the sit - to - stand ( sts ) movement is an important functional task , and it is a prerequisite 
 for upright mobility during the activities of daily living1 . in the initial phase of normal sts movement , the activity of the 
 tibialis anterior ( ta ) muscle increases to begin the weight shift . during the executive 
 phase , the quadriceps ( qua ) and ta muscles are maximally activated , after which activity 
 usually decreases in amplitude until the standing position is fully reached . in the full 
 standing position , the qua and ta muscles become inactive , but the hamstrings and soleus 
 remain active for stabilization while standing2 . patients with neurological diseases , such as stroke , have 
 difficulty performing the sts movement due to pain , spasticity , muscle weakness , sensory 
 problems , and balance deficits in the affected limb3 , 
 4 . in stroke patients , the muscle 
 recruitment patterns in the unaffected limb compensate for the muscle deficiencies of the 
 affected or paretic limb . this compensatory pattern is often created to achieve balance , and 
 indicates that the unaffected ta and qua muscles are recruited earlier than those in a 
 normal pattern2 . additionally , abdominal 
 muscles are activated to flex the trunk in the initial phase of the sts movement . however , 
 previous studies only focused on the activation timing patterns of the leg muscles in 
 individuals with stroke . to our knowledge , no previous studies have assessed the activation timing patterns ( e.g. , 
 reaction time ) of deep abdominal muscles , such as the internal oblique ( io ) and transverse 
 abdominis ( tra ) , during the sts movement in individuals with hemiparetic stroke . an 
 investigation to clarify the reaction time of the io and tra muscles in individuals with 
 hemiparetic stroke will provide important clinical information for understanding the 
 relationship between trunk and leg muscle activation during the sts movement . therefore , the 
 purpose of the present study was to determine the activation timing patterns ( muscular 
 reaction time ) of the abdominal and leg muscles during the sts movement in individuals with 
 chronic hemiparetic stroke . twenty adults with chronic hemiparetic stroke ( 10 males and 10 females ) participated in the 
 study . all 
 protocols used in the study were approved by the university of daejeon . before the study 
 began , its procedures , risks , and benefits were explained to all participants , who gave 
 their informed consent . the inclusion criteria were as follows : ( 1 ) more than 6 months after 
 the clinical diagnosis of ischemic or hemorrhagic hemiparetic stroke , ( 2 ) sufficient 
 cognitive function , as determined by a score of at least 24 out of 30 on the korean version 
 of the mini - mental state examination , and ( 3 ) ability to walk without the use of a walking 
 aid . the exclusion criteria included a history or current diagnosis of other neurological or 
 musculoskeletal diseases , hemineglect , visual lesions , and pain . among the 20 hemiplegic 
 patients the average 
 age , height , and weight of subjects were 57.3  7.6  years , 165.7  9.1  cm , and 66.5  
 13.9  kg , respectively . surface electromyography ( emg ) was used to measure muscular reaction time in the affected 
 and unaffected abdominal and leg muscles during the sts movement . were placed on the right and left tra / io , rectus femoris 
 ( rf ) , and ta muscles . to acquire emg data during the sts movement , the subjects were seated 
 on an armless and backless chair , and the chair seat was adjusted to the height of their 
 knee joints . the sts movement was performed barefoot , and the distance between each foot was 
 1015  cm depending on body size . the sts movement began with a straight trunk , 10 degrees of 
 ankle dorsiflexion , and 100105 degrees of knee flexion measured using a goniometer . all 
 subjects performed the initial posture to prevent impacting the timing of preparation and 
 execution of the sts movement . subjects moved at a self - selected velocity , as comfortable , 
 and performed the sts movement five times without using their hands2 . before each movement , they received a standard instruction : 
  when you detect the sound , please stand up at a comfortable pace . the acquired raw emg data were 
 processed a 60  hz notch filter to reduce the noise associated with electrical interference . the root mean - square emg amplitude for the tra / io , rf , and ta muscles was computed , and the 
 emg signal was full - wave rectified and filtered using a band - pass filter at 20500  hz . the 
 emg onset time of each muscle was identified to determine the muscular reaction time ( or the 
 time between the auditory stimulus and emg onset time of each muscle ) . the onset time was 
 determined mathematically by using matlab r2008a software ( mathworks inc . , natick , ma , usa ) 
 based on an algorithm that identified the point at which the mean amplitude of 50 
 consecutive samples reached three standard deviations from the mean of the baseline 
 amplitude recorded immediately before the movement stimulus5 . one - way anova with repeated measures was used to compare differences in the emg reaction 
 time between the affected and unaffected sides of the tra / io , rf , and ta muscles , as well as 
 between these muscles . the statistical 
 package for the social sciences for windows , version 12.0 ( spss , chicago , il , usa ) was used 
 for statistical analysis . during the sts movement , there were significant differences in the emg reaction time 
 between the affected and unaffected sides in individuals with chronic hemiparetic stroke 
 ( table 1table 1.comparison of the emg reaction time ( sec ) between the affected and unaffected 
 sides of the abdominal and leg musclesmuscleaffected sideunaffected sidetra / io1.16  0.290.99  0.31*rf1.30  0.141.11 tra / io : transverse abdominis / internal oblique ; 
 rf : rectus femoris ; ta : tibialis anterior . * significant differences ( p < 0.05 ) ) . according to the bonferroni post hoc test , there were also significant 
 differences in the emg reaction time between the tra / io and ta muscles ( p = 0.024 ) and the 
 rf and ta muscles ( p = 0.000 ) , although not between the tra / io and rf muscles ( p = 
 0.067 ) . tra / io : transverse abdominis / internal oblique ; 
 rf : rectus femoris ; ta : tibialis anterior . the purpose of this study was to investigate the activation timing patterns ( emg reaction 
 time ) of the bilateral tra / io , rf , and ta muscles during the sts movement in individuals 
 with chronic hemiparetic stroke . as anticipated , muscles on the unaffected side of the body 
 had faster reaction time than those on the affected side or paretic muscles . the faster 
 reaction times of unaffected muscles compensate for the weakness and delayed activation of 
 affected or paretic limb muscles . engardt and olsson found that the weight - bearing limb on 
 the unaffected side ( compared with that on the affected side ) achieved balance more quickly 
 during the sts movement in individuals with hemiparesis6 . interestingly , the emg reaction time of the tra / io muscles was 
 delayed relative to that of the rf and ta muscles during the sts movement in the present 
 study . investigated changes in the onset latency of the neck , leg , and trunk 
 muscles during the sts movement of healthy adults under six conditions ( the reference 
 condition , feet forward , knees first , flexion of the trunk , head supported , trunk 
 straight)7 . they found earlier 
 activation of the tra / io muscles compared with the ta muscle in the trunk straight 
 condition . the tra / io muscles are activated in the initial phase of the sts movement to flex 
 the trunk . early activation of the ta muscle in stroke patients , as shown in our study , may 
 facilitate the sts movement by compensating for the delayed activation of the tra / io 
 muscles . delayed activation of the tra / io muscles and early activation of muscles on the 
 unaffected side may cause patients with hemiparetic stroke to fall during the position 
 changes in the sts movement or the reverse movement8 , 
 9 . therefore , the current findings 
 provide information that may aid clinicians in the examination and management of affected 
 muscles for transfers in individuals with chronic hemiparetic stroke .
[ purpose ] the purpose of this study was to determine the activation timing patterns of 
 abdominal and leg muscles during the sit - to - stand movement in individuals with chronic 
 hemiparetic stroke . 
 [ subjects ] twenty adults with chronic hemiparetic stroke participated 
 in this study . [ methods ] subjects performed five sit - to - stand movements at a self - selected 
 velocity without using their hands . 
 surface electromyography was used to measure the 
 reaction time of the bilateral transverse abdominis / internal oblique , rectus femoris , and 
 tibialis anterior muscles during the sit - to - stand movement . 
 [ results ] there were 
 significant differences in the reaction time between the affected and unaffected sides of 
 the abdominal and leg muscles . 
 muscles on the unaffected side had faster reaction time 
 than those on the affected side . 
 activation of the transverse abdominis / internal oblique 
 muscles was delayed relative to activation of the tibialis anterior muscle during the 
 sit - to - stand movement . 
 [ conclusion ] our findings provide information that may aid 
 clinicians in the examination and management of paretic muscles for transfers in 
 individuals with chronic hemiparetic stroke .