582
Effects of Age on Balance Control During Walking
Nataliya Shkuratova, BPht, Meg E. Morris, PhD, Frances Huxham, DipPT
ABSTRACT. Shkuratova N, Morris ME, Huxham F. Effects
of age on balance control during walking. Arch Phys Med
Rehabil 2004;85:582-8.
Objective: To determine the effects of aging on balance
control during walking.
Design: Two-group repeated-measures design.
Setting: Gait laboratory in Australia.
Participants: Convenience sample of 20 healthy older subjects (mean age, 72y) and 20 healthy young subjects (mean age,
24y).
Interventions: Changes in locomotor performance in response to perturbations to balance were quantified for healthy
older adults compared with healthy young adults for (1)
straight line walking at preferred speed, (2) straight line walking at fast speed, (3) figure-of-eight walking at preferred speed,
and (4) figure-of-eight walking while performing a secondary
motor task.
Main Outcome Measures: Gait speed, stride length, cadence, and double-limb support duration, using a footswitch
system.
Results: Healthy older people screened for pathology had
gait patterns comparable to young adults for straight line walking at preferred speed. However, multivariate analysis of variance (MANOVA) showed a significant interaction between age
and speed when balance was perturbed by requiring subjects to
change from walking at preferred to fast speeds (Pillai-Bartlett
trace⫽.259, F4,35⫽3.06, P⬍.029, partial ␩2⫽.259). This occurred because older people did not increase their speed
(F1,38⫽7.65, P⬍.01, partial ␩2⫽.168) or stride length
(F1,38⫽12.23, P⬍.01, partial ␩2⫽.243) as much as did the
young adults. MANOVAs did not show statistically significant
interactions between age and turning conditions or age and dual
task conditions, although older people walked more slowly and
with shorter steps when turning or performing a secondary
task.
Conclusions: Balance strategies during gait are task specific
and vary according to age. In response to challenges to balance
imposed by the requirement to change from preferred to fast
walking, older people did not increase their speed and stride
length to the same extent as did younger adults. This was
possibly a strategy to maintain their stability.
Key Words: Aging; Balance; Gait; Geriatrics; Locomotion;
Rehabilitation.
© 2004 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and
Rehabilitation
From the School of Physiotherapy, La Trobe University, Bundoora, Melbourne,
Australia.
Supported by the Australian Association of Gerontology and the National Health
and Medical Research Council of Australia (doctoral stipend).
No commercial party having a direct financial interest in the results of the research
supporting this article has or will confer a benefit on the author(s) or on any
organization with which the author(s) is/are associated.
Reprint requests to Meg Morris, PhD, Sch of Physiotherapy, La Trobe University,
3086, Australia, e-mail: M.Morris@latrobe.edu.au.
0003-9993/04/8504-8129$30.00/0
doi:10.1016/j.apmr.2003.06.021
Arch Phys Med Rehabil Vol 85, April 2004
HE ABILITY TO CONTROL balance while walking is a
T
fundamental skill that is frequently compromised by advanced age. In humans, the ability to walk depends not only on
being able to generate a rhythmic locomotor pattern, to maintain upright stance, and to control the trajectory of the center of
mass (COM) despite a narrow and moving base of support.1,2
For older people, control of dynamic balance can become
increasingly difficult,3,4 and walking is associated with an
increased risk of falls.5,6
The effect of age on balance control during walking is not
well understood. Until recently, balance research mainly focused on the ability of young and older adults to maintain
equilibrium in standing or to recover steady stance after perturbations to the COM, by using stepping strategies.7-10 Some
standing balance experiments measured the ability of older
people to prepare for and respond to preplanned or unexpected
perturbations to stability arising from pushing or pulling forces.10,11 Other experiments measured the ability of older people
to recover standing balance in response to multidirectional
floor platform translations.12 Still others measured the ability of
older adults to step in response to large pushing or pulling
forces or support surface motion.9,13 Older people typically
showed increased postural sway in steady stance,14 inability to
execute effective stepping responses, and difficulty controlling
displacements of the COM and center of pressure relative to
their limits of stability.15 Whether these standing balance findings generalize to the dynamic task of walking remains a
question.
