walking refers to alternating anterior movements of the trunk and legs in a simultaneous 
 and continuous manner while maintaining stability in the stance phase .
this is the most 
 fundamental movement of the human body , and it is realized through interactions between the 
 musculoskeletal and nervous systems1 , 2 .
stairs area circumstance that individuals are frequently exposed to in daily life during 
 walking . in stair
walking , each step starts on the toes and the ball of the foot rather than 
 the heel .
in addition , the vertical upward movement of body weight requires external forces , 
 while the vertical downward movement of body weight requires control of falling3 .
stair walking differs from horizontal 
 walking in terms of the changes in characteristics of the force generated in the 
 lower - extremity segments according to the angle of inclination4 .
in addition , as stair walking progresses , the body is lifted at the 
 same time as it is moved horizontally5 . 

therefore , stair walking requires more 
 frequent muscle activities and a higher level of balance control than just walking on the 
 ground .
the foot angle describes the location of the foot in relation to its moving direction 
 during walking and refers to the angle between the foot s baseline ( the line that connects 
 the heel s center and the third metatarsus ) and the foot s moving direction . in general , 
 when a foot lands on the ground during walking , the foot s end turns outward in relation to 
 the moving direction . in - toeing or out - toeing
can be influenced by factors such as the 
 movement of the hip joint , the degree of distortion in the tibia and malleolus , and 
 adduction or abduction of the talus in relation to the foot7
. in - toeing and out - toeing also affect the movement of thigh muscles 
 during open kinetic chain exercises8 . 
 given the structure of the human body , a normal foot angle is around 15 ; angles smaller 
 than this are defined as in - toeing and angles larger than this as out - toeing7 .
plantar foot pressure is the pressure applied to the entire foot as well as specific 
 regions of the foot .
it measures and reflects the status of balance and walking of the human 
 body9 , 10.the measurement of plantar foot pressure is clinically useful , as 
 it helps to identify anatomical foot deformities and diagnose and treat walking disorders 
 and impairments in walking ability11 . 

plantar foot pressure is usually measured using a force plate , pressure plate , or in - shoe 
 sensor .
however , the methods that use force or pressure plates can not fully measure pressure 
 on each region of the foot .
the method that measures plantar foot pressure using in - shoe 
 sensors is useful for obtaining various types of information on changes in plantar foot 
 pressure12 .
a number of existing studies have researched plantar foot pressure on the ground and stairs 
 according to age group and disease type , and many of these performed kinetic analyse of 
 plantar foot pressure on the ground according to foot angle .
however , studies that have 
 compared plantar foot pressure according to foot angle in various environments are few . 

therefore , the purpose of this study was to compare plantar foot pressure and the center of 
 pressure ( cop ) trajectory length according to in - toeing , out - toeing , and a normal foot angle 
 using an f - scan system , which enables the observation of the distribution of plantar foot 
 pressure , during ascent and descent of stairs .
the subjects of this study were free of orthopedic diseases , open wounds , or diseases of 
 the foot or lower extremities .
before the experiment , the purpose of this study was 
 explained to the subjects , and their consent to participation was obtained .
this study was 
 approved by the institutional review board of the local ethics committee in accordance with 
 the ethical principles of the declaration of helsinki .
the general characteristics ( meansd ) 
 of the subjects were : an age of 21  2.16 years a foot size of 235  7.24  mm , a height of 
 158  4.17  cm tall , and a weight of 45  8.22  kg .
the plantar foot pressure measuring system f - scan ( tekscan inc . , usa ) was used to measure 
 plantar foot pressure and the cop trajectory length .
this system consists of an insole - type 
 sensor that can be tailored to measure plantar foot pressure , conversion devices that can be 
 attached to the legs , cables that connect the conversion devices to a computer , a computer , 
 and software for the analysis of plantar foot pressure .
the insole - type sensor is thin 
 ( 0.18  mm thick ) , inflexible , and consists of 960 pressure sensors evenly distributed in a 
 grid pattern with a spacing of 0.2 inches .
the insole sensor was cut to fit the foot size of 
 each subject and then installed in his / her shoe .
the input signals were delivered to a 
 computer via a 10-meter cable connected to the computer interface attached to the waist .
the 
 subjects were instructed to insert the insole - type sensors that had been cut to fit the size 
 of their shoes inside each shoe and then walk .
the distribution of plantar foot pressure 
 data was collected at a rate of 60  hz using tekscan s commercial program . in this study
, the 
 foot was divided into six regions : anterior - medial , anterior - lateral , medio - medial , 
 medio - lateral , posterior - medial , and posterior - lateral .
the cop trajectory 
 length was analyzed by dividing it into the anterior - posterior , medial - lateral , and total 
 trajectory lengths .
spss 12.0 for windows was used for the statistical processing of the 
 collected data .
one - way anova was performed to compare plantar foot pressure and the cop 
 trajectory length according to foot angles during stair walking .
in addition , fisher s least 
 significant difference ( lsd ) test was performed as a posthoc test .
in stair walking , the maximum pressure showed statistically significant differences in the 
 anterior - lateral region .
the results of the posthoc test showed there were statistically 
 significant differences between normal and out - toeing , normal and in - toeing , and in - toeing 
 and out - toeing walking ( p < 0.05 ) ( table 
 1table 1.comparison of maximumforce on the stair up ( unit : kpa)anteriormiddleposteriormediallateralmediallateralmediallateralnormal12.81.413.81.54.30.98.31.68.11.17.90.8out - toeing10.21.113.41.44.50.86.91.49.11.18.90.9in - toeing11.31.28.91.13.30.58.71.47.70.96.70.8values are meansd , * p<0.05 .  
significant difference between out - toeing and in - toeing the cop trajectory did not show statistically significant differences in the 
 anterior - posterior , medial - lateral , and total trajectory lengths ( p > 0.05 ) ( table 2table 2.comparison of cop on the stair up ( unit : cm)apmltotalnormal13.80.51.80.213.90.5out - toeing14.60.42.00.114.80.4in - toeing14.10.82.20.214.30.8values are meansd , ap : anterior posterior , ml : medial lateral ) .
values are meansd , ap : anterior posterior , ml : medial lateral in stair descending , the maximum pressure showed statistically significant differences in 
 the anterior - lateral , medio - medial , medio - lateral , posterior - medial , and posterior - lateral 
 regions . the results of the posthoc test revealed there were statistically significant 
 differences in the anterior - lateral and medio - medial regions between in - toeing and 
 out - toeing walking , as well as statistically significant differences in the medio - lateral 
 region between normal and in - toeing walking and in - toeing and out - toeing walking .
the 
 posterior - medial and posterior - lateral regions revealed statistically significant 
 differences between normal and out - toeing walking and in - toeing and out - toeing walking ( p 
 <
0.05 ) ( table 3table 3.comparison of maximum force during stair descent ( unit : kpa)anteriormiddleposteriormediallateralmediallateralmediallateralnormal9.91.09.61.13.80.75.90.94.80.84.80.6out - toeing7.50.812.31.55.20.86.31.07.41.07.80.9in - toeing10.41.17.21.02.90.410.52.14.70.64.30.6values are meansd , * p<0.05 .  
values are meansd , * p<0.05 .   significant difference between normal 
 and out - toeing .  
significant difference between out - toeing and in - toeing the cop trajectory length showed statistically significant differences in the 
 medial - lateral trajectory length .
the post - hoc test exhibited statistically significant 
 differences between normal and in - toeing walking and in - toeing and out - toeing walking ( p 
 < 0.05 ) ( table 4table 4.comparison of cop during stair descent ( unit : cm)apmltotalnormal14.80.52.40.215.00.5out - toeing14.40.82.40.114.60.8in - toeing12.70.63.00.213.10.6values are meansd , * p<0.05 , ap : anterior posterior , ml : medial lateral . 
 
values are meansd , * p<0.05 , ap : anterior posterior , ml : medial lateral . 
 
the purpose of this study was to perform a comparative analysis of plantar foot pressure 
 and cop trajectory length during stair climbing and descending by subjects with in - toeing , 
 normal , and out - toeing foot angles . in this study , the maximum pressure during stair climbing showed statistically significant 
 differences in the anterior - lateral region , whereas the cop trajectory length did not reveal 
 statistically significant differences in the anterior - posterior , medial - lateral , and total 
 trajectory lengths . in stair
descending , the maximum pressure showed statistically 
 significant differences in the anterior - lateral , medio - medial , medio - lateral , 
 posterior - medial , and posterior - lateral regions .
the cop trajectory length exhibited 
 statistically significant differences in the medial - lateral trajectory length .
han et al . researched plantar foot pressure during level walking , stair climbing , and slope 
 climbing , and reported that , compared to level walking , stair walking yielded increases in 
 pressure on the fourth and fifth toes and the fourth and fifth metatarsus , and decreases in 
 pressure on the mid - foot and hindfoot13 . 

rao and carter found increases in pressure on both the anterior - medial and anterior - lateral 
 regions during stair climbing14 .
of the 
 results of these two studies regarding the pressure on the anterior - lateral region are in 
 agreement with that of the present study .
in addition , han et al . compared the cop 
 trajectory length of level and stair walking and discovered that the anterior - posterior and 
 total trajectory lengths declined during stair walking .
while many previous studies simply observed changes in plantar foot pressure on the ground 
 according to foot angle , the present study measured foot plantar pressure during stair 
 walking .
the results of the 
 present study are similar to those of presious studies that compared level and stair walking 
 and reported pressure increases in the foot s anterior - lateral region , and decreases in the 
 hindfoot . during stair
climbing , the maximum pressure on the anterior - lateral region 
 decreased in in - toeing walking compared to out - toeing and normal walking , and the 
 medial - lateral trajectory length increased in in - toeing walking .
this shows that pressure 
 was not properly supported in the lateral region , which led to increases in the 
 medial - lateral movement .
in addition , during stair descent , in the case of in - toeing 
 walking , the maximum pressure on the anterior - lateral and posterior - lateral regions 
 decreased , and the maximum pressure on the medio - lateral region increased .
. in - toeing walking appears 
 to increase the loads on the mid - foot and medial - lateral region . in - toeing hinders the even 
 distribution of an individual s weight and thus raises the risk of a fall . in other words , 
 in - toeing and out - toeing cause anatomical changes in the location of the hip joint , which 
 result in walking patterns that consume high levels of energy due to low stability15 , 16 . in conclusion
, this study demonstrated that differences in foot angle influence plantar 
 foot pressure and the cop trajectory length during walking .
the concentration of pressure on 
 a specific region of the foot due to abnormal foot angles can cause foot deformities and 
 physical disabilities .
in addition , it can have substantial effects on the forces required 
 for inward and outward turns2 , thereby 
 dispersing the force that moves the body forward7 .
excessive pressure applied during consecutive motions such as 
 walking is highly likely to impair the body s actions to protect itself14 .
the results of this study may help to provide basic data on plantar foot pressure and cop 
 trajectory length in abnormal gait patterns . to better understand the effect of foot angle 
 on muscles and the musculoskeletal system , in addition to the types of foot angle , the 
 effects of kinematic and kinetic variables related to joint angles and muscles on the lower 
 extremities should be investigated .
moreover , additional studies should research changes in 
 gait patterns according to relevant kinematic interventions .
 [ purpose ] walking with the feet turned inward or outward often causes issues for the 
 people with these walking patterns . 
 the purpose of this study was to examine the influence 
 of in - toeing and out - toeing on maximum force and the center of pressure ( cop ) trajectory 
 length during stair walking . 
 [ subjects and methods ] the subjects were 30 female university 
 students without orthopedic diseases of the foot . the foot angle was divided into three 
 types : in - toeing , normal , and out - toeing . 
 a plantar pressure measurement instrument was 
 used , and the maximum force was obtained by dividing the foot into six regions covering 
 the anterior medial - lateral , middle medial - lateral , and posterior medial - lateral regions . 
 
 the cop trajectory length was statistically calculated by measuring the medial - lateral , 
 anterior - posterior , and total travel distances . 
 [ results ] during stair climbing , the 
 maximum force was significantly different in the anterior lateral region . during stair 
 descending , the maximum force was significantly different in the anterior lateral , middle 
 medial , middle lateral , posterior medial , and posterior lateral regions . 
 the cop 
 trajectory length showed a statistically significant difference in the medio - lateral 
 travel distance . 
 [ conclusion ] walking with abnormal foot angles causes deformed foot 
 structures and can result in musculoskeletal disabilities in the long term . 
 therefore , 
 therapeutic intervention is required to maintain normal foot angles . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION