Attention and sensory integration for gait in young adults with autism spectrum disorder.

INTRODUCTION: Altered sensorimotor function is a common feature of autism spectrum disorder (ASD). As a result, spatiotemporal walking patterns are typically affected. Attentional processes relevant for locomotion may be altered in people with ASD. This study assessed the extent to which gait alterations observed under sensory challenging conditions are due to reduced attention-related processes in young adults with ASD. METHODS: Twenty-one adults with ASD and 21 age- and sex-matched neurotypical participants walked at a self-selected pace on a 10-m walkway under 12 sensory/attention conditions: hard or carpet flooring; well-lit or dim lighting; no attention task, an auditory choice-reaction time information-processing task, or a simple reaction time information-processing task. Gait data were collected with a 12-marker motion capture set and a trunk accelerometer. Spatiotemporal characteristics of gait were derived and compared between the two groups across gait conditions. RESULTS: Floor/light conditions impacted gait speed, average step length, average stance time, average step width, and step width variability similarly in both groups (p<0.05). The information processing tasks impacted average step length, gait speed, and step length variability (p<0.05). Group differences were found in step length metrics: the ASD group had decreased average step length during the simple reaction time information-processing task and neurotypical participants did not (p=0.039); the ASD group had increased variability on carpet compared to hard floor and the neurotypical group had no change in variability due to floor (p=0.015). SIGNIFICANCE: These results suggest that attentional set-shifting and somatosensory inputs may play an important role in ASD-related gait alterations. Step length metrics appear to be sensitive to group differences between ASD and neurotypical adults during sensory challenging conditions.

Ladder Use Ability, Behavior and Exposure by Age and Gender.

This study aimed to quantify and compare ladder use ability and behavior in younger and older men and women from three ladder use behavior experiments. The experimental tasks comprised (1) changing a lightbulb on a household stepladder under two cognitive demands (single and dual task), (2) clearing a simulated roof gutter on a straight ladder and (3) querying ladder choice in different exigency scenarios. Ladder use ability and behavior data were captured from recorded time, performance, motion capture and user choice data. In addition, this study surveyed ladder use frequency and habitual behaviors. The experimental findings indicate that older adults require more time to complete ladder tasks; younger adults display riskier ladder use behaviors; men and women display similar ladder use ability; and men are more willing to climb riskier ladders. The survey found older adults to report more frequent ladder use than younger adults, and men use straight ladders more frequently than women. These results suggest that the reported higher ladder fall rates experienced by older adults and men are linked to increased ladder use exposure and riskier ladder choice. This knowledge can help guide population-specific interventions to reduce ladder falls in both young and older people.

The association of chemotherapy-induced peripheral neuropathy with reduced executive function in chemotherapy-treated cancer survivors: A cross-sectional study.

INTRODUCTION: Chemotherapy-induced peripheral neuropathy (CIPN) is common and disabling among cancer survivors. Little is known about the association of CIPN with other measures of the nervous system's integrity, such as executive dysfunction. We compared measures of executive function in older chemotherapy-treated cancer survivors with and without CIPN. MATERIALS AND METHODS: This cross-sectional study enrolled 50 chemotherapy-treated cancer survivors (65.6 ± 11.5 years, 88% female) post-chemotherapy treatment who were previously referred for outpatient rehabilitation at the request of the cancer survivor or a medical provider. Twenty-two participants (44%) had CIPN defined by patient-reported distal paresthesia or numbness, which began with chemotherapy and continued to the time of cognitive testing. Measures of executive function included Trails-B, Stroop, and rapid reaction accuracy (RRA) and were evaluated between cancer survivors with and without CIPN using t-tests. Multivariable models were then used to determine whether CIPN was an independent determinant of the measures of executive function (Trails-B, Stroop Incongruent, and RRA). Models were adjusted for age, sex, history of anxiety, and benzodiazepine use due to their known associations with CIPN and executive function. RESULTS: Cancer survivors with CIPN (CIPN+) had reduced executive function compared to survivors without CIPN (CIPN-) on Trails-B (CIPN+: 84.9 s ± 44.1 s, CIPN-: 59.1 s ± 22.5 s, p = 0.01), Stroop (CIPN+: 100.6 s ± 38.2 s, CIPN-: 82.1 s ± 17.3 s, p = 0.03), and RRA (CIPN+: 60.3% ± 12.9%, CIPN-: 70.6% ± 15.7%, p = 0.01). There were no differences in cancer stage severity or functional status by patient report or sit-to-stand function. The association between CIPN and reduced executive function was found in multivariable models after adjusting for age, sex, anxiety, and benzodiazepine use for Trails-B (ß:17.9, p = 0.046), Stroop (ß:16.9, p = 0.02), and RRA (ß:-0.072, p = 0.03). DISCUSSION: In this population, CIPN is associated with reduced executive function in older cancer survivors treated with chemotherapy. Future research is required to further understand this preliminary association, the causality, and the potential risk factors.

Fear of falling in community-dwelling older adults: What their gait acceleration pattern reveals.

BACKGROUND: Fear of Falling (FOF) is common among community-dwelling older adults and is associated with increased fall-risk, reduced activity, and gait modifications. OBJECTIVE: In this cross-sectional study, we examined the relationships between FOF and gait quality. METHODS: Older adults (N=232; age 77±6; 65 % females) reported FOF by a single yes/no question. Gait quality was quantified as (1) harmonic ratio (smoothness) and other time-frequency spatiotemporal variables from triaxial accelerometry (Vertical-V, Mediolateral-ML, Anterior-Posterior -AP) during six-minute walk; (2) gait speed, step-time CoV (variability), and walk-ratio (step-length/cadence) on a 4-m instrumented walkway. Mann Whitney U-tests and Random forest classifier compared gait between those with and without FOF. Selected gait variables were used to build Support Vector Machine (SVM) classifier and performance was evaluated using AUC-ROC. RESULTS: Individuals with FOF had slower gait speed (103.66 ± 17.09 vs. 110.07 ± 14.83 cm/s), greater step time CoV (4.17 ± 1.66 vs. 3.72 ± 1.24 %), smaller walk-ratio (0.53 ± 0.08 vs. 0.56 ± 0.07 cm/steps/minute), smaller standard deviation V (0.15 ± 0.06 vs. 0.18 ± 0.09 m/s2), and smaller harmonic-ratio V (2.14 ± 0.73 vs. 2.38 ± 0.58), all p<.01. Linear SVM yielded an AUC-ROC of 67 % on test dataset, coefficient values being gait speed (-0.19), standard deviation V (-0.23), walk-ratio (-0.36), and smoothness V (-0.38) describing associations with presence of FOF. CONCLUSION: Older adults with FOF have reduced gait speed, acceleration adaptability, walk-ratio, and smoothness. Disrupted gait patterns during fear of falling could provide insights into psychosocial distress in older adults. Longitudinal studies are warranted.

Balance strategies for recovery from perturbed overground walking.

Bipedal locomotion is naturally unstable and requires active control. Walking is believed to be primarily stabilized through the selection of foot placements; however, other strategies are available, including regulation of ankle inversion/eversion, ankle push-off, and angular momentum through trunk postural adjustments. The roles of these strategies in maintaining overall stability are often masked by the dominant foot placement strategy. The objectives of this study were to describe how the four strategies are used to respond to medial or lateral ground perturbations during overground walking in healthy individuals and determine reliance on each strategy. Fifteen healthy adults walked with and without perturbations applied to the right foot at heel strike while body kinematics and surface electromyographic activity were measured. Medial perturbations resulted in decreased step width on the first step after the perturbation, increased ankle inversion, increased ankle push-off, and rightward trunk sway. Lateral perturbations resulted in increased step width, decreased ankle inversion, no change in ankle push-off, and leftward trunk sway. EMG activity was consistent with the observed strategies (e.g. increased peroneus longus EMG activity during ankle eversion) with the exception of increased bilateral erector spinae activity for all perturbations. Foot placement was the dominant strategy in response to perturbations, with other strategies showing reduced, yet significant, roles. This work demonstrates that multiple strategies are recruited to improve the balance response in addition to foot placement alone. These results can serve as a reference for future studies of populations with impaired balance to identify potential deficits in strategy selection.

