the feet receive some stimulation whenever humans walk1 , and we wear shoes to protect our feet , to absorb impact , and to 
 make human gait natural and comfortable2 . 

therefore , one guideline for the selection of shoes could be the efficiency of protection 
 from injuries and impacts3 , 4 .
however , most women consider design and fashion rather than 
 health and comfort as their top priorities when selecting shoes5 .
according to a survey on the wearing of shoes , 3769% of 
 women prefer to wear a high heel , but high - heeled shoes with an excessive focus on fashion 
 can induce musculoskeletal diseases such as plantar fasciitis , hallux valgus , ankle sprain , 
 and chronic lower back pain6,7,8,9,10,11 .
high heels may contribute to changes in the muscles around the 
 knee joint12 ; they could also increase 
 the risks of developing of patellofemoral pain ( pfp ) and knee osteoarthritis , by increasing 
 the joint reaction force via the higher knee extensor moments and knee flexion angles 
 induced13 , 14 .
furthermore , wearing high heels may increase the risks of back 
 pain and strain injury , as heel height is associated with local muscle activity , 
 fatigue8 , 15 , and over - loading of the muscles6 .
the musculoskeletal disorders and deformities described above are related to increased 
 forefoot pressure16 , 17 .
cong et al.10 
 reported that peak pressure and shear stress shifted from the lateral to the medial forefoot 
 as the heel height increased from 30 to 70  mm .
speksnijder et al.16 found that walking in high - heeled shoes ( 5.91 cm ) 
 increased the peak pressure on the medial forefoot relative to low - heeled ( 1.95 cm ) shoes . 

additionally , song et al.18 observed that 
 the peak pressures on the forefoot were 4.54.8 times and 2.32.5 times greater than those 
 on the middle foot and rear foot when women wore high heels and kill heels .
therefore , a 
 study on the distribution of foot pressure is necessary to predict the deformity associated 
 with the wearing of high heels .
additionally , wearing high - heeled shoes has been associated with increased potential for 
 slips and falls , because the consequent changes in local sensation around the ankle may 
 affect women 's postural balance19,20,21,22 . therefore , some studies have suggested 
 that the best heel height for maintaining balance is from 3 to 5  cm22,23,24 .
if the heel height were greater than 5 cm , women would 
 tire easily because it would be more difficult for the feet to balance the body weight20 .
lee et al.2 reported that heel thickness and height are related to walking 
 stability , and oh et al.25 found that 
 high heels may be disadvantageous for the maintenance of balance . according to previous studies , heel height may have a direct impact on musculoskeletal 
 disorders and body stability .
many research have studied the effects of high heels , but the 
 effect of wearing flat shoes has not been studied . recently ,
flat shoes have been recognized 
 as conferring feminine beauty and lauded as the most favorable type of shoe for women 
 because of the comfortable , classical elegance that they provide26 .
therefore , clinical studies are required to study the 
 effect of wearing flat shoes as well .
it is also necessary to verify whether wearing high 
 heels in the short term affects the body .
the purpose of this study was to determine the most appropriate heel height by measuring 
 the changes in cop and foot pressure produced by walking for 1 hour in shoes with various 
 heel heights : flat ( 0.5 cm ) , middle - heeled ( 4 cm ) , and high - heeled ( 9 cm ) shoes .
* m : mean , sd : standard deviation fifteen healthy women participated in this experiment after providing their informed 
 consent .
subjects were excluded if they had experienced foot pain within the previous 6 
 months , had any history of previous foot surgery , or had congenital or acquired foot 
 deformities , blisters or corn on the feet , or problems with the feet and the legs at the 
 time of the study16 .
we also excluded 
 women who had worn high - heeled shoes ( higher than 7 cm ) more than 3 times per week for 2 
 years to minimize the differences in the levels of habituation .
the mean age of the participants was 20.9  years , their mean height was 161  cm , and their 
 mean foot length was 234.3  mm ( table 1 ) .
we used the fdm - s ( zebris medical gmbh , germany ) to measure the plantar foot pressure and 
 displacement of cop of all subjects .
this system uses a pressure board , with 2,560 embedded 
 sensors and the pressure is recorded by each sensor .
we chose only 3 different heel heights , 0.5 cm , 4 cm , and 9 cm .
we used a 
 single - subject design in which each subject wore all 3 types of shoe in a random order in 
 order to minimize the effects caused by cumulative muscle fatigue .
the walking route included an uphill road , a downhill road , a flat section , and 
 stairs to faithfully simulate the types of walking that people perform daily life . in order 
 to control the walking speed
this was set according to 
 the scientific results of 2 different studies that determined the average stride length and 
 walking pace of typical women in korea to be 0.66 m / step and 1.17 m / s , respectively20 .
we measured the foot pressure after 
 having each subject walk barefoot for 10 to 20 seconds in order to minimize the resistance . 

we drew an outline of the foot on the force plate in order to control the foot position and 
 directed the subjects to stand above the outline and look at a line in front of them at 
 approximately eye level .
the paired t - tests 
 was used to compare the results obtained before and after walking for 1 hour wearing each 
 type of shoe .
analysis of variance ( anova ) with the posthoc scheffe test was used to 
 identify the differences in the changes among the heel heights .
the statistical significance 
 level was 0.05 , and spss 18.0 was used for the analysis .
the distributions of foot pressure of both feet shifted from the forefoot to the hindfoot 
 after walking for 1 hour in flat ( 0.5  cm ) shoes , and the difference between the 
 distributions before and after walking was significant ( p<0.05 ) . for high - heeled shoes 
 ( 9  cm ) ,
the distributions of pressure in both feet shifted from the hindfoot to the forefoot 
 after walking for 1 hour , and the difference between the distributions before and after 
 walking was significant ( p<0.05 ) .
however , there was no significant difference between 
 the pressure distributions before and after walking in either foot when the subjects walked 
 wearing 4-cm heels ( p>0.05 ) ( table 2 )
. the cop was significantly displaced ( p<0.05 ) after walking while wearing either flat 
 shoes ( 0.5  cm ) or high heels ( 9  cm ) , but not after walking while wearing middle height heels 
 ( 4  cm ) ( table 3 ) .
we investigated the relationships of the distribution of foot pressure and the displacement 
 of cop with the height of the shoe heel worn by women , and found that both the distribution 
 of foot pressure and the displacement of cop altered after walking for 1 hour wearing either 
 flat ( 0.5  cm ) or high - heeled ( 9  cm ) shoes .
the distributions of foot pressure shifted toward 
 the hindfoot and the forefoot after walking in flat ( 0.5  cm ) and high - heeled ( 9  cm ) shoes , 
 respectively , for 1 hour . the distribution of foot pressure moved from the hindfoot to the 
 forefoot as the heel height increased .
consistent with our findings , hong et al.28 reported that increasing the heel height 
 shifted the distribution of foot pressure toward the forefoot and altered the biomechanics . 

cong et al.10 and speksnijder et al.16 suggested that 7-cm- and 6-cm - heeled shoes 
 increased the peak pressure in the medial forefoot .
in addition , song et al.18 reported that the peak pressures of the 
 forefoot were 4.54.8 times and 2.32.5 times greater than those of the middle foot and rear 
 foot , respectively , in subjects wearing high heels or kill heels .
one possible reason for 
 this change in the distribution of foot pressure may be related to the walking pattern . 
 because of the heel height , walking while wearing high heels involves more contact of the 
 forefoot than of the hindfoot , and walking in flat shoes involves more contact of the 
 hindfoot than of the forefoot . in running ,
the running pattern is more important than 
 whether the subject is barefoot or shod .
in contrast , the use of a forefoot heel - strike pattern in barefoot 
 running reduces the impact load and stride length30 . the walking pattern
while wearing flat shoes may resemble the 
 barefoot running pattern in that the heel strike pattern is maintained despite the change in 
 footwear . according to hatala et al.31 , 
 factors such as running speed , training level , substrate mechanical properties , running 
 distance , and running frequency , influence the selection of foot strike patterns .
we suggest 
 heel height is an additional factor influencing the selection of foot strike pattern .
the 
 second possible reason for the observed changes may be the over use of specific muscles . 

high heels induce greater plantar flexion , whereas flat heels induced greater dorsiflexion 
 of the ankle .
this means that compared to high - heeled shoes , women wearing flat shoes use 
 specific muscles more heavily than others and shift their bodies anteriorly .
the overuse of 
 specific muscles during walking may also cause musculoskeletal disorders . in our study , wearing either flat or high - heeled shoes altered the distribution of foot 
 pressure .
the body was measurably affected even though each type of shoe was worn for only 1 
 hour .
therefore , both flat shoes and high - heeled shoes may increase the risk of 
 musculoskeletal disorders .
however , wearing middle - heeled ( 4  cm ) shoes did not change the 
 distribution of foot pressure , suggesting that a middle height heel ( 4  cm ) is the optimal 
 height for preventing musculoskeletal disorders .
notably , we studied the effect of heel 
 height after walking for just 1 hour rather than for a long period . therefore , our results 
 can not predict the effects of wearing these types of shoes long - term .
the cop is the point on a body at which the total sum of the pressure acts , causing a force 
 with no moment about that point .
the cop has been used for several years as an index of 
 standing postural stability .
paik and im32 suggested that cop 
 parameters quantitatively reflect biomechanical alternations of the foot , and that walking 
 in high - heeled shoes displaced the cop medially and anteriorly relative to walking in low 
 heels .
some studies have recommended a heel height of between from 3  cm to 5  cm as the best 
 for maintaining balance20 , 22 , 23 .
oh et al.25 reported that high - heeled shoes induced 
 extra - muscular effort in the ankle joint .
in the present study , walking in 
 middle - heeled ( 4 cm ) shoes did not cause significant cop displacement ( p>0.05 ) , but both 
 flat shoes ( 0.5 cm heel ) and high - heeled ( 9 cm ) shoes caused significant displacements .
as suggested by the above studies , wearing either high - heeled or flat shoes may induce 
 biomechanical alternation and compensatory movement .
these changes may in turn decrease the 
 ability to balance , explaining why the displacement of cop was greater for flat and 
 high - heeled shoes .
we conclude that both flat shoes and high - heeled shoes cause bodily 
 instability that could lead to falls .
this study addressed the effects of wearing shoes for relatively brief periods of time . 

although the subjects wore the shoes for just 1 hour , we observed significnat effects on the 
 displacement of cop as well as the distribution of foot pressure . in a study by kim , 
 subjects walked in high - heeled shoes for 50 hours ( 5 hours per day)24 .
hyun and kim8 examined the effect of high heels on back muscle fatigue after 
 walking on a treadmill for 1 hour , and found that even short - term wearing of high heels 
 could affect the body .
their results resemble our findings that both high - heeled and flat 
 shoes change the cop and distribution of foot pressure after walking for 1 hour .
this means 
 that even brief walking in inappropriate shoes may negatively affect the body 's 
 function .
our study found that both high - heeled and flat shoes could have adverse functional effects 
 on the body .
however , we did not consider the subjects ' walking habits , enrolled only 
 college students in their 20s rather than subjects of various ages , and examined only the 
 short - term effects of wearing . in conclusion
, we suggest that it would be better to choose shoes not for style alone , but 
 also for whether they have positive or negative effects on the feet .
our results indicate 
 that middle - heeled ( 4 cm ) shoes are the most suitable for women .
   [ purpose ] this study aimed to determine the most appropriate height for shoe heels by 
 measuring the displacement of the cop ( center of pressure ) and changes in the distribution 
 of foot pressure after walking in flat ( 0.5 cm ) , middle - heeled ( 4 cm ) , and high - heeled ( 9 
 cm ) shoes for 1 hour . 
 [ methods ] a single - subject design was used , with 15 healthy women 
 wearing shoes with heels of each height in a random order . the foot pressure and 
 displacement of cop before and after walking in an ordinary environment for 1 hour were 
 measured using an fdm - s ( zebris medical gmbh , germany ) . 
 [ results ] the distribution of foot 
 pressure did not change significantly after walking in middle - heeled ( 4 cm ) shoes but did 
 change significantly after walking in either flat ( 0.5 cm ) or high - heeled ( 9 cm ) shoes . 
 similarly , the cop was not significantly displaced after walking in middle - heeled ( 4 cm ) 
 shoes but was significantly displaced after walking in either flat ( 0.5 cm ) or high - heeled 
 ( 9 cm ) shoes . 
 [ conclusion ] both flat and high - heeled shoes had adverse effects on the 
 body . 
 middle - heeled ( 4 cm ) shoes are preferable to both flat ( 0.5 cm ) and high - heeled ( 9 
 cm ) shoes for the health and comfort of the feet . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION