square turning is frequently used for corners , and semicircular turning is often used to 
 avoid obstacles during activities of daily living1 . balance is challenged during turning gaits , and this is one of the 
 most common reasons for falls by older adults1 , 2 .
many older adults have decreased postural 
 stability and have considerable visual through , for example , cataracts , glaucoma , or macular 
 degeneration , the leading cause of visual impairment3 .
vision plays a key role in stabilizing balance in a number of ways . 
 visual cues before and during gait help us determine our speed of locomotion , and vision 
 also allows us to influence the alignment of the body with reference to gravity and the 
 environment during walking .
previous biomechanical studies have indicated that head 
 stabilization and motion coordination between the head and trunk enhance postural control to 
 balance the moving body and visual acuity for navigational control through a cluttered 
 environment4 , 5 .
however , few studies have investigated the effects of gait velocity 
 and com during square and semicircular turning gaits of older people with pbva .
therefore , 
 the purpose of this study was to investigate gait velocity and center of mass ( com ) during 
 square and semicircular turning gaits of elderly women with good and poor visual acuity .
a total of 20 elderly women who could walk independently were recruited from among 
 community dwellers .
visual acuity was measured with hahn s vision test chart ( kor ) . the 
 participants binocular visual acuity ( bva )
was evaluated separately with and without 
 participants own spectacles before they performed the tasks .
the participants were 
 categorized into two groups : those with poor vision ( pbva ; corrected bva 0.5 ) and those 
 with good vision ( gbva ; corrected bva 0.7 ) .
the pbva group consisted of subjects aged 75.00 
 ( mean )  6.14 ( standard deviation ) years , with average height and weight of 149.26  4.68  cm 
 and 50.06  5.85  kg , respectively , and left side va and right side va of 0.34  0.11 and 
 0.31  0.17 , respectively .
the gbva group consisted of subjects aged 77.45  6.15  years , 
 with average height and weight of 149.43  3.89  cm and 50.42  6.24  kg , respectively , and 
 left side va and right side va of 0.72  0.13 and 0.73  0.15 , respectively .
the inclusion 
 criteria were as follows : older than age 65  years with bva of 5/10 or worse for the pbva 
 group , older than age 65  years with bva of 7/10 or better for the gbva group , the ability to 
 walk independently without any assistive device , and a score > 24 on the korean version of 
 the mini - mental state exam .
each subject provided her informed consent before participating 
 in this study , which was approved by the inje university faculty of health sciences human 
 ethics committee .
gait velocity and com during square and semicircular turning gaits were 
 measured with a tri - axial accelerometer ( fit dot life , suwon , korea ) .
the accelerometer was 
 35  35  13  mm in size and weighed 13.7 grams .
the range of the sensor is 8 g and + 8  g , 
 and it can be adjusted using the data acquisition software ( fitmeter manager 2 , ver . 
 1.2.0.14 , korea ) .
we recorded the raw data using the x- , 
 y- , and z - axes of acceleration .
the data were 
 automatically transferred to a computer via a usb cable connection . in the present study , we 
 selected a range of 2  g. data
the investigator explained the procedure of the tests 
 before the participants walked along pathways which were marked with colored tape on the 
 floor to indicate inner leg placement .
the square turning pathway consisted of a 3-m 
 straight path , a 1.5-m 90 turn , and a 3-m straight return path .
the semicircular turning 
 pathway consisted of a 3-m straight path , a 2.35-m semicircular curved path with a radius of 
 0.75 m , and a 3-m straight return path .
the accelerometer was fixed 
 with double - sided adhesive tape over participants l3 spinous process .
the participants were 
 asked to walk on the pathway with bare feet at a self - determined speed for the two tasks : 
 walking along the square turning gait pathway with a left turn and , walking along the 
 semicircular turning gait pathway with a left turn .
participants started and finished 
 walking 2  m before and after the start and end of the pathways , respectively , to avoid the 
 effects of acceleration and deceleration on measurements7 .
the velocities of square and semicircular turning ( 64.60  6.80 and 69.87  6.48 [ cm / sec ] , 
 respectively ) in the gbva group were significantly higher than those of the pbva group 
 ( 49.78  4.87 and 53.58  6.86 [ cm / sec ] , respectively ; p < 0.05 ) .
the com of square and 
 semicircular turning ( 1147.45  121.36 and 1289.71  199.35 [ cm / s ] , 
 respectively ) of the gbva group was significantly lower than that of the pbva group ( 1355.32 
  224.76 and 1542.48  289.03 [ cm / s ] , respectively ; p < 0.05 ) .
in the present study , we found that the velocity of the gbva group during square and 
 semicircular turning gaits was significantly higher than those of the pbva group , and the 
 com of the gbva group during square and semicircular turning gaits was significantly less 
 than that of the pbva group .
these findings indicate that visual acuity affects gait 
 velocity and balance during square and semicircular turning gaits .
rhea and rietdyk8 investigated the roles of visual 
 exproprioception in navigating obstacles during walking under four visual conditions .
they 
 occluded that visual exproprioceptive information is used to finely regulate the lower limb 
 trajectory during obstacle avoidance .
thus , the gait velocity and balance control ability of 
 older adults with gbva during square and semicircular turning are higher than those of older 
 adults with pbva performing the same conditions . in this study , although the gait velocity 
 of the pbva group was slower , their com movements were significantly greater than those of 
 the gbva group . walking directly forward
demands that equal forces be imparted to the body 
 from by limbs , whereas turning requires limb kinetic asymmetry .
furthermore , a greater 
 threat to balance emerges because the com leans toward the inner side of the turning 
 path9 .
our findings suggest that older 
 adults with pbva use more cautious gait strategies to perform changes in the direction of 
 travel , decreasing gait velocity to prevent falls . however , gait velocity frequently changed 
 during turning gaits . therefore , we suggest that complex tasks such as changing the 
 direction of travel while walking are among the biggest challenges for elderly people with 
 pbva . thus , elderly people with pbva require balance and gait training in a diverse 
 environment to prevent falls .
 [ purpose ] the purpose of this study was to investigate gait velocity and center of mass 
 ( com ) during square and semicircular turning gaits between two groups of elderly people 
 with differing visual acuity . 
 [ subjects ] twenty elderly korean women who could walk 
 independently and who lived in the community were recruited . 
 [ methods ] we measured gait 
 velocity and com using an accelerometer during two different turning gaits . 
 [ results ] the 
 velocity during square and semicircular turning gaits of participants with good binocular 
 visual acuity ( gbva ) was significantly higher than that of participants with poor 
 binocular visual acuity ( pbva ) . 
 the com during square and semicircular turning gaits of 
 the gbva group was significantly decreased compared with that of the pbva group . 
 
 [ conclusion ] these findings suggest that visual acuity affects velocity and com during 
 square and semicircular turning gaits of elderly people . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION