functional movements and balance are elements that decrease the risk of injuries1 . functional movement is defined as the 
 ability to produce and maintain a balance between mobility and stability through the kinetic 
 chain while performing fundamental patterns with accuracy and efficiency2 . the functional movement screen ( fms ) is a valid and reliable method 
 of assessing symmetry of motion and risk of injury4 . three of the seven kinds of movement of the fms are correlated with 
 the function of the lower extremity . there movements are the deep squat , hurdle step , and 
 in - line lunge . chronic ankle instability ( cai ) has been linked to several mechanical and functional 
 insufficiencies , and several mechanical impairments have been identified as contributing 
 factors for cai5 . deficits in postural 
 control and other functional impairments are thought to be the result of a loss of 
 somatosensory information due to damaged ligament mechanoreceptors6 . postural stability can be defined as postural balance or 
 postural steadiness while postural balance is defined as the ability to stay upright or to 
 recover equilibrium after external dynamic perturbations ; under altered somatosensory 
 conditions , postural steadiness , sometimes refers to standing as still as possible on a 
 force platform7 . postural control is facilitated by postural movements that control body sway such that the 
 center of mass remains above the area of support8 . direct measures of the postural control movements quantified the 
 sway angle of the center of mass or the kinematics of specific joints9 . indirect methods include , for example , the quantification 
 of the center of pressure ( cop ) movement or the measurement of activation of muscles 
 involved in postural control10 . these 
 represent outcomes of the inertial forces of the body and restoration of equilibrium forces 
 of the postural control system11 , 12 . recently , the wii , designed and marketed 
 by nintendo , has attracted considerable attention as a new generation device . as an 
 accessory of the wii thus , cai patients should realize that assessment of functional movements and balance as a 
 possible means of injury prevention is as important as evaluating and treating injuries . the 
 purpose of this study was to compare the cop displacement during two kinds of movement of 
 the fms measurable on a wbb in patients with cai and healthy subjects . we recruited cai patients ( n=25 ) and healthy subjects ( n=25 ) who worked at a rehabilitation 
 center in the republic of korea . subjects were classified as having cai if they reported having 
 the following : ( 1 ) instability that they attributed to an initial injury , ( 2 ) giving way in 
 the last 6 months , and ( 3 ) one or more problems according to the items of the foot and ankle 
 disability index ( fadi ) . subjects were excluded if they reported any of the following : ( 1 ) 
 bilateral ankle instability , ( 2 ) history of ankle fracture , ( 3 ) ankle injury within 3 months 
 of participation , and ( 4 ) history of balance disorder . participation in the study was 
 voluntary , and the subjects fully understood the content of the study . after providing an 
 explanation of the study s purpose and the experimental method and processes , written 
 informed consent was obtained from all the subjects . each item is scored from 0 ( unable to do ) to 
 4 ( no difficulty at all ) . the subjects characteristics are summarized in table 1table 1.characteristics of subjectspatients with cai(n=25)control(n=25)gender ( person)male ( n)1011female ( n)1514age ( yrs)24.81.527.43.1height ( cm)165.36.9168.57.5weight ( kg)59.912.465.311.1bmi ( kg / m)21.54.023.12.6rom - na ( deg)34.66.738.27.1rom - a ( deg)28.27.439.54.2fadi ( % ) 77.27.3100.00.0meanssd . for the control group , affected is the dominant lower extremity and 
 non - affected is the non - dominant lower extremity . bmi : body mass index ; rom : range of motion ; na : non affected ; a : affected ; cai : 
 chronic ankle instability ; fadi : the foot and ankle disability index . for the control group , affected is the dominant lower extremity and 
 non - affected is the non - dominant lower extremity . bmi : body mass index ; rom : range of motion ; na : non affected ; a : affected ; cai : 
 chronic ankle instability ; fadi : the foot and ankle disability index all participants performed cop measures and fms testing . the fms was developed as an 
 evaluation tool for functional movement15 . balance was assessed on a wbb with the feet apart during the deep squat and hurdle 
 step . each position was measured three times . for the current study , sampling for data 
 collection was performed at 50  hz and 10  hz ( using a low - pass filter ) . measurements were 
 taken for 15 and 30 seconds with a 60-second rest between each task . the reliability had an 
 icc ranging from 0.660.94 , and the pressure points on the center of pressure validity had 
 an icc ranging from 0.770.8916 . parameters calculated from the cop data included the standard deviation of the path length , 
 velocity , and area of the 95% confidence ellipse ( area 95)17 . for the deep squat , the subject assumed the starting position by placing the feet shoulder 
 width apart on the wbb . the subject then rested the dowel on top of the head and adjusted the hand position so that 
 the elbows were at 90. the subject then slowly performed the deepest squat possible , 
 keeping the heels on the floor , head and chest facing forward , and the dowel raised as high 
 as possible overhead . the subject was instructed to keep the knees aligned over the feet , 
 with no valgus collapse . if 
 the subject could not meet the conditions for a score of 3 in the deep squat , then the 
 movement was performed again with an fms kit board placed under the heels for evaluation of 
 a score of 2 . if requirements listed for a score of 2 were not achieved , then the subject 
 received a score of 1 . if the subject experienced pain during the movement , a final score of 
 zero was given for the deep squat test . for the hurdle step , the height of the tibia was measured from the floor using the tibial 
 tuberosity as a reliable landmark and a dowel as the measuring device . the dowel was positioned across the shoulders 
 behind the neck , and the subject stood on a wbb . the subject stepped over the hurdle with 
 one leg , touched his / her heel to the floor while maintaining the stance leg in an extended 
 position , and then returned the moved leg to the starting position . the same procedure was 
 repeated with the other , and leg scored the hurdle - stepping leg . a score of 3 was given for 
 the hurdle step if the subject s hips , knees , and ankles remained aligned in the sagittal 
 plane , there was minimal to no lumbar movement , and the dowel and hurdle remain parallel . if 
 any of the criteria were not achieved for a score of a 3 , a score of 2 was given , and if the 
 criteria for a score of 2 could not be achieved , a score of 1 was given . if the subject 
 experienced pain during the movement , a final score of a zero was given for the hurdle 
 step1 , 15 , 
 18 . descriptive statistics of the means and standard deviations of all data measured in this 
 study were produced using pasw statistics 18.0 ( spss , chicago , il , usa ) . shapiro - wilk tests 
 of normality were used to determine if the dependent variables were normally distributed . differences in cop excursion are presented in table 
 2table 2.center of pressure outcome measurestaskpatients with caicontrol95% confidence intervallowerupperdeep squatpath length ( cm)55.5812.6251.627.392.89 10.83 velocity ( cm / s)6.471.176.131.400.51 1.20 area95 ( cm)22.548.8921.449.534.97 7.16 hs - napath length ( cm)75.5818.3765.2811.880.06 20.54 velocity ( cm / s)8.721.517.461.490.27 2.25 area95 ( cm)64.4627.2849.2215.270.56 29.93 hs - apath length ( cm)70.0714.5369.0110.457.31 9.41 velocity ( cm / s)8.171.327.941.670.76 1.22 area95 ( cm)70.3226.7869.7832.4022.04 17.12 meanssd * p<0.05 . for the control group , affected is the dominant lower extremity and 
 non - affected is the non - dominant lower extremity . cai : chronic ankle instability ; na : non affected limb stepping ; a : affected limb 
 stepping ; hs : hurdle step . significant differences were observed between groups in comparisons of the 
 cop path length , velocity , and area 95 in the hurdle step with the non - affected limb 
 ( p<0.05 ) . however , there were no significant differences in the deep squat and hurdle 
 step with the affected limb between the groups ( p>0.05 ) . meanssd * p<0.05 . for the control group , affected is the dominant lower extremity and 
 non - affected is the non - dominant lower extremity . cai : chronic ankle instability ; na : non affected limb stepping ; a : affected limb 
 stepping ; hs : hurdle step this study sought to investigate differences in postural control between cai patients and 
 healthy subjects . impairments in feedback sensorimotor function have long been thought to be 
 a consequence of an initial lateral ankle sprain and a mechanism of cai . recent research has 
 indicated that central changes in sensorimotor function are present in patients with 
 cai19 . cai patients showed more 
 postural sway compared with normal subjects in the hurdle step supported by the affected 
 lower extremity . the area 95 represents the cop of the area formed by an oval shape about 
 the center of the cop and is used to assess the spatial aspect of balance17 . in the present study , the sway distance 
 was longer , the velocity was faster , and the area 95 was wider in the hurdle step with the 
 non - affected limb compared with that with the affected limb . this indicates that the cai 
 patient s ability to balance is deteriorated compared with that of a healthy subject20 . the hurdle step also measures single - leg stability , as well as stability in the knees and 
 hips . in a previous study , subjects with a unilateral chronic ankle sprain showed weakness 
 involving the ipsilateral hip abductor due to cai . after lower limb ligamentous injuries , 
 dynamic postural stability of the lumbopelvic complex decreases21 . this has an effect on postural control , and it also seems 
 to have an influence on the cop path length , velocity , and area 95 . these corrections , or 
 postural sway , keep the cop within the base of support during the hurdle step22 . small postural sway adjustments can be 
 used as ankle strategies in maintaining balance . during changes in balance , excessive 
 lateral displacement of the center of gravity when the ankle is unable to compensate 
 adequately for this lateral sway , then a hip strategy is initiated , which helps to prevent 
 the ankle from excessive inversion movement , and it has been suggested that altered 
 sensation in the ankle joint can lead to muscle function changes in another , more proximal 
 joint22 . the deep squatting posture can be described as a sitting posture with ankle dorsiflexion , 
 knee flexion , and hip flexion24 . in this 
 study , there was no statistically significant difference in the results from deep squat 
 assessment of cop path length , velocity , and area 95 in healthy subjects and those with cai . 
 when deep squat assessment of the fms , any of the criteria for a score of three are not 
 achieved , performing the test with the board from the described fms kit ( 2 inch ) under the 
 heels . because of this influence , when removing the kit and to the assessment would have 
 seemed the differences between the two groups . however , when there is no kit , lifting the 
 heel higher than the full squatting position is known to shift the center of mass forward 
 and the whole body is adjusted through segmental linkage coordination . when the heel was 
 raised , this postural adjustment made stability critical . the tip - toe squatting condition 
 places the center of pressure within a small area of the base of support ( bos ) , and the bos 
 length may influence subjects ability to perform the squat movement25 . this deep squat evaluation seems difficult to determine the difference from the subjects 
 because the operation using all of the both limb . it is possible to evaluate the deep squat 
 with a wbb ; however , this requires precise , symmetrical positioning of the feet and 
 precludes the assessment of individual limb cop movements . consequently , the force under 
 each foot is typically measured independently , which requires a wbb26 . regardless of the lower extremity muscle activation 
 pattern , these data suggest that supraspinal aspects of motor control are susceptible to 
 cai . significant differences in cop path length , velocity , and area 95 in the hurdle step with 
 the affected lower extremity were identified as significant predictors of cai patients and 
 thus decreased postural stability compared with that of normal subjects . these findings help 
 elucidate the factors contributing to cai and may be helpful in the development of methods 
 of preventing and treating cai
[ purpose ] the aim of this study was to evaluate postural control during two different 
 movements of the functional movement screen in patients with chronic ankle instability 
 compared with healthy subjects . [ subjects ] this study was a cross - sectional survey of 50 
 participants comprised of 25 chronic ankle instability patients and 25 healthy subjects . 
 [ methods ] all subjects were subjected to measurement of the foot and ankle disability 
 index and center of pressure and functional movement screen testing . 
 the deep squat and 
 hurdle step were performed for the lower extremities in functional movement screen 
 testing . 
 then , the center of pressure was measured with balance assessment software using 
 a nintendo wii balance board . 
 the center of pressure path length , velocity , and area of 
 the 95% confidence ellipse and functional movement screen scores were evaluated for all 
 subjects . 
 [ results ] the results showed significant differences in center of pressure path 
 length , velocity , and area of the 95% confidence ellipse between the groups for the hurdle 
 step with the non - affected limb . 
 however , there were no significant differences between 
 groups for the deep squat and hurdle step with the affected limb . 
 [ conclusion ] the results 
 of this study showed that there was a difference in the hurdle step with the non - affected 
 limb in chronic ankle instability patients compared with normal subjects .