aquatic therapy has been suggested as an effective approach for improving trunk activity in 
 stroke patients1,2,3,4 . typically , stoke patients suffer from deficits in their functional 
 ambulation capacities , balance , walking velocities , cadences , stride lengths , and 
 temporal - gait and muscular - activity patterns5,6,7,8 .
an understanding of the physical properties 
 of water and the physiology of human immersion , coupled with the skills necessary to analyze 
 human movement , have helped physiotherapists use hydrotherapy as a tool for facilitating 
 movement and restoring functionality9 . 
 because of its wide margin of therapeutic safety and clinical adaptability , aquatic therapy 
 has also proved very useful in clinical settings for rehabilitating patients with 
 musculoskeletal problems , neurologic problems , cardiopulmonary pathologies , and other 
 conditions10 . among the suggested 
 aquatic exercise techniques , the halliwick method uses fluid mechanics to help patients most 
 achieve stability and controlled movement in water1 , 
 11
the ten point program is a 
 structured learning process that facilitates the practical application of the halliwick 
 concept , and its elements are taught and learned logically and gradually through games and 
 activities .
watsu ( water shiatsu ) , another water therapy , has also been widely applied in 
 various therapeutic settings , including treatment for chronic conditions with disabilities 
 like back pain , neuromuscular activity , cerebral palsy , osteoarthritis , rheumatoid 
 arthritis , cardiovascular fitness , and stroke2 , 3 , 9 , 12,13,14,15,16 .
watsu is a complementary therapeutic 
 treatment comprising passive stretch and massage techniques administered in appropriately 
 warm water17 .
recent studies on trunk 
 exercise in water have assessed the surface emg activity of the rectus abdominals , external 
 obliques , lower abdominals , multifidus , and erector spine during aquatic therapy12 , 13 .
however , studies on the relationship between trunk - muscle activity 
 and gait parameters after therapeutic aquatic exercises aimed at treating stroke patients 
 are rare .
therefore , the purpose of the present study was to investigate the relationship 
 between trunk - muscle activity and gait parameters following aquatic trunk exercise in stroke 
 patients .
the participants in this study included thirteen hemiplegic patients ( ten males and three 
 females ) who had received stroke diagnoses and were receiving admission or outpatient 
 treatment at p rehabilitation center .
the inclusion criteria for subject selection were as 
 follows : the patient had to ( 1 ) have a history of only one cerebrovascular accident , ( 2 ) 
 exhibit an independent gait ( without the assistance of a device ) , ( 3 ) have a stable of 
 cardiovascular status , ( 4 ) be experiencing no significant musculoskeletal problems 
 ( fracture , back pain , etc . ) , and ( 5 ) have a korean mini - mental state examination ( k - mmse ) 
 score > 24 points .
the aquatic therapy consisted of administering concentrative aquatic 
 therapy for four weeks ( 30  min per session , three days per week ) in a therapeutic pool with 
 a water depth equal to the xiphoid process ( 115120 cm ) and a water temperature of 30  c 
 ( air temperature=24  c)1 , 8 . the aquatic - therapy regimen was based on halliwick , watsu , 
 and trunk - specific exercise methods , and its purpose was to improve the activation of trunk 
 muscles associated with gait parameters in stroke patients .
aquatic exercise sessions 
 consisted of a warm - up , trunk - specific exercises , and then a cool - down period ( table 1table 1.interventional program of aquatic exercise during the four weekswarming up ( 5 min ) trunk control sessionhalliwick ten point programsagittal rotation controltransversal 
 rotation controllongitudinal rotation controlcombined rotation controltreatment ( 20 min ) trunk - specific exercise session1 . abdominal hollowing2 . abdominal bracing3 .
mediolateral ( ml ) pelvic tiltscool down ( 5 min ) trunk control sessionhalliwick ten point programsagittal rotation controltransversal 
 rotation control longitudinal rotation controlcombined rotation controlwatsu)18,19,20 .
the basic 
 exercises in the halliwick method for balance restoration concentrate on sagittal rotation 
 control ( bending from left to right or transferring weight while in an upright position ) , 
 longitudinal rotation control ( the ability to control movement around the sagittal - frontal 
 axis whether in the vertical position or floating horizontally , e.g. , to rotate in the same 
 place while standing or to do so while supine and floating prone with one s face in the 
 water ) , transversal rotation control ( around the transverse axis with the subject moving 
 from standing to supine and then returning to the standing position ) , and combined rotation 
 control ( a combination of transverse sagittal and longitudinal rotations ) ( fig . 1fig .
1.photographic representation of the procedure for the aquatic trunk exercise in 
 hemiplegic stroke patients .
gait parameters and muscle activities were measured using 
 a gait analysis system and electromyogram , as described in the subjects and methods 
 section .
a , start of aquatic trunk exercise ; p , end of aquatic trunk exercise ; pt : 
 physical therapist ; pt : stroke patient)21 .
watsu is a body - based method 
 comprising buoyancy , passive stretching , and massage techniques , including massage and 
 palpation of acupuncture points administered in warm water3 .
all participants received conventional multidisciplinary physical 
 and occupational therapy , as provided by the rehabilitation staff , and they were mainly 
 focused on neurodevelopmental treatments .
gait parameters were measured using a gait 
 analysis system ( gait trainer 2 analysis system , biodex medical systems inc . , shirley , ny , 
 usa ) adjusted to each subject s comfortable walking speed .
this equipment can analyze 
 various walking parameters , such as walking speed , walking cycle , affected - side stance 
 phase , affected - side stride length , stance - phase symmetry index , and stride - length symmetry 
 index , using a sensor installed on the treadmill floor .
outcomes were measured twice , once 
 before training and once after four weeks of training .
furthermore , emg data were collected 
 using a bts freeemg 1000 ( bts s.p.a .
, via della croce rossa , italy ) with surface electrodes 
 and the sampling rate set at 1,000  hz per channel ; the emg signals were band - pass filtered 
 from 20 to 500  hz12 , 13 .
pre - gelled , bipolar silver / silver - chloride surface electrodes ( 3 m , 
 maplewood , mn , usa ) were placed with an interelectrode distance of 20  mm .
emg signals were 
 recorded for the rectus abdominis ( ra ) , external abdominal oblique ( eo ) , transversus 
 abdominis / internal - abdominal oblique ( tra / io ) , and erector spine ( es ) of each patient s 
 paretic side .
the electrode attachment regions were as follows : ( 1 ) for the ra , 5  cm above 
 the umbilicus and 3  cm lateral from the midline ; ( 2 ) for the eo , approximately 15  cm lateral 
 to the umbilicus ; ( 3 ) for the io , 2  cm inter - medial to the anterior superior iliac spine 
 ( asis ) ; ( 4 ) for the es , 3  cm lateral to the spine ( l45 spinous process ) .
each electrode was 
 attached by a qualified physiotherapist to regions identified using anatomical landmarks , 
 which had previously been shaved and cleaned using alcoholic wipes .
the emg values for the 
 ra and io muscles were measured during maximal voluntary isometric contraction ( mvic ) .
emg 
 values for the es were measured during reference voluntary contraction ( rvc ) because of how 
 strokes can make mvic movement difficult .
the obtained emg values were normalized ( % mvic , 
 % rvc ) for comparison with the mean .
each muscle s performance was measured by mvic / rvc three 
 times to determine an average value . the contraction time was 5 seconds , and normalized 
 values were recorded for the middle three - second mvic values12 , 13 . while recording these 
 measurements , the examiner verbally encouraged the subjects to put forth the maximum effort 
 possible .
statistical analyses were conducted using the pasw statistics software ( version 
 18.0 ) to calculate averages and standard deviations .
the significance level was set to =0.05 when performing the paired 
 t - test .
the study s protocol was approved by the committee of ethics in research at the 
 university of yongin , in accordance with the terms of resolution 5 - 1 - 20 .
photographic representation of the procedure for the aquatic trunk exercise in 
 hemiplegic stroke patients .
gait parameters and muscle activities were measured using 
 a gait analysis system and electromyogram , as described in the subjects and methods 
 section .
a , start of aquatic trunk exercise ; p , end of aquatic trunk exercise ; pt : 
 physical therapist ; pt : stroke patient
the clinical and general characteristics of the 13 participants are listed in table 2table 2.clinical characteristics of the hemiplegic stroke patientsvariablestroke patientsage ( yr)50.5  2.9gendermale ( % ) 10 ( 76.9)female ( % ) 3 ( 23.1)height ( cm)166.4  1.9weight ( kg)66.6  2.9bmi ( kg / m)24.0  0.8cause of strokeinfarction ( % ) 10 ( 76.9)hemorrhage ( % ) 3 ( 23.1)affected sideright ( % ) 10 ( 76.9)left ( % ) 3 ( 23.1)onset ( mo)24.1  3.8k - mmse ( score)24.9  0.4all data are presented as the meanse .
bmi : body mass index ; k - mmse : korean version 
 of the mini - mental state examination .
