Differences Between Gait on Stairs and Flat Surfaces in Relation to Fall Risk and Future Falls.

We used body-worn inertial sensors to quantify differences in semi-free-living gait between stairs and on normal flat ground in older adults, and investigated the utility of assessing gait on these terrains for predicting the occurrence of multiple falls. Eighty-two community-dwelling older adults wore two inertial sensors, on the lower back and the right ankle, during several bouts of walking on flat surfaces and up and down stairs, in between rests and activities of daily living. Derived from the vertical acceleration at the lower back, step rate was calculated from the signal's fundamental frequency. Step rate variability was the width of this fundamental frequency peak from the signal's power spectral density. Movement vigor was calculated at both body locations from the signal variance. Partial Spearman correlations between gait parameters and physiological fall risk factors (components from the Physiological Profile Assessment) were calculated while controlling for age and gender. Overall, anteroposterior vigor at the lower back in stair descent was lower in subjects with longer reaction times. Older adults walked more slowly on stairs, but they were not significantly slower on flat surfaces. Using logistic regression, faster step rate in stair descent was associated with multiple prospective falls over 12 months. No significant associations were shown from gait parameters derived during walking upstairs or on flat surfaces. These results suggest that stair descent gait may provide more insight into fall risk than regular walking and stair ascent, and that further sensor-based investigation into unsupervised gait on different terrains would be valuable.

Gyroscopic corrections improve wearable sensor data prior to measuring dynamic sway in the gait of people with Multiple Sclerosis.

Accelerometers are incorporated into many consumer devices providing new ways to monitor gait, mobility, and fall risk. However, many health benefits have not been realised because of issues with data quality that results from gravitational 'cross-talk' when the wearable device is tilted. Here we present an adaptive filter designed to improve the quality of accelerometer data prior to measuring dynamic pelvic sway patterns during a six minute walk test in people with and without Multiple Sclerosis (MS). Optical motion capture was used as the gold standard. Improved wearable device accuracy (≤4.4% NRMSE) was achieved using gyroscopic corrections and scaling filter thresholds by step frequency. The people with MS presented significantly greater pelvis sway range to compensate for their lower limb weaknesses and joint contractures. The visualisation of asymmetric pelvic sway in people with MS illustrates the potential to better understand their mobility impairments for reducing fall risk.

Wearable pendant device monitoring using new wavelet-based methods shows daily life and laboratory gaits are different.

Morbidity and falls are problematic for older people. Wearable devices are increasingly used to monitor daily activities. However, sensors often require rigid attachment to specific locations and shuffling or quiet standing may be confused with walking. Furthermore, it is unclear whether clinical gait assessments are correlated with how older people usually walk during daily life. Wavelet transformations of accelerometer and barometer data from a pendant device worn inside or outside clothing were used to identify walking (excluding shuffling or standing) by 51 older people (83 ± 4 years) during 25 min of 'free-living' activities. Accuracy was validated against annotated video. Training and testing were separated. Activities were only loosely structured including noisy data preceding pendant wearing. An electronic walkway was used for laboratory comparisons. Walking was classified (accuracy ≥97 %) with low false-positive errors (≤1.9%, κ ≥ 0.90). Median free-living cadence was lower than laboratory-assessed cadence (101 vs. 110 steps/min, p < 0.001) but correlated (r = 0.69). Free-living step time variability was significantly higher and uncorrelated with laboratory-assessed variability unless detrended. Remote gait impairment monitoring using wearable devices is feasible providing new ways to investigate morbidity and falls risk. Laboratory-assessed gait performances are correlated with free-living walks, but likely reflect the individual's 'best' performance.

Head and pelvis stride-to-stride oscillations in gait: validation and interpretation of measurements from wearable accelerometers.

Unstable gait is a risk factor for falls. Wearable accelerometers enable remote monitoring of daily walking. Here, new methods for measuring stride-to-stride oscillations are validated against optical motion capture, normative data determined, and dependency on walking speed investigated. Walks by 13 young people (mean age 32 years) at fast, usual, and slow speeds were completed. Accelerometers were attached to the head and pelvis and stride-to-stride oscillation velocity and displacement were measured. Continuous tilt corrections were applied, filter cut-offs scaled by step frequency, and thresholds optimized using optical motion capture as a reference. Oscillations depended on walking speed, accelerometer placement, and measurement axis. Vertical oscillations increased with walking speed (Pearson's r = 0.78-0.89) and were the most accurate (1.4-2.3% error). Mediolateral or anterioposterior oscillations were less accurate (5.9-19.5% error) and had more complex relationships with walking speed (increasing, decreasing, uncorrelated, and/or 'U-shaped' minimum at usual speed). In healthy gait, the head and pelvis undergo regular oscillations, measurable with accelerometers. The results suggest head oscillations in the transverse plane are attenuated by the trunk, and there may be advantages in minimizing stride-to-stride oscillations that coincide with self-selected usual pace. These methods may prove useful for remote assessment of changing health, mental status, and/or fall risk.

Uncontrolled head oscillations in people with Parkinson's disease may reflect an inability to respond to perturbations while walking.

Fall injuries in people with Parkinson's disease (PD) are a major health problem. Increased sway while walking is a risk factor and further understanding of this destabilizing gait change may assist with rehabilitation and help prevent falls.Here, stride-to-stride head oscillations are used to help characterise different aspects of gait impairment in 10 people with PD on medication (67 years, SD 4), 10 healthy age-matched (HAM) participants (66 years, SD 7), and 10 young (30 years, SD 7). A wearable accelerometer was used to analyse head oscillations during five repeat 17 m walks by each participant.People with PD had significantly faster transverse plane head oscillations than the HAM or young groups; both along mediolateral (PD 47.2 cm s(-1), HAM 32.5 cm s(-1), and young 32.7 cm s(-1)) and anterioposterior axes (PD 33.3 cm s(-1), HAM 24.5 cm s(-1), and young 20.6 cm s(-1)). These differences were uncorrelated with reduced vertical oscillation velocity (PD 15.5 cm s(-1), HAM 18.8 cm s(-1), and young 20.1 cm s(-1)) and reduced walking speed (PD 1.2 m s(-1), HAM 1.4 m s(-1), and young 1.4 m s(-1)).Increased transverse plane head oscillations in people with PD may reflect motor impairment and the inability to respond sufficiently to perturbations while walking, which appears to be distinct from gait hyperkinesia, reduced vertical oscillations, step length, and walking speed.

Symmetry matched auditory cues improve gait steadiness in most people with Parkinson's disease but not in healthy older people.

BACKGROUND: Unsteady gait and falls are major problems for people with Parkinson's disease (PD). Symmetric auditory cues at altered cadences have been used to improve walking speed or step length. However, few people are exactly symmetric in terms of morphology or movement patterns and effects of symmetric cueing on gait steadiness are inconclusive. OBJECTIVES: To investigate if matching auditory cue a/symmetry to an individual's intrinsic symmetry or asymmetry affects gait steadiness, gait symmetry, and comfort to cues, in people with PD, healthy age-matched controls (HAM) and young. METHODS: Thirty participants; 10 with PD, 11 HAM (66 years), and 9 young (30 years), completed five baseline walks (no cues) and twenty-five cued walks at habitual cadence but different a/symmetries. Outcomes included; gait steadiness (step time variability and smoothness by harmonic ratios), walking speed, symmetry, comfort, and cue lag times. RESULTS: Without cues, PD participants had slower and less steady gait than HAM or young. Gait symmetry was distinct from gait steadiness, and unaffected by cue symmetry or a diagnosis of PD, but associated with aging. All participants maintained preferred gait symmetry and lag times independent of cue symmetry. When cues were matched to the individual's habitual gait symmetry and cadence: Gait steadiness improved in the PD group, but deteriorated in the HAM controls, and was unchanged in the young. Gait outcomes worsened for the two PD participants who reported discomfort to cued walking and had high New Freezing of Gait scores. CONCLUSIONS: It cannot be assumed all individuals benefit equally from auditory cues. Symmetry matched auditory cues compensated for unsteady gait in most people with PD, but interfered with gait steadiness in older people without basal ganglia deficits.

Good lateral harmonic stability combined with adequate gait speed is required for low fall risk in older people.

BACKGROUND: Good lateral harmonic stability in gait may be important for minimising fall risk in older people because many falls occur during walking when the base of support is narrowest in the mediolateral (ML) direction. However, the traditional ML harmonic ratio (MLHR) may be a sub-optimal measure of gait quality because of insufficient frequency resolution. OBJECTIVE: The primary objective was to investigate if a new measure of lateral harmonic stability, the 8-step MLHR, could discriminate older fallers from non-fallers while taking different walking speeds into account. METHODS: Repeat walks over 20 m were completed by 96 older people (mean age 80, SD 4 years); 35 participants had a history of one or more falls in the past year. The traditional MLHR and the 8-step MLHR were obtained from an accelerometer attached to the sacrum. RESULTS: Compared to the traditional MLHR, the 8-step MLHR demonstrated similar univariate ability to identify significant differences in fall risk based on age, walking speed and physiology (p ≤ 0.05). When differences in walking speed were taken into account, we observed that participants who walked both faster than average and had above-average lateral harmonic stability (by the 8-step MLHR) were 5.3 times less likely to be fallers than all other participants (relative risk: 0.19, 95% confidence interval: 0.06-0.57). For the traditional MLHR, however, no significant differences between the fallers and non-fallers were evident. CONCLUSIONS: The findings indicate that good lateral harmonic stability interacts with adequate gait speed and, when coincident, are associated with reduced fall risk in older people. Future research could examine whether interventions focusing on enhancing both gait speed and lateral stability can reduce fall risk and whether these combined gait measures can remotely predict deteriorating health using wearable technology.

Visuospatial tasks affect locomotor control more than nonspatial tasks in older people.

BACKGROUND: Previous research has shown that visuospatial processing requiring working memory is particularly important for balance control during standing and stepping, and that limited spatial encoding contributes to increased interference in postural control dual tasks. However, visuospatial involvement during locomotion has not been directly determined. This study examined the effects of a visuospatial cognitive task versus a nonspatial cognitive task on gait speed, smoothness and variability in older people, while controlling for task difficulty. METHODS: Thirty-six people aged ≥75 years performed three walking trials along a 20 m walkway under the following conditions: (i) an easy nonspatial task; (ii) a difficult nonspatial task; (iii) an easy visuospatial task; and (iv) a difficult visuospatial task. Gait parameters were computed from a tri-axial accelerometer attached to the sacrum. The cognitive task response times and percentage of correct answers during walking and seated trials were also computed. RESULTS: No significant differences in either cognitive task type error rates or response times were evident in the seated conditions, indicating equivalent task difficulty. In the walking trials, participants responded faster to the visuospatial tasks than the nonspatial tasks but at the cost of making significantly more cognitive task errors. Participants also walked slower, took shorter steps, had greater step time variability and less smooth pelvis accelerations when concurrently performing the visuospatial tasks compared with the nonspatial tasks and when performing the difficult compared with the easy cognitive tasks. CONCLUSIONS: Compared with nonspatial cognitive tasks, visuospatial cognitive tasks led to a slower, more variable and less smooth gait pattern. These findings suggest that visuospatial processing might share common networks with locomotor control, further supporting the hypothesis that gait changes during dual task paradigms are not simply due to limited attentional resources but to competition for common networks for spatial information encoding.

Inertial measurements of free-living activities: assessing mobility to predict falls.

An exploratory analysis was conducted into how simple features, from acceleration at the lower back and ankle during simulated free-living walking, stair ascent and descent, correlate with age, the overall fall risk from a clinically validated Physiological Profile Assessment (PPA), and its sub-components. Inertial data were captured from 92 older adults aged 78-95 (42 female, mean age 84.1, standard deviation 3.9 years). The dominant frequency, peak width from Welch's power spectral density estimate, and signal variance along each axis, from each sensor location and for each activity were calculated. Several correlations were found between these features and the physiological risk factors. The strongest correlations were from the dominant frequency at the ankle along the mediolateral direction during stair ascent (Spearman's correlation coefficient p = - 0.45) with anterioposterior sway, and signal variance of the anterioposterior acceleration at the lower back during stair descent (p = - 0.45) with age. These findings should aid future attempts to classify activities and predict falls in older adults, based on true free-living data from a range of activities.

Age-associated changes in head jerk while walking reveal altered dynamic stability in older people.

Many older people have impaired dynamic stability, and up to one in three people over 65 fall each year. It is thought that older people walk more slowly to compensate for reduced capabilities. Here, we investigate whether head jerk, the first time derivative of acceleration, can further our understanding of age-associated changes in dynamic stability while walking. Gait parameters including cadence, step length, walking speed, harmonic ratios, step time variability, and jerk were measured in 43 young and 100 older people using accelerometers securely attached to the head and pelvis. Older people presented significantly (p ≤ 0.004) more mediolateral (ML) head jerk, but significantly less vertical (VT) head jerk. The dimensionless ratio, ML/VT jerk, demonstrated superior ability (89 % accuracy) in differentiating older from younger people. Principal component analysis indicated that ML/VT jerk was a distinct gait construct. ML/VT jerk was highly reliable, normally distributed, independent of stature or gender, and relatively unaffected by walking speed. In older people, reduced VT head jerk may indicate reduced gait vigour, and increased ML head jerk may indicate age-associated changes to dynamic stability. The smoother head movements evident in our younger group may be because they were more able to rely on automatic control and the dynamic (pendulum-like) stability of their systems.

Comparison of handheld video camera and GAITRite® measurement of gait impairment in people with early stage Parkinson's disease: a pilot study.

In this pilot study, we investigated the validity and reliability of low-cost handheld video camera recordings for measuring gait in people with early stage Parkinson's disease (PD). Five participants with PD, Hoehn & Yahr stage I-II, mean age 66.2 years and five healthy age-matched controls were recruited. Participants walked across a GAITRite® electronic walkway at self-selected pace while video was simultaneously recorded. Data from both systems were analyzed and compared. Step time variability, measured from handheld video recordings, revealed significant (p ≤ 0.05) differences between the gait of early stage PD and controls. Concurrent validity between video analyses and GAITRite were good (ICC(2,1) ≥ 0.86) for mean step time and mean dual support duration. However, the inter-assessor reliability for the video analysis was poor for step time variability (ICC(2,1) = 0.18). More reliable measurement of step time variability may require a system to measure extended periods of walking. Further research involving longer walks and more participants with higher stages of PD is required to investigate if step time variability can be measured with acceptable reliability using video recordings. If this could be demonstrated, this simple technology could be adapted to run on a tablet or smart phone, providing low cost gait assessments without the need for specialized equipment and expensive infrastructure.