One of the few studies that has measured balance while
walking of young adults compared with older adults is that of
Gabell and Nayak.16 They concluded that pathology rather than
chronologic age was the main cause of postural instability
during gait. This conclusion was based on their finding that
healthy older and young adults showed similar levels of variability and mean values for stride width and double-limb support duration, which, they argued, represented compensations
for balance disturbance. Stringent medical screening to exclude
pathology left only 32 of 1187 older individuals in their sample. Unfortunately, they did not include pathology screening of
the young adults. The nonsignificant differences between
groups in spatiotemporal gait variables might have arisen because variability was abnormally low in the pathology-free
older people yet relatively high in the younger subjects—some
of whom may have had musculoskeletal or neurologic disorders. The danger in assuming that pathology is the main cause
of balance disturbance in older people is that clinicians might
bias prescribed interventions to prevent falls toward people
with diagnosed pathology, thus overlooking healthy older people until they fall.
The experiment by Gabell and Nayak16 also set a precedent
for assessing “balance” separately from “locomotion.” This
artificial division is no longer considered valid because it is
now recognized that motor control and postural control are
inextricably related. All motor tasks, unless performed while a
subject is fully supported, require a complex interaction of
postural adjustments to maintain intersegmental coordination
and equilibrium during the focal activity.17 A further assumption by Gabel and Nayak16 was that stride width and double
support are the primary spatiotemporal variables that reflect
583
AGE EFFECTS ON BALANCE DURING GAIT, Shkuratova
Table 1: Characteristics of the 20 Young and 20 Older Subjects
Group
Age (y)
Height (cm)
Weight (kg)
Leg Length (cm)
No. of Coins
Transferred
BMI (kg/m2)
Young
Older
25.25⫾5.95
71.50⫾5.03
166.78⫾10.15
165.68⫾11.02
60.86⫾9.75
69.10⫾16.01
88.45⫾6.42
91.25⫾5.44
4.6⫾2.1
4.5⫾1.6
21.8
25.0
NOTE. Values are mean ⫾ standard deviation (SD).
Abbreviation: BMI, body mass index.
balance disturbance during gait. Although this may apply for
straight line walking on wide pathways at preferred speed, the
ability to adapt walking speed, cadence (stepping rate), and
stride length might be equally as important in maintaining
dynamic balance for other tasks and contexts.
In this study, we defined balance during walking as the
ability to successfully integrate postural adjustments with locomotor strategies to maintain safe gait for a range of tasks of
different complexity. Postural adjustments are defined as
changes in walking speed, cadence, stride length, and doublelimb support duration that occur in response to perturbations
during walking.
The major aim of this study was to examine whether older
people adapt their stepping behavior differently than do young
adults in response to various balance perturbations during
locomotion. A secondary aim was to examine whether changes
in speed, stride length, double-limb support, and cadence are
task specific and vary according to the types of balance perturbations encountered. We used a narrow pathway for all gait
trials because this type of environmental constraint increases
demands on balance.
We assessed the effects of age on balance control during
walking by comparing differences in performance between
young and older groups in the following tasks: (1) straight line
walking at preferred speed, (2) straight line walking at fast
speed, (3) figure-of-eight walking at preferred speed, and (4)
figure-of-eight walking while performing a secondary motor
task. Fast walking challenges balance because it requires rapid
postural responses to control the increased accelerations acting
on the body.18,19 The turning condition (figure-of-eight) was
included because it increases the motor control requirements
for controlling the speed and trajectory of the COM and forward momentum.20,21 Turning is also associated with increased
risk of falling in elderly adults.6,22 The secondary task (transferring coins from 1 pocket to another) increases the motor
demands on balance control mechanisms and is a common
activity of daily living.23
METHODS
Participants
Twenty healthy older adults and 20 young adults were recruited for this study from local clubs and volunteer associations in the Melbourne metropolitan region and La Trobe
University, Australia. There were 11 women and 9 men in each
group, and all subjects were screened by the researchers before
testing. To be included, participants had to meet the following
criteria: able and willing to provide informed consent according to the 1964 Declaration of Helsinki, aged between 65 to 85
years (elderly adults) and 20 to 40 years (young adults), and
able to walk without assistance of any kind. Subjects were
excluded if they reported any history of neurologic, orthopedic,
cardiovascular, or psychiatric disorders; if they reported falls in
the past 12 months; if they were taking tranquillizers or other
medications that could affect balance; or if they reported hav-
ing a fear of falling. Four older subjects (1 woman, 3 men)
were excluded from the study. The woman was excluded
because she was taking tranquillizers. The men were excluded
because they reported having had more then 1 fall in the past
12 months. The characteristics of the subjects in each group are
reported in table 1.