their pre- and post - training % mvic values for the tra / io were compared 
 statistically ( pre , 51.1  1.8 ; post , 56.2  1.9 ; p=0.041 ) .
there was no statistically 
 significant difference between pre - training and post - training % mvic values for the ra , but 
 those for the eo tended to improve ( pre , 55.6  2.0 , and post , 55.9  1.9 for the ra ; pre , 
 51.8  1.9 , and post , 54.6  1.9 , for the eo ) ( table 
 3table 3.changes of muscle activity of the paretic side using emg after the four - week 
 interventionvariablebefore treatmentafter treatmentra ( % mvic)56.0  1.856.2  1.7eo ( % mvic)51.6  1.655.1  1.7tra / io ( % mvic)51.1  1.856.2  1.9es ( % rvc)58.3
ra : rectus abdominis ; eo : external abdominal 
 oblique , tra / io : transversus abdominis / internal - abdominal oblique ; es : erector spine ; 
 mvic : maximal voluntary isometric contraction ; rvc : reference voluntary contraction . 

. there was also no statistically significant improvement in the % rvc values 
 for the es after four weeks ; indeed , they tended to worsen ( pre , 58.3  1.8 ; post , 57.0  
 1.5 ; p=0.485 ) ( table 3 ) .
however , almost every 
 gait factor was significantly improved , including walking speeds ( pre , 51.4  5.1 ; post , 
 57.9  7.0 ; p=0.020 ) , walking cycles ( pre , 0.45  0.03 ; post , 0.41  0.04 ; p=0.011 ) , 
 affected - side stance phases ( pre , 36.2  4.2 ; post , 46.5  3.0 ; p=0.004 ) , affected - stride 
 lengths ( pre , 60.2  4.5 ; post , 67.7  5.4 ; p=0.009 ) , and stance - phase symmetry indices 
 ( pre , 62.6  12.4 ; post , 84.2  9.0 ; p=0.41 ) ( table 
 4table 4.changes of gait parameters after the four - week interventionvariablebefore treatmentafter treatmentwalking speed ( cm / sec)51.4  5.157.9  7.0walking cycle ( cycle / sec)0.35 
0.030.41  0.04affected - side stance phase ( sec/%)36.2  4.246.5  3.0affected - side stride length ( cm)60.2  4.567.7  5.4symmetry index of stance phase ( % ) 62.6  12.484.2  9.0symmetry index of stride length ( % ) 92.9  5.597.0 
5.7all data are presented as the meanse . * p < 0.05 ; * * p < 0.01 ) . although not significant , there was also improvement in the patients 
 stride - length symmetry indices ( pre , 92.9  5.5 ; post , 100.0  5.7 ; p=0.545 ) ( table 4 ) .
bmi : body mass index ; k - mmse : korean version 
 of the mini - mental state examination all data are presented as the meanse .
ra : rectus abdominis ; eo : external abdominal 
 oblique , tra / io : transversus abdominis / internal - abdominal oblique ; es : erector spine ; 
 mvic : maximal voluntary isometric contraction ; rvc : reference voluntary contraction . 

the present study demonstrates that four weeks of aquatic exercise using a program based on 
 the halliwick and watsu methodologies , as well as trunk - specific exercises , improves some 
 muscle activity and gait parameters .
regarding the collected emg values for the subjects 
 trunk muscles , there were no significant differences , but the subjects gait parameters did 
 improve , despite the relatively short duration of this study . according to previous studies 
 on trunk - muscle activity in water and on land ,
trunk muscle activation is lower in water 
 than on land when subjects perform the same trunk exercises .
nevertheless , the present study 
 shows that trunk exercises in the water enhance emg values in trunk muscle , especially the 
 tra / io muscles , which are activated during trunk rotation . additionally , tra / io muscles 
 experience greater activation than other trunk muscles during abdominal hollowing and 
 bracing .
thus , it is thought that activation of the tra / io would improve trunk functionality 
 more than other trunk exercises from the halliwick and trunk - specific portions of this 
 study s experimental regimen22 , 23 .
meanwhile , the results of the present study showed that 
 the emg values for the patients es muscles tended to decrease at the end of the treatment 
 period .
emg values for the patients es muscles were measured as the % rvc in the present 
 study because of movement difficulties mvic measurements would have entailed . in previous 
 studies on the trunk muscle activity of stroke patients ,
paretic - side es muscles were shown 
 to undergo greater activation than their non - paretic counterparts during their work and rest 
 phases .
the reasons for higher emg es values in stroke patients were likely augmented by an 
 increase in their use of motor units to compensate for stroke - induced decreases in discharge 
 rate during motor unit firing24 . also
, 
 explanations for these differences might depend on the extent to which cortical influences 
 on muscles are disrupted by a stroke24 . 
 therefore , these results indicate that the subjects trunk stability improved over the 
 course of the study s experimental aquatic therapy .
previous studies have also found that 
 trunk flexion and extension muscle weakness were correlated with the berg balance scale 
 score and locomotion and transfer items in the functional independence measure25 . moreover , verheyden et al . reported that 
 trunk performance remains impaired after a stroke and that the strong correlation between 
 this and measurements of balance , gait , and functional abilities confirm the importance of 
 trunk rehabilitation26 .
however , studies 
 about the effectiveness of aquatic therapy in improving trunk activity and gait parameters 
 in stroke patients have rarely been performed . similar research suggests that postural 
 balance and knee flexor strength were improved after aquatic therapy based on the halliwick 
 and ai chi methods in stroke survivors , and such studies have also reported that there is no 
 significant change in gait .
likewise , one study evaluated gait improvement using to modified 
 motor assessment scale gait score ( range 06 ) , but this tool is insufficient for analyzing 
 gait parameters in stroke patients1 .
the 
 present study utilized a gait trainer 2 and gaitrite system to analyze gait parameters with 
 a sensor installed on the treadmill s floor .
this method has been used in many studies to 
 provide adequate assessments of hemiplegic gait parameters , and the present results coincide 
 with those of previous studies that have used gait trainer systems to evaluate gait 
 parameters in stroke patients27 .
mumma attests that the greatest loss 
 after a stroke is gait ability and that hemiplegic patients exhibit slow gait velocities and 
 unaffected lower - extremity compensation movements29 .
some studies have not only emphasized the nature of the 
 relationships between gait speed and other temporal and spatial gait parameters but also 
 associated them with walking speed and symmetry in patients with stroke - induced 
 hemiplegia30 , 31 . according to the present data , subjects walking speeds and cycles 
 improved significantly , as did their affected - side stance phases , affected - stride lengths , 
 and stride - length symmetry indices .
thus , the present results demonstrate that aquatic 
 therapy as part of a supervised program greatly benefits gait parameters in stroke patients . 

this is clearly due to how the water environment acts as a partial support for the body , 
 allowing for mobilization of joints .
also , aquatic therapy provides motor and sensory 
 stimuli that can potentially improve balance and muscle function4 , 32 .
the popularity 
 of aquatic physical therapy has increased recently among neurological - rehabilitation 
 physical therapists and researchers because of the many benefits such therapy provides . 

furthermore , the buoyancy of water might allow stroke patients to move with less effort and 
 across movement planes that would be impossible on land without assistance33 .
thus , one may conclude that aquatic 
 therapy is a beneficial therapeutic method for gait training in stroke patients who 
 experience trunk control difficulties . in summary ,
trunk exercise combined with aquatic 
 therapy achieves clinically relevant improvements in tra / io activation and gait parameters . 
 however , to design and carefully implement a long - term intervention for stroke patients , 
 more multidimensional and scientific investigations are needed34,35,36
 [ purpose ] the purpose of this study was to investigate the relationship between muscle 
 activity and gait function following aquatic trunk exercise in hemiplegic stroke patients . 
 [ subjects and methods ] this study s participants included thirteen hemiplegic patients 
 ( ten males and three females ) . 
 the aquatic therapy consisted of administering 
 concentrative aquatic therapy for four weeks in a therapeutic pool . 
 gait parameters were 
 measured using a gait analysis system adjusted to each subject s comfortable walking 
 speed . 
 electromyographic signals were measured for the rectus abdominis , external 
 abdominal oblique , transversus abdominis / internal - abdominal oblique , and erector spine of 
 each patients . 
 [ results ] the pre- and post - training performances of the transversus 
 abdominis / internal - abdominal oblique were compared statistically . 
 there was no statistical 
 difference between the patients pre- and post - training values of maximal voluntary 
 isometric contraction of the rectus abdominis , but the external abdominal oblique values 
 tended to improve . 
 furthermore , gait factors improved significantly in terms of walking 
 speeds , walking cycles , affected - side stance phases , affected - stride lengths , and 
 stance - phase symmetry indices , respectively . 
 [ conclusion ] these results suggest that the 
 trunk exercise during aquatic therapy may in part contribute to clinically relevant 
 improvements in muscle activities and gait parameters . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION