Alan Godfrey

Direct measurement of human movement by accelerometry

Human movement has been the subject of investigation since the fifth century when early scientists and researchers attempted to model the human musculoskeletal system. The anatomical complexities of the human body have made it a constant source of research to this day with many anatomical, physiological, mechanical, environmental, sociological and psychological studies undertaken to define its key elements. These studies have utilised modern day techniques to assess human movement in many illnesses. One such modern technique has been direct measurement by accelerometry, which was first suggested in the 1970s but has only been refined and perfected during the last 10-15 years. Direct measurement by accelerometry has seen the introduction of the successful implementation of low power, low cost electronic sensors that have been employed in clinical and home environments for the constant monitoring of patients (and their controls). The qualitative and quantitative data provided by these sensors make it possible for engineers, clinicians and physicians to work together to be able to help their patients in overcoming their physical disability. This paper presents the underlying biomechanical elements necessary to understand and study human movement. It also reflects on the sociological elements of human movement and why it is important in patient life and well being. Finally the concept of direct measurement by accelerometry is presented with past studies and modern techniques used for data analysis.

Are behavioral interventions effective in increasing physical activity at 12 to 36 months in adults aged 55 to 70 years? A systematic review and meta-analysis.

BackgroundRetirement represents a major transitional life stage in middle to older age. Changes in physical activity typically accompany this transition, which has significant consequences for health and well-being. The aim of this systematic review was to evaluate the evidence for the effect of interventions to promote physical activity in adults aged 55 to 70 years, focusing on studies that reported long-term effectiveness. This systematic review adheres to a registered protocol (PROSPERO CRD42011001459).MethodsRandomized controlled trials of interventions to promote physical activity behavior with a mean/median sample age of 55 to 70 years, published between 2000 and 2010, were identified. Only trials reporting the long-term effect (≥ 12 months) on objective or self-reported physical activity behavior were included. Trials reporting physiological proxy measures of physical activity were excluded. Meta-analyses were conducted when trials provided sufficient data and sensitivity analyses were conducted to identify potential confounding effects of trials of poor methodological quality or with attrition rates ≥ 30%.ResultsOf 17,859 publications identified, 32 were included which reported on 21 individual trials. The majority of interventions were multimodal and provided physical activity and lifestyle counselling. Interventions to promote physical activity were effective at 12 months (standardized mean difference (SMD) = 1.08, 95% confidence interval (CI) = 0.16 to 1.99, pedometer step-count, approximating to an increase of 2,197 steps per day; SMD = 0.19, 95% CI = 0.10 to 0.28, self-reported physical activity duration outcome), but not at 24 months based on a small subset of trials. There was no evidence for a relationship between intervention effectiveness and mode of delivery or number of intervention contacts; however, interventions which involved individually tailoring with personalized activity goals or provision of information about local opportunities in the environment may be more effective.ConclusionsInterventions in adults aged 55 to 70 years led to long term improvements in physical activity at 12 months; however, maintenance beyond this is unclear. Identified physical activity improvements are likely to have substantial health benefits in reducing the risk of age-related illnesses. These findings have important implications for community-based public health interventions in and around the retirement transition.

Activity classification using a single chest mounted tri-axial accelerometer

Accelerometer-based activity monitoring sensors have become the most suitable means for objective assessment of mobility trends within patient study groups. The use of minimal, low power, IC (integrated circuit) components within these sensors enable continuous (long-term) monitoring which provides more accurate mobility trends (over days or weeks), reduced cost, longer battery life, reduced size and weight of sensor. Using scripted activities of daily living (ADL) such as sitting, standing, walking, and numerous postural transitions performed under supervised conditions by young and elderly subjects, the ability to discriminate these ADL were investigated using a single tri-axial accelerometer, mounted on the trunk. Data analysis was performed using Matlab® to determine the accelerations performed during eight different ADL. Transitions and transition types were detected using the scalar (dot) product technique and vertical velocity estimates on a single tri-axial accelerometer was compared to a proven discrete wavelet transform method that incorporated accelerometers and gyroscopes. Activities and postural transitions were accurately detected by this simplified low-power kinematic sensor and activity detection algorithm with a sensitivity and specificity of 86-92% for young healthy subjects in a controlled setting and 83-89% for elderly healthy subjects in a home environment.

Validation of an Accelerometer to Quantify a Comprehensive Battery of Gait Characteristics in Healthy Older Adults and Parkinson's Disease: Toward Clinical and at Home Use

Measurement of gait is becoming important as a tool to identify disease and disease progression, yet to date its application is limited largely to specialist centers. Wearable devices enables gait to be measured in naturalistic environments, however questions remain regarding validity. Previous research suggests that when compared with a laboratory reference, measurement accuracy is acceptable for mean but not variability or asymmetry gait characteristics. Some fundamental reasons for this have been presented, (e.g., synchronization, different sampling frequencies) but to date this has not been systematically examined. The aims of this study were to: 1) quantify a comprehensive range of gait characteristics measured using a single triaxial accelerometer-based monitor; 2) examine outcomes and monitor performance in measuring gait in older adults and those with Parkinsons disease (PD); and 3) carry out a detailed comparison with those derived from an instrumented walkway to account for any discrepancies. Fourteen gait characteristics were quantified in 30 people with incident PD and 30 healthy age-matched controls. Of the 14 gait characteristics compared, agreement between instruments was excellent for four (ICCs 0.913-0.983); moderate for four (ICCs 0.508-0.766); and poor for six characteristics (ICCs 0.637-0.370). Further analysis revealed that differences reflect an increased sensitivity of accelerometry to detect motion, rather than measurement error. This is most likely because accelerometry measures gait as a continuous activity rather than discrete footfall events, per instrumented tools. The increased sensitivity shown for these characteristics will be of particular interest to researchers keen to interpret “real-world” gait data. In conclusion, use of a body-worn monitor is recommended for the measurement of gait but is likely to yield more sensitive data for asymmetry and variability features.

Free-living monitoring of Parkinson's disease: Lessons from the field.

Wearable technology comprises miniaturized sensors (eg, accelerometers) worn on the body and/or paired with mobile devices (eg, smart phones) allowing continuous patient monitoring in unsupervised, habitual environments (termed free‐living). Wearable technologies are revolutionizing approaches to health care as a result of their utility, accessibility, and affordability. They are positioned to transform Parkinsons disease (PD) management through the provision of individualized, comprehensive, and representative data. This is particularly relevant in PD where symptoms are often triggered by task and free‐living environmental challenges that cannot be replicated with sufficient veracity elsewhere. This review concerns use of wearable technology in free‐living environments for people with PD. It outlines the potential advantages of wearable technologies and evidence for these to accurately detect and measure clinically relevant features including motor symptoms, falls risk, freezing of gait, gait, functional mobility, and physical activity. Technological limitations and challenges are highlighted, and advances concerning broader aspects are discussed. Recommendations to overcome key challenges are made. To date there is no fully validated system to monitor clinical features or activities in free‐living environments. Robust accuracy and validity metrics for some features have been reported, and wearable technology may be used in these cases with a degree of confidence. Utility and acceptability appears reasonable, although testing has largely been informal. Key recommendations include adopting a multidisciplinary approach for standardizing definitions, protocols, and outcomes. Robust validation of developed algorithms and sensor‐based metrics is required along with testing of utility. These advances are required before widespread clinical adoption of wearable technology can be realized.

The association between retirement and age on physical activity in older adults

BACKGROUND retirement is a major life change that is likely to affect lifestyles and yet little is still known about its influence on physical activity (PA). This study objectively quantified sedentary behaviour and ambulatory activity outcomes in retired and non-retired older, community-dwelling adults. METHODS PA was quantified in 98 community-dwelling older adults (69.1 ± 7.6 years) who wore an activPAL PA monitor (accelerometer) for seven consecutive days. Outcomes representing the volume, pattern and variability of sedentary behaviour and ambulatory activity were derived from the cross-sectional accelerometer data. The association between retirement, ageing and their interaction on sedentary and ambulatory outcomes were examined. RESULTS being retired was associated with a reduced percentage of sedentary behaviour; reduced long bouts of sitting (>55 min) and increased the percentage of ambulatory activity. The volume of sedentary behaviour increased with age, whereas ambulatory activity reduced with age. Measures of pattern and variability did not change with retirement or age. With respect to recommended amounts of PA, there was no difference between retired and employed adults and only 21% achieved the recommended 150 min/week (accumulated in ≥10 min bouts of walking). CONCLUSION while retirement was associated with a greater volume of PA, most older adults do not meet current recommended PA guidelines. Interventions are needed to increase PA in older adults in the years leading to and after the transition to retirement.

Instrumenting gait with an accelerometer: A system and algorithm examination

Highlights • Detailed investigation to explain poor variability/asymmetry agreement between accelerometers and instrumented walkway.• Caution is urged in the choice of reference system for validation studies.• Accelerometers have potential to gather continuous and robust spatio-temporal gait data, representative of normal living.• Further refinement of the gait algorithms are required.

Free-living gait characteristics in ageing and Parkinson’s disease: impact of environment and ambulatory bout length

BackgroundGait is emerging as a powerful diagnostic and prognostic tool, and as a surrogate marker of disease progression for Parkinson’s disease (PD). Accelerometer-based body worn monitors (BWMs) facilitate the measurement of gait in clinical environments. Moreover they have the potential to provide a more accurate reflection of gait in the home during habitual behaviours. Emerging research suggests that measurement of gait using BWMs is feasible but this has not been investigated in depth. The aims of this study were to explore (i) the impact of environment and (ii) ambulatory bout (AB) length on gait characteristics for discriminating between people with PD and age-matched controls.MethodsFourteen clinically relevant gait characteristics organised in five domains (pace, variability, rhythm, asymmetry, postural control) were quantified using laboratory based and free-living data collected over 7 days using a BWM placed on the lower back in 47 PD participants and 50 controls.ResultsFree-living data showed that both groups walked with decreased pace and increased variability, rhythm and asymmetry compared to walking in the laboratory setting. Four of the 14 gait characteristics measured in free-living conditions were significantly different between controls and people with PD compared to two measured in the laboratory. Between group differences depended on bout length and were more apparent during longer ABs. ABs ≤ 10s did not discriminate between groups. Medium to long ABs highlighted between-group significant differences for pace, rhythm and asymmetry. Longer ABs should therefore be taken into account when evaluating gait characteristics in free-living conditions.ConclusionThis study provides encouraging results to support the use of a single BWM for free-living gait evaluation in people with PD with potential for research and clinical application.

The features of interventions associated with long-term effectiveness of physical activity interventions in adults aged 55-70 years: a systematic review and meta-analysis

Content, delivery and effects of physical activity (PA) interventions are heterogeneous. There is a need to identify intervention features (content and delivery) related to long-term effectiveness. Behaviour change techniques (BCTs) and modes of intervention delivery were coded in 19 randomised controlled trials included in a systematic review of PA interventions for adults aged 55–70 years, published between 2000 and 2010, with PA outcomes ≥12 months after randomisation; protocol registration: PROSPERO CRD42011001459. Meta-analysis, moderator analyses and meta-regression were conducted. Meta-analysis revealed that interventions were effective in promoting PA compared with no/minimal intervention comparators [d = 0.29, 95% CI = 0.19–0.40, I2 = 79.8%, Q-value = 89.16 (df = 18, p < 0.01)]. Intervention features often concurred and goal setting was the most commonly used BCT. Subgroup analyses suggested that interventions using the BCT feedback may be more effective, whilst interventions using printed materials or the BCTs information on where and when to perform the behaviour and information on consequences of behaviour to the individual may be less effective. Meta-regression revealed that neither the number of BCTs nor self-regulatory BCTs significantly related to effect size. Feedback appears to be a potentially effective candidate BCT for future interventions promoting long-term PA. Considering concurrence of intervention features alongside moderator analyses is important.

Motion analysis in delirium: a novel method of clarifying motoric subtypes.

The usefulness of motor subtypes of delirium is unclear due to inconsistency in subtyping methods and a lack of validation with objective measures of motor activity levels. We studied patients with hyperactive, hypoactive, and mixed presentations of delirium were studied with 24-h accelerometer-based monitoring. The procedures were well tolerated and motor presentations were readily distinguished using the accelerometer-based measurements. The system was capable of identifying static versus dynamic activity and the frequency of changes in posture. Electronic motion analysis concurs with observed gross movement and can distinguish motorically defined subtypes according to quantitative and qualitative aspects of movement.