The mean age ⫾ standard deviation was 25.3⫾5.9 years for
the young adults and 71.5⫾5.0 years for older adults. There
were no significant differences between groups in height (mean
young adults, 166.8⫾10.2cm; older adults, 165.7⫾11.0cm),
leg length (mean young adults, 88.45⫾6.4cm; older adults,
91.25⫾5.4cm), or weight (mean young adults, 60.9⫾9.8kg;
older adults, 69.1⫾16.0kg).
Apparatus
Spatiotemporal changes in the footstep patterns of all subjects were measured with a Clinical Stride Analyzera (CSA),
according to a protocol specified previously.24 The CSA is
composed of foot switches, a data-logger unit, a handheld
control switch, and a waist belt. The footswitches were placed
inside the shoes and were positioned under the heel, first and
fifth metatarsal heads, and the great toe of each foot. Triggering
the control switch activated the CSA. The data-logger unit,
worn at the waist, recorded average stride length in meters,
cadence in steps per minute, speed in meters per minute, and
the percentage of the gait cycle spent in double-limb support.
For the CSA, stride length is a derived measure, and total
double-limb support duration values represent the sum of initial
and terminal double-limb supports.
Several investigations have established the accuracy and
high reliability of gait analysis using the CSA. Bilney et al25
showed high correlations (intraclass correlation coefficient
[ICC]) between the CSA and the GAITRite walking system for
gait speed (ICC2,1⫽.99), stride length (ICC2,1⫽.99), and cadence (ICC2,1⫽.99). Morris et al26 found high repeatability of
CSA measures for speed, cadence, stride length, and doublelimb support in patients with Parkinson’s disease and in older
control subjects (ICC2,1 range, .92–.99). Hill et al27 also documented high retest reliability of CSA spatiotemporal gait
measures in subjects with hemiplegia (ICC2,1 range, .82–.98).
In research, it is important to establish whether measured
differences represent true change or measurement error. To
evaluate which gait changes represented true changes in performance rather than changes resulting from measurement error, 95% confidence intervals (CIs) for estimating changes
outside the boundaries of measurement error have been previously calculated in healthy older people.26 If the change scores
were beyond the limits of these CIs, it was concluded that the
measured changes in postural adjustments were over and above
measurement error. The lower and upper 95% CIs reported by
Morris26 were, respectively, as follows: walking speed, –.046
to .117m/s; stride length, –.034 to .072m; cadence, –3.392 to
6.564 steps/min; and double-limb support, –1.106 to 1.128
steps/min. Thus, for example, double-limb support would need
to reduce by more than 1.1% of the gait cycle or increase by
Arch Phys Med Rehabil Vol 85, April 2004
584
AGE EFFECTS ON BALANCE DURING GAIT, Shkuratova
Fig 1. The walkway used for straight line walking tasks.
more than 1.3% to show that a real change in double-limb
support had occurred. Bilney et al25 also showed that the
measurement error for the clinical stride analyzer was 30mm
for stride length, .18 steps/min for cadence, and .65m/s for gait
speed, and 3.06% of the gait cycle for double-limb support
duration.
The secondary motor task was a coin transfer task validated
by O’Shea et al.23 Twelve 20-cent coins were transferred by the
subjects from the right to the left pocket as quickly as possible.
Custom-made pockets measuring 19⫻20cm were made from
plain cotton material and worn attached to a waist belt. Subjects practiced the coin transfer for 2 minutes before data
collection to familiarize themselves with this task.
Walkway for Straight Line Walking Task
For the assessment of balance control during straight line
walking, 2 lines 14m long and spaced 150mm apart were
marked on the floor with blue tape (fig 1). Data were collected
from the middle 10m of the walkway to sample steady-state
walking.
Walkway for Turning Tasks
To assess balance control during turning, subjects were
required to walk around a series of 10m-long figure-of-eight
pathways as described by Johansson and Jarnlo.28 The 10-m
figures-of-eights comprised 2 circular paths, each 150mm wide
with an inner diameter of 1.5m and an outer diameter of 1.65m
(fig 2). All subjects began and ended their walking 0.5m
outside each figure-of-eight to minimize acceleration and deceleration effects on performance.
Testing was performed in the Gait Laboratory at La Trobe
University. After completing informed consent procedures, all
subjects were interviewed about their falls history, fear of
falling, medical history, and type and scheduling of medication. Height, weight, and leg length were also measured, because these variables can influence the temporal and spatial
parameters of gait.1 Gait and balance data were then collected.
Each testing session lasted approximately 90 minutes.
Data for 6 trials under each condition were gathered. The
first 3 trials for each task were carried out at self-selected
(preferred) walking speed, and the remaining 3 were conducted
at fast speed. Standardized instructions were given for each
activity.
For straight line walking: “Walk between the 2 blue lines to
the end of the walkway at your comfortable speed/as fast as
you can, starting when I say ‘Go.’ Do not step on or over the
blue lines.” For the unitask turning condition: “Walk within the
figure-of-eight in a clockwise direction at your own comfortable speed/as fast as you can, starting when I say ‘Go.’ Do not
step on or over the blue lines.” For the dual-task turning
condition: “Walk within the figure-of-eight in a clockwise
direction at your comfortable speed/as fast as you can, starting
when I say ‘Go.’ Do not step on or over the blue lines. This
time, concentrate on the coins task, trying to transfer as many
Arch Phys Med Rehabil Vol 85, April 2004
coins as you can from the right to the left pocket, using your
right/left hand.”
The order of conditions was counterbalanced to minimize
series effects.
A series of 2 (age) ⫻ 2 (condition) mixed-design multivariate analysis of variance (MANOVA) tests were conducted to
analyze differences in postural adjustments during walking
between young and older subjects. The dependent variables
were gait speed (meters per second), stride length (length of 2
consecutive steps in meters), cadence (steps per minute), and
double-limb support duration expressed as a percentage of the
gait cycle. If a statistically significant interaction between age
and walking condition was detected, data for the older and
young subjects were analyzed separately with a 2-factor mixeddesign analysis of variance (ANOVA) with repeated measures.
To avoid the accumulation of type I error, ␣ was adjusted to
.025.
RESULTS
As seen in table 2 and figures 1 through 4, healthy older
people screened for pathology had gait patterns comparable to
young adults for straight line walking at preferred speed.
Postural Adjustments When Changing From Preferred to
Fast Walking
Both young and older adults significantly increased walking
speed, stride length, and cadence and decreased double-limb
support duration when changing from preferred to fast walking
(table 2). A 2 (age) ⫻ 2 (condition: preferred walking vs fast
walking) MANOVA was conducted with the 4 measures of
postural adjustment (gait speed, stride length, cadence, doublelimb support duration). This showed a main effect for condition
(Pillai-Bartlett trace⫽.886, F4,35⫽68.09, P⬍.001, partial
␩2⫽.886). Univariate F tests showed that when changing from
walking at preferred speed to walking at fast speed, both
groups increased their walking speed (F1,38⫽244.07, P⬍.001,
partial ␩2⫽.865), stride length (F1,38⫽167.48, P⬍.001, partial
␩2⫽.815), and cadence (F1,38⫽202.55, P⬍.001, partial
␩2⫽.842) and decreased double-limb support duration
(F1,38⫽20.12, P⬍.001, partial ␩2⫽.346).
The mixed-design MANOVA also showed a main effect for
age (Pillai-Bartlett trace⫽.476, F4,35⫽7.94, P⬍.001, partial
Fig 2. The walkway used for figure-of-eight walking tasks.
585
AGE EFFECTS ON BALANCE DURING GAIT, Shkuratova
Table 2: Parameters of Postural Adjustments During Straight Line Walking at Preferred and at Fast Speeds
Straight Line Walking at Preferred Speed
Speed
(m/s)
Group
Young
Older
M
SD
M
SD
1.23
0.21
1.25
0.21
Strl
(m)
1.38
0.12
1.35
0.17
Cad
(steps/m)
106.84
11.85
111.63
11.23
Straight Line Walking at Fast Speed
DBS
(%)
25.66
1.95
30.93
4.51
Speed
(m/s)
Strl (m)
‡
‡
1.83*
0.29
1.67*
0.27
1.63*
0.14
1.50*
0.19
Cad
(steps/m)
DBS (%)
133.63*
16.81
134.37*
13.56
22.14*
2.21
28.89*‡
7.09
Abbreviations: Cad, cadence; DBS, double support (as a percentage of the gait cycle); M, mean; Strl, stride length.
*Significant changes within the group (P⬍.001).
‡
Significant differences between groups (P⬍.001).
␩2⫽.476). Follow-up univariate F tests showed that, when
compared with younger adults, older subjects had higher double-limb support duration values overall (F1,38⫽22.55,
P⬍.001, partial ␩2⫽.372).
The MANOVA showed a statistically significant interaction
between age and speed (Pillai-Bartlett trace⫽.259, F4,35⫽3.06,
P⬍.029, partial ␩2⫽.259). Subsequent univariate F tests found
the interaction effect only to be significant in relation to gait
speed (F1,38⫽7.65, P⬍.01, partial ␩2⫽.168) and stride length
(F1,38⫽12.23, P⬍.01, partial ␩2⫽.243). Two-factor mixeddesign ANOVAs with repeated measures showed that both
older (F1,19⫽72.31, P⬍.001, partial ␩2⫽.792) and young
adults (F1,19⫽197.28, P⬍.001, partial ␩2⫽.912) significantly
increased their walking speed when walking along the narrow
pathway; however, young adults increased their walking speed
to a greater extent than older adults. Both older (F1,19⫽42.02,
P⬍.001, partial ␩2⫽.689) and young adults (F1,19⫽143.94,
P⬍.001, partial ␩2⫽.883) also significantly increased their
stride length. However, young adults showed a greater increase
than did the older subjects.
Postural Adjustments When Required to Turn While
Walking
As shown in table 3, all subjects significantly decreased
their walking speed, stride length, and cadence when chang-
Fig 3. Means and standard error of mean (SEM) for gait speed
during walking at preferred and at fast speeds for young and older
groups.
ing from straight line walking to walking and turning around
a figure-of-eight, although double-limb support duration
showed little change. A 2 (age) ⫻ 2 (condition: straight line
walking vs walking and turning) mixed-design MANOVA
was conducted with the gait speed, stride length, cadence,
and double-limb support duration data. This showed a main
effect for condition (Pillai-Bartlett trace⫽.756, F4,35⫽27.11,
P⬍.001, partial ␩2⫽.756). Follow-up univariate F tests
showed that when changing from straight line walking to
walking and turning around a figure-of-eight, all subjects
walked slower (F1,38⫽113.01, P⬍.001, partial ␩2⫽.748)
with shorter strides (F1,38⫽82.28, P⬍.001, partial ␩2⫽.684)
and decreased cadence (F1,38⫽51.25, P⬍.001; partial
␩2⫽.574).
The mixed-design MANOVA also showed a main effect for
age (Pillai-Bartlett trace⫽.756, F4,35⫽7.94, P⬍.001, partial
␩2⫽.476). Subsequent univariate F tests showed that, compared with young adults, older people generally walked with
increased double-limb support duration (F1,38⫽19.92, P⬍.001,
partial ␩2⫽.344). Despite this, there was no significant interaction between age and turning condition.
Postural Adjustments When Changing From Unitask
Turning to Dual-Task Turning
Table 4 shows that both young adults and older people
significantly decreased their stride length and increased their
Fig 4. Means and SEM for stride length during walking at preferred
and at fast speeds for young and older groups.
Arch Phys Med Rehabil Vol 85, April 2004
586
AGE EFFECTS ON BALANCE DURING GAIT, Shkuratova
Table 3: Parameters of Postural Adjustments During Straight Line Walking at Preferred Speed and Unitask Figure-of-Eight Walking
Straight Line Walking at Preferred Speed
Group
Young
Older
M
SD
M
SD
Unitask Figure-of-Eight Walking
Speed (m/s)
Strl (m)
Cad (steps/m)
DBS (%)
Speed (m/s)
Strl
(m)
Cad (steps/m)
DBS (%)
1.23
0.21
1.25
0.21
1.38
0.12
1.35
0.17
106.84
11.85
111.63
11.23
25.66
1.95
30.93
4.51
0.91*
8.82
0.96*
8.51
1.14*
0.097
1.11*
0.16
95.86*
13.60
103.59*
8.66
25.82
3.09
30.21‡
4.73
*Significant changes within the group (P⬍.001).
‡
Significant differences between groups (P⬍.001).
cadence when changing from unitask figure-of-eight walking to
figure-of-eight walking while performing a secondary motor
task, although walking speed and double-limb support duration
remained unchanged. A 2 (age) ⫻ 2 (condition: unitask vs dual
task) mixed-design MANOVA was conducted with the gait
speed, stride length, cadence, and double-limb support duration
data. This showed a significant main effect for task condition
(Pillai-Bartlett trace⫽.482, F4,35⫽48.13, P⬍.001, partial
␩2⫽.482). This was because both groups walked with shorter
strides (F1,38⫽16.97, P⬍.001, partial ␩2⫽.304) and increased
cadence (F1,38⫽11.93, P⬍.01, partial ␩2⫽.239) during dualtask conditions. MANOVA also showed a main effect for age
(Pillai-Bartlett trace⫽.363, F4,35⫽4.98, P⬍.01, partial
␩2⫽.363), resulting from higher cadence (F1,38⫽5.58, P⬍.05,
partial ␩2⫽.128) and longer time spent in double-limb support
(F1,38⫽14.625, P⬍.001, partial ␩2⫽.278) in the older group.
Again, however, there was no significant interaction between
age and the dual-task walking and turning condition.
Coins Transferred
Young and older subjects transferred a similar number of
coins during figure-of-eight walking, with means of 4.6⫾2.1
coins for the young group and 4.5⫾1.6 coins for the older
group (table 1).
DISCUSSION
This study is among the first systematic and controlled
evaluations of the effects of age on balance control during gait.
All activities were measured on a narrow pathway to ensure an
adequate challenge to balance. The differences between performances at preferred and fast speeds, and during figure-ofeight walking with and without a secondary task, were evaluated. The major finding was that healthy older people selected
strategies that maximized stability when balance was perturbed
during dynamic motor tasks. In particular, when required to
change from walking at preferred speed to walking quickly,
older people failed to achieve the same increases in speed and
stride length relative to the increases achieved by young adults.
Nevertheless, healthy older people who had been screened to
exclude pathology had walking patterns that were comparable
with younger adults when they were required to walk in a
straight line at preferred speed.
Effects of Speed on Straight Line Walking of All Subjects
The results of this study support the findings of Craik,29
Ferrandez et al,19,30 Craik and Dutterer,31 all of whom showed
that older people retain some capacity for modulations of gait
speed, stride length, and double-limb support duration with
advancing age. When instructed to walk quickly, healthy older
adults were able to increase their gait speed and stride length
considerably and to decrease their double-limb support duration. However, their mean speed and stride length values were
reduced, and their mean double-limb support values remained
higher than in younger subjects. Reduced walking speed and
stride length and increased double-limb support duration in
older adults are usually interpreted as age-related adaptations to
produce gait that is safer and less destabilizing, to compensate
for increased accelerations acting on the body during fast
walking.19,29-31 Maki32 noted that shorter stride length and
slower walking speed were related to fear of falling and suggested that reduction in these variables might represent fearrelated adaptations in an attempt to increase postural stability.
Postural Adjustments When Required to Turn While
Walking
Both young adults and older people significantly decreased
their walking speed, stride length, and cadence when changing
from straight line walking to walking and turning around a
figure-of-eight, although double-limb support duration showed
little change. These adaptations presumably enabled people to
maintain stability by slowing down the forward momentum
during turning.
Effects of Turning During Walking for Unitask and
Dual-Task Conditions
When changing from the unitask to dual-task figure-of-eight
walking, all subjects walked with shorter steps, and the older
Table 4: Parameters of Postural Adjustments During Unitask and Dual-Task Figure-of-Eight Walking
Unitask Figure-of-Eight Walking
Group
Young
Older
M
SD
M
SD
Dual-Task Figure-of-Eight Walking
Speed
(m/s)
Strl
(m)
Cad
(steps/m)
DBS
(%)
Speed
(m/s)
Strl
(m)
Cad
(steps/m)
DBS
(%)
0.91
8.82
0.96
8.51
1.14
0.10
1.11
0.16
95.86
13.60
103.59
8.66
25.82
3.09
30.21
4.73
0.92
13.11
0.95
8.71
1.08*
0.13
1.03*
0.14
100.97*
18.15
111.15*‡
10.97
25.73
3.07
31.27‡
5.87
*Significant changes within the group (P⬍.001).
‡
Significant differences between groups (P⬍.001).
Arch Phys Med Rehabil Vol 85, April 2004
AGE EFFECTS ON BALANCE DURING GAIT, Shkuratova
group walked with a higher cadence. Double-limb support
duration and walking speed, however, remained relatively unchanged. These results did not support Gabell and Nayak’s
assumption16 that increased balance difficulty would result in
changes in double-limb support duration and stride width only.
The narrow pathway constrained the ability of subjects to
compensate for mediolateral instability by increasing stride
width. The increased cadence may therefore have been an
effort to adjust for this constraint. However, because a faster
stepping rate during walking and turning may compromise
stability by increasing COM accelerations, the effects of increased cadence on postural stability during turning require
further investigation.
Postural Adjustments to Balance Perturbations During
Gait Are Task Specific
This study provides new data showing that changes in postural adjustments in young and older adults are task specific
and vary according to the type of perturbation encountered.
Previous investigators16 assumed that balance could be assessed separately from gait and that double-limb support duration and stride width were the only spatiotemporal variables
that compensated for challenges to balance during walking. In
contrast, our study showed that young and older adults adjusted
their walking speed, stride length, cadence, and double-limb
support duration differently, depending on which type of balance demand was encountered. When required to change from
self-selected to fast walking speed, all subjects increased their
walking speed, stride length, and cadence and decreased double-limb support duration. When required to shift from straight
line walking to walking and turning, both groups decreased
their speed and stride length. When required to transfer from
unitask to dual-task performance for figure-of-eight walking
along a narrow pathway, all subjects decreased their stride
length, and the older adults increased their cadence rate Thus,
stride width and double-limb support duration were not the
only variables that changed in response to altered balance
demands during walking.
To date, clinical assessments of balance in older people have
mainly examined balance in standing and unperturbed walking
and have not fully captured the complex array of balance
responses available for movement-related tasks. The results of
this study indicate that assessing locomotor responses to balance perturbations during walking provides valuable information about how older people maintain equilibrium during walking. When clinicians perform a comprehensive assessment of
balance, therefore, it may be advantageous to examine the
strategies used to maintain equilibrium during gait in a variety
of functional tasks. These could include straight line walking
on pathways of different widths at different speeds, walking
and turning with different turn angles, walking and turning
while performing a secondary motor or cognitive task, walking
over surfaces with different friction coefficients or slopes, or
negotiating obstacles of different heights and widths during
gait.
CONCLUSIONS
The postural adjustments used by young and older adults in
response to perturbations to balance during walking were task
specific and varied according to the type of perturbation encountered. When required to walk quickly, older people were
not able to increase their speed and stride length to the same
extent as younger adults. This was presumably because the
older adults were more cautious and opted for greater stability.
When required to perform a secondary motor task during
587
figure-of-eight walking, older people showed higher cadence
rates and reduced stride length than did young adults. The high
cadence was an unexpected finding not readily explained by
attempts to improve stability. Further experiments are planned
to investigate this phenomenon more closely. The current study
was, however, confined to the analysis of balance control in
healthy, independent ambulators who had not reported falling.
Further research should examine whether older people with a
history of falls adequately alter their postural adjustments to
maintain equilibrium when their balance is challenged during
gait.
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