measurement of muscle strength in rehabilitation is important for the evaluation of 
 treatment outcomes .
simple manual muscle testing can be performed , or a measuring device can 
 be used for quantitative measurement of muscle strength . in particular , a hand - held 
 dynamometer ( hhd ) is a relatively inexpensive and very portable instrument , and has been 
 used in a variety of situations for measuring muscle strength .
previous reports have demonstrated the high reliability of measuring muscle strength with 
 an hhd1 , 2 .
however , it has also been reported that the results of measuring 
 muscle strength with an hhd are influenced by the position of the testee s lower extremity , 
 fixation of the device , and the skill of the examiner3,4,5,6,7 . for improving reliability ,
a strap or a fixing frame has been used 
 to make fixation holding the measuring device by hand8 , and both methods provide high reliability .
also , using an hhd 
 attached with a belt has been reported to be high reliable , overcoming the problem of 
 examiners skills9,10,11,12 . in terms of measurement modes
, it has been reported that the break test requires greater 
 strength of the examiner to resist the strength of the examinee than the make test13,14,15 .
furthermore , the reliability of the 
 results of the break test has been reported to be low16 . when measuring muscle strength with an hhd attached by a belt , muscle strength is measured 
 by pushing a part of the body against the sensor pad . in measurement of isometric knee 
 extension strength
, a sensor pad is attached to the front of the distal lower extremity to 
 measure strength .
some patients complain of pain and discomfort at the distal lower 
 extremity when this method is used , and the pain becomes a limiting factor , preventing the 
 exertion of full muscle strength , particularly in cases of high muscle strength values .
when the thickness and shape of the cushion of the sensor pad are changed for the 
 measurement of isometric knee extension strength using an hhd attached by a belt , values of 
 muscle strength are reproducible , but muscle strength values are strongly influenced by the 
 pain experienced at the time of measurement . therefore , to improve the appropriateness of 
 measured values of muscle strength , it may be necessary to use a pad of sufficient thickness 
 with an appropriate curve to eliminate pain . in rehabilitation , the muscle strength of elderly individuals and subjects with reduced 
 muscle mass is often measured .
compared with healthy adults , soft tissue at the front of the 
 distal lower extremity is often thin , and , accordingly , the measurement procedure can be 
 painful .
therefore , in measurement of isometric knee extension strength using an hhd with 
 attachment of a fixation belt , pain at the front of the distal lower extremity remains a 
 problem . to overcome this problem , mobie ,
a new device for measuring muscle strength using a pull 
 sensor , rather than pushing a limb against the sensor , was developed .
the intra - class correlation coefficient ( icc ) is used as a statistical analysis method of 
 reliability . however , in cases of data with large individual differences and measurements 
 with marked variability , inter - examiner differences and errors become relatively small and 
 the coefficient becomes large .
recently , the reliability of an hhd was examined using 
 standard error of measurement ( sem ) and minimal detectable change ( mdc ) in addition to 
 icc17,18,19,20,21,22 .
there are random errors and systematic errors , and the former can be reduced by increasing 
 the number of subjects and repetition of measurements , whereas the latter is an error in 
 which measurements deviate with a specific bias , and it can not be minimized by increasing 
 the number of subjects or measurements . therefore , it is necessary to extract systematic 
 errors .
systematic errors are proportional and constant . proportional errors increase or decrease 
 with the true value with a specifi bias , whereas constant errors have aspecific bias 
 irrespective of the true value .
systematic errors can be identified using bland - altman 
 analysis23 , and using the degree of 
  variability  between two measurements , it is possible to determine the reliability of the 
 measurement and its appropriateness for clinical application . in this study intra - examiner reliability and inter - examiner reliability of an hhd with a 
 pull sensor
the subjects were 54 healthy adults ( 35 males and 19 females ; mean age , 23.26.8  years ; 
 height , 166.38.4  cm ; weight , 60.012.6  kg ) ( table 
 1table 1.the characteristics of the subjects ( n=54)age ( yrs ) 23.2  6.8height ( cm ) 166.3  8.4 weight ( kg ) 60.0  12.6bmi ( kg / m ) 21.6  4.1 data are means  sd ) .
