Gyroscope sensor data of shank motion during normal and barefoot walking.

In recent years, shank angular velocity (SAV) has emerged as a valuable tool for accurate temporal gait analysis and motion pattern assessment. To explore SAV among healthy subjects and its capability to distinguish differences between walking conditions, three-dimensional SAV data was measured with a gyroscope sensor during normal and barefoot walking. The resulting dataset contains measurement data from 58 healthy adult subjects aged 19 to 75 years. A single gyroscope was positioned on the lateral side of both shanks just above the lateral malleolus. The data collection involved the subjects walking a 10 m distance three times, both wearing shoes and barefoot. The subjects were instructed to walk with their own natural walking velocity, and each walk began from a stationary position. The dataset has the potential to provide information on how height and weight affect gait kinematics and how barefoot walking differ from walking with shoes. The data also supports designing the collection protocol for more extensive datasets of IMU-based shank motion during gait.

Unsupervised gait detection using biomechanical restrictions.

Quantification of human gait with sensors has enormous potential in health and rehabilitation applications. Objective measurement of gait features in the home and community can reveal the true nature of impact of disease on activities of daily living or response to interventions. Previously reported gait event detection methods have achieved good success, yet can produce errors in some irregular gait patterns. In this paper, we propose a novel unsupervised detection of gait events and gait duration by combining two exclusive processes: (i) exploration of gait event candidates based on iterative running of existing methods with changing parameters and, (ii) selection of the candidate which satisfies gait-specific biomechanical restrictions (e.g., when one leg is in swing, another leg is likely to be in stance). We evaluated this approach using data from a single-axis gyroscope on the left and right ankles in three experimental conditions. The proposed method decreased the timing error for detection of gait events (toe off and heel strike) in irregular gait patterns compared with the conventional method. It also improved the accuracy of measurement of gait duration in a longitudinal free-living dataset and distinguishing gait from non-gait actions.

Concussion is associated with altered preparatory postural adjustments during gait initiation.

Gait initiation is a useful surrogate measure of supraspinal motor control mechanisms but has never been evaluated in a cohort following concussion. The aim of this study was to quantify the preparatory postural adjustments (PPAs) of gait initiation (GI) in fifteen concussion patients (4 females, 11 males) in comparison to a group of fifteen age- and sex-matched controls. All participants completed variants of the GI task where their dominant and non-dominant limbs as the 'stepping' and 'support' limbs. Task performance was quantified using the centre of pressure (COP) trajectory of each foot (computed from a force plate) and a surrogate of the centre of mass (COM) trajectory (estimated from an inertial measurement unit placed on the sacrum). Concussed patients exhibited decreased COP excursion on their dominant foot, both when it was the stepping limb (sagittal plane: 9.71mm [95% CI: 8.14-11.27mm] vs 14.9mm [95% CI: 12.31-17.49mm]; frontal plane: 36.95mm [95% CI: 30.87-43.03mm] vs 54.24mm [95% CI: 46.99-61.50mm]) and when it was the support limb (sagittal plane: 10.43mm [95% CI: 8.73-12.13mm] vs 18.13mm [95% CI: 14.92-21.35mm]; frontal plane: 66.51mm [95% CI: 60.45-72.57mm] vs 88.43mm [95% CI: 78.53-98.32mm]). This was reflected in the trajectory of the COM, wherein concussion patients exhibited lower posterior displacement (19.67mm [95% CI: 19.65mm-19.7mm]) compared with controls (23.62mm [95% CI: 23.6-23.64]). On this basis, we conclude that individuals with concussion display deficits during a GI task which are potentially indicative of supraspinal impairments in motor control.

Quantification of postural control deficits in patients with recent concussion: An inertial-sensor based approach.

BACKGROUND: The aim of this study was to quantify postural control ability in a group with concussion compared with a healthy control group. METHOD: Fifteen concussion patients (4 females, 11 males) and a group of fifteen age- and sex-matched controls were recruited. Participants were tested during the performance of the three stance variants (bilateral, tandem and unilateral) of the balance error scoring system standing on a force place, while wearing an inertial measurement unit placed at the posterior aspect of the sacrum. FINDINGS: The area of postural sway was computed using the force-plate and the '95% ellipsoid volume of sway' was computed from the accelerometer data. Concussed patients exhibited increased sway area (1513mm2 [95% CI: 935 to 2091mm2] vs 646mm2 [95% CI: 519 to 772mm2]; p=0.02) and sway volume (9.46m3s-6 [95% CI: 8.02 to 19.94m3s-6] vs 2.68m3s-6 [95% CI: 1.81 to 3.55m3s-6]; p=0.01) in the bilateral stance position of the balance error scoring system. The sway volume metric also had excellent accuracy in identifying task 'errors' (tandem stance: 91% accuracy [95% CI: 85-96%], p<0.001; unilateral stance: 91% accuracy [95% CI: 86-96%], p<0.001). INTERPRETATION: Individuals with concussion display increased postural sway during bilateral stance. The sway volume that was calculated from the accelerometer data not only differentiated a group with concussion from a healthy control group, but successfully identified when task errors had occurred. This may be of value in the development of a pitch-side assessment system for concussion.

Continuous real-world gait monitoring in community-based older adults.

This paper describes the collection of real-world gait data in a cohort of 7 community living older adults, who have fallen at least once in the previous year, while they live in a smart apartment for four days. It describes the approach used to collect various gait metrics, from inertial sensors placed on the lower shanks, where gait bouts can be contextualised by smart home data. Results from this study are presented with a brief discussion into the smart-home based contextualisation of outliers in the gait data. Future work will investigate the normative ranges of various gait metrics, and how such real-world gait data may be integrated into clinical practice.

Context aware falls risk assessment: A case study comparison.

This paper describes three retrospective case studies to illustrate the potential clinical value of a system capable of capturing objective gait metrics and environment data from older adults with a history of falls while they go about their daily lives. Participants in this study wore an inertial sensor above each ankle and a wearable camera around their neck for seven consecutive days. Selected metrics are presented to illustrate scenarios where the data collected by the system could be of clinical value. Evidence suggests that obtaining objective gait metrics and environment data from older adults may not only allow healthcare professionals to assess gait more accurately, but also to design treatment plans and falls prevention strategies that are more specifically tailored to each individual.

Context focused older adult mobility and gait assessment.

This paper presents an initial overview of insights gained into how older adults mobilize in the home and community, based on data from inertial sensors which were worn by study participants over a 7-day period. The addition of a wearable camera provided additional contextual information which can be used to assess mobility and understand the factors that influence it in the free living environment. Seven days of data collected from a group of older adults who had experienced one or more falls in the previous six months was compared to that of a control group with no history of falling. Results showed that both groups spent relatively little time walking in challenging environmental conditions, and that the fallers spent significantly less time walking under regular conditions (no effect on gait) and outdoors. Analysis of gait metrics showed that the fallers were slightly slower in general, and more noticeable differences were observed when the participants were regrouped according to mobility levels determined from baseline assessments using traditional methods.

Does external walking environment affect gait patterns?

The objective of this work is to develop an understanding of the relationship between mobility metrics obtained outside of the clinic or laboratory and the context of the external environment. Ten subjects walked with an inertial sensor on each shank and a wearable camera around their neck. They were taken on a thirty minute walk in which they mobilized over the following conditions; normal path, busy hallway, rough ground, blind folded and on a hill. Stride time, stride time variability, stance time and peak shank rotation rate during swing were calculated using previously published algorithms. Stride time was significantly different between several of the conditions. Technological advances mean that gait variables can now be captured as patients go about their daily lives. The results of this study show that the external environment has a significant impact on the quality of gait metrics. Thus, context of external walking environment is an important consideration when analyzing ambulatory gait metrics from the unsupervised home and community setting.

Nanopattern transfer from high-density self-assembled nanosphere arrays on prepatterned substrates.

We have fabricated nanoimprint moulds with high-density well-defined nanopatterns by pattern transfer from self-assembled nanosphere arrays on prepatterned substrates. Silica nanospheres of 100 and 25 nm diameter were regularly arranged over large areas in a self-assembling manner by capillary force via a dip-coating technique on topographically patterned substrates having 220 nm pitch line/space patterns. The nanosphere arrays were used as etching masks, and nanodot arrays with the same arrangements were created on the silica substrate surfaces by reactive ion etching (RIE). By developing a combined pattern transfer process using Ru and SiO(x) mask layers and CF4 and O2 RIE, the aspect ratio between the height and diameter of the nanodots made from the 25 nm nanospheres is improved to about two. It is demonstrated that the nanopatterns of the moulds can be inversely transferred into polymer surfaces reproducibly by UV nanoimprint process.