Journal of Rehabilitation Medicine 51-1CompleteIssue | Page 75

72
K. Akizuki et al.
effect of BBS or TUG in this population. The
Unstable Board Balance Test was also designed to
be portable and not restricted by the measurement
environment, as well as providing objective, quanti-
tative measures promptly. Therefore, the purpose of
the current study was to determine the sensitivity
and specificity of the Unstable Board Balance Test
in differentiating individuals with a positive history
for falls among a group of healthy, active, elderly
individuals, and to compare the results with those
from the TUG and FRT. If the Unstable Board
Balance Test is valid in detecting slight reductions in
the balance capacity of individuals with a fall history,
then the test could be useful for early identification of
those at risk of falls in the community, allowing for the
opportunity to provide a falls prevention intervention.
METHODS
Subjects
In this study, we recruited elderly people living near the Iwatsuki
Campus of Mejiro University, who attended the Saitama City
Silver Resource Center between 28 February 2017, and 4 August
2017. The inclusion criteria were as follows: (i) age ≥ 65 years;
(ii) living independently in the community; (iii) ability to walk
independently, without an assistive device; and (iv) ability to
visit the university facility where the study was conducted,
without assistance. Individuals with a history of orthopaedic
surgery that could affect balance or neurological diseases, as
well as those with pain when performing the unstable board
balance test and those with a Mini-Mental State Examination
(MMSE) score < 24 were excluded.
In order to calculate the sample size required for the study,
a preliminary survey of 29 subjects was performed. The effect
size of the Medial-lateral Stability Index (MLSI), the primary
outcome of the Unstable Board Balance Test, was 1.33, with
a ratio of 5:24 between individuals with a history of fall (fal-
lers) and those without a history of falls (non-fallers). Using
G*power 3.1.9.2 software (17), the required sample size was
calculated for an alpha value of 0.05 and power (1 – β) of 0.80.
A sample size of 36 individuals (6 fallers and 30 non-fallers)
was required. In order to control for confounding variables
during the matching between fallers and non-fallers, we made
the decision to recruit 58 individuals, to have at least 10 fallers
and appropriate non-faller matched controls.
A preliminary explanation of the details of the study was
given to all subjects, and written consent was obtained. The
study protocol was approved by the institutional review board
of Mejiro University (approval number 17-004).
a)
b)
Fig. 1. The unstable board used in this study. (a) Top surface, (b) bottom
surface.
Unstable Board Balance Test. All tests were performed using
the DYJOC unstable board (SAKAI Medical Co. Ltd, Tokyo,
Japan). The DYJOC board has a dimension, of 300 × 500 × 30
mm with 2 semi-circular bosses (φ160 × 60 mm) attached to the
rear of the platform. For this study, the 2 bosses were attached
to restrict the tilt movement to the medial-lateral (ML) direction
(Fig. 1), as allowing unrestricted movement in all directions ma-
kes the task too difficult to complete for elderly individuals. In
addition, blocks were inserted on either side of the board to allow
a maximum tilt angle of 12° (Fig. 2). The board was fitted with
a small 3-axial accelerometer and a 3-axial gyroscope (multi
sensor θ, SAKAI Medical Co. Ltd) to measure the tilt degree
and the acceleration. The data were transmitted to a personal
computer via a dedicated data logger (Data Logger, SAKAI
Medical Co. Ltd). The MLSI was calculated using analysis
software (MS DYJOC, SAKAI Medical Co. Ltd), as follows:
MLSI = √ ∑–(0–x)
n
,
where x is the degree of tilt of the board in the ML plane and n
the number of samples (sampling frequency, 100 Hz). Because
the given stability index reflects the change in the inclination
of the unstable board per unit time, a larger value indicates a
greater degree of fluctuation in ML balance control.
Subjects were instructed to stand on the board, with feet at
shoulder width and arms along the side of the body, and to
maintain the position of the unstable board as parallel to the
floor as possible. Subjects were asked to fix their gaze on a focal
point placed 1 m in front of them, which was adjusted to eye
level for each subject. All measurements were obtained without
shoes. Each subject completed 3 20-s trials.
2
Functional reach test (FRT). The subject was instructed to stand
sideways along a wall, to which a measuring tape was affixed,
with the arm closest to the wall at 90° of shoulder flexion. In this
standardized standing position, the location of the tip of the third
Experimental design and outcome
This was a case-control study, with the following measures ob-
tained for analysis: demographic and personal information (age,
body height, body weight, history of falls over the past year)
and balance performance outcomes (Unstable Board Balance
Test score, the FRT and the TUG). The BBS was not included
due to its previously reported ceiling effect for healthy, active,
elderly individuals (13, 15). The measurement method for each
balance performance test is described below.
www.medicaljournals.se/jrm
Fig. 2. Tilt angle adjustment method. The maximum tilt angle was
limited to 12° by placing a 2.5-cm plate on both sides of the board.