walking is one of the most fundamental actions required for human life , and feet play a 
 particularly important role in supporting the human body and maintaining balance during 
 walking1 .
because of this , incorrect 
 walking habits primarily appear as an imbalance between the two feet .
in particular , 
 flatfoot is characterized by a medial longitudinal arch that is lowered in a chronic or 
 abnormal way , resulting in hyperextension of the plantar fascia , spring ligament , and tendon 
 of the tibialis posterior2 . as the ability 
 to receive and disperse weight decreases due to the abnormality of the sole structure , 
 excessive compensation by the outer muscles occurs and causes foot imbalance3 .
hence , flatfoot walking induces excessive 
 pronation of the feet , which delivers the weight load to the tibia , causing pain in the 
 tibia and knee . this can result in damage to the lower limb4 . in a study using functional foot orthotics ( ffos ) to solve the problem of foot deformity , 
 pratt5 examined the prevention or 
 correction of deformity , formation of sufficient supporting ground , promotion of standing or 
 walking exercise , and improvement of walking efficiency .
feet play an important role in the 
 lower kinetic chain ; they distribute the weight load generated during exercise and disperse 
 it in the stance period during walking .
moreover , an appropriate shoe liner and orthotic can decrease muscle 
 activity and provide comfort , while increasing exercise performance ability7 , 8 .
as 
 the ffo supports a balanced weight distribution in the plantar area and arch , it aids in 
 efficient shock absorption , including the ground reaction generated during walking or 
 running , which reduces pain and unstable joint motion9 . as such ,
although there are a number of studies analyzing the ankle and knee , research studying the 
 pelvis , which is used as a center point of the body , during walking is scarce .
hence , this 
 study examined the impact of wearing ffos on the pelvic angle among young adults who have 
 flatfoot , using a vicon motion system device .
the subjects of this study consisted of 15 college students enrolled in university k , 
 located in cheonan city , korea , from september 1 to 20 in 2015 .
the study included 
 participants with no musculoskeletal disease who were diagnosed with flatfoot and have a 
 calcaneal pitch angle less than 15 , indicated by radiological measurements .
this study 
 acquired approval from the clinical test screening committee at korea nazarene university 
 and was reviewed according to the declaration of helsinki .
the general characteristics of 
 the research subjects who participated in this study are summarized in table 1table 1.general participant characteristicssubjects ( n=15)gender ( m / f)8/7age ( yrs)21.1  3.4height ( cm)162.1  6.1weight ( kg)63.1  7.1calcaneal pitch angle ( )13.5  1.2values are presented as the mean  sd .
values are presented as the mean  sd the ffos worn by the subjects in this study were customized for each individual s foot 
 shape and created with thermoplastic materials .
a high - density resistance elastic pad , cup 
 sole for the plantar arch , low - elasticity pad for shock absorption in the heel , and 
 ethylenevinylacetate ( eva ) were used to create the ffos . when designing the foot orthotic 
 for a subject , the researcher positioned the heel bone vertical to the ground and let the 
 subtalar joint maintain its natural position . while preventing pronation of the subject s 
 feet and excluding excessive foot movement , measurements were taken and an evaluation was 
 performed while weight was loaded under the realigned condition of the foot .
specifically , the experimenter measured and evaluated the subjects feet and molded both 
 foot shapes using pedilen foam . with a prepared positive plaster model , plaster correction 
 was performed ( checking pressure points or sensitive parts of the feet ) , followed by shell 
 production and modeling with thermoplastic .
next , posting and grinding ( trimming and 
 alignment adjustment ) were performed and the production of the foot orthotic was finalized 
 with a covering material10 , 11 .
the study equipment consisted of six mx - f40 cameras ( vicon , hansung , korea ) , two or6 - 7 
 force plates ( amti , usa ) , and nexus software .
each mx camera forms the two - dimensional 
 images obtained from optical markers into three - dimensional images , so that in addition to 
 the location data of the markers , measurements for each segment of the body can be obtained . 

the force plates express the ground reaction 
 force of both feet during walking as vectors .
moreover , an ultranet system synchronized the 
 motor mechanic data from the camera and the kinematic data from the force plate into the 
 same frame12 , 13 . to compute the pelvic joint angle , a plug - in gait model , based on the newington - helen hayes 
 gait model , was used .
this was measured by the three - dimensional motion capture device from 
 the vicon motion system .
the local coordinate system of each segment was created using the 
 three - dimensional spatial coordinates of each measured marker point , and a euler algorithm 
 was derived .
each gait cycle was differentiated using the heel strike as a standard , and one 
 gait cycle of walking from each subject was extracted for time normalization12 . in this experiment , only the results from 
 the mid - swing and mid - stance periods of the gait cycle were extracted , which provides the 
 highest and lowest points , respectively . in this study , to measure the change in the pelvic angle , walking on a previously 
 fabricated walkway before and after wearing the customized ffos was analyzed using 
 high - quality 3d cameras and the vicon motion system ( vicon , oxford , uk ) . to measure the 
 pelvic angle in the stance period during walking , markers were placed on the anterior 
 superior iliac spine ( asis ) and anterior inferior iliac spine ( aiis ) bilaterally .
moreover , 
 the dynamic change was quantified to compute the difference in the pelvic angle on the left 
 and right sides .
all subjects performed a preliminary motion five times to become familiar 
 with the test .
data for three walking trials were processed for quantitative computation and 
 their average values were analyzed .
the changes before and after wearing the orthotic were analyzed using paired t - tests .
examining the change in the pelvic angle in the experimental group before and after wearing 
 the ffo revealed large changes in the pelvic angle on both the left and right sides during 
 the pre - stance and mid - stance and pre - swing and mid - swing periods of the gait cycle before 
 wearing the orthotic .
however , no significant differences were observed in the pelvic angle changes 
 of the left versus right side after wearing the orthotic ( p>0.05 ; table 2table 2.comparison of the pelvic angle before and after wearing the foot orthoticpre - stance ( )mid - stance ( )pre - swing (  ) mid - swing ( )pretestposttestpretestposttestpretestpretestpretestpretestright4.2  0.22.6  0.6*6.5  0.64.4  0.2 * 3.5  0.21.9  0.5 * 7.5  0.54.8  0.2*left4.4  0.72.2  0.3*6.2  0.54.2  0.4 * 3.0 
0.32.1  0.7 * 7.0  0.75.0  0.4*values are presented as the mean  se .
values are presented as the mean  se . * significant difference from the pre - test value , p<0.05
this study examined the change in the pelvic angle at the mid - stance and mid - swing phases 
 of walking before and after wearing ffos , in a sample of young adults who have flatfoot , 
 with the expectation that wearing ffos will affect the pelvic angle during the gait cycle 
 among those with flatfoot . examining the change in the pelvic angle during the stance period 
 before and after wearing
the ffo revealed that the angle significantly decreased on the left 
 and right sides in the pre - stance and mid - stance and pre - swing and mid - swing periods after 
 wearing the ffo .
although the angle decreased after wearing the ffo , compared to before , the 
 decrease was not significant .
this implies that wearing a custom - fit ffo ameliorates tension 
 in the sole muscle and fascia and prevents the decrease of the plantar arch during the 
 mid - stance and mid - swing periods in flatfoot walking , resulting in a decrease in the pelvic 
 angle .
an ffo can reduce the height change of the foot arch , which eventually prevents its 
 collapse during dynamic movement .
moreover , ffos support effective energy consumption during 
 walking by reducing fatigue in the foot muscles , which is frequently observed among flatfoot 
 patients13 .
they also help reverse 
 abnormal changes in the joints and revert the joint positions back to their natural 
 locations .
hence , a change was observed that restricted movement to the side of the pelvis 
 joint in the sagittal plane of the pelvis after wearing ffos .
wu14 reported that foot orthotics are used for foot alignment 
 and support , prevention and correction of foot deformity , and improvement of foot function . 

if individuals with flatfoot develop disorders of the joints and feet , ffos can alter the 
 walking mechanism , which consequently affects the other lower limb joints15 .
moreover , they help evenly disperse shock 
 on the sole by compensating for functional insufficiencies in the flat foot in each phase of 
 walking16 . as such
, the improved 
 results in the lower limb and foot accomplished by wearing an ffo that are reported in 
 previous literature were likely accomplished through organic changes in the pelvic angle via 
 the functional changes observed in this study .
future studies based on these results that 
 examine complex organic changes in all joints of the lower limb after wearing ffos will 
 contribute to further advancement in orthotics .
 [ purpose ] this study examined the impact of wearing a functional foot orthotic on the 
 pelvic angle of young adults who have flatfoot . [ subjects and methods ] a total of 15 
 college students diagnosed with flatfoot were included in the study . 
 changes in the pelvic 
 angle in the stance period during walking before and after orthotic use were measured 
 using a vicon motion system ( vicon , hansung , korea ) . 
 the data were analyzed using spss 
 12.0 for windows . 
 [ results ] in the experimental group , the pelvic angle during the 
 mid - stance and mid - swing periods of the gait cycle significantly decreased on the left and 
 right sides after wearing the orthotic , compared to the measurements taken before orthotic 
 usage . 
 the pelvic angle change on the left and right sides also decreased after wearing 
 the orthotic , though this difference was not significant . 
 [ conclusion ] the pelvic angle of 
 college students with flatfoot decreased after they wore orthotics . 
 this implies that 
 wearing orthotic shoes can greatly benefit individuals during normal walking by promoting 
 passive changes that decrease the pelvic angle . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION