the human foot posture is generally characterized by the alignment of the foot skeleton , 
 and it varies considerably between individuals .
variation from a normal foot posture has 
 long been thought to influence the function of the foot and lower limb during gait , thereby 
 predisposing them to injury1 .
while the 
 link between altered foot posture and injury is still unclear , several studies have 
 demonstrated that foot posture influences lower limb muscle electromyographic ( emg ) 
 activity2 and joint kinematics3 , 4 
 during gait .
flat feet have been associated with altered foot function , including prolonged calcaneal 
 eversion , increased tibial internal rotation , increased forefoot abduction , reduced 
 efficiency of gait , and reduced shock absorption5 .
several kinematic studies have compared subjects with flat feet to 
 those with a normal foot posture3 , 4 . based on the fact that those with flat feet more easily feel muscle fatigue of the lower 
 extremities and have a higher risk of damage to the musculoskeletal system than those with 
 normal feet , this study s intent was to examine differences resulting from flat feet in 
 comparison with normal feet while the subjects walked on an ascending slope , such as when 
 climbing a mountain .
the subjects who participated in this study were divided into people with normal feet 
 ( n=15 ) and those with flat feet ( n=15 ) .
sufficient explanations of this study s intent and the overall purpose were given , and 
 voluntary consent to participate in this study was obtained from all of the subjects .
all 
 procedures were reviewed and approved by the institutional ethics committee of eulji 
 university hospital .
the diagnosis of flatfoot was confirmed by posture analysis ( gps400 , 
 redbalance , italy ) . as described by clarke6
, strake s line and marie s line were used to confirm flatfoot . a 
 treadmill
( ac5000 m , scifit , berkshire , uk ) was used to see the kinematic features during 
 gait .
the average gait velocity of the men at slow , normal , and fast paces were 3 , 4 , and 
 5  km / h , respectively , using a slope of 10% , and those of the women were 2.7 , 3.7 , and 
 4.7  km / h , respectively , also using a slope of 10%7 .
the subjects walked for one minute to ensure a natural gait 
 velocity before the experiment , and then subsequently all subjects walked barefoot for five 
 minutes on the treadmill .
gait data were obtained using a 6-camera motion analysis system ( eagle system , motion 
 analysis , santa rosa , ca , usa ) and sampling at 120  hz .
hemispherical reflective markers 
 ( 25  mm in diameter ) were applied to the following sites on both sides of the body : anterior 
 superior iliac spine , superior aspect of the l5-sacral interface , thigh ( lower thigh below 
 the midpoint ) , medial femoral condyle , lateral femoral condyle , shank ( lower shank below the 
 midpoint ) , medial malleolus , lateral malleolus , posterior calcaneus , and the center of the 
 foot between the 2nd and 3rd metatarsals . to facilitate application and visualization of the 
 markers ,
the subjects wore a pair of skin - tight cycling shorts and a sleeveless top .
the 
 evart and orthotrak software ( motion analysis , santa rosa , ca , usa ) were used for processing 
 the data . after a test walk to become accustomed to the experimental procedure , the subjects 
 were asked to walk for 30 seconds at each speed on the treadmill , and the average values of 
 the data were used .
the general subject characteristics were tested for homogeneity using the independent 
 t - test .
data were analyzed by repeated anova in spss for windows ( version 17.0 ) , and the 
 differences between groups at the different gait velocities were examined with the 
 independent t - test .
the general characteristics of the subjects are shown in table 1table1.general characteristics of each groupeg ( n=15)cc ( n=15)number of individuals ( male / female)5/106/9age ( years)21.41.322.10.6height ( cm)164.21.6167.42.1body weight ( kg)61.2.357.22.4foot length ( mm)254.24.2257.22.7ankle width ( cm)5.60.36.21.2eg : experimental group , cg : control group .
both groups showed significant differences in the sagittal , frontal , and 
 transverse planes according to the changes in speed ( p<0.05 ) . after comparing the lower 
 extremity kinematics between the subjects with flat feet and those with normal feet
, 
 significant differences were found with respect to hip adduction ( frontal plane ) in the 
 stance phase and hip internal rotation ( transverse plane ) in the swing phase ( p<0.05 ) 
 ( tables 2table 2.comparison of parameters of the lower extremity joints by different velocities on 
 a 10% slope in the sagittal planegroupslownormalfasthip ( )d1eg26.62.136.02.642.84.1cg25.31.634.92.445.44.4d2eg21.21.119.61.210.91.2cg21.60.818.40.711.40.7d3eg20.31.717.41.39.92.2cg20.91.417.70.910.71.2d4eg26.02.236.62.643.73.9cg26.31.636.72.346.54.0knee ( )d1eg7.61.69.51.08.01.7cg7.81.58.01.57.01.1d2eg6.71.410.62.511.32.6cg7.21.111.91.212.03.9d3eg24.73.134.13.140.65.6cg23.92.433.63.842.85.7d4eg43.73.462.22.575.61.5cg47.16.761.63.473.80.9ankle ( )d1eg2.30.82.71.02.70.8cg2.40.72.41.02.90.9d2eg10.52.012.62.313.53.5cg10.21.013.01.014.11.0d3eg10.12.212.31.117.21.6cg10.32.013.22.013.71.0d4eg14.02.420.31.127.82.5cg14.22.021.13.823.92.2*p<0.05 , d1 : flexion at initial contact , d2 : max . ext . in stance phase ,
eg : experimental group , cg : 
 control group , 3table 3.comparison of parameter of the lower extremity joints by different velocities on 
 a 10% slope in the frontal planegroupslownormalfasthip ( )d5eg0.60.20.40.20.60.3cg0.60.30.60.40.70.4d6*eg5.51.16.81.28.91.4cg4.30.55.90.38.80.8d7eg4.20.95.61.26.61.1cg2.90.76.21.17.70.9d8eg4.10.66.01.07.00.9cg3.20.96.80.68.10.6knee ( )d5eg1.61.31.81.91.92.0cg0.81.52.11.82.01.7d6eg1.80.22.50.53.80.5cg1.90.02.80.74.20.7d7eg0.50.42.70.63.00.7cg0.40.32.20.92.90.9d8eg2.00.53.40.73.60.7cg2.50.43.40.63.70.8ankle ( )d5eg1.60.61.80.72.40.5cg2.00.72.40.62.01.1d6eg3.91.13.20.42.00.7cg3.40.72.40.82.61.2d7eg1.60.61.90.92.40.4cg1.80.62.40.72.20.9d8eg3.20.73.50.83.51.0cg3.50.43.80.73.90.5*p<0.05 , d5 : adduction at initial contact , d6 : max .
d7 : 
 adduction at preswing , d8 : max . abd . in swing ,
eg : experimental group , cg : control 
 group , 4table 4.comparison of parameters of the lower extremity joints by different velocities on 
 a 10% slope in the transverse planegroupslownormalfasthip ( )d9eg5.92.25.21.54.21.1cg6.32.15.51.64.21.4d10eg10.11.712.11.613.82.7cg10.11.712.41.813.32.7d11eg3.10.73.80.92.30.8cg3.40.83.60.82.60.7d12*eg10.11.614.90.716.00.9cg10.41.812.61.514.91.7knee ( )d9eg3.71.84.42.74.92.8cg4.91.05.12.05.53.1d10eg3.61.25.91.97.92.5cg5.21.46.41.78.92.2d11eg1.61.21.71.52.31.5cg2.20.62.31.52.41.6d12eg8.91.39.80.914.92.6cg9.31.110.31.016.01.4ankle ( )d9eg2.71.24.11.44.21.2cg3.21.43.81.04.11.3d10eg10.31.511.81.314.02.5cg10.41.912.51.515.01.8d11eg8.00.55.40.97.30.6cg7.91.16.20.57.10.4d12eg0.30.31.20.91.71.4cg0.30.41.40.82.41.3*p<0.05 , d9 : int . rot . at initial contact ,
int . rot . in swing phase , eg : experimental 
 group , cg : control group ) .
values are expressed as meanssd * p<0.05 , d1 : flexion at initial contact , d2 : max .
eg : experimental group , cg : 
 control group * p<0.05 , d5 : adduction at initial contact , d6 : max .
d7 : 
 adduction at preswing , d8 : max . abd . in swing ,
eg : experimental group , cg : control 
 group * p<0.05 , d9 : int . rot . at initial contact ,
this study was conducted to investigate the kinematic difference between people with flat 
 feet and those with normal feet according to changes in walking speed on an ascending slope . 

three - dimensional gait analysis is now commonly used in research and as a tool in guiding 
 the treatment of gait disorders8 .
the 
 results for the lower extremity kinematic features of the subjects during gait on an 
 ascending slope showed that overall , their joint angles increased according to the increase 
 in gait speed , and there were significant differences between the two groups with respect to 
 hip adduction and the hip internal rotation angle .
because hip adduction and the internal 
 rotation angle on the lower extremity have a tendency to increase in response to an increase 
 in gait velocity on an ascending slope , we can expect that the hip adductor muscles and 
 internal rotator muscles of a subject with flat feet would be used much more than those of a 
 subject with normal feet when they perform actions which require a lot of power , such as 
 walking on an ascending slope and walking quickly .
the hip internal rotation in the stance 
 phase is increased in subjects with flat feet compared with subjects with normal feet , this 
 causes the patellofemoral joint s internal pressure to increase , and the deformity of the 
 patella increases in accordance with the increase in the angle of the knee joint9 .
increased pressure on the lower extremity 
 is related to tibia shock , and the internal rotation of the tibia in subjects with flat 
 feet10 .
first , the small sample size may have influenced 
 certain variables and impacted on the results .
 [ purpose ] the purpose of the study was to discover why people who have flat feet show a 
 higher risk of damage to the musculoskeletal system than those who have normal feet . 
 
 furthermore , we examined the kinematic differences in the lower extremity between flat 
 feet and normal feet in individuals on an ascending slope using three - dimensional gait 
 analysis . 
 [ subjects ] this study was conducted on 30 adults having normal feet ( n = 15 ) and 
 flat feet ( n = 15 ) , all of whom were 21 to 30  years old . [ methods ] a treadmill ( ac5000 m , 
 scifit , berkshire , uk ) was used to analyze the kinematic features during gait . 
 these 
 features were analyzed at slow , normal , and fast gait velocities on an ascending slope . 
 
 gait data were obtained using a 6-camera motion analysis system ( eagle system , motion 
 analysis , santa rosa , ca , usa ) . 
 [ results ] both groups showed significant differences in 
 the sagittal , frontal , and transverse planes according to the speed changes . 
 after 
 comparing the lower extremity kinematics between those with flat feet and those with 
 normal feet , significant differences were found with respect to hip adduction ( frontal 
 plane ) in the stance phase and hip internal rotation ( transverse plane ) in the swing 
 phase . 
 [ conclusion ] due to hip adduction , the internal rotation angle of the lower 
 extremity has a tendency to increase according to the increase in gait velocity on an 
 ascending slope , and we can expect that the hip adductor muscles and internal rotator 
 muscles in individuals with flat feet are used much more than would be the case for those 
 with normal feet when they perform actions that require a lot of power , such as walking on 
 an ascending slope and walking quickly . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION