the feet support the body s weight and play the role of levers when an individual is 
 performing work1 .
the body weight normally 
 falls on the center of the foot , and balance is maintained by the muscle activity of the 
 foot2 .
if the foot becomes diseased or 
 deformed , the foot adapts to perform its functions under the conditions of disease or 
 deformity3 .
weakening of the gluteus 
 maximus is a cause of foot deformities that induces the hip joint to internally rotate and 
 the foot to pronate4 . within the sole are the lateral longitudinal arch , the medial longitudinal arch ( mla ) , and 
 the transverse arch5 .
the mla is 
 controlled with the assistance of bone structures , ligaments , and the extrinsic and 
 intrinsic muscles of the foot6 . among 
 these muscles ,
the abductor hallucis ( abdh ) has been reported to control excessive foot 
 pronation7 .
the abdh has also been 
 reported to be important for stabilization of the mla and indispensable for toe - off during 
 gait8 .
although there are many exercises 
 for strengthening the abdh , the toe - spread ( ts ) exercise has been shown to achieve higher 
 levels of abdh muscle activity in when compared to the short - foot exercise ; however , the 
 difference was not statistically significant when both exercises were performed in the 
 sitting position9 . among selective gluteus maximus strengthening exercises ,
the one performed by slightly 
 lifting the knee while maintaining the hip joint in external rotation and the knee joint at 
 90 flexion while in the prone position was reported to be the most effective10 .
although there is literature indicating that the plantar arches and the iliacus muscle 
 affect each other , studies identifying the effect are rare . therefore , subjects were divided 
 into two exercise groups in this study : one group strengthened only the abductor halluces 
 ( which directly affects the plantar arches ) , while the other group strengthened both the 
 abductor hallucis and the gluteus maximus .
the lower - extremity muscle activity levels of the 
 two groups during the gait were compared in order to propose the most effective method to 
 strengthen the mla .
a total of 18 healthy adults were selected after excluding subjects with a history of 
 arthritis , foot or ankle surgery , diabetes , foot abnormalities , or present cuts to the lower 
 extremities .
the study subjects were selected from among those who had foot pronation 
 ( > 10  mm ) based on navicular drop ( nd ) tests11 .
the participants were provided with a written informed consent 
 form in accordance with the ethical standards of the declaration of helsinki .
the mean age , 
 height , and weight of the study subjects who strengthened both the gluteus maximus and the 
 abdh simultaneously were 21.89  1.69  years , 163  7.26  cm , and 57.56  14.33  kg , 
 respectively .
the mean age , height , and weight of the study subjects who strengthened only 
 the abdh were 22.3  2.06  years , 164.7  8.53  cm , and 62.22  12.04  kg , respectively .
the study subjects performed their respective exercises three times per week in the 
 laboratory and two times per week at home for four weeks .
the subjects who performed both 
 gluteus maximus and ts exercises did three sets of 20 repetitions of exercises that 
 selectively strengthened the gluteus maximus in the prone position and 100 repetitions of ts 
 exercises in the sitting position while maintaining both the hip joints and the knee joints 
 at 90 flexion .
, az , usa ) was used 
 to record and process the emg signals from the gluteus maximus , the vastus medialis , the 
 tibialis anterior , and the abdh . for the gluteus maximus
, the emg electrodes were placed at 
 the midpoint of the sacral vertebrae and the greater trochanter .
emg electrodes for the 
 vastus medialis were placed four - fifths of the way aling a line from the asis and the joint 
 space in front of the anterior border of the medial ligament , while electrodes for the 
 tibialis anterior were placed 1/3 on the line between the tip of the fibula and the tip of 
 the medial malleolus .
electrodes for the abductor hallucis were placed approximately 12  cm 
 posterior to the navicular tuberosity .
the 
 signals were extracted at a rate of 1,500  hz and noises in raw emg signals were removed 
 through 20500  hz bandpass filters and 60  hz notch filters .
the muscles emg signals were 
 processed into root mean square ( rms ) , and the emg data were analyzed using the myoresearch 
 master 1.07 xp program ( noraxon inc .
after determining the three most stable gait 
 cycles , we found average values of heel - strike , foot - flat , toe - off muscle activity .
paired t - tests were used to measure changes in 
 lower extremity pre- and post - exercise emg measurements in each group .
foot switches were 
 attached to the center of the heel , below the first and fifth metatarsals , before walking in 
 order to divide the gait cycle into the heel - strike , foot - flat , and toe - off phases ; lower 
 extremity emg was performed in each individual phase .
the nd was 5.53  1.58 in the group that performed both gluteus maximus and ts exercises 
 and 7.632.27 in the group that performed only ts exercises .
therefore , the nd in the group 
 that performed both gluteus maximus and ts exercises decreased significantly more than the 
 group that performed only ts exercises ( table 
 1table 1.comparison of nd test results between the group that performed both gluteus 
 maximus ( gm ) and ts exercises and the group that performed only ts exercises 
 ( n=18)gm exercises and ts exercisesmean ( sd)ts exercises onlymean ( sd)pre nd ( mm)11.9 ( 2)11.4 ( 1.4)4 weeks nd ( mm)5.5 ( 1.6)7.6 ( 2.3)gm : gluteus maximus , ts : toe spread , nd : navicular drop , sd : standard deviation .
the % mvc values of the gluteus maximus ( 11.97  7.26% ) and the vastus 
 medialis ( 13.2 5 8.38% ) were significantly increased during heel - strike , and the % mvc 
 value of the abdh ( 13.1  13.47% ) was significantly increased during toe - off in the group 
 that performed both gluteus maximus and ts exercises ( table 2table 2.%mvc values before and after exercises ( n=9)musclegm exercises and ts exercisests exercises onlypre mean ( sd)4 weeks mean ( sd)pre mean ( sd)4 weeks mean ( sd)heel strikegm21.5 ( 11.8)33.4 ( 11.5)17.7 ( 12.7)22.1 ( 14.4)vmo27.1 ( 11.2)40.3 ( 9.7)21.3 ( 16.2)26.2 ( 7.4)ta29.4 ( 10.8)29.4 ( 9.8)21.9 ( 12.4)28.4 ( 8.8)abdh16.2 ( 6.8)17 ( 9.5)18.3 ( 8.8)20.5 ( 6)foot flatgm17.7 ( 13.3)18.2 ( 10.7)10.8 ( 6.4)12.8 ( 4.9)vmo26.8 ( 18.5)22.2 ( 7.8)13 ( 4.6)15.9 ( 4.2)ta15.1 ( 8.9)17.5 ( 9.5)16.1 ( 13.1)16.8 ( 10.6)abdh15.9 ( 9.5)22.3 ( 9.9)18.6 ( 10.2)22.3 ( 7)toe offgm11.5 ( 13.3)14 ( 10.2)10 ( 8.7)16.3 ( 12.1)vmo12 ( 8.4)14.4 ( 5.5)12.9 ( 13.2)17.9 ( 14.2)ta16.9 ( 7.7)15.2 ( 3.4)15.8 ( 16.1)11 ( 5)abdh28.5 ( 11.1)41.6 ( 10.3)28 ( 14.4)39.6 ( 11.4)gm : gluteus maximus , vmo : vastus medialis , abdh : abductor hallucis , ts : toe spread , 
 sd : standard deviation , mvc : maximal voluntary contractionp<0.05 ) . in the group that performed only ts exercises ,
the % mvc value for the abdh 
 ( 11.58  13.46% ) was significantly increased during toe - off ( table 2 ) . after four weeks
, there was no significant difference 
 between combined gluteus maximus and ts exercise and only ts exercise ( table 3table 3.comparison of % mvc values between the group that performed both gluteus maximus 
 and ts exercises and the group that performed only ts exercises after 4 weeks 
 ( n=18)musclegm exercises and ts exercisesmean ( sd)ts exercises onlymean ( sd)heel strikegm33.4 ( 11.5)22.1 ( 14.4)vmo40.3 ( 9.7)26.2 ( 7.4)ta29.4 ( 9.8)28.4 ( 8.8)abdh17 ( 9.5)20.5 ( 6)foot flatgm18.2 ( 10.7)12.8 ( 4.9)vmo22.2 ( 7.8)15.9 ( 4.2)ta17.5 ( 9.5)16.8 ( 10.6)abdh22.3 ( 9.9)22.3 ( 7)toe offgm14 ( 10.2)16.3 ( 12.1)vmo14.4 ( 5.5)17.9 ( 14.2)ta15.2 ( 3.4)11 ( 5)abdh41.6 ( 10.3)39.6 ( 11.4)gm : gluteus maximus , vmo : vastus medialis , abdh : abductor hallucis , ts : toe spread , 
 sd : standard deviation , mvc : maximal voluntary contraction ) .
gm : gluteus maximus , ts : toe spread , nd : navicular drop , sd : standard deviation .
p<0.05 gm : gluteus maximus , vmo : vastus medialis , abdh : abductor hallucis , ts : toe spread , 
 sd : standard deviation , mvc : maximal voluntary contraction gm : gluteus maximus , vmo : vastus medialis , abdh : abductor hallucis , ts : toe spread , 
 sd : standard deviation , mvc : maximal voluntary contraction
in a study that used insoles for mla correction , the researchers stated that this was not 
 recommendable because inconvenience in the lower extremity related to physical stress was 
 not improved13 .
osullivan reported that 
 when subjects with pronation received mla support with tape and had their standing foot 
 pressure measured the results indicated that pressure was decreased in the front and middle 
 parts of the feet14 .
, taping was applied to five subjects with pronated 
 feet and the researchers identified that the height of the mla increased and excessive 
 muscle use decreased compared to levels measured without taping15 ; however , in relation to muscle activity , the researchers 
 advised that they could not know how taping increased the height of the arch of the foot . 

given these results , short - term effects can be expected from using aids for maintaining or 
 increasing the height of the mla , but long - term effects can not be expected ; also , no effect 
 can be expected when no aid is used .
many studies have been conducted on various exercise 
 methods using muscles directly connected to the mla to supplement such shortcomings .
since 
 many studies set the criterion for pronated feet as 10  mm or greater nd16 , the subjects in the present study were selected based on 
 that criterion .
subjects were randomly divided with one group of nine subjects performing 
 both gluteus maximus and ts exercises three times per week for four weeks , while another 
 group of nine subjects performed only ts exercises .
feet with smaller values in the height 
 of the nd were less pronated , and the group that added gluteus maximus strengthening 
 exercises showed decreased values in the height of the nd compared to the group that 
 performed only ts exercises .
the gluteus maximus is an external rotation muscle of the hip 
 joint , and it is proposed to have externally rotated the alignment of the lower extremity to 
 reduce the foot pronation in these patients . in normal gait , it is said that the muscle activity of the gluteus muscle group , the 
 quadriceps , and the tibialis anterior increases during heel - strike and that the muscle 
 activity of the calf muscle and the intrinsic foot muscles increases during toe - off5 .
the group that performed both gluteus 
 maximus and ts exercises showed significantly higher muscle activity of the gluteus maximus 
 and the vastus medialis during heel - strike and high muscle activity of the abdh during 
 toe - off , while the group that performed only ts exercises showed only increased muscle 
 activity of the abdh during toe - off . when compared to the muscle activity during normal 
 gaits reported by neumann5 ,
the group that 
 added gluteus maximus strengthening exercises showed muscle activity much closer to that of 
 normal gaits . given the changes in the height of the nd and the changes in the emg of the 
 lower extremity during gait , strengthening both the ts and the gluteus maximus is considered 
 more effective for correction of the mla than performing only ts exercises .
first , in determining the criteria for subjects 
 normal feet , nd tests were not sufficient , and the number of subjects was not large enough 
 for generalization . in addition , although the abdh is the most superficial muscle of the 
 foot , it is a small muscle and is susceptible to cross talk from other intrinsic and 
 extrinsic muscles .
another limitation is the fact that changes over time were not assessed 
 after the four - week exercise intervention period was over .
future studies should consider 
 these limitations and conduct motion analyses and radioactive examinations to study diverse 
 methods of mla correction .
 [ purpose ] the purpose of the present study is to examine the effects of abductor hallucis 
 and gluteus maximus strengthening exercises on pronated feet . 
 [ subjects and methods ] the 
 present study was conducted with 18 adults without no history of surgery on the foot or 
 ankle . 
 one group performed both gluteus maximus strengthening exercises and abductor 
 hallucis strengthening exercises , while the other group performed only abductor hallucis 
 strengthening exercises five times per week for four weeks . 
 [ results ] the group that 
 performed both gluteus maximus and abductor hallucis strengthening exercises showed 
 smaller values in the height of navicular drop than the group that performed only abductor 
 hallucis strengthening exercises . 
 the muscle activity of the gluteus maximus and the 
 vastus medialis increased during heel - strike in the group that added gluteus maximus 
 exercises , and the muscle activity of the abductor hallucis significantly increased in 
 both groups . 
 [ conclusion ] given the results of the present study , it can be suggested that 
 strengthening the gluteus maximus while also performing exercises to correct the pronated 
 foot is an effective method for achieving normal gait . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION