many older adults have substantial vision problems such as cataracts , glaucoma , and macular 
 degeneration , which are the leading causes of reduced visual acuity1 . poor vision is one of the most important risk factors 
 associated with falls among older people2 . vision plays a key role in maintaining balance by providing information about the 
 environment and constant information to the central nervous system about body orientation in 
 space and relative to other body parts3 . achieving effectively maintained balance during functional dynamic balance tasks requires 
 energy efficiency to minimize fatigue , which is associated with postural control deficits , 
 and stability to prevent falling or injury4 . among the clinical balance tests , the single - limb stand ( sls ) is a 
 commonly used clinical tool for assessing postural stability in the elderly and individuals 
 with various balance disorders . the y - balance test ( ybt ) , which was developed by clinical 
 applications of the star excursion balance test , involves maintaining a sls while reaching 
 as far as possible with the other leg . as a dynamic sls balance test , the ybt has been used 
 to prospectively identify individuals who have chronic ankle instability and greater risk of 
 lower extremity injury in sports and as a post - rehabilitation test5 . recently , the test has been used as a screening tool for 
 elderly participation6 . however , no 
 studies have investigated energy expenditure during the dynamic single - limb balance test in 
 older adults with different visual acuities . therefore , this study compared energy 
 expenditure in the ybt , the functional dynamic single - limb balance test , in elderly people 
 with good and poor binocular visual acuity ( bva ) . a total of 21 elderly females from community housing were enrolled in the present study . visual acuity was measured by use of a , jin s vision test chart ( jv institute , seoul , south 
 korea ) . each participant s bva was evaluated with and without their own spectacles for 
 classification into two groups : poor bva ( corrected bva  0.4 logarithm of the minimum angle 
 of resolution [ logmar ] ) and good bva ( corrected bva  0.3 logmar)7 . in the poor bva group , the participants average age 
 ( meansd ) , height , and weight were 78.555.24  years , 148.862.77  cm , and 49.466.05  kg , 
 respectively ; they had a left side va and right side va of 0.530.15 logmar and 0.540.16 
 logmar , respectively . in the good bva group , the participants average age , height , and 
 weight were 76.406.13  years , 147.004.00  cm , and 48.994.91  kg , respectively ; they had a 
 left side va and right side va of 0.230.07 logmar and 0.230.09 logmar , respectively . all 
 participants could walk independently without an assistive device and scored greater than 24 
 points on the korean version of the mini - mental state examination . they had no past or 
 present neurological disorder , no musculoskeletal disease that could interfere with daily 
 activities , and no significant auditory impairments , and they were not taking drugs that 
 could have influenced the results of this study . ethical approval was obtained from the inje 
 university faculty of health science human ethics committee , and all subjects signed an 
 informed consent form prior to their participation . a triaxial accelerometer ( fit . life , suwon , south korea ) was used to measure energy 
 expenditure during the ybt . we measured the raw data using the x , y , and z variables of 
 acceleration reformed as acceleration due to activity by removing gravitational 
 acceleration . moreover , we calibrated the single vector magnitude ( svm ) by summing the 
 acceleration of the three axes8:svm =   in the present study , a range of 2 g was selected . data were collected at a sampling rate 
 of 32  hz . before the task , the participant s dominant leg was determined by kicking a soccer ball . 
 for normalization , the lower limb lengths of all participants were measured in supine 
 position from the anterior superior iliac spine to ipsilateral medial malleolus using a 
 cloth tape measure . reach distance was normalized to limb length , and the maximum reach 
 distance was expressed as a percentage of limb length ( % maxd ) . the normalized value was 
 calculated as reach distance divided by limb length and then multiplied by 100 . composite 
 reach distance was the sum of the three reach directions divided by 3 times the limb length , 
 which was then multiplied by 100 . the accelerometer was fixed with double - sided adhesive tape 
 over the l3 spinous process9 . for the test , the participants stood with one foot on the center footplate from the ybt 
 kit ( move2perform , evansville , in , usa ) at the starting line and their hands 
 on their pelvis . they were asked to push the reach - indicator block with the free limb in the 
 anterior ( a ) , posterior medial ( pm ) , and posterior lateral ( pl ) directions in relation to 
 the stance foot on the central footplate . the testing order was trial standing on the right 
 foot reaching in the a direction ( right a reach ) followed by trial standing on the left foot 
 reaching in the a direction . after the test trials were 
 completed , each participant was given a 2-minute rest period and then conducted three test 
 trials in each direction11 . a trial was classified as invalid if the 
 participant did not return to the starting position , placed the reach foot on the ground on 
 either side of the line or tube , raised or moved the stance foot during the test , or kicked 
 the plate with the reach foot to gain more distance . if an invalid trial occurred , the data 
 were discarded , and the participant repeated the trial . statistical analysis was performed using the spss software ( version 18.0 for windows , spss 
 inc . , a paired t - test was used to examine differences between right and 
 left limb reach distances . as no differences were found , for the data analysis , we used the 
 dominant limb distance in each direction ( right side ) . the differences in reach distance and 
 energy expenditure were analyzed using the independent t - test for comparisons between 
 groups . effect sizes ( cohen s d ) for test differences were calculated by 
 determining the difference between the poor bva and good bva group mean values and dividing 
 by the pooled standard deviation12 . the normalized reach distance ( % maxd ) in the good bva group ( a , 60.84.3 ; pm , 94.36.1 ; pl , 
 88.97.8 ) during the ybt in the three directions and composite reach ( 81.34.8 ) were 
 significantly longer ( p < 0.05 ) compared with the values in the poor bva group ( a , 
 55.65.9 ; pm , 84.29.9 ; pl , 81.75.4 ; composite , 73.86.2 ) . the energy expenditure 
 ( cm / s ) in the good bva group during the ybt in the three directions ( a , 
 413.8145.2 ; pm , 490.0189.4 ; pl , 585.8209.7 ) was significantly reduced ( p < 0.05 ) 
 compared with the values in the poor bva group ( a , 697.4231.6 ; pm , 698.8227.3 ; pl , 
 791.6182.7 ) . the effect size value of the reach distance and energy expenditure showed that 
 the results were large for the a ( 1.064 and 1.525 ) , pm ( 1.268 and 1.044 ) , pl directions 
 ( 1.187 and 1.104 ) and composite reach ( 1.412 ) in terms of the differences between the good 
 and poor bva groups . this study was designed to compare energy expenditure and reach distance during the ybt in 
 elderly women with good bva and poor bva . it showed that normalized reach distances in the 
 a , pm , and pl directions and the composite reach of the good bva group were significantly 
 greater compared with the values in the poor bva group . the reach distance during the ybt 
 reflected the degree of dynamic balance control . a longer reach thus , our findings suggest that visual acuity affects the 
 functional dynamic sls in the a , pm , and pl directions . moreover , older adults with poor bva 
 are more balance challenged compared with those with good bva . in the a reach direction , participants received visual feedback during the ybt . wang et 
 al.13 showed that reduction of the 
 stability boundary of the multi - joint coordination patterns in maintaining the sls in the 
 absence of vision could lead to increased rotation of segments around the center of mass . hallemans et al.14 reported that no 
 vision conditions limited movements of the hip and ankle in the sagittal plane compared with 
 a full vision condition . although , visual awareness is reduced in the pm and pl directions 
 compared with the a direction , participants with good bva have a longer reach compared with 
 those with poor bva . when one sense diminishes , it is common to find a greater dependence on 
 other sensory cues to preserve balance15 . 
 however , hazime et al.16 reported that 
 vision had a key role in the sls , requiring greater balance ability , whereas perturbation in 
 proprioception showed effects only in the double- limb stance . the stance platform of the 
 ybt kit is elevated 1 inch , and its width is 5.2 inches ; thus , maintaining 
 balance in the dynamic sls on the balance platform of the ybt kit is greater 
 challenge than doing so on the ground in elderly subjects . the results show that elderly 
 people with good and poor bva rely more on visual input than other sensory inputs for 
 postural control . in addition , in this study , the energy expenditure during the ybt in three 
 directions in the poor bva group was significantly increased compared with the values in the 
 good bva group . an accelerometer was used as an objective tool for assessing physical 
 activity level related to energy expenditure . accelerometry has been shown to have 
 intra - rater reliabilities ( 0.9250.994 ) and correlation with scores on the commonly used 
 physical activity questionnaire ( r = 0.830)17 . our results imply that the velocity of trunk segment motion 
 frequently changes and fluctuates , and that ineffective biomechanical cost strategies in 
 terms of energy efficiency are performed . individuals with poor bva may habituated to 
 discomforts visual acuity and rely more on ankle proprioception to control their posture 
 during quiet standing . when balance challenged with conditions such as the sls , vision play 
 a major role compared with in a normal standing position . thus we surmise that these 
 individuals compensate with trunk rotation during ybt in order to maintain postural 
 stability16 , 18 . hence , participants with good bva have a longer reach in the ybt 
 compared with those with poor bva . first , it only measured reaching distances and energy 
 expenditure . measurements of muscle activation and range of motion in the trunk and lower 
 extremities were not taken . thus , we could not explain the connection between energy 
 expenditure and fatigue or trunk lean during the ybt . second , the valid of the triaxial 
 accelerometry in measurement of energy expenditure during a short period of activity has not 
 been verified . in addition , the sample size was small , so caution should be used when 
 generalizing the results . further studies should investigate kinematic and kinetic data , as 
 well as the correlation of the ybt with gait parameters in elderly subjects with poor 
 bva .
[ purpose ] this study compared the energy expenditure during the y - balance test ( ybt ) 
 between elderly women with good binocular visual acuity ( bva ) and those with poor bva . 
 [ subjects ] twenty - one elderly women who could walk independently were recruited from a 
 community dwelling . 
 eleven participants had a bva equal to or less than 0.4 logarithm of 
 the minimum angle of resolution ( logmar ) , and the other 10 participants had a bva equal to 
 or better than 0.3 logmar . 
 [ methods ] the participants had an accelerometer attached over 
 the l3 spinous process for measurement of energy expenditure and performed the ybt in the 
 anterior , posteromedial , and posterolateral directions . [ results ] the normalized reach 
 distance in the good bva group during the ybt in three directions and composite reach 
 distance were significantly longer compared with the values in the poor bva group . 
 the 
 energy expenditure in the good bva group during the ybt in the three directions was 
 significantly reduced compared with the values in the poor bva group . 
 [ conclusion ] we 
 suggest that visual acuity in the elderly influences dynamic balance and energy 
 expenditure . elderly subjects with poor bva showed poor dynamic balance control and an 
 inefficient biomechanical cost strategy compared to subjects with good bva .