the 35 subjects ( 21 males and 14 females ) in their 20s were examined the most . the aims and 
 contents of the study
permission to 
 conduct this study was provided by the human research ethics committee of tokyo college of 
 allied medicine physical therapy . a manual muscle strength monitor ( mobie ; sakai medical co. , ltd . )
mobie is an hhd 
 with a thin sensor . unlike conventional hhds that measure force by pushing the body against 
 the sensor , this device senses
muscle strength by pulling a distortion gauge , and muscle 
 strength can be measured with a fixation belt attached . to examine inter - examiner differences in the mobie hhd measurements ,
measurements were 
 performed by two examiners : one female physical therapist ( pt ) ( examiner a ) with 21  years of 
 clinical experience and skill in handling hhds , and one male third - grade student on a 
 four - year physical therapy course ( examiner b ) .
he practiced the method of the measurement 
 that had defended notes the day before the measurements began . on the first day , examiner a 
 and examiner b measured one leg of each subject , and the next day they measured the other 
 leg .
for all measurements , isometric knee extension was performed at 
 maximum effort for approximately 3 seconds . for the measurements , the subjects sat on the edge of a bed with their feet not touching 
 the floor , and their arms crossed in front of the body .
subjects were asked ; to maintain the 
 trunk in the upright position ; to keep the buttocks on the bed ; and to exert muscle power to 
 extend the knee joint without a swing movement . prior to measurement ,
an appropriate posture for measurement was explored . since the muscle 
 to be measured is the femoral quadriceps , the occurrence of compensatory movement due to 
 exertion of muscle power in isometric knee extension
was examined in two postures : 
 supporting both arms at the back of the bed with the pelvic tilted backward and the trunk in 
 extension , similar to the posture for manual muscle testing ; and with both arms crossed in 
 front of the trunk .
elevation of the pelvis was more likely to appear in the posture similar to that for manual 
 muscle testing than in the posture with both arms crossed in front of the trunk , and it was 
 necessary for the examiner to fix both sides of the pelvis manually in addition to 
 controlling the device to block this compensaory movement .
therefore , considering rapid and 
 simple measurement with blocking of compensaory movement in clinical practice , the posture 
 with both arms crossed in front of the trunk was selected for this study .
the pad of the 
 measuring device was attached around the distal lower extremity and controlled with a belt 
 fastened to the examination pole so that the lower extremity was perpendicular to the floor . 

the sensor was set parallel to the floor with the fixation belt , and positioned midway 
 between the lower extremity and the examination bed . since this measuring device senses 
 tension ,
a hand of the examiner supported to the sensor and to prevent gravity - derived 
 downward tension during calibration and measurement .
in addition , to avoid popliteal pain by 
 compression measurement , a bath towel was spread over the site .
icc was calculated based on the muscle strengths measured by examiners a and b , and 
 intra - examiner reliability and inter - examiner reliability were examined using bland - altman 
 analysis .
when no systematic error was recognized , the mdc of the 95% confidence interval 
 ( mdc95 ) was calculated .
mdc95 and sem were calculated according to 
 the following formula.mdc95 = sem  1.96 .sem = 
 standard deviation of difference between two measurements ( s ) /.
inter - examiner reliability was examined with icc ( 1,1 ) and ( 1,3 ) over the three 
 measurements .
the first and second measured values were examined bilaterally using 
 bland - altman analysis . for inter - examiner reliability ,
icc ( 2,1 ) and icc ( 3,1 ) were 
 calculated to examine both the random effect and the fixation effect , respectively . in both 
 intra - examiner reliability and inter - examiner reliability , systematic errors and the limit 
 of agreement ( loa ) , the permissible range of errors between two measurements , were 
 calculated .
loa was calculated according to the following formula.[(d  1.96s ) 
 + tse loa ] ~ [ ( d + 1.96s )  tse 
 loa]*d : average of difference between two 
 measurements se loa= t : t value for the degree of freedom n  1 for data analysis , ibm spss statistics 21 was used .
table 2table 2.the average values of the measured strengtha examiner ( kgf ) b examiner ( kgf ) right ( average 3 times ) 39.4  10.6 39.5  11.2 left ( average 3 times ) 39.4  10.6 39.2  9.9 right 1 test39.0  10.739.1  11.62 test 39.5  10.4 39.3  11.13 test 39.9  10.8 40.2  11.1 left 1 test38.5  10.639.3  9.62 test 39.5  10.539.1  10.33 test 40.2  10.739.3  10.1data are means  sd shows the averages of muscle strength as measured by examiner a and examiner 
 b. the average right muscle strength was 45.6  9.0 kgf in males and 28.2  3.8 kgf in 
 females by examiner a , and 45.9  8.4 kgf in males and 27.9  4.9 kgf in females by examiner 
 b. with regard to intra - examiner reliability , both icc ( 1,1 ) and icc ( 1,3 ) were 0.9 or 
 higher ( table 3table 3.the intra - examiner reliabilities of the measured strengthicc(1,1 ) icc(1,3 ) loa bland - altman analysisadding errorproportional error95% confidence intervalpresence or absence the slope of the regression linepresence or absence examiner0.960.993.97 1.05absence 0.14absence a right   to 3.17 to 0.26examiner0.940.986.50 2.01absence 0.06absence a left   to 4.5 to 0.01examiner0.950.985.951.34absence 0.16absence a right   to 5.35 to 0.74examiner0.940.984.861.13absence 0.21absence a left   to 5.06 to 0.75 ) .
bland - altman analysis indicated there were no constant or proportional 
 errors by examiner a or examiner b ( table 
 3 ) .
the loa of the right extremity was 3.97 to 3.17 by examiner a and 5.95 to 5.35 by 
 examiner b , while the loa of the left extremity was 6.50 to 4.50 by examiner a and 4.86 to 
 5.06 by examiner b. since no systematic error was found , mdc95 of the right and 
 left extremities were 4.7 kgf and 7.3 kgf , respectively , by examiner a , and 7.5 kgf and 6.7 
 kgf , respectively , by examiner b. these results indicate that when muscle strength was 
 measured twice in the same subject , mdc95 within 4.7 kgf for the right extremity 
 by examiner a was considered a measurement error and mdc95 more than 4.7 kgf was 
 judged as true change caused by intervention for the subject . in terms of inter - examiner reliability , both icc ( 2,1 ) and icc ( 3,1 ) in the first through 
 the third measurements were 0.9 or higher for the right extremity and 0.8 or higher for the 
 left extremity ( table 4table 4.the intra - examiner reliabilities of the measured strengthicc(2,1)icc(3,1)loa   bland - altman analysisadding errorproportional error95% confidence intervalpresenceor absence the slope of the regression linepresenceor absence a right 0.920.929.02 1.74absence 0.17absence 1 testto 14.50to 1.522 test0.920.928.53 1.48absence 0.13absence to 14.21to 1.683 test0.90 0.90 10.262.13absence 0.04absence to 16.0to 1.53a left 0.890.90 10.172.52absence 0.17absence 1 testto 14.53to 0.922 test0.90 0.90 8.971.13absence 0.02absence to 15.73to 0.753 test0.880.889.311.06absence 0.1absence to 17.34to 2.66 ) . in the first through the third measurements , neither constant nor 
 proportional errors were identified by bland - altman analysis ( table 4 ) .
no subject complained of pain due to the pad attached 
 around the lower extremity while muscle power was being exerted .
to investigate intra - examiner and inter - examiner reliability of isometric muscle strength 
 as measured using the mobie hhd with a pull sensor , measurement was repeated three times by 
 a pt with clinical experience and a pt student without clinical experience .
previously , we 
 reported that for subjects in their 20s24 , which accounted for the largest proportion of subjects , isometric 
 knee extension strength of males and females was 60.4  8.1 kgf and 37.1  8.9 kgf , 
 respectively .
compared with these results , the muscle strength of the subjects in this study 
 was slightly weaker .
therefore , compensaory movement was unlikely to have occurrde and both 
 intra - examiner variability and inter - examiner variability in measurements were smaller , and 
 systematic errors were unlikely to have occurred . with regard to intra - examiner reliability , icc ( 1,1 ) was 0.94 to 0.96 , and the reliability 
 was judged as 
no systematic error was found , indicating that there is no 
 problem with intra - examiner reliability .
when icc ( 1,1 ) and icc ( 1,3 ) were compared , icc 
 ( 1,3 ) was slightly higher showing that reliability was higher , as expected , when the same 
 examiner carried out the same measurement more than once . with regard to inter - examiner reliability , both icc ( 2,1 ) and icc ( 3,1 ) were 0.88 to 0.92 , 
 and the reliability was considered 
icc ( 2,1 ) and icc 
 ( 3,1 ) were slightly reduced as measurement was repeated from the first through the third 
 time , and the variability was attributed to fatigue . however , since icc ranged between 0.88 
 and 0.92 and no constant or proportional errors were found , there was no problem 
 inter - examiner reliability . from the study of examiner
a with clinical experience and skill in handling hhds , and those 
 by examiner b , a pt student with no experience of measuring muscle strength with hhd , the 
 examiner can carry out measurement even if he / she has no experience on the operation of the 
 device as long as he / she gives the subjects the notification at measurement and measures 
 according to the predetermined procedure .
although pain remains a problem in muscle strength measurement with an hhd and a fixation 
 belt , the device used in this study caused no pain and had no influence on the muscle power 
 exerted .
therefore , when knee extension strength is measured using an hhd with a pull 
 sensor , the measurement is accurate and , since the subjects experienced no pain while 
 exerting muscle power , measurement is possible without inducing pain in cases of thin soft 
 tissue at the front of distal lower extremities in frail elderly people .
moreover , 
 quantitative muscle strength measurement is expected to be possible in a variety of 
 subjects . in this study ,
the subjects were healthy adults , but compensatory movement is likely during 
 the exertion of muscle power by subjects with high muscle power levels such as athletes . 
 however , compensatory movement is unlikely to occur in the elderly . whether knee joint 
 extension without a swing movement is possible or not influences the measurement errors of 
 the measuring device
. it will be necessary to further investigate the utility of 
 measurements with a pull - type hhd using subjects with different muscle power levels , elderly 
 people , and patients .
 [ purpose ] the purpose of this study was to examine the intra - examiner and inter - examiner 
 reliabilities of measurements of knee extensor muscle strength using a pull - type hand - held 
 dynamometer ( hhd ) . 
 [ subjects ] fifty - four healthy adults ( 35 males ; average age , 23  years ) 
 participated in this study . [ methods ] 
 knee extensor muscle strength of each leg was 
 measured three times using the hhd . to examine the intra- and inter - examiner 
 reliabilities , 
 measurements were performed by two examiners , a physical therapist and a 
 physical therapy student . 
 [ results ] the intra - examiner reliabilities , icc ( 1 , 1 ) and icc 
 ( 1 , 3 ) ranged from 0.940.99 . 
 the inter - examiner reliabilities , icc ( 2 , 1 ) and icc ( 3 , 1 ) 
 ranged from 0.900.92 for the right leg , and 0.880.90 for the left leg . 
 neither constant 
 nor proportional errors were found by bland - altman analysis . 
 [ conclusion ] intra - examiner 
 and inter - examiner reliabilities were acceptable , indicating that muscle strength can be 
 measured with the pull - type hhd without dependence on skill of measurement . 
 pain was not 
 caused by measurements with the pull - type hhd . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION