Ruth E. Mayagoitia

A portable system for collecting anatomical joint angles during stair ascent: a comparison with an optical tracking device

BackgroundAssessments of stair climbing in real-life situations using an optical tracking system are lacking, as it is difficult to adapt the system for use in and around full flights of stairs. Alternatively, a portable system that consists of inertial measurement units (IMUs) can be used to collect anatomical joint angles during stair ascent. The purpose of this study was to compare the anatomical joint angles obtained by IMUs to those calculated from position data of an optical tracking device.MethodsAnatomical joint angles of the thigh, knee and ankle, obtained using IMUs and an optical tracking device, were compared for fourteen healthy subjects. Joint kinematics obtained with the two measurement devices were evaluated by calculating the root mean square error (RMSE) and by calculating a two-tailed Pearson product-moment correlation coefficient (r) between the two signals.ResultsStrong mean correlations (range 0.93 to 0.99) were found for the angles between the two measurement devices, as well as an average root mean square error (RMSE) of 4 degrees over all the joint angles, showing that the IMUs are a satisfactory system for measuring anatomical joint angles.ConclusionThese highly portable body-worn inertial sensors can be used by clinicians and researchers alike, to accurately collect data during stair climbing in complex real-life situations.

The kinematics of the swing phase obtained from accelerometer and gyroscope measurements

The kinematics needed to calculate the knee moment during the initial swing phase were obtained from a set of eight leg-mounted uni-axial accelerometers and two gyroscopes. The angular and linear accelerations of shank and thigh were calculated from the signals of two accelerometers mounted on each of the leg segments directed tangentially and radially to the movement. The angular velocities of shank and thigh were measured by the gyroscopes. The absolute angles of shank and thigh were obtained by integration of the gyroscope signal plus an added offset angle, estimated from radial and tangential accelerometer signals registered while standing. Movement was assumed to be in the saggital plane. The accuracy of the quantities found from the leg mounted sensors was calculated in terms of correlation and the RMS error by comparing against measurements obtained by a VICON/sup TM/ system. The results were indistinguishable. The system was later applied in research measurements.

Some social consequences of remodelling English sheltered housing and care homes to ‘extra care’

ABSTRACT Across the United Kingdom, new build and remodelled ‘extra care’ schemes are being developed in many areas on the assumption that they offer older people with care needs an alternative to residential care. This paper reports an evaluation by a multi-disciplinary team of 10 extra-care schemes remodelled from sheltered housing or residential care units. The evaluation audited buildings and identified social and architectural problems. No two schemes in the sample were alike; some aimed for a dependency balance and others set a dependency threshold for admission. The three criteria used for assessing eligibility were the number of paid care hours the older person had at home, their property status and the type of disability. This article focuses on the wide variation in assessing eligibility for an extra-care place and on some social consequences of remodelling. A number of tenants remained in situ during the remodelling process in six of the schemes. Building professionals were unanimous that retaining some tenants on site caused significant development delays and increased the remodelling costs. There was also a social price to pay. ‘Old’ tenants resented their scheme changing into extra care and were hostile towards ‘new’ tenants who had obvious needs for support. In some extra-care schemes, ‘old’ tenants were refusing to participate in meals and all social activities.

Assessing Gait Patterns of Healthy Adults Climbing Stairs Employing Machine Learning Techniques

So far, stair climbing has not been studied as extensively as gait has, although the significance of the prevention of falling on stairs has been well recognized. Based on acceleration data taken from 25 healthy subjects climbing up and down a set of 13 stairs with an accelerometer placed on the lumbo‐sacral joint, this paper aims to assess gait patterns of younger and older adults climbing stairs using a machine learning approach. A total of 14 gait features were extracted and analyzed. The performance of six representative classification models: Multilayer Perceptron (MLP), KStar, Support Vector Machine (SVM), Naïve Bayesian (NB), C4.5 Decision Trees, and Random Forests were evaluated in terms of their ability to discriminate between younger and older adults climbing up‐ and downstairs. MLP was found to provide the highest accuracy for classification. Accuracy of 95.7% was found for classifying a subject walking either up or down the stairs and an accuracy of 80.6% for classifying whether the subject was younger or older. An evaluation of individual features showed poor performance of classification for younger and older subjects climbing up‐ and downstairs, and in most cases failed to distinguish between the two classes. To access which set of features derived from a triaxial accelerometer can better describe the performance differences between younger and older adults climbing up‐ and downstairs, two feature selection algorithms, sequential feature selection and correlation‐based feature selection, were implemented. Results show that 10 features derived from correlation‐based feature selection were able to produce a 96.8% accuracy for classification between subjects climbing up and down. A subset of seven features achieved a performance of 84.9% accuracy for classification between younger and older subjects.

Exploring the use of sensors to measure behavioral interactions: an experimental evaluation of using hand trajectories.

Humans appear to be sensitive to relative small changes in their surroundings. These changes are often initially perceived as irrelevant, but they can cause significant changes in behavior. However, how exactly people’s behavior changes is often hard to quantify. A reliable and valid tool is needed in order to address such a question, ideally measuring an important point of interaction, such as the hand. Wearable-body-sensor systems can be used to obtain valuable, behavioral information. These systems are particularly useful for assessing functional interactions that occur between the endpoints of the upper limbs and our surroundings. A new method is explored that consists of computing hand position using a wearable sensor system and validating it against a gold standard reference measurement (optical tracking device). Initial outcomes related well to the gold standard measurements (r = 0.81) showing an acceptable average root mean square error of 0.09 meters. Subsequently, the use of this approach was further investigated by measuring differences in motor behavior, in response to a changing environment. Three subjects were asked to perform a water pouring task with three slightly different containers. Wavelet analysis was introduced to assess how motor consistency was affected by these small environmental changes. Results showed that the behavioral motor adjustments to a variable environment could be assessed by applying wavelet coherence techniques. Applying these procedures in everyday life, combined with correct research methodologies, can assist in quantifying how environmental changes can cause alterations in our motor behavior.

Remodelling to extra care housing: some implications for policy and practice

Extra care housing is seen as a popular option for older people by families, some older people, policy‐makers and practitioners. Some new build is being provided but another option, for which grants are available, is to remodel existing outmoded buildings. This research reports on recent attempts from 10 case‐study areas in England to remodel sheltered housing and residential care homes to extra care housing. The results are mixed, with satisfaction reported by many new tenants, anger by some existing ones, challenges at every stage of the project for design and construction teams, and issues over the provision of assistive technology and care. Nearly all the schemes experienced unexpected problems during the course of construction. Remodelling is not necessarily faster or cheaper than commissioning a purpose‐designed new building. Nevertheless, remodelling may be the only viable option for some unpopular or outdated schemes. The research showed that remodelling is not a quick fix, but that it did have considerable advantages for many of the older people and support staff who were living and working in the remodelled buildings. The research concluded that remodelling should only be undertaken when other options have been carefully examined. Drawing on the research findings, advice to policy‐makers and practitioners who are considering this course of action is outlined in the discussion.

Extra care housing: a concept without a consensus

Extra care housing has developed from sheltered housing and has increasingly been seen as a popular option by policy‐makers for a number of reasons. These include the inability of conventional sheltered housing to be an adequate solution for a growing population of very old people, the decline in popularity and high costs of residential care and perceived problems with older people staying in mainstream housing. There is, however, no agreed definition of extra care housing, even though a growing number of government grants are becoming available for this type of housing. This is causing confusion for providers and for older people and their families who are not sure exactly what is provided. This lack of clarity means that this form of housing has become an erratic and piecemeal form of provision.

Using a body sensor network to measure the effect of fatigue on stair climbing performance

In terms of self-rated health, the most important activities of daily living are those involving mobility. Of these activities stair climbing is regarded as the most strenuous. A loss of stair climbing ability with age is normally associated with a loss of muscle strength and power, while other factors that influence muscle function, such as fatigue, are often not taken into account. So far no research has been published on how long-lasting fatigue affects activities of daily living, despite the fact that it has been repeatedly proven, in laboratory settings, to influence muscle force production over long periods of time. Technological advances in body sensor networks (BSNs) now provide a method to measure performance during complex real-life situations. In this study the use of a BSN was explored to investigate the effects of long-lasting fatigue on stair climbing performance in 20 healthy adults. Stair climbing performance was measured before and after a fatiguing protocol using a BSN. Performance was defined by temporal and spatial parameters. Long-lasting fatigue was successfully induced in all participants using an exercise protocol. The BSN showed that post-exercise fatigue did not influence stair climbing times (p > 0.2) and no meaningful changes in joint angles were found. No effect on overall stair climbing performance was found, despite a clear presence of long-lasting fatigue. This study shows that physiological paradigms can be further explored using BSNs. Ecological validity of lab-based measurements can be increased by combining them with BSNs.

Quantifying the stability of walking using accelerometers

A dynamic analysis method is sought to measure the relative stability of walking, using a triaxial accelerometer. A performance parameter that can be calculated from the data from the accelerometer is defined; it should give a measure of the stability of the subject. It is based on the balancing forces as reflected in the power spectrum. Preliminary experiments have been done. The results suggest that the performance parameter can order different gait patterns in terms of relative stability. Further experiments are being set up to test the usefulness of the performance parameter in clinical applications and other parameters may be defined.

A novel method for determining ground-referenced contacts during stair ascent: Comparing relative hip position to quiet standing hip height

Stair climbing can be measured using body-fixed sensors, whereby the origin and axes of the coordinate system are fixed with respect to the geometry of a body segment. These sensors can be part of a portable system, which provides the possibility to collect data in complex real-life environments. However due to the fact that the sensors are body-fixed, difficulties in determining the ground-based parameters of stair ascent can occur. The purpose of this study is to present a new approach for determining initial contacts based on a multi-chain biomechanical model combined with a new analysis method, in which relative hip height is compared to hip height during normal standing. Initial contacts obtained from the proposed method were compared to those obtained using an optical tracking device. An average absolute timing difference ranging from 0.04 (SD + or - 0.03) to 0.06 (+ or - 0.03) s and a root mean square error ranging from 0.05 to 0.07 s were found between the two techniques. This shows that the new approach presented in this study can be used to accurately determine initial contacts during stair ascent using portable equipment.