in stroke patients with upper extremity paralysis , the affected arm can remain 
 nonfunctional even at 6 months after disease onset in 66% of the surviving stroke 
 patients1 , 2 .
inappropriate motor unit recruitment appearing after stroke onset 
 reduces the motor neuron firing rate , and increased muscle tone may cause severe 
 paralysis3 , 4 . limited motor function of the upper extremity , and subsequent 
 non - use and contracture may cause changes in the mechanics and biomechanics of the muscles 
 over time5,6,7 .
nuclear chain fibers of the 
 muscle spindle , responsible for the changes in muscle velocity , depend on the velocity of 
 movement and hyperexcitability during a quick passive stretch to increase the tension level 
 more and more .
in contrast , the tendon , which softens the muscle contraction and adjusts the 
 excessive muscle tone , is unable to function normally8 . excessive muscle tone may affect the gross movement patterns caused 
 by abnormal motor control .
in addition , increased muscle tone significantly correlates with 
 the limit of upper extremity motor function9 , reduction in daily living activities10 , and prolonged length of hospital stay11 .
data obtained by the biomechanical investigation of 
 increased muscle tone would not only identify prognostic variables of functional recovery in 
 stroke patients , but would also be helpful for promoting self - exercise to reduce the risk of 
 hypertonia8 .
in addition , increased muscle tone has been identified as predicting the motor function of 
 the upper extremity within 12 months after stroke onset12 .
a study of the correlation between recovery and increased muscle 
 tone of the upper extremity in stroke patients suggested that the patients whose motor 
 function of the upper extremity became relatively weaker within 48 hours after stroke onset 
 would be 12.8 times more likely to experience hypertonia within 6 months than the patients 
 with normal motor function8 .
in addition , 
 the patients with severe arm paresis were > 10 times more likely within a month13 , and > 22 times more likely within a 
 year post - stroke to experience hypertonicity10 .
our previous study defined muscle tone as the degree of resistance 
 during passive movement in 8 different directions13 .
however , this definition is too limited to determine in which 
 muscle the hypertonicity might occur , and would have influenced the external validity of the 
 study because patients without paralysis and patients with severely limited motor function 
 of upper extremity were included as study subjects .
furthermore , a 1  year follow - up study of 
 stroke patients demonstrated the difficulty of predicting the risk of hypertonicity and 
 identifying the patients whose hypertonicity could be prevented10 .
earlier prospective studies targeted chronic - stroke patients with disability from stroke 
 for more than 12 months who showed little recovery of motor function .
their findings were 
 limited because the relationship between the motor function of the upper extremity and 
 muscle tone was unclear .
in addition , chronic - stroke patients do not recover functionally 
 after spontaneous recovery and are likely to experience non - use syndrome as a result of 
 long - time non - use , even though they learn how to acquire motor skills with the affected 
 arm8 , 10 .
however , few studies have investigated how the major impairments 
 of chronic - stroke patients are related to the recovery of upper extremity motor 
 function .
this study investigated whether the degree of upper extremity motor function was 
 discriminative in predicting the risk of hypertonia in chronic - stroke survivors who had 
 experienced disability from stroke for more than 12 months , and analyzed the correlation 
 between arm motor function and hypertonia to determine is predictive validity .
forty - six chronic stroke patients were recruited and screened by 
 research assistants using the following criteria .
the participants were chronic stroke 
 patients who were diagnosed with stroke for the first time > 12 months previously , who : 1 ) 
 scored 24 or more in the mini - mental state examination , 2 ) had no secondary deformation due 
 to musculoskeletal disease in the upper extremities , 3 ) had no unadjusted diabetes mellitus , 
 4 ) were able to flex their affected wrist joint 10 and actively move 2 fingers14 , and 5 ) had no shoulder subluxation of a 
 distance less than half of a fingerbreadth when the humeral head of the affected arm and 
 subacromial space were palpated by the index finger without traction in a sitting 
 posture15 , 16 . because upper extremity pain might have affected the examination 
 results , a discrimination test of the pain degree was conducted through external rotation 
 and abduction of the shoulder joint by placing the palm on the back ( hand - behind - neck 
 test)15 , 17 .
a research assistant instructed participants to express their 
 degree of pain verbally based on a numerical rating scale when their affected arm was moved 
 passively18 .
pain of 5 on a visual 
 analog scale in the hand - behind - neck test was considered the threshold value of probability 
 and subjects reporting pain 5 were excluded from this study17 , 19 .
forty - three chronic 
 stroke patients who fulfilled the criteria participated in the study .
the baseline 
 characteristics of our subjects are shown in table 
 1table 1.characteristics of the participantscharacteristicsvaluesgender ( male / female)23/20age ( years)57.887.92duration after stroke ( months)15.213.32affected side ( left / right)24/19subtype of stroke ( infarction / hemorrhage)29/14the values are presented as mean  sd or mode .
all the participants provided their signed informed consent after receiving 
 an explanation of the purpose and procedure of the study .
the values are presented as mean  sd or mode the elbow flexor tone was assessed using the modified ashworth scale ( mas ) . in most cases , 

a stroke patient s muscle tone is difficult to evaluate because abduction and external 
 rotation of the shoulder joint decreases regardless of the presence of upper extremity 
 muscle tone .
therefore , the elbow flexor tone was selected because spasticity of the elbow 
 flexor is common in stroke patients8 , 15 . for the test ,
the forearm was placed in 
 the supine position with the patients sitting comfortably . to determine the scope of 
 movement of the forearm
, the assessor instructed the participants to relax comfortably when 
 the elbow joint was fully stretched .
thus , this study used a dichotomous variable 0 for mas 1 ; 1 for mas 1 . 

muscle tone increased significantly when the patients with mas>1held an 
 object and then released it compared with the patients with mas of 0 or 1 .
this value has a 
 high inter - rater reliability ( weight =0.770.96 ) and intra - rater reliability ( weight =0 . 

the motor recovery of the upper extremity was evaluated using the fugl - meyer ( fm ) 
 assessment .
the score for the upper extremity has a total possible score of 66 , and the 
 scores for the wrist and hand have a total possible scores of 24 ; their reported inter - rater 
 ( r=0.94 ) and intra - rater ( r=0.99 ) reliabilities are also high21 .
the action research arm test ( arat ) was used to measure the limit of motor function in the 
 affected arm .
the inter - rater reliability of the test is r=0.99 , and its test - retest 
 reliability is r=0.9822 .
to 
 help the subjects understand each examination , they were given verbal instructions or 
 demonstrations 2 times , after which their sessions began with 2 minutes rest time between 
 each session .
pearson s correlation coefficient was 
 calculated to investigate the correlation between variables , and the receiver operating 
 characteristic ( roc ) curve was used to identify the cutoff values that could predict 
 increased muscle tone ( elbow flexor hypertonicity was mas1 ) for all examination 
 tools .
examination accuracy was measured by the area under the roc curve ( auc ) and 
 classified as non - informative ( auc=0.5 ) , low accuracy ( 0.5<auc0.7 ) , moderately accurate 
 ( 0.7<auc0.9 ) , very accurate ( 0.9<auc<1 ) , and perfect ( auc=1)20 . to predict the risk of hypertonia , logistic regression 
 analysis was conducted .
the  test was performed to investigate the relationship 
 between intergroup fm - ue depending on the cutoff value , elbow flexor tone , and 
 fm - wrist / hand , and arat . the independent t - test
was used to compare scores between 
 fm - wrist / hand and arat depending on the cutoff value of fm - ue and the effect size was 
 analyzed using cohen s d , the standardized difference between the means of 
 the groups with lower motor function ( fm24 points ) and the groups with higher motor 
 function ( fm>24 points ) .
the effect is very high when d1.2 , high when 
 d > 0.8 , and moderate when d has a value between 0.6 
 and 0.8 .
the correlations between hypertonia and the arm motor function variables are shown in table 2table 2.correlations between hypertonia and arm motor functionvariableshypertonia(mas1)fm - u / efm - wrist / handfm - ue0.72*fm - wrist / hand0.34 * 0.78*arat0.41 * 0.72 * 0.62**significant , * p<0.05 .
mas : modified ashworth scale ; 
 fm - ue : fugl meyer - upper extremity ; fm - wrist / hand : 
 fugl - meyer - wrist / hand ; arat : action research arm test .
mas negatively correlated with fm - ue , fm - wrist / hand , and arat ( r=0.34 to 
 0.72 , p<0.01 ) ; fm - ue positively correlated with fm - wrist / hand and arat ( r=0.78 to 0.72 , 
 p<0.01 ) ; and fm - wrist / hand positively correlated with arat ( r=0.62 , p<0.01 ) . the 
 prediction of hypertonia ( mas1 ) is shown in table 3table 3.prediction of hypertonia ( mas 1 ) in participantspredictionscriteriacut - off pointsensitivity(%)specificity(%)auc(95% ci)fm - uemas<1 vs 
 mas124/ 66 score0.820.650.80 * * ( 0.680.93)fm - wrist / hand5.5/ 24 score0.830.730.86 * * ( 0.750.97)arat15.50/ 57score0.820.620.76 * ( 0.610.90)*significant , * p<0.01 , * * p<0.001auc : area under the roc curve ; mas : modified ashworth scale ; 
 fm - ue : fugl meyer - upper extremity ; fm - wrist / hand : fugl 
 meyer - wrist / hand ; arat : action research arm test .
roc curve analysis indicated the cutoff values for predicting hypertonia were 
 24 for fm - ue , 5.5 for fm - wrist / hand , and 15.50 for arat .
thus , it was likely that the 
 reference point that was able to predict the risk factor for hypertonia was 
 mas1
. the odds ratio of being mas 1 for each outcome variable is 
 shown in table 4table 4.odds ratios of being mas 1 for each outcome variablepredictionscriteriasewaldodds ratiop ( 95% ci)fm - uemas1 vs mas10.2690.1066.4250.7640.011 * ( 0.620.94)arat0.3070.1504.1691.3590.051 ( 1.011.82)fm - wrist / hand0.5280.3142.8260.5900.093 ( 0.321.09)*significant , * p<0.05dependent variable : 0 = mas 1 , 1 = mas 1independent variable : sex , age , affected side , durationmas : modified ashworth scale ; fm - ue : fugl meyer - upper 
 extremity ( 0=24 score , 1=>24 score ) ; arat : action research arm test 
 ( 0=15.50 score , 1=>15.50 score ) ; fm - wrist / hand : fugl meyer - wrist / hand 
 ( 0=5.5 score , 1=>5.5 score ) .
fm - ue was most influential in elbow flexor spasticity ( mas1 ) , 
 and the probability that it would be higher than mas1 was 0.764 times greater 
 in the subjects with fm - ue cutoff values 24 than in the subjects with fm - ue cutoff values 
 > 24 .
the correlation between mas and arm motor function according to the fm - ue cutoff 
 value is shown in table 5table 5.correlation between mas and arm motor function according to the cutoff value of 
 fm - uevariablesfm - ue cutoff value(>24 score)(n=23)fm - ue cutoff value(24 score)(n=20)(mas  1)13 ( 56.52%)1 ( 5%)12.932*(mas  1)10 ( 43.48%)19 ( 95%)fm - wrist / hand ( 5.5 score)4 ( 17.39%)18 ( 90%)22.572*fm - wrist / hand ( > 5.5 score)19 ( 82.61%)2 ( 10%)arat(15.50 score)1 ( 4.35%)18 ( 90%)31.823*arat ( > 15.50 score)22 ( 95.65%)2 ( 10%)*significant , * p<0.001 .
fm - ue : fugl meyer - upper extremity ; 
 mas : modified ashworth scale ; fm - wrist / hand : fugl 
 meyer - wrist / hand ; arat : action research arm test .
the comparison of arm motor function according to the fm - ue cutoff value is 
 shown in table 6table 6.comparison of motor function according to the cutoff value of fm - uevariablesfm - ue cutoff value(>24 score)(n=23)fm - ue cutoff value(24 score)(n=20)tcohen dfm - wrist / hand ( score)11.136.742.802.025.314 * 1.27arat ( score)35.7014.287.506.138.186 * 1.56*significant , * p<0.001 .
cohen d = size effect 
 d = > 1.2 ( very large ) , > 0.8 ( large ) , 0.6  0.8 ( moderate ) . 

fm - ue : fugl meyer - upper extremity ; fm - wrist / hand : fugl 
 meyer - wrist / hand ; arat : action research arm test .
the effect size was cohen s d1.27 , suggesting that the 
 better the proximal part function , the better the distal part function .
mas : modified ashworth scale ; 
 fm - ue : fugl meyer - upper extremity ; fm - wrist / hand : 
 fugl - meyer - wrist / hand ; arat : action research arm test * significant , * p<0.01 , * * p<0.001 auc : area under the roc curve ; mas : modified ashworth scale ; 
 fm - ue : fugl meyer - upper extremity ; fm - wrist / hand : fugl 
 meyer - wrist / hand ; arat : action research arm test * significant , * p<0.05 dependent variable : 0 = mas 1 , 1 = mas 1 independent variable : sex , age , affected side , duration mas : modified ashworth scale ; fm - ue : fugl meyer - upper 
 extremity ( 0=24 score , 1=>24 score ) ; arat : action research arm test 
 ( 0=15.50 score , 1=>15.50 score ) ; fm - wrist / hand : fugl meyer - wrist / hand 
 ( 0=5.5 score , 1=>5.5 score ) * significant , * p<0.001 .
fm - ue : fugl meyer - upper extremity ; 
 mas : modified ashworth scale ; fm - wrist / hand : fugl 
 meyer - wrist / hand ; arat : action research arm test * significant , * p<0.001 .
cohen d = size effect 
 d = > 1.2 ( very large ) , > 0.8 ( large ) , 0.6  0.8 ( moderate ) . 

fm - ue : fugl meyer - upper extremity ; fm - wrist / hand : fugl 
 meyer - wrist / hand ; arat : action research arm test
severe upper motor neuron damage not only slows down motor recovery but also aggravates 
 characteristics such as hyperexcitability23 . in stroke patients , increased muscle tone negatively correlates 
 with motor function24 . in the present 
 study ,
elbow flexor tone was found to negatively correlate with fm - ue ( r=0.72 ) , 
 fm - wrist / hand ( r=0.34 ) , and arat ( r=0.41 ) . in most stroke patients ,
the range of motion of 
 abduction and external rotation in the shoulder decreases regardless of upper extremity 
 muscle tone8 , 15 , and the gross movement patterns of shoulder flexion and internal 
 rotation , forearm pronation , and elbow , wrist , and finger flexion make normal movement 
 difficult12 .
in particular , excessive 
 elbow flexor tone reduces the stability and mobility of the wrist and makes fine finger 
 movement difficult5 .
previous studies have demonstrated that poor motor function predicts the risk of 
 hypertonia8 , 23 . in the present study ,
the cutoff values for upper extremity motor 
 function assessments that can predict hypertonia were identified as 24 for fm - ue , 5.5 for 
 fm - wrist / hand , and 15.5 for arat . as a reference point that can predict the risk factors for 
 hypertonia ,
the probability of mas1 is high for elbow flexor spasticity , and 
 the auc were all at 76% or more , which was satisfactory .
a previous study suggested that 
 patients with fm - ue18 within 48 hours after stroke are 12.8 times more likely to experience 
 hypertonicity ( mas 1 ) within 6 months after onset than patients with 
 fm - ue>186 . using this cutoff value 
 ( fm - ue 18 ) , a significant difference that could predict the risk of hypertonia
fm - ue 18 could distinguish patients with increased hypertonicity ( mas 
 1 ) with 68% sensitivity , which is lower than the 82% sensitivity of fm - ue 
 24 , and could distinguish patients without hypertonicity with 64% specificity , similar to 
 the 65% specificity of fm - ue 24 .
therefore , fm - ue 24 was used as the cutoff value to 
 distinguish chronic - stroke patients with increased elbow joint flexor muscle tone , and these 
 patients also had poor motor function of the upper extremity , because the gross movement 
 patterns including internal rotation of the shoulder and flexion of wrist and finger 
 appeared when holding or manipulating an object with their hands .
limited arm motor function 
 in chronic - stroke patients can increase the risk of severe hypertonia , but various factors 
 such as individual physical characteristics , specific treatment , and life habits can also 
 influence muscle tone5 .
in addition , the 
 subjects had experienced disability due to stroke for 15.21 months on average after onset , 
 but the motor function of the upper extremity had improved through self - effort and 
 treatment .
our fm - ue cutoff value was 6 points higher than that of a previous study 
 indicating that spontaneous recovery can no longer be expected in patients with disability 
 for 15 months after stroke onset ; however , because the effect size of the intervention and 
 spontaneous effort is high , their condition can be improved . by examining the risk of hypertonia using the cutoff value of arm motor function in the 
 present study , elbow joint flexor hypertonicity ( mas1 )
was found to be most 
 influenced by fm - ue , and when the fm - ue cutoff value was 24 , it is likely to increase with 
 a probability of 0.764 times ( odds ratio ) compared with subjects with fm - ue cutoff values 
 > 24 .
fm - wrist / hand and arat are largely used to examine the distal upper extremity and 
 thus can not be used to predict the risk of hypertonia .
the subjects showed difficulty with 
 hand functions such as manipulation , grip , pinch , and release ; therefore , their fm - ue , 
 fm - wrist / hand , and arat scores were lower . in fm - ue , the scores of the forearm , wrist , and 
 hand ( finger)-related items were not high , suggesting that the characteristics of the tool 
 used to examine the distal upper extremity are most influential for elbow flexor tone . in 
 the examination of upper extremity motor function , most subjects showed relatively high 
 wrist joint and elbow flexor tone and , in particular , it is said that appropriately 
 releasing an object is more difficult than gripping or holding an object25 .
for the upper extremity function , the 
 fingers , hand , and wrist need to cooperate and selectively adjust .
the muscle paralysis 
 caused by central nervous system damage is more influential in distal than proximal parts 
 and delays recovery26 .
fm - wrist / hand and 
 arat showed significantly lower scores in predicting elbow flexor spasticity .
elbow flexor 
 spasticity is a common phenomenon , and excessive elbow flexor tone prevents appropriated 
 coordination of elbow extension , inhibiting the stability and movement of the hand and 
 wrist . when elbow joint flexor hypertonicity is present , sophisticated movement of the hand 
 is impossible due to the lack of stability in the elbow joint .
in addition , the rubrospinal 
 tract is responsible for the arm stability , external support , and arm strength use to 
 control the hand , and the corticospinal tract also plays a role in elbow flexion .
thus , it 
 provides the basic background that enables sophisticated movements such as holding , 
 gripping , and manipulating because it regulates the stability of the elbow and wrist and 
 harmonious coordination with the extensors .
recovery after stroke is more rapid in the 
 proximal than in the upper distal parts , seemingly because the elbow subluxation , 
 impingement syndrome , supraspinatus tendinitis , and biceps tendinitis that commonly occur in 
 stroke patients is influential in elbow flexor spasticity .
given that the coordination of 
 elbow flexors and extensors in the movement of upper distal parts is an essential factor for 
 forearm , wrist , and finger movements , it can be deduced that elbow flexor spasticity has a 
 negative impact on upper extremity movement in stroke patients , and rotator cuff muscle and 
 elbow extensor weakening form the upper extremity flexor pattern . when muscle tone is mas 1 , muscle resistance during passive stretch increases 
 more than for mas of 0 or 1 , and the mechanical characteristics of the muscle change due to 
 reflex hyperexcitability that may lead to contracture5 , 8 .
therefore , the elbow flexor 
 is clinically useful for examining the muscle tone of the upper extremity8 .
an appropriate elbow flexor tone makes 
 coordination with the elbow extensor possible , provides stability to the joint s distal 
 parts , and allows appropriate wrist and finger movements27 .
moreover , better motor function in the proximal parts of the upper 
 extremity means there is less risk of increased muscle tone and better motor function in the 
 distal parts of the upper extremity .
better stability in the proximal part of the shoulder 
 ( fm - ue>24 ) implies a lower elbow flexor tone and better distal part function of the upper 
 extremity .
the sample size was too small to generalize the results , 
 and there were limitations in the definition of spasticity and determining whether elbow 
 flexor hypertonicity reflects the typical characteristics of upper extremity muscle tone . 

however , given that coordination of the elbow flexors and extensors is an essential factor 
 in forearm , wrist , and finger movement , it can be said that elbow flexor spasticity 
 negatively influences the upper extremity movement of stroke patients .
therefore , further 
 studies need to quantitatively investigate the impact of shoulder subluxation and pain 
 degree on muscle tone and study the correlation between elbow flexor activity and amplitude 
 and the muscle tone as well as analysis of upper extremity movement biomechanics .
 [ purpose ] muscle tone is known to predict the motor function of the upper extremity 
 within 12 months after onset in stroke survivors . 
 the aim of this study was to investigate 
 whether motor function of the upper extremity can predict the risk of hypertonia in 
 chronic stroke survivors , and to analyze the correlation between the two variables to 
 determine the predictive validity . 
 [ subjects and methods ] forty - three chronic stroke 
 survivors were assessed using the modified ashworth scale ( mas ) for elbow flexor tone , the 
 fugl - meyer assessment of the upper extremity ( fm - ue ) , and the action research arm test 
 ( arat ) for upper extremity motor recovery and function . 
 [ results ] elbow flexor tone 
 ( mas1 + ) increased by 0.246 compared with the baseline muscle tone even at 
 month 12 and appeared to negatively affect the motor function of the upper extremity . the 
 cutoff value for predicting muscle tone 
 ( mas1 + ) was 24 for fm - ue and 15.5 for 
 arat . 
 fm - ue had the biggest impact on elbow flexor tone ( mas1 + ) , and the risk 
 of elbow flexor hypertonia ( mas1 + ) increased 0.764-fold for a cutoff value of 
 fm - ue24 compared with a cutoff value of fm - ue>24 . 
 [ conclusion ] the results show that 
 the most important variable for predicting muscle tone of the elbow flexor in stroke 
 survivors is the fm assessment of the upper extremity . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION