Challenging Gait Conditions Predict 1-Year Decline in
Gait Speed in Older Adults With Apparently Normal
Gait
Jennifer S. Brach, Subashan Perera, Jessie M.
VanSwearingen, Elizabeth S. Hile, David M. Wert and
Stephanie A. Studenski
PHYS THER. 2011; 91:1857-1864.
Originally published online October 14, 2011
doi: 10.2522/ptj.20100387
The online version of this article, along with updated information and services, can be
found online at: http://ptjournal.apta.org/content/91/12/1857
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Advances in
Disability Research
Challenging Gait Conditions Predict
1-Year Decline in Gait Speed in Older
Adults With Apparently Normal Gait
Jennifer S. Brach, Subashan Perera, Jessie M. VanSwearingen, Elizabeth S. Hile,
David M. Wert, Stephanie A. Studenski
Background. Mobility often is tested under a low challenge condition (ie, over a
straight, uncluttered path), which often fails to identify early mobility difficulty. Tests
of walking during challenging conditions may uncover mobility difficulty that is not
identified with usual gait testing.
Objective. The purpose of this study was to determine whether gait during
challenging conditions predicts decline in gait speed over 1 year in older people with
apparently normal gait (ie, gait speed of ⱖ1.0 m/s).
Design. This was a prospective cohort study.
Methods. Seventy-one older adults (mean age⫽75.9 years) with a usual gait speed
of ⱖ1.0 m/s participated. Gait was tested at baseline under 4 challenging conditions:
(1) narrow walk (15 cm wide), (2) stepping over obstacles (15.24 cm [6 in] and 30.48
cm [12 in]), (3) simple walking while talking (WWT), and (4) complex WWT. Usual
gait speed was recorded over a 4-m course at baseline and 1 year later. A 1-year
change in gait speed was calculated, and participants were classified as declined
(decreased ⱖ0.10 m/s, n⫽18), stable (changed ⬍0.10 m/s, n⫽43), or improved
(increased ⱖ0.10 m/s, n⫽10). Analysis of variance was used to compare challenging
condition cost (usual ⫺ challenging condition gait speed difference) among the 3
groups.
Results. Participants who declined in the ensuing year had a greater narrow walk
and obstacle walk cost than those who were stable or who improved in gait speed
(narrow walk cost⫽0.43 versus 0.33 versus 0.22 m/s and obstacle walk cost⫽0.35
versus 0.26 versus 0.13 m/s). Simple and complex WWT cost did not differ among the
groups.
Limitations. The participants who declined in gait speed over time walked the
fastest, and those who improved walked the slowest at baseline; thus, the potential
contribution of regression to the mean to the findings should not be overlooked.
Conclusions. In older adults with apparently normal gait, the assessment of gait
during challenging conditions appears to uncover mobility difficulty that is not
identified by usual gait testing.
J.S. Brach, PT, PhD, Department of
Physical Therapy, School of Health
and Rehabilitation Sciences, University of Pittsburgh, 6035 Forbes
Tower, Pittsburgh, PA 15260
(USA). Address all correspondence
to Dr Brach at: jbrach@pitt.edu.
S. Perera, PhD, Division of Geriatric Medicine, Department of Medicine and Department of Biostatistics, Graduate School of Public
Health, University of Pittsburgh.
J.M. VanSwearingen, PT, PhD,
FAPTA, Department of Physical
Therapy, School of Health and
Rehabilitation Sciences, University
of Pittsburgh.
E.S. Hile, PT, PhD, NCS, Department of Physical Therapy, School
of Health and Rehabilitation Sciences, University of Pittsburgh.
D.M. Wert, PT, Department of
Physical Therapy, School of Health
and Rehabilitation Sciences, University of Pittsburgh.
S.A. Studenski, MD, MPH, Division
of Geriatric Medicine, Department
of
Medicine,
University
of
Pittsburgh.
[Brach JS, Perera S, VanSwearingen JM, et al. Challenging gait
conditions predict 1-year decline
in gait speed in older adults with
apparently normal gait. Phys Ther.
2011;91:1857–1864.]
© 2011 American Physical Therapy
Association
Published Ahead of Print: October
14, 2011
Accepted: March 13, 2011
Submitted: November 15, 2010
Post a Rapid Response to
this article at:
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1857
Prediction of Decline in Gait Speed in Older Adults With Normal Gait
M
obility disability in older
adults is a major factor in loss
of independence and contributes to higher rates of morbidity
and mortality.1– 4 In addition, mobility disability is considered to be a
sentinel predictor of other disabilities that restrict independent living.5
Although the current practice is to
maintain fitness in individuals who
are healthy, or wait until walking is
difficult and then rehabilitate it, an
alternative is to develop novel ways
to anticipate future walking difficulty and prevent it. In order to
prevent a problem, screening tests
are needed that detect the problem
at an earlier and possibly more
treatable phase.
Gait speed is a simple measure that
can serve as a screening test to
detect risk for future mobility disability, but it is limited because of insensitivity to early but important mobility changes.5 Although a gait speed
of less than 1.0 m/s is considered
“abnormal,” and is a consistent indicator of increased risk of future problems,4 older adults with “normal”
gait speeds greater than 1.0 m/s
continue to have significant rates of
morbid outcomes, including mobility disability rates of 38% within 3
years.4 Fried and colleagues5 concluded that gait speed alone is not
a sufficiently sensitive indicator of
early
decline
or
preclinical
disability.
Gait speed traditionally is measured
under ideal conditions (well-lit,
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unobstructed walkway) without distractions, but ideal conditions may
not provide sufficient challenge to
stress the ability to adapt walking in
the presence of subclinical physiological abnormalities. Challenging
gait conditions combine walking
with other physically and cognitively
demanding tasks that require shared
attention.6 Challenging gait conditions are thought to approximate
“real-world” walking. Examples of
some challenging gait conditions
reported in the literature include
stepping over obstacles, carrying an
object, walking on uneven surfaces
or around curves, and walking while
talking.6 –10 Challenging gait conditions may stress the ability to adapt
walking in the presence of subclinical abnormalities. Thus, challenging
walking conditions may provide the
means to detect early alterations in
walking and a potential strategy to
detect and characterize underlying
biomechanical and subclinical physiological abnormalities. The use of
challenging conditions to detect subclinical risk has been reported in
other types of aging research. For
example, fall risk was predicted
more accurately by gait characteristics on an irregular, challenging surface compared with a smooth, nonchallenging surface in individuals
with peripheral neuropathy.11 In
addition, in a systematic review, gait
performance under challenging conditions was predictive of falls; however, this association was found to
be stronger in frail older adults compared with older adults who are
healthier.12
Method
The purpose of this study was to
determine whether gait during challenging conditions predicts decline
in gait speed over 1 year in older
people with apparently normal gait
(ie, gait speed of ⱖ1.0 m/s). The
assessment of gait during challenging conditions may uncover mobility
difficulty that is not identified with
usual gait testing.
Procedure
This study was a 1-year cohort study
with clinic visits at baseline, 6
months, and 12 months. All testing
was conducted at the University of
Pittsburgh Pepper Center SMART
(Senior Mobility Aging Research
Training) Center by physical therapists or researchers trained in the
measures. Testing sessions lasted, on
Participants
The study participants were 120
community-dwelling older adults
who were participating in an observational cohort study at the University of Pittsburgh Pepper Center,
Pittsburgh, Pennsylvania. Participants were recruited from the University of Pittsburgh Pepper Center
Research Registry of older adults
who previously consented to be contacted for studies of balance and
mobility. Individuals were included
if they were 65 years of age or older
and had the ability to walk a minimum of a household distance with or
without an assistive device and without the assistance of another person.
Participants were excluded if they
had any of the following conditions
that would affect safety during testing or that would affect mobility
over the following year: neuromuscular disorders that impair movement, cancer with active treatment,
hospitalization for a life-threatening
illness or major surgery in the previous 6 months, severe pulmonary disease, or chest pain with activity or a
cardiac event such as a heart attack
in the previous 6 months. One hundred twenty individuals were
enrolled in the main study. For the
current analyses, those with a baseline gait speed of ⬍1.0 m/s (n⫽36)
or missing data at the 1-year
follow-up (n⫽13) were excluded,
leaving a total of 71 participants. All
participants
provided
written
informed consent prior to the study.
