motor and cognitive impairments in stroke patients dramatically reduce their independence 
 in activities of daily living ( adl ) . in particular , the physical symptoms of stroke have a 
 greater effect on the patients independence than the cognitive component1 . therefore , understanding the relationship 
 between motor function and adl is important to design efficient rehabilitation programs 
 aimed at improving adl performance .
this ability to perform adl is influenced by motor functions of the upper and lower 
 limbs2 , 3 and the trunk4,5,6 . 

likhi et al.7 reported that adl 
 performance in stroke patients correlated more closely with the impairment level of the 
 trunk than that of the upper limb , whereas lower limb impairment showed no correlation with 
 adl .
however , fong et al.8 reported that 
 lower limb impairment correlated more closely with adl than upper limb impairment . in 
 contrast
, ezure et al.9 reported that the 
 upper limb , lower limb , and trunk functions were significantly correlated with adl .
multiple 
 linear regression analysis revealed that trunk function exhibited a stronger relationship 
 with adl than the affected side function .
therefore , the impact of limb and trunk function 
 impairment on adl in stroke patients remains highly controversial .
this is consistent with the well - known 
 strong association between motor functions of the affected upper and lower limbs .
for instance , a correlation analysis 
 between the affected upper limb function and adl must be conducted in the absence of the 
 effect of the affected lower limb function on adl . to the best of our knowledge ,
no study 
 has conducted partial correlation analyses between limb or trunk function impairment and adl 
 in stroke patients .
therefore , the present study aimed to investigate the independent 
 influence of the affected upper and lower limb , trunk , and unaffected side function on adl 
 using partial correlation analysis .
the study cohort included 
 77 stroke patients ( 53 males and 24 females ) who were admitted to the northern fukushima 
 medical center between october 2010 and november 2013 .
they fulfilled the following 
 inclusion criteria : first stroke ; unilateral supratentorial hemispheric lesion ; absence of 
 marked cognitive deterioration [ 5 cognitive items of the functional independence measure 
 ( fim)11 , described below ] ; and 
 unilateral spatial neglect based on the stroke impairment assessment set12 ( sias ; described below ) .
the mean patient 
 age was 68.5  years , and the mean time from stroke onset was 84.8 days .
subject 
 characteristics are listed in table 1table 1.stroke-related characteristics of study subjectsmeansdrangeage , years68.512.73693time post - stroke , days84.837.437236males , % 69.2right - sided hemiparesis , % 48.8affected upper limb function ( 010)6.43.0010affected lower limb function ( 015)11.73.8115trunk function ( 06)5.31.006unaffected side function ( 06)5.30.926barthel index ( 0100)86.817.75100motor item of fim ( 1391)73.316.02291fim : functional independence measure . the study protocol was approved by the institutional ethics review board of 
 northern fukushima medical center ( fukushima , japan ) .
fim : functional independence measure we compiled data on motor function , trunk function , and unaffected side function from the 
 sias , barthel index ( bi)13 , and fim 
 evaluations . the sias test ( 05 ) items evaluate motor function of the affected limb 
 ( knee - mouth , finger function , hip flexion , knee extension , and foot - pat tests ) , the trunk 
 ( abdominal muscle strength and verticality ) , and the unaffected side ( strength of knee 
 extension and grip strength ) .
details on the method , reliability , and validity of sias have 
 been reported elsewhere12 , 14,15,16 .
in addition , the independence index of adl was determined 
 using the bi and motor items of the fim scoring system . in the present study ,
the affected upper limb function was calculated from the total score 
 of the knee - mouth and finger function tests .
lower limb function was calculated from the 
 total score of the hip flexion , knee extension , and foot - pat tests .
furthermore , trunk 
 function was calculated from the total score of the abdominal muscle strength and 
 verticality tests , and the unaffected side function was calculated from the total score of 
 grip strength and knee extension strength tests .
we used simple correlation and partial 
 correlation analyses to remove the effect of age and other motor function parameters 
 ( affected upper limb , lower limb , trunk , and unaffected side function ) , and estimated the 
 independent effect of the affected upper limb , lower limb , trunk , and unaffected side 
 functions on bi or fim .
all correlations were investigated using spearman s rank correlation 
 analysis with spss version 22.0 for windows ; p values < 0.05 were considered statistically 
 significant .
it was observed that half of the patients ( 48.8% ) had right - sided hemiparesis , with mild to 
 moderate impairment of the upper and lower limbs .
simple and partial correlation analyses 
 were conducted between the parameters of motor function ( affected upper limb , lower limb , 
 trunk , and unaffected side function ) and adl ( bi or fim scores ) ( table 2table 2.simple and partial correlation analyses between motor functions and indexes of 
 activities of daily living ( fim and bi ) in stroke patientssimple correlation ( n=77)partial correlation ( n=77)fimbifimbiaffected upper limb function0.31**0.34**0.020.07affected lower limb function0.51**0.51**0.48**0.42**trunk function0.37**0.33**0.150.13unaffected side function0.38**0.34**0.32**0.27*values are spearman s rank coefficients ; * * p0.01 .
fim : functional independence 
 measure ; bi : barthel index ) . moreover , simple correlation analyses revealed significant positive 
 correlations for all comparisons . partial correlation analyses generated remarkably 
 different data when the effect of age and other body part functions on adl were excluded . 

significant positive correlations were found between the affected lower limb or unaffected 
 side function and bi or fim . in contrast
, there was no significant correlation between the 
 affected upper limb or trunk function and bi or fim .
this discrepancy is explained by the 
 strong functional interactions between the affected upper limb and lower limb functions and 
 between the trunk and unaffected side functions ( table 
 3table 3.simple correlation analyses between motor functions in stroke patientsaffected u / l functionaffected l / l functiontrunk functionunaffected side functionaffected u
/ l function0.68**0.010.08affected l / l function0.68**0.140.03trunk function0.010.140.39**unaffected side function0.080.030.39**values are spearman s rank coefficients ; * * p0.01 .
fim : functional independence 
 measure ; bi : barthel index ; u / l : upper limb ; l / l : lower limb ) .
fim : functional independence 
 measure ; bi : barthel index values are spearman s rank coefficients ; * * p0.01 .
fim : functional independence 
 measure ; bi : barthel index ; u / l : upper limb ; l /
the present study provides insightful information on the relationship between motor 
 function and adl in stroke patients .
the ongoing debate on motor functions affecting adl was 
 resolved by designing partial correlation analysis protocols considering the possible 
 interactions between body parts .
simple correlation analysis suggested that the affected 
 upper limb , lower limb , unaffected limbs , and trunk influence adl performance .
in contrast , 
 partial correlation analysis , excluding age and the influence of other body parts , revealed 
 the absence of correlation between the affected upper limb or trunk function and adl in 
 stroke patients .
this discrepancy was explained by the strong interactions between the 
 affected upper and lower limb functions and between trunk and unaffected side functions . 

this new information on motion dynamics in stroke patients should lead to the development of 
 more efficient rehabilitation programs .
this study demonstrates that adl performance in stroke subjects is hindered more by the 
 affected lower limb than by the unaffected side .
previous studies reported that balance2 , gait17 , 18 , and stair19 performance are affected by lower limb 
 function .
thrane et al.20 reported that 
 the affected lower limb function is associated with self - care dependency .
further , the 
 present study also indicates that the affected lower limb function plays an important role 
 in adl .
we established a considerable relationship between the unaffected side function and adl , 
 based on the strength of the quadriceps muscle of the lower limb and the grip strength .
it 
 has been reported that the strength of quadriceps muscle influences sit - to - stand21 and transfer22 activities in stroke subjects .
colebatch et al.24 indicated that the strength of muscles ipsilateral to the lesion 
 was reduced in hemiplegic patients compared with healthy subjects . therefore , rehabilitation 
 programs aiming to improve adl should target the muscle strength on the unaffected side .
the lack of correlation between the affected upper limb function and adl may be explained 
 by the fact that most activities can be performed with the unaffected upper limb .
further , 
 previous studies mentioned that the upper limb function is required to reach a certain 
 threshold before performance actually starts to increase25 , and improvement in the functional limitations of the upper limb 
 does not necessarily lead to a full recovery of adl function26 .
therefore , there may be a non - linear relationship between the 
 affected upper limb function and adl .
thrane et al.20 reported no significant relationship between the affected upper 
 limb impairments and adl using lower limb function as covariate , as in our study .
thus , the 
 impact of upper limb function impairments on everyday activities may be lower than 
 expected27 .
the close relationship between trunk function and adl has been reported by previous 
 studies4,5,6,7 , 
 9 . however , to the best of our 
 knowledge , this is the first study to identify the independent effect of trunk function on 
 adl using partial correlation analysis .
in addition , our results suggest that the impact of 
 trunk function on adl is lower than expected .
however , the average score of trunk function 
 in our patients was very high , suggesting that a relationship between trunk function and adl 
 could have been missed due to the ceiling effect . therefore , this result should be carefully 
 interpreted .
first , simple and partial correlation analyses 
 can only detect linear relationships between two variables .
. the correlations between each motor function and adl 
 may differ depending on the adl independence level .
 [ purpose ] this study aimed to clarify the independent impact of the affected upper and 
 lower limb , trunk , and unaffected side motor functions on activities of daily living in 
 stroke patients using partial correlation analysis . 
 [ subjects and methods ] this 
 retrospective study included 77 stroke patients . 
 motor functions were assessed using the 
 stroke impairment assessment set , and the activities of daily living performance was 
 assessed using the barthel index or functional independence measure . 
 further , simple and 
 partial correlation analyses were conducted between each motor function and activities of 
 daily living parameter . 
 [ results ] simple correlation analysis identified significant 
 positive correlations for each pair . in contrast , partial correlation analysis only 
 identified significant positive correlations between the affected lower limb or unaffected 
 side functions and the barthel index or functional independence measure . 
 this discrepancy 
 between the two tests was explained by the significant interaction between the affected 
 upper and lower limb functions and between the trunk and unaffected side functions . 
 
 [ conclusion ] the present study identified the affected lower limb and unaffected side 
 motor functions as the major determinants of activities of daily living performance in 
 stroke patients . 
 these findings suggest that rehabilitation programs can be improved by 
 targeting these areas . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION