foot orthoses is often used to correct the foot alignment for the treatment or prevention 
 of the injuries and for performance enhancement . clinically , patients who have foot as well 
 as knee and hip joint problems use foot orthoses to alleviate symptoms . in sports , foot 
 orthoses is sometimes prescribed for improving propulsion force transmission , absorbing 
 ground reaction force , and increasing or decreasing muscle activity level . the effect of 
 orthoses has been researched and recent systematic review regarding orthoses reported that 
 kinematic , shock attenuation , and neuromuscular paradigms are the main effects of 
 orthoses1 . specifically , kinematic 
 changes led by orthotic use have been reported in numerous studies . these studies described 
 that foot eversion angle and moment are reduced by orthoses2 , 3 . in recent years , the 
 number of studies reporting the effect of orthoses on neuromuscular paradigms has been 
 increasing . tibiails posterior ( tp ) , peroneus longus ( pl ) and flexor digitorum longus ( fdl ) produce a 
 torque toward plantar flexion , which functions as propulsion force during walking . in 
 addition to this , these muscles control foot pronation or supination and maintain the arches 
 of the foot4,5,6 . these functions can change 
 the foot rigidity and flexibility that adapt the mechanical demands on the foot . orthoses 
 are considered to compensate the function of the calf muscles and alter the muscle activity 
 pattern . several studies researched the effect of the orthoses on the tp , pl , and 
 gastrocnemius muscle7,8,9 . the results of those 
 studies showed that the muscle activity level of tp decreased , while the pl demonstrated 
 increased muscle activity level during walking . however , no study has researched the effect 
 of orthoses on the muscle activity level of the tp , pl , and fdl simultaneously . therefore , the purpose of this study was to determine the tp , fdl , and pl muscle activity 
 change resulting from orthotic insertion during the walking stance phase by using a 
 fine - wire and a surface electromyography ( emg ) . moreover , stance phase was divided into 
 three phases and muscle activity alteration of each muscle was analyzed in each phase . sixteen healthy male students ( age : 24  4.9  years , height : 168.4  5.1  cm , and weight : 
 60.9  7.8  kg ) participated in this study . participants who had injuries or surgical 
 intervention for the lower extremities in the past year or had a neurological problem were 
 excluded . the 
 ethical committee of waseda university approved this experiment in accordance with the 
 helsinki declaration ( ethics i d : 2015 - 010 ) . the fine - wire intramuscular electrodes were inserted into 
 the right tp muscle belly . during insertion , the tip of the needle and muscles were observed 
 by using an ultrasound system ( logiqe , ge , usa ) . , 
 the fine - wire intramuscular electrodes were also inserted into the right fdl . accurate 
 insertion into tp and fdl was checked with the muscle activity level during active foot 
 pronation , adduction , and plantar flexion for the tp and toe flexion for the fdl . if the emg 
 amplitude did not appear for each motion , it was defined as failed insertion and excluded 
 from the data . for the pl measurement , surface electrodes ( bluesensor n-00-s , mets co. , 
 japan ) were placed on the muscle belly of the right pl . the skin was rubbed with an abrasive 
 and alcohol to decrease skin impedance . a wireless emg telemeter system ( biolog dl-5000 , 
 s&me co. , japan ) gait tasks were performed under three conditions : ( 1 ) barefoot , ( 2 ) with footwear , and ( 3 ) 
 with footwear plus orthoses ( orthoses ) . all participants wore the same type of footwear 
 ( calcetto le3 , asics , japan ) and prefabricated orthoses ( athlete grip7 , winning one inc . prefabricated orthoses was employed in this study because it is more clinically 
 meaningful if easy and low cost prefabricated orthoses can change the muscle activity 
 pattern of the calf muscles . the upper layer of the prefabricated insole was made of poly 
 microsuede and the base material was ethyl vinyl acetate . the orthoses had three arch 
 supports for the medial longitudinal , lateral longitudinal , and transverse arches . a force plate ( kistler instrument ag , switzerland ) was placed on the middle of the walkway . the force plate and emg system were synchronized for simultaneous data collection . in each 
 condition , participants were instructed to walk at comfortable speed on the walkway and step 
 on the force plate with the right foot during gait trials . prior to measurement , sufficient 
 practice was allowed for the participants to become familiarized with the task . maximum voluntary 
 isometric contractions ( mvics ) for tp , pl , and fdl were measured after completing the gait 
 tasks in each condition . all mvic measurements were performed in a sitting position . over 
 five seconds of mvics were measured for each muscle . one - second periods of time , including 
 the maximum root mean square ( rms ) from the entire mvics data , were recorded and used as the 
 mvic values for each muscle . one stance phase per gait trial , which was defined from the force plate data , was selected 
 to analyze the muscle activity level of each muscle . when the vertical ground force exceeded 
 more than 10 n when the 
 vertical ground reaction force decreased less than 10 n , the time frame was defined as toe 
 off . in addition , the stance phase was further divided into contact , midstance , and 
 propulsion phases . the anterior - posterior force value from the force plate data was used to 
 define these phases ( fig . 1.definition of the phases based on the anterior - posterior force data during stance 
 phasethe contact phase was defined from the beginning of the stance phase to the 
 negative peak value . the midstance phase was defined from the negative peak value to 
 the zero value . the propulsion phase was defined from the zero value to the end of the 
 stance phase . ) . the contact phase was defined from heel contact to the negative peak value of the 
 anterior - posterior force . the midstance was defined from the negative peak value to the time 
 frame when the anterior - posterior force value reached zero . the propulsion phase extended 
 from zero value of the anterior - posterior force to toe off . the sampling rate of emg and the 
 force plate data was 1,000  hz . raw emg signals were analyzed with software ( bimutas - video , 
 kissei comtec co. , ltd . the emg data were rectified , high - pass filtered at 20  hz , 
 and low - pass filtered at 500  hz to remove motion artifacts . data from the gait tasks was 
 normalized with mvic values , using a rms value presenting as % mvic . the % mvic values from 
 one stance phase from each trial and task were averaged and used for statistical 
 analysis . definition of the phases based on the anterior - posterior force data during stance 
 phasethe contact phase was defined from the beginning of the stance phase to the 
 negative peak value . the midstance phase was defined from the negative peak value to 
 the zero value . the propulsion phase was defined from the zero value to the end of the 
 stance phase . in order to confirm the normal distribution of emg data , kolmogorov - smirnov test was 
 employed . because all data had a normal distribution , one - way repeated measure anovas was 
 conducted to compare the muscle activity level of each muscle in the three conditions during 
 each phase . if mauchley s test detected a violation of the assumption for sphericity , the 
 f - ratio was determined from the greenhouse - geisser epsilon . bonferroni 
 post hoc analysis was used if one - way repeated measures anovas detected significant 
 differences . because of the emg measurement failure for tp and fdl , the total number of participants 
 decreased to ten ( age : 25  5.0  years , height : 167.9  5.7  cm , weight : 61.5  7.8  kg ) . four 
 participants were excluded because of failed electrode insertion into the tp and two for 
 inaccurate placement in the fdl . the results of the % mvics for each muscle in each condition and phase are presented in 
 table 1table 1.% mvic comparison among three conditions in each phasemusclephaseconditionsbarefootfootwearorthosestptotal32.4  15.226.1  17.621.5  13.0contact24.6  20.923.3  20.619.7  14.2midstance*21.8  13.416.3  10.012.3  7.5propulsion*39.4  21.029.8  22.124.5  16.6**pltotal31.7  16.430.2  13.630.7  15.4contact14.4  6.316.7  8.014.5  8.4midstance22.3  15.922.3  13.821.2  13.6propulsion38.2  22.136.9  16.938.1  17.9fdltotal35.4  16.339.4  18.540.0  18.5contact19.7  11.517.5  7.513.7  5.5midstance26.3  19.523.3  12.720.4  14.0propulsion47.8  22.052.0  26.053.0  26.4tp : tibialis posterior , pl : peroneus longus , fdl : flexor digitorum longus . * one - way 
 repeated measures anova showed a significant difference ( p<0.05 ) . * * post hoc 
 analysis showed a significant difference between barefoot and orthoses ( p<0.05 ) . the tp showed a significant difference in the % mvic among three conditions 
 in midstance ( f(2,18)=4.66 , p=0.023 , es = 0.34 ) and propulsion 
 phase ( f(2,18)=3.64 , p=0.047 , es=0.29 ) . there was no significant 
 difference in the total stance and contact phase ( p>0.05 ) . bonferroni post hoc analysis 
 revealed that the orthoses condition showed significantly less % mvic value of tp compared 
 to barefoot condition in the propulsion phase alone ( p<0.036 ) . although a significant 
 difference was detected by one - way repeated measures anovas in midstance phase , post hoc 
 analysis did not show a significant difference among three conditions ( p>0.05 ) . the 
 average waveform of tp during the stance phase of walking is shown in fig . the % mvic of the fdl and pl showed that there were no statistical differences 
 between the three conditions in each phase ( p>0.05 ) ( table 1 ) . tp : tibialis posterior , pl : peroneus longus , fdl : flexor digitorum longus . * one - way 
 repeated measures anova showed a significant difference ( p<0.05 ) . * * post hoc 
 analysis showed a significant difference between barefoot and orthoses ( p<0.05 ) waveform of tp muscle activity in each condition during gait the current study is the first study that assessed the effect of the orthoses on emg 
 amplitude change of tp , pl , and fdl simultaneously during gait . the current study revealed 
 that the orthoses significantly reduced muscle activity level of tp in midstance and 
 propulsion phases during gait . in contrast , muscle activity level of the pl and fdl remained 
 the same for all conditions in each phase . the function of tp during gait is to prevent excessive foot 
 pronation during the contact phase and to increase the stiffness of foot during the 
 propulsion phase4 , 11 . in addition , the medial longitudinal arch is maintained by tp 
 during weight bearing activities12 . owing 
 to the relative distance between the axes of the subtalar joint and tp tendon , tp functions 
 as the strongest supinator muscle of the hindfoot5 , 
 13 . foot supination in the propulsion 
 phase is fundamental in increasing rigidity of the foot , a function known as midtarsal 
 locking mechanism that has an advantage of improving force transmission efficiency14 . considering this reduction of the muscle 
 activity level of tp in the propulsion phase with orthoses , the rearfoot might be 
 stabilized , and the function of tp , which increase the stiffness of the foot , can be 
 compensated by the orthoses . however , this result is inconsistent with a previous study . the 
 results of the previous study reported that a significant reduction in the rms amplitude of 
 tp was found during the contact phase of gait with prefabricated and customized foot 
 orthoses compared to shoes only condition7 . in the previous study , there were no significant differences in rms 
 amplitude during midstance / propulsion phase among the conditions . because the previous study 
 divided the contact phase into 2 phases ; contact phase and midstance / propulsion phase based 
 on the emg pattern , number of phases and hence the definition of phases are different from 
 the current study . these differences might have led to the inconsistent results . although 
 the phase where the reduction of tp muscle activity found was different , orthoses can 
 decrease the muscle activity level of tp while walking . contraction of pl during gait results in decreased foot rigidity 
 and increased energy dissipation rate4 . these mechanisms are antagonistic in function with tp and are important for shock 
 attenuation . the effect of orthoses on pl activity has been described by several 
 studies8 , 15 , 
 16 . two studies showed that significantly higher muscle activity level was 
 observed with orthoses8 , 15 . however , a previous study reported that muscle activity 
 level of the pl did not alter15 . 
 significant increase of the pl muscle activity level was considered due to laterally 
 unstable conditions caused by posting . in order to stabilize the subtalar joint against the 
 tilting this may influence the result that orthoses did not affect the muscle activity 
 level of pl . the muscle activity of fdl also showed no difference in the three conditions in all phases . because no previous study assessed the fdl activity change with orthoses , the results can not 
 be compared to those of other researches . in normal gait , the fdl contracts from midstance 
 to toe off during gait17 . similar to tp , 
 fdl isometrically contracts to maintain the height of the longitudinal arch of the foot 
 thereby improving the propulsion force transmission efficacy6 . although orthoses might be able to support medial and lateral 
 longitudinal arches as well as transverse arch , it might not be sufficient to support arches 
 and compensate for the activity of fdl . clinically , the reduction of the muscle activity level of tp might be beneficial for some 
 injuries . the traction force applied to the medial distal tibia is one of the mechanisms 
 resulting in medial tibial stress syndrome ( mtss ) . recent studies demonstrated that tp does 
 not have direct insertion into the symptomatic location of the medial distal tibia18 , the tp , fdl , and soleus muscles are 
 responsible for generating the traction force on the medial distal tibia via the crural 
 fascia19 . consequently , the reduction 
 of tp muscle activity with orthoses can be beneficial for patients who have mtss . the sample size decreased due 
 to technical errors in measuring the fine - wire emg . precise insertion of the electrodes into 
 the muscle belly of tp and fdl is technically challenging and must be carefully performed to 
 avoid damaging these structures10 . additionally , muscle contraction of the calf muscles pulls out the wires even when the tips 
 are properly inserted . more stable and accurate insertion technique should be considered for 
 future studies . in summary , the current study assessed the muscle activity change of the tp , fdl , and pl in 
 three conditions , barefoot , footwear , and orthoses , during gait . gait with orthoses 
 exhibited significantly less tp muscle activity than that in the barefoot condition . pl and fdl had no 
 significant muscle activity changes in the three conditions in all phases . reduction of tp 
 muscle activity might be beneficial for patients who have excessive tp contraction related 
 injuries , such as mtss . further research is required to clarify the clinical effect of 
 orthoses in patients with mtss .
[ purpose ] the purpose of the study was to assess the muscle activity change of the 
 tibialis posterior , flexor digitorum longus , and peroneus longus during gait with 
 orthoses . 
 [ subjects and methods ] sixteen healthy males participated in this study . 
 activity of each muscle was measured by using fine - wire and surface electromyography . 
 gait 
 task was performed by the participants barefoot , with footwear and with orthoses . 
 the 
 electromyography data from a stance phase of each gait trial were used for analysis . 
 the 
 stance phase was divided into contact , midstance , and propulsion phases . 
 the data from ten 
 participants were extracted for final analysis , as electromyography measurements were 
 unsuccessful for the other six . 
 [ results ] the results demonstrated that orthoses 
 significantly reduced the tibialis posterior muscle activity in the propulsion phase 
 compared to that in the barefoot condition . 
 although there was a significant difference in 
 the midstance phase , post hoc analysis did not indicate significant differences among the 
 phases . 
 no significant electromyography amplitude change was detected in flexor digitorum 
 longus and peroneus longus . [ 
 conclusion ] orthothes reduced the tibialis posterior activity 
 level during gait . this result may be beneficial for patients with injuries related to 
 excessive activity of tibialis posterior .