A flow diagram of the study participants is presented in Figure 1.
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Prediction of Decline in Gait Speed in Older Adults With Normal Gait
average, 3 to 4 hours, with adequate
rest breaks.
Gait Measures
Usual gait speed. Usual gait
speed was determined as the participants walked over a 6-m course.
A stopwatch was used to time the
participants as they walked at their
usual speed over the central 4 m of
the 6-m course. The initial meter and
final meter were to allow for acceleration and anticipatory deceleration. The distance covered (ie, 4 m)
was divided by the time taken to
complete the 4-m walk to derive gait
speed in meters per second. Participants completed 2 trials, and the
mean of the 2 trials was considered
their usual gait speed. Measurements
of usual gait speed were collected at
baseline and at the 12-month visit.
The outcome of interest, change in
gait speed, was defined as follows:
(1) decline—a decline in gait speed
from baseline to 12 months of ⱖ0.10
m/s, (2) stable—an increase or
decrease in gait speed from baseline
to 12 months of ⬍0.10 m/s, and
improvement—an increase in gait
speed from baseline to 12 months of
ⱖ0.10 m/s.13
Figure 1.
Narrow
walk. As
previously
described by Bandinelli et al,6 participants were asked to walk a 4-m
distance at their usual walking pace
within a 15-cm-wide path marked on
the floor with tape. They were
instructed to walk keeping their feet
within the taped lines. The time for
each participant to complete this
task and the number of deviations
from the 15-cm-wide path were
recorded. Participants who could
not complete the task independently
or who stepped outside the walkway
more than 10 times were classified as
“unable.” The distance covered (4
m) was divided by the time to determine gait speed for the narrow walk.
Each participant completed 2 trials,
and the mean from the 2 trials was
calculated. Narrow walk cost was
December 2011
Flow diagram of study participants.
determined by subtracting the mean
baseline narrow walk speed from the
baseline usual gait speed. The intraclass correlation coefficient (ICC) for
test-retest reliability of the narrow
walk was .76.6
Obstacle walk. As previously
described by Bandinelli et al,6 participants were asked to walk a 7-m
course at their usual pace and step
over 2 obstacles of different heights.
One obstacle was 6 cm tall and positioned 2 m from the starting line, and
the other obstacle was 30 cm tall and
positioned 4 m from the starting line.
Participants were instructed to “get
past the obstacles without touching
them.” The time for each participant
to complete the task was recorded.
The distance covered (7 m) was
divided by the time to determine gait
speed for the obstacle walk. Each
participant completed 2 trials, and
the mean of the 2 trials was calculated. Obstacle walk cost was
determined by subtracting the
mean baseline obstacle walk speed
from the baseline usual gait speed.
The obstacle walk has demonstrated
test-retest
reliability
(ICC⫽.89).6
Simple and complex walking
while talking tasks. The simple
and complex walking while talking
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1859
Prediction of Decline in Gait Speed in Older Adults With Normal Gait
(WWT) tasks were developed as cognitive challenges during walking by
imposing a need for divided attention.9 During the simple WWT task,
participants were asked to say the
letters of the alphabet out loud while
walking down a 6.1-m (20-ft) corridor. The complex WWT task differs
from the simple WWT task in that
participants are asked to say every
other letter of the alphabet out loud
over the 6.1-m corridor. Participants
were instructed to pay equal attention to both tasks. The distance covered (6.1 m) was divided by the time
to determine gait speed for the simple and complex WWT tasks. Each
task was repeated twice, and an average for each task was calculated. Simple and complex WWT task cost was
determined by subtracting the mean
baseline simple or complex WWT
task gait speed from the baseline
usual gait speed. The interrater reliability for the simple WWT task was
demonstrated by a Pearson r value of
.60. The simple WWT task has demonstrated a specificity of 89.4% and a
sensitivity of 46.1%, with a threshold
time of 20 seconds or longer (on a
40-foot corridor), as a predictor of
falls.9 The complex WWT task predicts falls in older adults with a
threshold time of 33 seconds or longer (on a 40-foot corridor) with a
specificity of 95.6% and a sensitivity
of 38.5%.9
Other Measures
Demographics. Data were collected on the following demographic
factors: age, sex, race or ethnicity,
and education level.
Comorbidity Index. This measure
is a self-report of common physiciandiagnosed
medical
conditions,
including cardiovascular disease
(angina, congestive heart failure, or
heart attack), neurologic conditions
(stroke or Parkinson disease), lung
disease, musculoskeletal conditions
(arthritis, osteoporosis, fracture, or
joint replacement), general condi1860
f
tions (depression, sleep problems, or
chronic pain syndrome), cancer, diabetes, or visual conditions (glaucoma
or cataracts).14 For each medical
condition, participants were asked if
they had ever been told by a physician that they had the condition. The
number of affirmative responses was
summed to yield a total score.
Body mass index. Height and
weight were measured using a
Tanita BWB-800 scale and HR-200
wall-mounted height rod (Perspective Enterprises, Portage, Michigan).
Participants were measured while
wearing indoor clothing and socks
without shoes. Assistance was given
to get into position for both height
and weight measurements, including
cues to stand up straight with heels
against the wall for assessment of
height, but measurements were
recorded in unsupported stance.
Weight was recorded to the nearest
tenth of a kilogram, and height was
recorded to the nearest tenth of a
centimeter, with the height rod at
the top of the participant’s head in
midline. Height and weight measurements were used to determine body
mass index (BMI).
Fall history questionnaire. Participants were asked to respond to
the following questions: (1) Are you
afraid of falling? and (2) Have you
had a fall in the previous year?
Responses to the questions were
recorded as “yes” or “no.”
Data Analysis
Differences in baseline characteristics between the gait speed change
groups (declined, stable, and
improved) were described and
tested using the chi-square test for
categorical measures and one-way
analysis of variance (ANOVA) for
continuous measures. Differences in
usual gait speed, challenging task
speed, and challenging task cost
(usual speed minus challenging task
speed) were described and com-
pared among the 3 gait speed change
groups using ANOVA.
Because the 3 gait speed change
groups differed on baseline gait
speed, additional analyses were conducted in an attempt to account for
these differences in gait speed. First,
the differences in challenging task
cost among gait speed change
groups were compared using
ANOVA in a subgroup of participants
with similar baseline gait speeds (ie,
baseline gait speed between 1.0 and
1.4 m/s). Second, logistic regression
models were used to examine the
association between each challenging task cost and decline in gait
speed 1 year later (combining the
stable and improved groups), adjusting for baseline gait speed as a covariate. Odds ratios (ORs) corresponding to 0.1 m/s in gait speed and 95%
confidence intervals (CIs) are
reported. In order to assess the sensitivity of the findings, all analyses
were repeated using challenging task
cost normalized to usual baseline
gait speed (ie, challenging task cost
divided by usual gait speed). All
analyses were performed using SAS
statistical software, version 9.2
(SAS Institute Inc, Cary, North
Carolina).
Role of the Funding Source
This work was supported by the
Pittsburgh Older Americans Independence Center (National Institute
on Aging grant P30 AG024827) and a
Beeson Career Development Award
(National Institute on Aging grant
K23 AG026766).
Results
Table 1 provides the baseline characteristics of the entire study cohort
and the cohort stratified by gait
speed change over the 1-year
follow-up period. The study cohort
was
predominantly
Caucasian
women who were college educated.
More than half of the cohort
reported their health as very good or
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December 2011
Prediction of Decline in Gait Speed in Older Adults With Normal Gait
Table 1.
Baseline Characteristics of 71 Participants Stratified by Subsequent Gait Speed Decline Over 1 Year
Total
Cohort
(Nⴝ71)
Declined 0.1 m/s
or More in
Gait Speed
(nⴝ18)
No Decline
(Change of
<0.1 m/s) in
Gait Speed
(nⴝ43)
Improved
0.1 m/s or More
in Gait Speed
(nⴝ10)
P
Age (y), X (SD)
75.9 (5.8)
76.2 (5.9)
76.3 (5.7)
74.1 (6.6)
.55
Caucasian, n (%)
65 (92)
16 (89)
40 (93)
9 (90)
.86
Male, n (%)
20 (28)
3 (17)
13 (30)
4 (40)
.38
College education, n (%)
54 (76)
13 (72)
32 (74)
9 (90)
.53
41 (58)
11 (61)
24 (56)
6 (60)
.92
Variable
Demographics
Health related
Self-reported health as very good
or excellent, n (%)
No. of chronic conditions X (SD)
4.3 (2.1)
4.9 (1.8)
4.4 (2.2)
3.1 (1.5)
.08
Body mass index (kg/m2), X (SD)
28.4 (4.9)
28.5 (5.0)
28.6 (5.4)
27.5 (2.2)
.84
Fallen in previous year, n (%)
34 (49)
9 (50)
20 (48)
5 (50)
.98
Fearful of falling, n (%)
28 (40)
7 (39)
18 (43)
3 (30)
.75
excellent. Of the 71 participants, 18
(25%) experienced a decline in gait
speed of at least 0.10 m/s over the
1-year follow-up period, and 10
(14%) experienced an improvement in gait speed of at least 0.10
m/s. Participants who had a decline
in gait speed over the 1-year
follow-up period did not differ on
the baseline characteristics compared with participants who did
not decline or improved in gait
speed (Tab. 1).
Participants who declined in gait
speed over the 1-year follow-up
period walked the fastest at baseline,
and individuals who improved in gait
speed walked the slowest at baseline
(Tab. 2). Gait speed during the challenging conditions at baseline did
not differ among the gait speed
change groups (all P⬎.40). However, participants who declined in
gait speed had a greater cost during
the narrow walk and obstacle walk
conditions than those who were stable or who improved in gait speed
(narrow walk cost⫽0.43 versus 0.33
versus 0.22 m/s, P⫽.009; obstacle
walk cost⫽0.35 versus 0.26 versus
0.13 m/s, P⫽.003). Simple and com-
Table 2.
Mean (SD) Gait Speed, Baseline Challenging Task Speed, and Baseline Challenging Task Cost by Gait Speed Change Status Over
1 Year
Declined in
Gait Speed
(nⴝ18)
Stable
Gait Speed
(nⴝ43)
Improved
Gait Speed
(nⴝ10)
P
Baseline usual gait speed, m/s
1.31 (0.17)
1.24 (0.15)
1.18 (0.10)
.09
12-mo usual gait speed, m/s
1.12 (0.18)
1.24 (0.15)
1.38 (0.08)
.0001
Narrow walk speed, m/s
0.90 (0.22)a
0.90 (0.23)b
0.97 (0.20)
.67
a
b
0.22 (0.18)
.009
1.05 (0.09)
.44
Variable
Narrow walk cost, m/s
0.43 (0.16)
Obstacle walk speed, m/s
0.96 (0.25)
0.97 (0.18)b
0.33 (0.17)
Obstacle walk cost, m/s
0.35 (0.15)
0.26 (0.12)
b
0.13 (0.11)
.003
Simple WWTc task speed, m/s
1.16 (0.15)
1.12 (0.19)
1.14 (0.14)
.79
Simple WWT task cost, m/s
0.14 (0.15)
0.11 (0.10)
0.05 (0.08)
.10
Complex WWT task speed, m/s
1.00 (0.24)
0.96 (0.22)
0.95 (0.23)
.79
Complex WWT task cost, m/s
0.31 (0.18)
0.28 (0.17)
0.24 (0.18)
.58
a
n⫽16.
b
n⫽42.
c
WWT⫽walking while talking.
December 2011
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1861
Prediction of Decline in Gait Speed in Older Adults With Normal Gait
0.6
Cost (m/s)
0.5
0.4
0.3
Declined
0.2
Stable
0.1
Improved
0
Narrow
Walk
Obstacle
Walk
Simple
WWT
Task
Complex
WWT
Task
Figure 2.
Baseline challenging task cost by gait speed change status over 1 year. Sample limited
to individuals with baseline gait speed between 1.0 and 1.4 m/s (declined, n⫽14;
stable, n⫽38; improved, n⫽10). *P⬍.05, **P⬍.01.
plex WWT task costs did not differ
among the groups.
In a subsample of the participants
who had a restricted range of gait
speeds at baseline (ie, 1.0 –1.4 m/s),
baseline gait speed was similar
among the 3 groups (declined: gait
speed⫽1.24 m/s, n⫽14; stable: gait
speed⫽1.20 m/s, n⫽38; and
improved: gait speed⫽1.18 m/s,
n⫽10; P⫽.42). However, narrow
walk cost and obstacle walk cost differed among the 3 groups, with
those who declined in gait speed
having the greatest cost and those
who improved having the lowest
cost (Fig. 2). Simple and complex
WWT task costs did not differ among
the 3 groups. Similar findings were
obtained from the gait speed–
adjusted logistic regression models.
In baseline gait speed–adjusted models, narrow walk cost (OR⫽1.46,
95% CI⫽1.02⫺2.11) and obstacle
walk
cost
(OR⫽1.82,
95%
CI⫽1.16⫺2.86) were related to
decline in gait speed 1 year later. In
other words, a 0.10-m/s increase in
narrow walk cost corresponded to a
46% increase in odds of gait speed
decline (P⫽.04) and a 0.10-m/s
increase in obstacle walk cost corre1862
f
sponded to an 82% increase in odds
of gait speed decline (P⫽.01). Simple and complex WWT task costs
were not related to decline in gait
speed. When analyses were repeated
using the alternative definition of
cost (ie, challenging task cost normalized to usual speed), all findings
were similar (data not shown).
Discussion
In older adults with apparently normal gait (ie, gait speed of ⱖ1.0 m/s),
challenging gait cost during the narrow walk and obstacle walk was a
significant predictor of decline in
gait speed over the following year.
Interestingly, the environmentally
induced challenges (narrow and
obstacle walk) were related to
decline, whereas the cognitive dualtask challenges were not. The cost of
completing a challenging gait task
may be a novel way to identify future
walking difficulty.
Gait during challenging conditions
may be an earlier indicator of future
disability than usual gait speed
because it uncovers underlying
impairments that are not apparent
during low challenge testing situations. Walking requires the success-
ful integration of numerous physiologic systems.15 The biologic systems
responsible for walking have an efficient adaptive response that can
restore the organism to equilibrium
during everyday challenges (eg, stepping over an object, walking on
curved paths). If there is a slight decrement in one system, other systems
may be able to compensate, and
under low challenge conditions, the
deficit may not be apparent.16,17 It is
only when the individual has to
adapt to a more challenging condition that the decrement becomes
apparent. Testing older people only
while walking in low challenge situations may fail to distinguish those
with early mobility difficulty. Individuals who are unable to adapt to the
more challenging circumstances (ie,
inadequate compensation) are likely
to have underlying (subclinical)
problems that would increase their
risk for future disability.
Because the walking difficulty was
not apparent under low challenge
conditions, it may be considered a
subclinical deficit similar to high
blood pressure or cholesterol. The
concept of early identification of gait
difficulty (ie, a subclinical mobility
deficit) and treatment with targeted
interventions to prevent the development of mobility disability is analogous to identification and treatment
of high blood pressure or cholesterol
for the prevention of stroke and
heart disease. Once the subclinical
deficit of walking difficulty is identified and the underlying impairments
are defined, preventive rehabilitation
(“prehabilitation”) could be instituted to treat the underlying deficits
before they can progress to overt
mobility disability. Prevention of
mobility disability may be a more
cost-effective alternative to the treatment of mobility disability once it
has occurred.
When interpreting our findings, several limitations should be consid-
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December 2011
Prediction of Decline in Gait Speed in Older Adults With Normal Gait
ered. First, our outcome was a
change (decline or improvement) in
gait speed of ⱖ0.10 m/s. We selected
a 0.10-m/s decline in gait speed
because we had previously shown it
is a meaningful decline in older
adults.13 It may be questioned
whether a decline of 0.10 m/s is
meaningful in older adults walking
faster than 1.20 m/s; that is, is a
decline in gait speed from 1.30 m/s
to 1.20 m/s meaningful? In a sample
of older adults for the Health Aging
and Body Composition Study who
walked at a desired speed, we have
shown that a 0.10-m/s change in gait
speed from 1.40 m/s to 1.30 m/s is
meaningful.18 Given that the group
of older adults who declined in gait
speed over time walked the fastest
at baseline and those who
improved in gait speed over time
walked the slowest at baseline, the
potential contribution of regression to the mean to the findings
should not be overlooked. However, several factors do not support
the regression to the mean explanation of findings.
First, although baseline gait speed
was different among the groups, the
baseline gait speed values were still
within the range of “normal usual
walking speed” and the range of
baseline gait speeds was similar
among the groups (declined⫽
1.05⫺1.65 m/s, stable⫽1.00⫺1.59
m/s, and improved⫽1.02⫺1.38
m/s). Second, we used different analytic techniques to control for the
differences in baseline gait speed (ie,
limiting the sample to a range of
baseline gait speeds and adjusting for
speed in the logistic regression analyses) and obtained similar findings.
Third, although the differences in
challenging condition costs were statistically significant, we do not know
whether these differences were clinically
meaningful.
Additional
research is needed to determine a
meaningful difference in challenging
condition cost. Fourth, differences in
December 2011
testing protocols (static versus
dynamic start and different distances) could explain some of the
differences in gait speeds recorded
for the usual and challenging conditions. Future studies examining challenging condition cost should use
similar testing protocols for the baseline usual and challenging conditions
to minimize the impact of the protocol on challenging condition cost.
Lastly, the group that demonstrated
an improvement in gait speed over
the 1-year period appeared to differ,
although the difference was not statistically significant, from the
declined and stable groups on the
baseline characteristics. Compared
with the declined and stable groups,
the group that improved was
younger, more likely to be college
educated, reported fewer chronic
conditions, and had a lower BMI, and
all of these factors potentially contribute to an improvement in gait
speed. Given the low power to
detect differences in baseline characteristics (ie, power ⬍0.80), it would
be important to repeat this study
with a larger sample.
Conclusion
In older adults with apparently normal gait, the assessment of gait during challenging conditions appears
to uncover mobility difficulty that is
not identified by usual gait testing.
Gait during challenging conditions
may be a way to anticipate future
walking difficulty so that interventions can be instituted to prevent the
decline in mobility instead of waiting
for the decline to occur and trying to
rehabilitate it.
Dr Brach, Dr VanSwearingen, and Dr
Studenski provided concept/idea/research
design. All authors provided writing. Dr
Brach, Dr Hile, and Mr Wert provided data
collection. Dr Brach and Dr Perera provided
data analysis. Dr Brach and Dr Hile provided
project management. Dr Brach provided
fund procurement and participants. Dr
Brach and Dr Studenski provided facilities/
equipment. Dr Perera, Dr VanSwearingen,
Dr Hile, Mr Wert, and Dr Studenski provided
consultation (including review of manuscript
before submission).
This study was approved by the Institutional
Review Board of the University of Pittsburgh.
A portion of this work was presented at the
Third International Congress on Gait and
Mental Function; February 26 –28, 2010;
Washington, DC.
This work was supported by the Pittsburgh
Older Americans Independence Center
(National Institute on Aging grant P30
AG024827) and a Beeson Career Development Award (National Institute on Aging
grant K23 AG026766).
DOI: 10.2522/ptj.20100387
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Physical Therapy Volume 91 Number 12
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December 2011
Challenging Gait Conditions Predict 1-Year Decline in
Gait Speed in Older Adults With Apparently Normal
Gait
Jennifer S. Brach, Subashan Perera, Jessie M.
VanSwearingen, Elizabeth S. Hile, David M. Wert and
Stephanie A. Studenski
PHYS THER. 2011; 91:1857-1864.
Originally published online October 14, 2011
doi: 10.2522/ptj.20100387
References
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