Brazilian Journal of Motor Behavior
Special issue:
Effects of aging on locomotor patterns
Becker, Rietdyk
385 of 399
Inadvertent obstacle contacts when older adults step over obstacles: Effect of sex, self-
reported fatigue, gait parameters, and prescription medications
Department of Health and Kinesiology, Purdue University, West Lafayette, Indiana, United States of America.
Indiana University School of Medicine, Indianapolis, Indiana, United States of America.
Center on Aging and the Life Course, Purdue University, West Lafayette, Indiana, United States of America.
Correspondence to:!Timothy Paul Becker. Current address: 465 Bonterra Blvd Apt 203, Fort Wayne, Indiana, 46845.
37% of older adults tripped on a stationary,
visible obstacle in the walkway.
Self-reported fatigue increased during walking
in the 30-40 minute protocol.
Those who tripped had higher fatigue, slower
gait speed, and took more medications.
Improving endurance is an important target
for fall intervention programs.
SDs Standard deviations
Received 28 09 2022
Accepted 09 12 2021
Published 15 12 2021
BACKGROUND: Tripping is a common cause of falls, but the factors associated with trip risk are understudied.
Factors that may affect trip risk include biological sex, fatigue, gait measures, and prescription medications.
AIM: To quantify inadvertent trips with a stationary, visible obstacle in older adults, and to determine if the
factors (e.g., fatigue) of older adults who trip are different from those who don’t trip.
METHOD: Forty-one participants walked on a 6 m walkway and stepped over a visible, stationary obstacle
(height: 25% of leg length) 100 times. We documented inadvertent trips with the obstacle, gait measures on a
clear walkway, self-reported fatigue every 25 obstacle crossing trials, and number of prescription medications.
RESULTS: The obstacle was contacted by 15 participants (37%) in 29 trials (0.7% of all trials); 52% of contacts
were with the lead limb. Self-reported fatigue increased during the obstacle crossing protocol (p<0.001).
Participants with 1 contacts had slower gait speed, shorter stride length, higher gait cycle time variability,
higher fatigue ratings, and a higher number of prescription medications (p0.041). Males and females were not
different in contact frequency (p=0.93).
CONCLUSION: Inadvertent trips were not uncommon in older adults, even with a visible, stationary obstacle.
Balance recovery from lead limb trips is difficult due to center of mass motion relative to the base of support and
highlights the difficulty older adults have recovering balance after a trip. The significant association between
fatigue (induced by walking) and impaired gait is highly relevant when quantifying gait in older adults, and also
when developing fall prevention programs.
KEYWORDS: Adaptive gait | Fall risk | Gait variability | Gait speed | Obstacle crossing
Falls are the number one cause of both fatal and non-fatal injuries among older
. Falls can be caused by a variety of events such as slipping, a misstep, loss of
support, or tripping
. Trips cause 34-53% of falls in community-dwelling older adults
Injuries associated with tripping increase with age as follows: Males increased from 8% to
12% to 19% and females increased from 17% to 21% to 23% for age groups 18-44, 45-64,
and 65+ years, respectively
. Therefore, quantifying trip-related behavior in older adults is
important to increase knowledge regarding the factors associated with trips. Reactive
recovery from trips is quantified with covert obstacles that unexpectedly arrest the forward
motion of the swinging limb
. Proactive gait adaptations are quantified with stationary,
visible obstacles in the walkway
. In proactive research, healthy adults occasionally
contact the stationary obstacle (referred to as inadvertent trips); these trials are typically
discarded. With normal vision and full lighting, inadvertent trips occur in 1-2% of trials
summarized in (Muir and colleagues
). Since inadvertent trips occur in a controlled setting,
they provide a unique opportunity to observe the circumstances of tripping and to quantify
BJMB! ! ! ! ! ! ! !
Becker, Rietdyk
386 of 399
Special issue:
Effects of aging on locomotor patterns
how various factors are associated with trips.
When a young adult trips on a visible and stationary obstacle, they trip with the
trail limb 86-92% of the time, where the trail limb is the second limb to cross the obstacle
. Conversely, older adults have more trips with the lead limb (67% of trips
). Lead limb
trips, relative to trail limb trips, pose a greater threat to balance since the center of mass is
beyond the stance limb and moving forward, drastically reducing the time for corrective
. The greater threat from a lead limb trip is also evident from the multiple steps
generally needed to recover from the trip, while normal gait was generally resumed in the
step following a trail limb trip
. Thus, older adults may be less likely to recover their
balance after tripping since they appear to be more likely to trip with the lead limb than
young adults
. However, the 67% lead limb trips in older adults resulted from a secondary
analysis of an existing dataset, and thus only three older adults were included in this
. Therefore, it is important to determine if the higher number of lead limb trips
observed in a small number of participants
is also evident with larger numbers of
Given that trips are a frequent cause of falls and fall-related injuries
, multiple
factors associated with falls (i.e., biological sex, gait parameters, fatigue, and prescription
are also likely associated with trip-risk. Regarding sex, older females
have more than twice as many trip-related injuries as older males, and trips accounted for
more injuries in older females than older males
. Gait parameters that have been
associated with falls include: speed, step length, step width, and/or variability of these
. Exercise-induced fatigue increases lower limb variability, impairs motor
, and increases trips on obstacles in relatively young firefighters
Furthermore, the effect of exercise-induced fatigue on movement was greater in adults
aged 40 and older compared to younger participants during level walking and obstacle
. However, fatigue may also increase when older adults walk, but it is unknown if
walking-induced fatigue increases trips. Prescription medications are associated with fall-
risk and may be associated with inadvertent trips as well, possibly due to side effects
including blurred vision, impaired depth perception, and/or other visuomotor skills
The purposes of this study were (1) to quantify the frequency and circumstances
(lead versus trail limb) of inadvertent trips in adults aged 65 and older, and (2) to determine
if older adults who trip are different from those who do not trip for the following factors: sex,
gait parameters, walking-induced fatigue, and prescription medications). Note that in
contrast to studies that induce fatigue through fatiguing protocols (for example, repeated
sit-to-stand 30 times per minute until fatigued
), here we quantified the fatigue that
participants reported before, during and after the walking and obstacle crossing trials (30-
40 minutes of walking, with rest breaks every 5-8 minutes). We hypothesized that 32% of
the inadvertent trips would occur with the lead limb (H1). This would mean that, when the
obstacle was contacted, older adults contacted with the lead limb four times more often
than young adults (lead limb contact occurred in 8% of contact trials in young adults,
We hypothesized that females would have a higher frequency of trips than males (H2). We
hypothesized that the older adults who tripped would have slower, more variable gait with
shorter step lengths (H3), higher self-reported fatigue (H4), and a higher number of
prescription medications (H5).
BJMB! ! ! ! ! ! ! !
Becker, Rietdyk
387 of 399
Special issue:
Effects of aging on locomotor patterns
Forty-one older adults (age: 76.6 + 6.9 years, 25 females) participated.
Participants walked without an aid, had no orthopedic or neuromuscular disorders (as
verified by self-report), and were independent in daily activities. Participants wore their
prescribed corrective lenses for all testing, including vision testing. Participants were
screened for cognitive impairments using a clock-drawing test
, and for visual acuity
using a Snellen chart (required visual acuity: 20/40 or better). All participants signed an
informed consent approved by the Institutional Review Board.
Participants completed two gait tasks, unobstructed gait and obstacle crossing
gait, and reported their fatigue at specified intervals during the protocol (Figure 1). The
participants walked for a total 30-40 minutes (including rest breaks); total distance walked
was 1.29 km (0.8 miles). Participants were asked not to talk during the gait tasks, as it is
known that talking alters walking behavior
Unobstructed Gait (steady state gait): Participants walked on a 15 m clear
walkway, turned around, and walked back to the start (Figure 1). Unobstructed gait was
assessed three times: at the beginning, after 50 obstacle crossing trials, and after 100
obstacle crossing trials. Gait measures were recorded with two wireless inertial
measurement units (GaitUp, Physilog, Lausanne, Switzerland); one unit was placed on
each foot.
Obstacle Crossing: Participants walked on a 6 m grey Berber carpet (a tightly
woven loop pile, with low pile height), stepped over an obstacle placed at 4 m, continued to
the end of the carpet, and returned to the start position without stepping over the obstacle
(Figure 1). Subjects self-selected which foot would cross the obstacle first. The obstacle
height was 25% of the subject’s leg length. This height was selected to allow comparison
with published research on young adults
and because higher numbers of contacts are
observed with taller obstacles
. Obstacle height range: 19.5-26 cm, in 0.5 cm
increments; 100 cm wide, 0.3 cm deep. The obstacles were made of Masonite and painted
flat black. To reduce risk of falling, obstacles were designed like a hurdle to tip over if
contacted, and an experimenter spotted participants using a gait belt. Participants were
instructed “Occasionally a person contacts the obstacle. If you contact the obstacle, it will
fall over like a hurdle. Please continue walking and we will pick it up.” If an obstacle contact
occurred, two experimenters independently recorded the trial number and the contact foot
(lead or trail: first or last limb to cross the obstacle). The participant’s lower limbs were
videotaped during obstacle crossing to confirm obstacle contacts offline. Obstacle crossing
was completed in four blocks of 25 trials each (Figure 1), with a 2-minute break after each
Self-reported fatigue was assessed with the rating-of-fatigue scale
. The rating-
of-fatigue scale describes fatigue level in three different formats: numerical (0-10),
descriptive (words), and diagrammatic (line drawing of person). The corresponding formats
are presented together. For example, the number 0 corresponds to the descriptive ‘not
fatigued at alland to a drawing of a person with eyes wide open, standing with arms high
in the air. The numerical 10 corresponds to ‘total fatigue and exhaustion nothing left’ and