Association of Gait Quality With Daily-Life Mobility: An Actigraphy and Global Positioning System Based Analysis in Older Adults.

OBJECTIVE: Walking is a key component of daily-life mobility. We examined associations between laboratory-measured gait quality and daily-life mobility through Actigraphy and Global Positioning System (GPS). We also assessed the relationship between two modalities of daily-life mobility i.e., Actigraphy and GPS. METHODS: In community-dwelling older adults (N = 121, age = 77±5 years, 70% female, 90% white), we obtained gait quality from a 4-m instrumented walkway (gait speed, walk-ratio, variability) and accelerometry during 6-Minute Walk (adaptability, similarity, smoothness, power, and regularity). Physical activity measures of step-count and intensity were captured from an Actigraph. Time out-of-home, vehicular time, activity-space, and circularity were quantified using GPS. Partial Spearman correlations between laboratory gait quality and daily-life mobility were calculated. Linear regression was used to model step-count as a function of gait quality. ANCOVA and Tukey analysis compared GPS measures across activity groups [high, medium, low] based on step-count. Age, BMI, and sex were used as covariates. RESULTS: Greater gait speed, adaptability, smoothness, power, and lower regularity were associated with higher step-counts (0.20<|ρp| < 0.26, p < .05). Age(ß = -0.37), BMI(ß = -0.30), speed(ß = 0.14), adaptability(ß = 0.20), and power(ß = 0.18), explained 41.2% variance in step-count. Gait characteristics were not related to GPS measures. Participants with high (>4800 steps) compared to low activity (steps<3100) spent more time out-of-home (23 vs 15%), more vehicular travel (66 vs 38 minutes), and larger activity-space (5.18 vs 1.88 km2), all p < .05. CONCLUSIONS: Gait quality beyond speed contributes to physical activity. Physical activity and GPS-derived measures capture distinct aspects of daily-life mobility. Wearable-derived measures should be considered in gait and mobility-related interventions.

Executive function is associated with balance and falls in older cancer survivors treated with chemotherapy: A cross-sectional study.

INTRODUCTION: Balance decrements and increased fall risk in older cancer survivors have been attributed to chemotherapy-induced peripheral neuropathy (CIPN). Cognition is also affected by chemotherapy and may be an additional contributing factor to poor balance through changes in executive functioning. We examined the association of executive function with balance and falls in older cancer survivors who had been treated with chemotherapy. MATERIALS AND METHODS: Fifty cancer survivors (aged 65.6 ± 11.5 years; 88% female) who were all treated with chemotherapy were included in this cross-sectional study at a tertiary medical center. Executive function was measured by Trails-B, Stroop, and rapid reaction accuracy, a measure emphasizing rapid inhibitory function. Balance was measured by five sit-to-stand time (5STS), repetitions of sit-to-stand in thirty seconds (STS30), and unipedal stance time (UST), which was the primary balance outcome measure. Self-reported falls in the past year were also recorded and was a secondary outcome. Bivariate analyses were conducted between executive function measures and balance variables. Multivariable models were constructed for UST and falls outcomes and included covariates of age and chemotherapy induced peripheral neuropathy status. RESULTS: Pearson correlations demonstrated significant relationships between two executive function measures (rapid reaction accuracy, Trails-B) and all the balance measures assessed (UST, STS30, and 5STS). Rapid reaction accuracy correlations were stronger than Trails-B. The Stroop measure correlated solely with UST. In multivariable models, rapid reaction accuracy was associated with better UST (standardized regression coefficient: 64.1, p < 0.01), decreased any fall (odds ratio = 0.000901, p = 0.04), and decreased recurrent falls (odds ratio = 0.0000044, p = 0.01). The interaction of CIPN with the inhibitory measures in the prediction of balance was not significant. DISCUSSION: Measures of executive function were associated with balance, but among the executive function tests, rapid reaction accuracy had the strongest correlations to balance and was independently associated with falls. The findings suggest that executive function should be considered when assessing fall risk and developing interventions intended to reduce fall risk in older chemotherapy-treated cancer survivors.

Accelerometry applications and methods to assess standing balance in older adults and mobility-limited patient populations: a narrative review.

Accelerometers provide an opportunity to expand standing balance assessments outside of the laboratory. The purpose of this narrative review is to show that accelerometers are accurate, objective, and accessible tools for balance assessment. Accelerometry has been validated against current gold standard technology, such as optical motion capture systems and force plates. Many studies have been conducted to show how accelerometers can be useful for clinical examinations. Recent studies have begun to apply classification algorithms to accelerometry balance measures to discriminate populations at risk for falls. In addition to healthy older adults, accelerometry can monitor balance in patient populations such as Parkinson's disease, multiple sclerosis, and traumatic brain injury. The lack of software packages or easy-to-use applications have hindered the shift into the clinical space. Lack of consensus on outcome metrics has also slowed the clinical adoption of accelerometer-based balance assessments. Future studies should focus on metrics that are most helpful to evaluate balance in specific populations and protocols that are clinically efficacious.

Head and vestibular kinematics during vertical semicircular canal impulses.

BACKGROUND: The video head impulse test (vHIT) is a common assessment of semicircular canal function during high-speed impulses. Reliability of the vHIT for assessing vertical semicircular canals is uncertain. Vertical head impulses require a complex head movement, making it difficult to isolate a single semicircular canal and interpret resulting eye rotations. OBJECTIVE: The purpose of this study was to provide descriptive head kinematics and vestibular stimuli during vertical plane impulses to ultimately improve impulse delivery and interpretation of vHIT results for vertical semicircular canals. METHODS: Six participants received right anterior (RA) and left posterior (LP) semicircular canal impulses. Linear displacements, rotational displacements, and rotational velocities of the head were measured. Peak velocities in semicircular canal planes and peak-to-peak gravitoinertial accelerations at the otolith organs were derived from head kinematics. RESULTS: The largest rotational velocities occurred in the target semicircular canal plane, with non-negligible velocities occurring in non-target planes. Larger vertical displacements and accelerations occurred on the right side of the head compared to the left for RA and LP impulses. CONCLUSIONS: These results provide a foundation for designing protocols to optimize stimulation applied to a singular vertical semicircular canal and for interpreting results from the vHIT for vertical semicircular canals.

Correction: Bohlke et al. The Effect of a Verbal Cognitive Task on Postural Sway Does Not Persist When the Task Is Over. Sensors 2021, 21, 8428.

There was an error in the original publication [...].

Uneven surface and cognitive dual-task independently affect gait quality in older adults.

BACKGROUND: Real-world mobility involves walking in challenging conditions. Assessing gait during simultaneous physical and cognitive challenges provides insights on cognitive health. RESEARCH QUESTION: How does uneven surface, cognitive task, and their combination affect gait quality and does this gait performance relate to cognitive functioning? METHODS: Community-dwelling older adults (N = 104, age=75 ± 6 years, 60 % females) performed dual-task walking paradigms (even and uneven surface; with and without alphabeting cognitive task (ABC)) to mimic real-world demands. Gait quality measures [speed(m/s), rhythmicity(steps/minute), stride time variability (%), adaptability (m/s2), similarity, smoothness, power (Hz) and regularity] were calculated from an accelerometer worn on the lower back. Linear-mixed modelling and Tukey analysis were used to analyze independent effects of surface and cognitive task and their interaction on gait quality. Partial Spearman correlations compared gait quality with global cognition and executive function. RESULTS: No interaction effects between surface and cognitive task were found. Uneven surface reduced gait speed(m/s) (ß = -0.07). Adjusted for speed, uneven surface reduced gait smoothness (ß = -0.27) and increased regularity (ß = 0.09), Tukey p < .05, for even vs uneven and even-ABC vs uneven-ABC. Cognitive task reduced gait speed(m/s) (ß = -0.12). Adjusted for speed, cognitive task increased variability (ß = 7.60), reduced rhythmicity (ß = -6.68) and increased regularity (ß = 0.05), Tukey p < .05, for even vs even-ABC and uneven vs uneven-ABC. With demographics as covariates, gait speed was not associated with cognition. Gait quality [lower variability during even-ABC (ρp =-.31) and uneven-ABC (ρp =-.28); greater rhythmicity (ρp between.22 and.29) and greater signal-adaptability AP (ρp between.22 and.26) during all walking tasks] was associated with better global cognition. Gait adaptability during even (ρp =-0.21, p = 0.03) and uneven(ρp =-0.19, p = 0.04) walking was associated with executive function. SIGNIFICANCE: Surface and cognitive walking tasks independently affected gait quality. Our study with high-functioning older adults suggests that task-related changes in gait quality are related to subtle changes in cognitive functioning.

Exercise interventions, postural control, and prefrontal cortex activation in older adults.

Improving postural control in older adults is necessary for reducing fall risk, and prefrontal cortex activation may also play a role. We sought to examine the impact of exercise interventions on postural control and prefrontal cortex activation during standing balance tasks. We hypothesized that balance would improve and prefrontal control would be reduced. We assessed a subset of participants enrolled in a randomized trial of two exercise interventions. Both groups completed strength and endurance training and the experimental treatment arm included training on timing and coordination of stepping. Postural control and prefrontal cortex activation were measured during dual-task standing balance tasks before and after the intervention. Eighteen participants in the standard strengthening and mobility training arm and 16 in the timing and coordination training arm were included. We examined pre- to post-intervention changes within each study arm, and compared them between interventions. Results did not show any pre- to post-intervention changes on standing postural control nor prefrontal cortex activation in either arm. In addition, there were no differences between the two intervention arms in either balance or prefrontal activation. While exercise interventions can improve mobility, we do not demonstrate evidence of improved standing balance or prefrontal control in standing.

Facilitators and barriers to real-life mobility in community-dwelling older adults: a narrative review of accelerometry- and global positioning system-based studies.

Real-life mobility, also called "enacted" mobility, characterizes an individual's activity and participation in the community. Real-life mobility may be facilitated or hindered by a variety of factors, such as physical abilities, cognitive function, psychosocial aspects, and external environment characteristics. Advances in technology have allowed for objective quantification of real-life mobility using wearable sensors, specifically, accelerometry and global positioning systems (GPSs). In this review article, first, we summarize the common mobility measures extracted from accelerometry and GPS. Second, we summarize studies assessing the associations of facilitators and barriers influencing mobility of community-dwelling older adults with mobility measures from sensor technology. We found the most used accelerometry measures focus on the duration and intensity of activity in daily life. Gait quality measures, e.g., cadence, variability, and symmetry, are not usually included. GPS has been used to investigate mobility behavior, such as spatial and temporal measures of path traveled, location nodes traversed, and mode of transportation. Factors of note that facilitate/hinder community mobility were cognition and psychosocial influences. Fewer studies have included the influence of external environments, such as sidewalk quality, and socio-economic status in defining enacted mobility. Increasing our understanding of the facilitators and barriers to enacted mobility can inform wearable technology-enabled interventions targeted at delaying mobility-related disability and improving participation of older adults in the community.

Impact of strength and balance on Functional Gait Assessment performance in older adults.

BACKGROUND: The Functional Gait Assessment (FGA) evaluates postural stability in gait and predicts fall risk in older adults. Individual tasks within the FGA consider aspects of mobility assumed to require strength and/or balance to complete. Identifying how quantitative measures of strength and balance relate to FGA performance would allow for more targeted interventions based on one's pattern of performance on different tasks. RESEARCH QUESTION: Is performance on the FGA (total score and individual task scores) related to measures of strength and balance in healthy older adults? METHODS: In a cross-sectional study, healthy older adults (N = 46) were evaluated with the FGA, measures of knee extensor strength, and balance (static stance and weight shifting) (N = 46). Correlational analyses were performed between FGA scores (total and individual) and measures of strength and balance. RESULTS: Total FGA performance was positively correlated with knee extensor strength (maximum torque and rate of torque development). Individual FGA tasks of walking backwards (task 9) and stair climbing (task 10) had the highest correlations with strength measures. Total FGA performance was correlated with reduced postural sway in static balance tasks, but not with balance performance on the weight shifting tasks. The individual FGA task that challenged proprioceptive (task 7) inputs for balance was associated with static balance. SIGNIFICANCE: The total FGA score is related to domains of strength and static balance. The results indicate that the FGA can be influenced by reduced strength and balance. The pattern of performance on individual FGA tasks may indicate whether reduced postural stability in gait is related to deficits in strength or balance domains in this older population.

The Effect of a Verbal Cognitive Task on Postural Sway Does Not Persist When the Task Is Over.

Dual-task balance studies explore interference between balance and cognitive tasks. This study is a descriptive analysis of accelerometry balance metrics to determine if a verbal cognitive task influences postural control after the task ends. Fifty-two healthy older adults (75 ± 6 years old, 30 female) performed standing balance and cognitive dual-tasks. An accelerometer recorded movement from before, during, and after the task (reciting every other letter of the alphabet). Thirty-six balance metrics were calculated for each task condition. The effect of the cognitive task on postural control was determined by a generalized linear model. Twelve variables, including anterior-posterior centroid frequency, peak frequency and entropy rate, medial-later entropy rate and wavelet entropy, and bandwidth in all directions, exhibited significant differences between baseline and cognitive task periods, but not between baseline and post-task periods. These results indicate that the verbal cognitive task did alter balance, but did not bring about persistent effects after the task had ended. Traditional balance measurements, i.e., root mean square and normalized path length, notably lacked significance, highlighting the potential to use other accelerometer metrics for the early detection of balance problems. These novel insights into the temporal dynamics of dual-task balance support current dual-task paradigms to reduce fall risk in older adults.

Mobility of Older Adults: Gait Quality Measures Are Associated With Life-Space Assessment Scores.

BACKGROUND: The relation of gait quality to real-life mobility among older adults is poorly understood. This study examined the association between gait quality, consisting of step variability, smoothness, regularity, symmetry, and gait speed, and the Life-Space Assessment (LSA). METHOD: In community-dwelling older adults (N = 232, age 77.5 ± 6.6, 65% females), gait quality was derived from (i) an instrumented walkway: gait speed, variability, and walk ratio and (ii) accelerometer: signal variability, smoothness, regularity, symmetry, and time-frequency spatiotemporal variables during 6-minute walk. In addition to collecting LSA scores, cognitive functioning, walking confidence, and falls were recorded. Spearman correlations (speed as covariate) and random forest regression were used to assess associations between gait quality and LSA, and Gaussian mixture modeling (GMM) was used to cluster participants. RESULTS: Spearman correlations of ρ p = .11 (signal amplitude variability mediolateral [ML] axis), ρ p = .15 and ρ p = -.13 (symmetry anterior-posterior-vertical [AP-V] and ML-AP axes, respectively), ρ p = .16 (power V), and ρ = .26 (speed), all p <.05 and marginally related, ρ p = -.12 (regularity V), ρ p = .11 (smoothness AP), and ρ p = -.11 (step-time variability), all p <.1, were obtained. The cross-validated random forest model indicated good-fit LSA prediction error of 17.77; gait and cognition were greater contributors than age and gender. GMM indicated 2 clusters. Group 1 (n = 189) had better gait quality than group 2 (n = 43): greater smoothness AP (2.94 ± 0.75 vs 2.30 ± 0.71); greater similarity AP-V (.58 ± .13 vs .40 ± .19); lower regularity V (0.83 ± 0.08 vs 0.87 ± 0.10); greater power V (1.86 ± 0.18 vs 0.97 ± 1.84); greater speed (1.09 ± 0.16 vs 1.00 ± 0.16 m/s); lower step-time coefficient of variation (3.70 ± 1.09 vs 5.09 ± 2.37), and better LSA (76 ± 18 vs 67 ± 18), padjusted < .004. CONCLUSIONS: Gait quality measures taken in the clinic are associated with real-life mobility in the community.

Attention and sensory integration for postural control in young adults with autism spectrum disorders.

Postural control impairments have been reported in adults with autism spectrum disorders (ASD). Balance relies on the integration of multisensory cues, a process that requires attention. The purpose of this study was to determine if the influence of attention demands on sensory integration abilities relevant for balance partially contributes to postural control impairments in ASD. Young adults with ASD (N = 24) and neurotypical participants (N = 24) were exposed to sensory perturbations during standing. An established dual-task paradigm was used, requiring participants to maintain balance in these sensory challenging environments and to perform auditory information processing tasks (simple reaction time task and choice reaction time task). Balance was assessed using sway magnitude and sway speed, and attention demands were evaluated based on the response time in the auditory tasks. While young adults with ASD were able to maintain balance in destabilizing sensory conditions, they were more challenged (greater sway speed) than their neurotypical counterparts. Additionally, when exposed for an extended amount of time (3 min) to the most challenging sensory condition included in this study, adults with ASD exhibited a reduced ability to adapt their postural control strategies (sway speed was minimally reduced), demonstrating a postural inflexibility pattern in ASD compared to neurotypical counterparts. Finally, the impact of performing an auditory information processing task on balance and the dual-task cost on information processing (response time) was similar in both groups. ASD may disrupt temporal adaptive postural control processes associated with sensory reweighting that occurs in neurotypicals.

Gait kinetics impact shoe tread wear rate.

BACKGROUND: Adequate footwear is an important factor for reducing the risk of slipping; as shoe outsoles wear down, friction decreases, and slip and fall risk increases. Wear theory suggests that gait kinetics may influence rate of tread wear. RESEARCH QUESTION: Do the kinetics of walking (i.e., the shoe-floor force interactions) affect wear rate? METHODS: Fourteen participants completed dry walking trials during which ground reaction forces were recorded across different types of shoes. The peak normal force, shear force, and required coefficient of friction (RCOF) were calculated. Participants then wore alternating pairs of shoes in the workplace each month for up to 24 months. A pedometer was used to track the distance each pair of shoes was worn and tread loss was measured. The wear rate was calculated as the volumetric tread loss divided by the distance walked in the shoes. Three, mixed linear regression models were used to assess the impact of peak normal force, shear force, and RCOF on wear rate. RESULTS: Wear rate was positively associated with peak RCOF and with peak shear force, but was not significantly related to peak normal forces. SIGNIFICANCE: The finding that shear forces and particularly the peak RCOF are related to wear suggests that a person's gait characteristics can influence wear. Therefore, individual gait kinetics may be used to predict wear rate based on the fatigue failure shoe wear mechanism.

Traction performance across the life of slip-resistant footwear: Preliminary results from a longitudinal study.

INTRODUCTION: Slips, trips, and falls are a major cause of injury in the workplace. Footwear is an important factor in preventing slips. Furthermore, traction performance (friction and under-shoe fluid drainage) are believed to change throughout the life of footwear. However, a paucity of data is available for how traction performance changes for naturally worn, slip-resistant footwear. METHOD: The presented research is a preliminary analysis from an ongoing, larger study. Participants wore slip-resistant footwear while their distance walked was monitored. Friction and under-shoe fluid pressures were measured using a robotic slip tester under a diluted glycerol contaminant condition after each month of wear for the left and right shoes. The size of the worn region was also measured. RESULTS: Friction initially increased and then steadily decreased as the distance walked and the size of the worn region increased. Fluid pressures increased as the shoes were worn and were associated with increased walking distance and size of the worn region. DISCUSSION: Consistent with previous research, increases in the size of the worn region are associated with increased under-shoe fluid pressures and decreased traction. These trends are presumably due to reduced fluid drainage between the shoe-floor interface when the shoe becomes worn. CONCLUSIONS: Traction performance changes with natural wear. The distance walked in the shoe and the size of the worn region may be valuable indicators for assessing loss of traction performance. Practical Applications: Current shoe replacement recommendations for slip-resistant shoes are based upon age and tread depth. This study suggests that tools measuring the size of the worn region and/or distance traveled in the shoes are appropriate alternatives for tracking traction performance loss due to shoe wear.