shoes provide protection from the environment and functional assistance , are fashionable , 
 and enable adjustments for deformed feet and treatment for musculoskeletal injuries . 

although the origin of shoe wearing by humans is not known , they have been worn for the 
 convenience of walking and protection of the feet for long1 .
the material and shape of shoes have evolved in modern times to 
 suit the purpose of wearing shoes , but the main purpose of wearing shoes in the past was for 
 protection2 .
shoes can be easily changed 
 to alter the load of the human body , since the material , shape , and heel height affect 
 mobility and stability3 .
body movements , such as walking , are facilitated by the movement of the skeleton through 
 muscle contraction , and the muscle activity can be analyzed using electromyography ( emg ) , 
 which is a method of obtaining muscle information .
it is essential to functionally analyze emg data during various activities to understand 
 the effects of changes to muscle length4 . 

functional analysis of emg data demonstrates the relationships between movements 
 and time about movement of the body , emg and power production , and emg and muscle 
 fatigue5 .
a previous study analyzed static balance and muscle activity of the lower extremities in 
 young adults depending on the period of high - heeled shoe wearing and reported that the 
 rectus femoris ( rf ) and tibia anterior ( ta ) muscles did not appear to show significant 
 differences6 .
another study related to 
 kinetic differences between normal running shoes and spring - loaded running shoes reported 
 that the rf activity on emg was higher with the latter shoes7 .
the effect of unstable sandals on instability during gait in 
 healthy adults has been previously examined , and unstable shoes showed significant 
 differences in the ankle joint and increased peroneal activity during pre - swing , while 
 stable shoes increased medial gastrocnemius ( gm ) and decreased ta activities during 
 mid - stance .
the stable shoes changed gait and muscle activity related to braking and 
 progression and a softer and less stable forefoot increased evertor action during toe - off in 
 the frontal plane .
although the use of and aesthetic interest in the shoes of young women have increased in 
 modern society , previous studies demonstrated that emg activity and muscle fatigue are 
 related to high - heeled shoes and functional running shoes .
thus , the purpose of this study 
 was to analyze the effects of muscle activity on walking according to various shoes 
 frequently worn by young women .
the 15 participants were students in their 20s at n university , cheonan - si , republic of 
 korea . they had not had any musculoskeletal or neurological injuries , an athletic career , or 

they were provided detailed information on this study and 
 voluntarily provided written informed consent before the experiment .
this study was approved 
 by the institutional review board of namseoul university . a body composition analyzer ( inbody720 ; biospace o. ltd . ,
seoul , republic of korea ) was 
 used to determine the general characteristics of the subjects . a treadmill
( sns care m-400 m ; 
 sns care co. , ltd . , goyang , republic of korea ) was used for walking , and a free emg system 
 ( free emg ; bts inc . ,
milan , italy ) was used to measure the muscle activity of the lower 
 extremities while the subjects wore different types of shoes and walked on the 
 treadmill .
the participants 
 were divided into three groups according to the types of shoes they wore : a converse 
 sneakers group , a rain boots group , and a combat boots group .
surface electrodes ( 3  m red 
 dot 2570 ; 3  m center , st .
paul minnesota , usa ) were cleaned using alcohol - soaked cotton to 
 minimize errors due to skin impedance and used to measure emg activity10 .
they were attached to the muscles at maximal static 
 contraction to avoid errors that could affect the results .
six muscles , namely , the rf , 
 vastus medialis ( vm ) , semimembranosus ( sm ) , ta , peroneus longus ( pl ) , and gm , were examined . 

the rf is halfway between the patella and iliac spine on the front of the femur11 .
the vm is 50 degrees on the femoral 
 longitudinal axis and 5  cm above the superomedial patella12 .
the sm is 3  cm from the lateral border of the thigh and halfway 
 along the distance from the gluteal fold to behind the knee13 .
the pl is 25% between the fibula head and lateral malleolus14 . finally , the gm is 35% medially from the distal midline of the 
 knee joint and 2  cm above this joint . in all cases ,
the root mean square of emg data was determined 
 during walking , and the maximal voluntary muscle contraction was used to eliminate data 
 errors due to personal characteristics .
the emg signal was normalized , the sampling rate was 
 1,000  hz , and the band - pass filter was 20500  hz .
the participants walked at a speed of 4  km / h15 for 30  min and rested 24  h between wearing each shoe to 
 avoid fatigue effects16 .
statistical analysis was performed using spss version 18.0 for windows ( spss , inc . , 

one - way analysis of variance ( anova ) was 
 used to compare differences in muscle activity among shoe groups .
if significant differences 
 were found , the scheffe test was used for post - hoc analysis .
the study participants were healthy women in their early 20s ( table 1table 1.general characteristics of the participantssubjectsage ( years)height ( cm)weight ( kg)m  sd20.5  0.5159.0  4.951.4  7.2 m  sd : means  standard deviation ) and wore three types of shoes during the test : converse sneakers , rain boots , 
 and combat boots ( table 2table 2.general characteristics of the shoesshoesweight ( kg)shaft height ( cm)converse sneakers0.7117rain boots0.8017combat boots1.0017 ) .
m  sd : means  standard deviation differences in the interaction effect of group and time were not noted in the one - way anova 
 used to compare muscle activity among the three groups .
however , the main effect of group showed significant differences for 
 the vm ( table 3table 3.comparison of pre- and post - test muscle electromyography signals according to the 
 groups ( mv)variablegrouppre - testpost - testm  sdm  sdrfconverse sneakers14.5  9.714.4  7.9rain boots11.2  4.116.9  10.7combat boots12.1  4.514.2  13.1vmconverse sneakers28.9  12.332.4  15.3rain boots42.3  18.042.5  21.5combat boots50.2  32.052.0  24.0smconverse sneakers213.8  125.8220.7  116.8rain boots169.0  70.4224.4  134.8combat boots197.7  112.1215.4  89.7taconverse sneakers35.6  12.333.0  12.1rain boots38.4  18.933.9  11.2combat boots32.6  16.331.8  14.0plconverse sneakers37.2  12.432.1 
14.3rain boots36.2  18.338.4  17.7combat boots36.1  15.236.5  17.6gmconverse sneakers52.7  26.849.8  14.8rain boots43.3  23.145.0  22.4combat boots52.4  29.348.8  27.2*p
< 0.05 ; : significant differences between groups ; : 
 converse sneakers ; : rain boots ; : combat boots ; rf : rectus 
 femoris , vm : vastus medialis ; sm : semimembranosus ; ta : tibialis anterior ; pl : peroneus 
 longus ; gm : medial head of the gastrocnemius ; m  sd : mean  standard deviation ) .
further , in the results of multiple comparisons of vm , the rain boots group 
 showed significantly higher vm activity than the converse sneakers group , and the combat 
 boots group showed significantly higher vm activity than the rain boots group .
* p < 0.05 ; : significant differences between groups ; : 
 converse sneakers ; : rain boots ; : combat boots ; rf : rectus 
 femoris , vm : vastus medialis ; sm : semimembranosus ; ta : tibialis anterior ; pl : peroneus 
 longus ; gm : medial head of the gastrocnemius ; m  sd : mean  standard deviation
shoes that do not fit the feet change the foot bones and hamper gait posture , in addition 
 to causing various adverse conditions , including calluses , corns , neuroma , hallux valgus , 
 toe deformities , ankle sprains , achilles tendinitis , and knee and back pain . in modern 
 society , women tend to disregard their own physical characteristics while choosing 
 shoes17 .
the present study was conducted to analyze the muscle activity of the lower extremities 
 depending on shoe type during walking among individuals in their 20s .
the results showed 
 significant differences in the interaction effects of group and time or the main effect of 
 time .
vm activity 
 differed significantly among the three groups : the activity in the rain boots group was 
 significantly higher than that in the converse sneakers group , and that in the combat boots 
 group was significantly higher than the activity in the rain boots group .
a previous study found that the impulsive force increased rapidly at heel - strike , because 
 it made an angle like an edge , and the knee joint was unable to extend adequately at 
 heel - strike7 .
another study that 
 analyzed the effect of shoe sole form on knee and ankle joint muscle activity reported that 
 vm activity was higher with high - heeled shoes and house shoes than with shoes that had a 
 curved outsole . further , because high - heeled shoes elevate the anterior foot , the ta 
 activity increased , gm activity decreased and led to increased knee extension at 
 heel - strike , and vm activity increased10 . 

a previous study analyzed the effects of the form of the outsole on lower leg emg signals 
 during gait .
when shoes with a curved outsole were used , the ankle joint showed increased 
 dorsiflexion during heel - strike and the dorsiflexion state was maintained in the stance 
 phase , while joint motion was decreased in the sagittal plane .
the curved outsole reduced 
 the load on the joint , as dorsiflexion agonist activity increased and dorsiflexion 
 antagonist activity decreased .
in addition , as ankle push - off and push - off movement were 
 delayed , unnecessary movement was avoided and the center of gravity was maintained during 
 gait . for these reasons ,
the vm activity was increased when shoes with a curved outsole were 
 used as compared to other shoes , since muscle activity was balanced on a supporting base . 

similar effects were noted with shoes that had an insole of the elevator shoe type18 .
the vm activity emphasized the function 
 of contracture related to the stability of the medial knee joint at the end of 
 extension19 ; when foot orthotic 
 quadriceps and gluteus medius emg signals were tested during a selected exercise , the vm 
 activity was found to be higher in the three - orthotic condition ( 7 medial rearfoot post , 4 
 lateral rearfoot post , and neutral rearfoot post ) than the no - orthotic condition .
another study reported that the vm 
 activity induced mechanical changes in the patellofemoral joint to facilitate the vm 
 activity during an orthotic intervention20 .
further , the angle of the last rotation of tibialis anterior 
 reportedly increases vm activity21 .
the results of the present study showed significant differences in vm activity depending on 
 the shoe type : the rain boots group had significantly higher vm activity than the converse 
 sneakers group , and the combat boots group had significantly higher activity than the rain 
 boots group . in the groups of increasing vm activity ,
knee extension increased because of 
 gait to leaning the anterior part ; further , the angle of tibial rotation and mechanics of 
 the patellofemoral joint changed to prevent lateral tracking and improve medial stability 
 with the increase in knee extension .
vm activity was considered to increase for efficient 
 walking , as this reduced the load on the joint , prevented unnecessary movements , and 
 balanced the center of gravity and support base . in conclusion , this study analyzed the effects of various shoe types during treadmill 
 walking on lower extremity muscle activity determined using emg in healthy young women .
the 
 results of one - way anova that compared emg signals among three shoe type groups showed no 
 significant difference in the interaction effect of group and time .
the results of multiple comparison of vm activity showed 
 significant differences : the rain boots group had significantly higher than the converse 
 sneakers group , and the combat boots group had significantly higher activity than the rain 
 boots group .
the vm activity was higher in the former two groups and enabled more effective 
 walking and better balance , because shoe type affects tibial rotation depending on knee 
 joint movement .
 [ purpose ] the purpose of this study was to analyze the effects of different shoe types on 
 lower extremity muscle activity in healthy young women by using electromyography . 
 [ subjects and methods ] fifteen healthy young women in their 20s were included in this 
 single - group repeated measures study . 
 the subjects were divided into three groups : 
 converse sneakers , rain boots , and combat boots . 
 the subjects walked on a treadmill at 
 4  km / h for 30  min , during which six muscles were examined using electromyography : the 
 rectus femoris , vastus medialis , semimembranosus , tibialis anterior , peroneus longus , and 
 medial head of the gastrocnemius . between switching shoe types , 
 a 24-h rest period was 
 instated to prevent the fatigue effect from treadmill walking . 
 [ results ] one - way analysis 
 of variance used to compare electromyography results among the three groups showed that 
 the main effect of group differed significantly for the vastus medialis . 
 vastus medialis 
 activity was higher in the rain boots group than the converse sneakers group , and it was 
 higher in the combat boots group than rain boots group . 
 [ conclusion ] shoe type affects 
 lower extremity muscle activity . our findings may help individuals choose the ideal shoes 
 for daily walking . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION