjects practiced each of the four tasks 
 for 3 minutes with a 1-minute rest in between .
investigators supervised each session and 
 were responsible for ensuring that the amount and intensity of the exercise at each exercise 
 station was graded to each subject s level of functioning .
the independent t - test was used 
 to compare differences between group means and changes in values , and the paired t - test was 
 used to test differences in continuous variables within groups .
all patients completed the intervention and assessments . there were no significant 
 differences in gender , paretic side , age , weight , height or duration of onset between the 
 groups ( table 1table 1.general characteristics of subjectsexperimental group(n1=15)control group(n2=15)gendermale / female9/67/8paretic sideright / left6/95/10age ( year)62.89.0 * 65.115.7weight ( kg)63.36.258.09.0height ( cm)162.76.2161.16.5duration ( month)13.05.412.65.7*meansd ) .
differences in static sitting balance are presented in table 2table 2.comparison of cop results between pre- and post - testexperimental group(n1=15)control group(n2=15)va ( cm / s)pre3.00.2 * 3.00.3post2.90.23.00.3change0.60.10.10.1tl ( cm)pre89.56.989.49.3post87.86.991.18.7change1.73.21.64.1va : velocity average of cop , tl : total path length of cop . *
there were no significant differences in the average velocity and total path 
 length of cop sway between the groups .
va : velocity average of cop , tl : total path length of cop . *
p<0.05 differences in dynamic sitting balance are presented in table 3table 3.comparison of mfrt results between pre- and 
 post - testexperimental group(n1=15)control group(n2=15)mfrt - a ( cm)pre26.09.9 * 21.011.4post32.18.023.510.7change6.15.92.44.2mfrt - n ( cm)pre10.95.413.64.9post16.65.715.56.2change5.74.11.94.8mfrt - p ( cm)pre9.94.410.75.6post13.23.912.15.6change3.43.41.34.2mfrt - a : modified functional reach test - anterior reach .
non - paretic and paretic reach were 
 significantly higher in the experimental group ( p<0.05 ) .
after the intervention , anterior 
 reach was significantly higher ( p<0.05 ) in the control group .
there were no significant 
 differences in non - paretic and paretic reach in the control group .
differences in total 
 length of cop between pre- and post - intervention differed significantly between the two 
 groups ( p<0.05 ) .
in this study we investigated the effect of task - oriented training with wbv on the sitting 
 balance of stroke patients .
average velocity and total path length of cop sway were used to 
 evaluate the static balance of the sitting position .
force platforms have previously been 
 used to investigate the balance control of unsupported sitting of post - stroke individuals 
 through analysis of the cop sway21 , 22 .
previous research reported that a leg 
 exercise with wbv group and a leg exercise group without wbv showed similar improvements in 
 the average velocity of cop in a standing position23 with no significant difference between them .
these results were 
 similar to our present results , as we found no significant differences in average velocity 
 or total path length of cop sway between the groups .
it is possible that the training was 
 not sufficiently intense or long enough to elicit improvements in the subjects ; it is also 
 possible that the sensitivity of the assessment method was insufficient . in the current study ,
the mfrt was used to evaluate improvements in dynamic balance in the 
 sitting position .
the average anterior and lateral reach distances of adults between 60 and 
 70  years old are 346  mm and 206  mm , respectively24 . in our study , the anterior , nonparetic , and paretic reach of both 
 groups were below the normal averages at pretest , indicating that both groups had impaired 
 sitting balance . however , at posttest , the experimental group showed significant 
 improvements ( p<0.05 ) in the anterior , nonparetic , and paretic reach , demonstrating that 
 task - oriented training with wbv in a sitting position is a useful intervention for improving 
 the dynamic sitting balance of stroke patients .
vibration is a useful method for stimulating 
 proprioception and is capable of long - lasting postural improvement25 .
this 
 demonstrates that task - oriented training is a useful intervention for improving anterior 
 reach while sitting . in the experimental group ,
our study suggests that task - oriented training with wbv in the sitting position has 
 beneficial effects on some aspects of sitting balance of chronic stroke patients .
we 
 anticipate that this training method will be used in physical therapy at stroke patient care 
 centers as it is an effective form of training for balance functions .
further research is 
 needed with larger numbers of subjects to confirm and generalize our present findings .
 [ purpose ] the purpose of this study was to determine the effects of task - oriented 
 training with whole body vibration ( wbv ) on the sitting balance of stroke patients . 
 
 [ subjects ] the subjects were 30 stroke patients who were randomly divided into 
 experimental ( n1=15 ) and control ( n2=15 ) groups . [ methods ] subjects 
 in both groups received general training five times per week . subjects in the experimental 
 group practiced an additional task - oriented training program with wbv , which was performed 
 for 15 minutes , five times per week , for four weeks . 
 the center of pressure ( cop ) path 
 length and average velocity were used to assess subjects static sitting balance , and the 
 modified functional reach test ( mfrt ) was used to assess their dynamic sitting balance . 
 
 the paired t - test was performed to test the significance of differences between before and 
 after the intervention . the independent t - test 
 was conducted to test the significance of 
 differences between the groups . 
 [ results ] following the intervention , the experimental 
 group showed a significant change in mfrt . 
 [ conclusion ] the results of this study suggest 
 that task - oriented training with wbv is feasible and efficacious for stroke patients . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION