walking , which can be defined as moving the body to a target spot or destination using two 
 legs , is a complex and integrated activity requiring low energy consumption1 .
although it appears to be an 
 easy - to - perform task , it actually requires comprehensive use of all nerves and skeletal 
 muscles .
furthermore , learning to walk requires considerable practice and effort and takes 
 at least four years to master2 .
the gait 
 cycle is divided into stance and swing phases . during the stance phase ,
the foot is in 
 contact with the ground , whereas during the swing phase , the same foot lifts off the ground 
 and moves forward .
the 
 stance phase is divided into heel strike , foot flat , mid - stance , and toe off , whereas the 
 swing phase is divided into acceleration , mid - swing , and deceleration3 .
the pelvis is a structure located between the hip joint and lumbosacral region . with the 
 use of multiple muscles , the pelvis controls the movements of the hip joint and lumbosacral 
 region . in this respect ,
the pelvic position is the most important factor for determining 
 the body s sagittal alignment and posture4 . with the pelvis in the neutral position ,
correct posture can be 
 maintained , and movements occurring during activities of daily living and gait can be 
 improved via proper control of the upper and lower extremities in dynamic postures5 . in addition , mechanical problems in the 
 musculoskeletal system of the lumbar vertebrae can occur depending on the location of the 
 pelvis . moreover , forward and backward pelvic tilt exercises can influence spinal stability 
 and physical alignment .
lumbo - pelvic stabilization and posture have been shown to improve with bridge 
 exercises7 and various mat 
 exercises8 .
in addition , some studies 
 have examined postures9 or gait 
 variables10 through pelvic adjustment . 
 however
, none of the studies have addressed the correlations among pelvic positions and 
 differences in lower - extremity joint angles during walking .
thirty female students at the k university were selected as subjects . the average 
 ( meanstandard deviation ) age , height , and weight of the subjects were 22.33.4  years , 
 163.25.4  cm , and 53.55.7  kg , respectively .
the exclusion criteria were as follows : 
 musculoskeletal or neurological problems ; lumbar and pelvic pain during daily activities ; 
 incorrect posture due to scars related to previous burns or surgeries ; and inability to walk 
 normally .
this study was approved by the university s institutional review board , and the 
 subjects were safely protected during all experimental procedures .
all the subjects 
 understood the purpose of this study and provided written informed consent prior to their 
 participation , in accordance with the ethical standards of the declaration of helsinki .
this study measured the pelvic positions and differences in lower - extremity joint angles 
 during walking .
the backmapper ( abw , germany ) , a three - dimensional spinal diagnostic system , 
 was used to measure pelvic positions .
the backmapper is an apparatus that obtains precise 
 measurements of the spinal form , location , and degree of distortion , evaluating the spinal 
 form from the backward , forward , downward , and upward directions .
it analyzes the 
 inclination of the coronal plane , pelvic position ( ppo ) , left and right inclination of the 
 pelvis , pelvic torsion ( pto ) , degree of declination of the hip bone , and pelvic rotation 
 ( pro ) . the qualisys track manager ( qualisys ab , sweden ) , a three - dimensional wireless motion 
 analysis system with six cameras operating at 100  hz per second , was used to analyze the 
 kinematic motions of lower extremities in the subjects during walking .
the l - frame was fixed 
 on the starting point of walking to set the spatial coordinates . in terms of directions ,
the 
 upper vertical axis was set as the + z - axis , and the direction of motions and the horizontal 
 axis were set as the + y - axis and + x - axis , respectively .
based on the l - frame , the space 
 within which movements would be performed was defined using the t - wand to recognize markers 
 clearly .
reflective markers for static postures to form basic frames were attached to each 
 side of the sacrum , anterior superior iliac spine , thigh , and shank .
four markers were 
 attached to each side of the thigh and shank in a square form to create a three - dimensional 
 space .
in addition , reflective markers were attached to the medial and lateral epicondyles , 
 lateral malleolus , and medial malleolus on both sides of the body . in the segments of the 
 foot
, reflective markers were attached to specific areas of the foot surface , which 
 corresponded with the calcaneal tuberosity and the first and fifth metatarsal heads .
to 
 track the three - dimensional motions of three lower extremity joints during dynamic postures , 
 the markers for static postures , which had been attached to the medial and lateral 
 epicondyles , lateral malleolus , and medial malleolus , were removed prior to filming of the 
 respective motions . to reduce errors , a single well - trained person attached these reflective 
 markers .
motion analysis was performed to derive differences between left and right flexion , 
 abduction , and external rotation range of motion ( rom ) of hip joints , flexion , abduction , 
 and external rotation rom of knee joints , and dorsiflexion , inversion , and abduction rom of 
 ankle joints , according to the x , y , and z - axes .
the measured data were analyzed using the spss 12.0 ko ( spss , chicago , il , usa ) software , 
 and the collected data are presented in terms of means and standard deviations .
pearson s 
 correlation coefficient was used to observe correlations among the ppo , pto , pro , 
 differences between left and right hip flexion ( hxd ) , differences between left and right hip 
 abduction ( hyd ) , differences between left and right hip external rotation ( hzd ) , differences 
 between left and right knee flexion ( kxd ) , differences between left and right knee abduction 
 ( kyd ) , differences between left and right knee external rotation ( kzd ) , differences between 
 left and right ankle dorsiflexion ( axd ) , differences between left and right ankle inversion 
 ( ayd ) , and differences between left and right ankle abduction ( azd ) .
the ppo , pto , pro , hxd , hyd , hzd , kxd , kyd , kzd , axd , ayd , and azd measurements are 
 presented as meanstandard deviation in table 
 1table 1.meanstandard deviation of ppo , pto , pro , hxd , hyd , hzd , kxd , kyd , kzd , axd , ayd , 
 and azd ( unit - degree ) ppoptoprohxdhydhzdkxdkydkzdaxdaydazd2.70.93.61.72.21.55.21.83.51.75.11.46.31.66.41.66.21.45.81.55.51.05.81.4ppo : pelvic position , pto : pelvic torsion , pro : pelvic rotation , hxd : difference 
 between left and right hip flexion , hyd : difference between left and right hip 
 abduction , hzd : difference between left and right hip external rotation , kxd : 
 difference between left and right knee flexion , kyd : difference between left and right 
 knee abduction , kzd : difference between left and right knee external rotation , axd : 
 difference between left and right ankle dorsiflexion , ayd : difference between left and 
 right ankle inversion , azd : difference between left and right ankle abduction . in terms of correlations among these variables ,
ppo showed positive 
 correlations with hxd , hyd , kxd , kyd , and ayd . in other words ,
an increase in ppo resulted 
 in corresponding increases in hxd ( r=0.51 ) , hyd ( r=0.62 ) , kxd ( r=0.45 ) , kyd ( r=0.42 ) , and 
 ayd ( r=0.38 ) .
hxd exhibited a positive correlation with axd , as an increase in hxd resulted 
 in a corresponding increase in axd ( r=0.64 ) .
kxd also showed positive correlations with kyd 
 and ayd ; an increase in kxd led to corresponding increases in kyd ( r=0.41 ) and ayd ( r=0.45 ) , 
 as shown in table 2table 2.correlations among ppo , pto , pro , hxd , hyd , hzd , kxd , kyd , kzd , axd , ayd , and 
 azdcategoryppoptoprohxdhydhzdkxdkydkzdaxdaydazdppo1pto0.181pro0.010.121hxd0.51**0.020.301hyd0.62 * 0.020.020.261hzd0.370.11 - 0.170.150.081kxd0.45 * 0.250.030.210.000.341kyd0.42 * 0.040.020.320.310.000.41 * 1kzd0.150.280.110.100.040.190.100.151axd0.190.000.120.64**0.030.060.140.190.101ayd0.38 * 0.190.150.110.250.220.45 * 0.090.250.151azd0.100,000.110.240.070.250.00 - 0.110.160.290.131 * * p<0.01 , * p<0.05 .
ppo : pelvic position , pto : pelvic torsion , pro : pelvic 
 rotation , hxd : difference between left and right hip flexion , hyd : difference between 
 left and right hip abduction , hzd : difference between left and right hip external 
 rotation , kxd : difference between left and right knee flexion , kyd : difference between 
 left and right knee abduction , kzd : difference between left and right knee external 
 rotation , axd : difference between left and right ankle dorsiflexion , ayd : difference 
 between left and right ankle inversion , azd : difference between left and right ankle 
 abduction .
ppo : pelvic position , pto : pelvic torsion , pro : pelvic rotation , hxd : difference 
 between left and right hip flexion , hyd : difference between left and right hip 
 abduction , hzd : difference between left and right hip external rotation , kxd : 
 difference between left and right knee flexion , kyd : difference between left and right 
 knee abduction , kzd : difference between left and right knee external rotation , axd : 
 difference between left and right ankle dorsiflexion , ayd : difference between left and 
 right ankle inversion , azd : difference between left and right ankle abduction * * p<0.01 , * p<0.05 .
ppo : pelvic position , pto : pelvic torsion , pro : pelvic 
 rotation , hxd : difference between left and right hip flexion , hyd : difference between 
 left and right hip abduction , hzd : difference between left and right hip external 
 rotation , kxd : difference between left and right knee flexion , kyd : difference between 
 left and right knee abduction , kzd : difference between left and right knee external 
 rotation , axd : difference between left and right ankle dorsiflexion , ayd : difference 
 between left and right ankle inversion , azd : difference between left and right ankle 
 abduction
this causes them to experience pelvic 
 and lower - extremity misalignment , which in turn influence posture , gait patterns , and 
 balance .
the pelvis supports the abdomen and connects the vertebrae and lower extremities . 
 when an individual stands up from a seated position , the pelvis transfers the body weight 
 from the vertebrae to the lower extremities and maintains correct posture , thereby enabling 
 smooth movement of the upper extremities11 .
with the pelvis positioned in neutral , correct posture can be 
 maintained as well as appropriate motions can be performed during daily living activities ; 
 additionally , gait ability can be improved via proper control of the upper and lower 
 extremities during dynamic postures12 . in a similar study on the pelvis and walking , cho and jun selected 30 female university 
 students and randomly divided them into a pelvic adjustment group ( n=15 ) and a stretching 
 group ( n=15 ) , which served as the control group , and analyzed their gait .
they reported that 
 differences in step length , stance phase , swing phase , single support , and step time were 
 reduced with pelvic adjustment10 . 

moreover , cho selected 30 female university students and randomly divided them into a pelvic 
 adjustment group ( n=15 ) and a stretching group ( n=15 ) . after analyzing their postures , the 
 author reported that pelvic adjustment showed statistically significant effects on trunk 
 imbalance , ppo , pto , and the position of the scapulae9 .
in addition , a study reported that trunk stabilization exercises 
 enhanced normal gait patterns in stroke patients and their perception of the affected lower 
 extremity , promoting normal exercise modes and reducing excessive muscle tension by 
 increasing the symmetry of pelvic alignment13 .
several 
 existing studies have conducted gait analyses after various interventions in patients with 
 hemiplegia14 or cerebral palsy15 by employing three - dimensional gait 
 analysis techniques .
however , few studies have addressed correlations among pelvic positions 
 and differences in lower - extremity joint angles during walking .
the present study analyzed 
 correlations among ppo , pto , pro , hxd , hyd , hzd , kxd , kyd , kzd , axd , ayd , and azd .
ppo showed positive correlations with 
 hxd , hyd , kxd , kyd , and ayd ; in other words , an increase in ppo resulted in corresponding 
 increases in hxd , hyd , kxd , kyd , and ayd .
in addition , hxd showed a positive correlation 
 with axd , in which an increase in hxd led to a corresponding increase in axd .
moreover , kxd 
 exhibited positive correlations with kyd and ayd , as an increase in kxd resulted in 
 corresponding increases in kyd and ayd . to summarize these findings
, increases in left and right pelvic tilt resulted in 
 corresponding increases in differences between left and right hip flexion , hip abduction , 
 knee flexion , knee abduction , and ankle inversion .
this may have resulted from changes in 
 weight support and lower - extremity tilt according to changes in pelvic height on the left 
 and right sides .
therefore , both left and right pelvic tilt were important factors that led 
 to differences between the left and right lower - extremity joint angles during walking . when 
 these types of differences are present , pelvic adjustment is considered necessary for 
 balanced walking .
additional studies should be carried out to implement pelvic adjustment or 
 lumbo - pelvic stabilization exercises as interventions to reduce differences between the left 
 and right lower extremity joint angles during walking .
 [ purpose ] this study aimed to identify correlations among pelvic positions and 
 differences in lower extremity joint angles during walking in female university students . 
 [ subjects ] thirty female university students were enrolled and their pelvic positions and 
 differences in lower extremity joint angles were measured . 
 [ methods ] pelvic position , 
 pelvic torsion , and pelvic rotation were assessed using the backmapper . 
 in addition , 
 motion analysis was performed to derive differences between left and right flexion , 
 abduction , and external rotation ranges of hip joints ; flexion , abduction , and external 
 rotation ranges of knee joints ; and dorsiflexion , inversion , and abduction ranges of ankle 
 joints , according to x , y , and z - axes . 
 [ results ] pelvic position was found to be 
 positively correlated with differences between left and right hip flexion ( r=0.51 ) , hip 
 abduction ( r=0.62 ) , knee flexion ( r=0.45 ) , knee abduction ( r=0.42 ) , and ankle inversion 
 ( r=0.38 ) . in addition , the difference between left and right hip abduction showed a 
 positive correlation with difference between left and right ankle dorsiflexion ( r=0.64 ) . 
 
 moreover , differences between left and right knee flexion exhibited positive correlations 
 with differences between left and right knee abduction ( r=0.41 ) and ankle inversion 
 ( r=0.45 ) . 
 [ conclusion ] bilateral pelvic tilt angles are important as they lead to 
 bilateral differences in lower extremity joint angles during walking . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION