Ambulatory accelerometry to quantify motor behaviour in patients after failed back surgery: a validation study

Utilizing Data from Wearable Technologies in the Era of Telemedicine to Assess Patient Function and Outcomes in Neurosurgery: Systematic Review and Time-Trend Analysis of the Literature

BACKGROUND

The COVID-19 pandemic has driven the increased use of telemedicine and the adoption of wearable technology in neurosurgery. We reviewed studies exploring the use of wearables on neurosurgical patients and analyzed wearables' scientific production trends.

METHODS

The review encompassed PubMed, EMBASE, Web of Science, and Cochrane Library. Bibliometric analysis was performed using citation data of the included studies through Elsevier's Scopus database. Linear regression was utilized to understand scientific production trends. All analyses were performed on R 4.1.2.

RESULTS

We identified 979 studies. After screening, 49 studies were included. Most studies evaluated wearable technology use for patients with spinal pathology (n = 31). The studies were published over a 24-year period (1998-2021). Forty-seven studies involved wearable device use relevant to telemedicine. Bibliometric analysis revealed a compounded annual growth rate of 7.3%, adjusted for inflation, in annual scientific production from 1998 to 2021 (coefficient=1.3; 95% Confidence Interval = [0.7, 1.9], P < 0.01). Scientific production steadily increased in 2014 (n = 1) and peaked from 2019 (n = 8) to 2021 (n = 13) in correlation with the COVID-19 pandemic. Publications spanned 34 journals, averaged 24.4 citations per article, 3.0 citations per year per article, and 8.3 authors per article.

CONCLUSION

Wearables can provide clinicians with objective measurements to determine patient function and quality of life. The rise in articles related to wearables in neurosurgery demonstrates the increased adoption of wearable devices during the COVID-19 pandemic. Wearable devices appear to be a key component in this era of telemedicine and their positive utility and practicality are increasingly being realized in neurosurgery.

Quality Evaluation of Free-living Validation Studies for the Assessment of 24-Hour Physical Behavior in Adults via Wearables: Systematic Review

Background

Wearable technology is a leading fitness trend in the growing commercial industry and an established method for collecting 24-hour physical behavior data in research studies. High-quality free-living validation studies are required to enable both researchers and consumers to make guided decisions on which study to rely on and which device to use. However, reviews focusing on the quality of free-living validation studies in adults are lacking.

Objective

This study aimed to raise researchers’ and consumers’ attention to the quality of published validation protocols while aiming to identify and compare specific consistencies or inconsistencies between protocols. We aimed to provide a comprehensive and historical overview of which wearable devices have been validated for which purpose and whether they show promise for use in further studies.

Methods

Peer-reviewed validation studies from electronic databases, as well as backward and forward citation searches (1970 to July 2021), with the following, required indicators were included: protocol must include real-life conditions, outcome must belong to one dimension of the 24-hour physical behavior construct (intensity, posture or activity type, and biological state), the protocol must include a criterion measure, and study results must be published in English-language journals. The risk of bias was evaluated using the Quality Assessment of Diagnostic Accuracy Studies-2 tool with 9 questions separated into 4 domains (patient selection or study design, index measure, criterion measure, and flow and time).

Results

Of the 13,285 unique search results, 222 (1.67%) articles were included. Most studies (153/237, 64.6%) validated an intensity measure outcome such as energy expenditure. However, only 19.8% (47/237) validated biological state and 15.6% (37/237) validated posture or activity-type outcomes. Across all studies, 163 different wearables were identified. Of these, 58.9% (96/163) were validated only once. ActiGraph GT3X/GT3X+ (36/163, 22.1%), Fitbit Flex (20/163, 12.3%), and ActivPAL (12/163, 7.4%) were used most often in the included studies. The percentage of participants meeting the quality criteria ranged from 38.8% (92/237) to 92.4% (219/237). On the basis of our classification tree to evaluate the overall study quality, 4.6% (11/237) of studies were classified as low risk. Furthermore, 16% (38/237) of studies were classified as having some concerns, and 72.9% (173/237) of studies were classified as high risk.

Conclusions

Overall, free-living validation studies of wearables are characterized by low methodological quality, large variability in design, and focus on intensity. Future research should strongly aim at biological state and posture or activity outcomes and strive for standardized protocols embedded in a validation framework. Standardized protocols for free-living validation embedded in a framework are urgently needed to inform and guide stakeholders (eg, manufacturers, scientists, and consumers) in selecting wearables for self-tracking purposes, applying wearables in health studies, and fostering innovation to achieve improved validity.

The Long-term Effectiveness of the Automatic Position-Adaptive System in Spinal Cord Stimulation: A Retrospective Comparative Study with a Two-Year Follow-up

OBJECTIVE

To compare the nonadaptive manual system with the position-adaptive system in subjects with permanent spinal cord stimulator (SCS) implantation over a two-year follow-up period.

DESIGN

Retrospective study.

SETTING

Tertiary university-based national hospital.

SUBJECTS

Patients who underwent permanent SCS implantation procedures.

METHODS

Patients were divided into an adaptive group and a nonadaptive group according to the type of implanted SCS device. The primary outcome was the change (%) in pain intensity from baseline between the adaptive and nonadaptive groups at 24 months after SCS implantation. The secondary outcomes were comparisons of detailed clinical variables such as the scores of patient pain and satisfaction during the two-year follow-up after SCS therapy. Further, the number of subjects with SCS removal or revision within two years after SCS implantation was investigated.

RESULTS

Of 187 patients with permanent SCS implantation, 85 in the nonadaptive group and 64 in the position-adaptive group were finally analyzed. The reduction in pain intensity at 24 months was higher in the adaptive group (-38.6%) than in the nonadaptive group (-30.8%, P = 0.05). Similarly, patient satisfaction with the SCS treatment at 24 months was superior in the adaptive group than in the nonadaptive group (85.7% vs 67.5% were satisfied in each group, respectively, P = 0.024). During the two years, 5.3% of patients (N = 10) underwent SCS removal and 7.0% (N = 13) underwent revision procedures.

CONCLUSIONS

There was a trend of a sustained reduction in pain intensity as well as improvement in patient satisfaction at two-year follow-up in the position-adaptive system, suggesting long-term benefit over the nonadaptive manual system during SCS treatment.

Subgrouping patients with chronic low back pain: What are the differences in actual daily life behavior between patients classified as avoider or persister?

BACKGROUND AND OBJECTIVE

The purpose of this study is to determine whether patients, classified by their treating consultant in rehabilitation medicine as avoider or persister, show differences in a large set of detailed outcomes of actual, objectively measured daily physical behaviour.

METHODS

In this explorative cross-sectional study, 16 patients were included; 9 patients were categorized as avoider and 7 patients as persister. Subjects wore the VitaMove activity monitor, a high-end accelerometry-based device that allowed automatic detection of a large set of body postures and motions. Physical behaviour was assessed in detail by total duration of body postures and motions as percentages of 24 hours, as well as by the number of sit-to-stand transfers, overall activity level, walking speed, and the distribution of bouts of physical activity and sedentary behaviour. Differences between groups were tested with the Mann Whitney U test.

RESULTS

There were no significant differences between groups in any of the physical behaviour outcomes.

CONCLUSIONS

Our study showed that activity-related behavioural style categorization by consultants in rehabilitation medicine is not expressed in objectively measured detailed outcomes of daily physical behaviour.

Quantifying sit-to-stand and stand-to-sit transitions in free-living environments using the activPAL thigh-worn activity monitor

PURPOSE

Standing up, sitting down and walking require considerable effort and coordination, which are crucial indicators to rehabilitation (e.g. stroke), and in older populations may indicate the onset of frailty and physical and cognitive decline. Currently, there are few reports robustly quantifying sit-to-stand and stand-to-sit transitions in free-living environments. The aim of this study was to identify and quantify these transitions using the peak velocity of sit-to-stand and stand-to-sit transitions to determine if these velocities were different in a healthy cohort and a mobility-impaired population.

METHODS

Free-living sit-to-stand and stand-to-sit acceleration data were recorded from 21 healthy volunteers and 34 stroke survivors using activPAL3™ monitors over a one-week period. Thigh inclination velocity was calculated from these accelerometer data. Maximum velocities were compared between populations.

RESULTS

A total of 10,299 and 11,392 sit-to-stand and stand-to-sit transitions were recorded in healthy volunteers and stroke survivors, respectively. Healthy volunteers had significantly higher overall mean peak velocities for both transitions compared with stroke survivors [70.7°/s ± 52.2 versus 44.2°/s ± 28.0 for sit-to-stand, P < 0.001 and 74.7°/s ± 51.8 versus 46.0°/s ± 31.9 for stand-to-sit; P < 0.001]. Mean peak velocity of transition was associated with increased variation in peak velocity across both groups.

CONCLUSION

There were significant differences in the mean peak velocity of sit-to-stand and stand-to-sit transitions between the groups. Variation in an individual's mean peak velocity may be associated with the ability to perform these transitions. This method could be used to evaluate the effectiveness of interventions following injury such as stroke, as well as monitor decline in functional ability.

A Novel Tool for Quantifying and Promoting Physical Activity in Youths With Typical Development and Youths Who Are Ambulatory and Have Motor Disability

BACKGROUND

Several device-based instruments have been validated in the pediatric population, but none of these are clinically applicable and provide real-time feedback on actual physical activity in terms of postures and movements. A new device (Activ8) is promising for that purpose.

OBJECTIVE

The objective was to investigate the criterion validity of the Activ8 for measuring static (sitting, standing) and dynamic (walking, bicycling, running) activities, and for separating postures and movements within basic and complex activities in children and adolescents (youths) with typical development (TD) and peers with motor disability (not typical development [NTD]).

DESIGN

This was a criterion validation study.

METHODS

Ten participants with TD (mean age [standard deviation] = 14 [2.5] years) and 10 participants with NTD (mean age = 12.9 [2.1] years) performed a standardized series of basic and daily life (complex) activities. The Activ8 measured postures and movements, while camera recording served as a reference. The outcome measures were the mean time differences between the Activ8 output and video data for the merged categories "static" and "dynamic" and for the separate postures and movements.

RESULTS

For the merged categories static and dynamic, the criterion validity was found to be excellent both in participants with TD and participants with NTD within basic activities, and was found to be good to excellent in participants with TD and moderate to good in participants with NTD within complex activities. The detection of separate postures and movements was found to be poor to excellent in both groups within complex activities.

LIMITATIONS

The sample of youths with NTD was small and limited to youths who could be considered to be at least ambulatory within a household.

CONCLUSIONS

Activ8 is a valid tool when the merged categories static and dynamic are used to interpret physical activity in daily life in both youths with TD and youths with NTD and mild motor impairment. To optimize the quantification of separate postures and movements, adjustment of the existing algorithm is required.

Effect of different operationalizations of sedentary behavior in people with chronic stroke

Purpose: Sedentary behavior is common in people with stroke and has devastating impact on their health. Quantifying it is important to provide people with stroke with adequate physical behavior recommendations. Sedentary behavior can be quantified in terms of posture (sitting) or intensity (low energy expenditure). We compared the effect of different operationalizations of sedentary behavior on sedentary behavior outcomes (total time; way of accumulation) in people with stroke.Methods: Sedentary behavior was analyzed in 44 people with chronic stroke with an activity monitor that measured both body postures and movement intensity. It was operationalized as: (1) combining postural and intensity data; (2) using only postural data; (3) using only intensity data. For each operationalization, we quantified a set of outcomes. Repeated measures ANOVA and Bland-Altman plots were used to compare the operationalizations.Results: All sedentary behavior outcomes differed significantly between all operationalizations (p < 0.01). Bland-Altman plots showed large limits of agreement for all outcomes, showing large individual differences between operationalizations.Conclusions: Although it was neither possible nor our aim to investigate the validity of the two-component definition of sedentary behavior, our study shows that the type of operationalization of sedentary behavior significantly influences sedentary behavior outcomes in people with stroke.Implications for RehabilitationReliable assessment of sedentary behavior after stroke is important in order to provide adequate physical behavior recommendations for people with stroke.Sedentary behavior can be operationalized in terms of body posture (sitting time) or in terms of movement intensity (time <1.5 MET) or as a combination of both criteria; this study reveals that the type of operationalization affects the different outcome measures used to quantify sedentary behavior.Comparing sedentary behavior outcomes requires caution and should only be done when sedentary behavior is operationalized in the same way.

Quantification of discrete behavioral components of the MDS-UPDRS

INTRODUCTION

The Movement Disorder Society's Unified Parkinson's Disease Rating Scale (MDS-UPDRS) is the current gold standard means of assessing disease state in Parkinson's disease (PD). Objective measures in the form of wearable sensors have the potential to improve our ability to monitor symptomology in PD, but numerous methodological challenges remain, including integration into the MDS-UPDRS. We applied a structured video coding scheme to temporally quantify clinical, scripted, motor tasks in the MDS-UPDRS for the alignment and integration of objective measures collected in parallel.

METHODS

25 PD subjects completed two video-recorded MDS-UPDRS administrations. Visual cues of task performance reliably identifiable in video recordings were used to construct a structured video coding scheme. Postural transitions were also defined and coded. Videos were independently coded by two trained non-expert coders and a third expert coder to derive indices of inter-rater agreement.

RESULTS

50 videos of MDS-UPDRS performance were fully coded. Non-expert coders achieved a high level of agreement (Cohen's κ > 0.8) on all postural transitions and scripted motor tasks except for Postural Stability (κ = 0.617); this level of agreement was largely maintained even when more stringent thresholds for agreement were applied. Durations coded by non-expert coders and expert coders were significantly different (p < 0.05) for only Postural Stability and Rigidity, Left Upper Limb.

CONCLUSIONS

Non-expert coders consistently and accurately quantified discrete behavioral components of the MDS-UPDRS using a structured video coding scheme; this represents a novel, promising approach for integrating objective and clinical measures into unified, longitudinal datasets.

Daily physical activities of patients with chronic pain or fatigue versus asymptomatic controls. A systematic review

Objective: To gain an insight into the daily physical activity levels of patients with chronic pain or fatigue compared with asymptomatic controls.

Data sources: MEDLINE, EMBASE, PsycINFO, Picarta, Cochrane Database of Systematic Reviews, reference tracking and a manual search of relevant journals.

Review methods: A systematic, computerized database search of the medical databases up to September 2006 was performed. In addition, a hand search of relevant journals was carried out. Appropriate studies reported on the daily physical activities of adult patients with chronic pain or fatigue and included an asymptomatic control group. Two reviewers independently carried out methodological quality assessment and data extraction. A qualitative analysis was performed.

Results: Twelve studies were included, involving five different syndromes. Results show large heterogeneity in methods used and syndromes investigated, which limited evidence. Eleven different methods were used to assess daily physical activities resulting in 16 different outcome parameters. There seem to be differences between the different syndromes, but results are not conclusive. Eight studies reported a lower physical activity level in patients compared with controls. There seems to be a difference in results between studies using objective versus those using subjective methods.

Conclusions: Results reported in the literature with respect to the activity level of patients with chronic pain or fatigue compared with controls were too heterogeneous to give sufficient evidence and were not conclusive.

Long-term mobility monitoring of older adults using accelerometers in a clinical environment

Objective: To assess the accuracy of accelerometer-based mobility monitoring during extended measurements on older adults in a clinical setting and to evaluate two different approaches to thresholding.

Design: The monitoring device consisted of two Analog Devices ADXL202 accelerometers, an ambulatory data-logger and associated cabling. The monitoring system used custom-designed analysis software to detect activities of daily living, namely duration of sitting, standing, lying and moving during the period monitored. An investigator shadowed the subjects throughout the recording period.

Subjects and setting: This study monitored five older adults, with varying degrees of mobility, resident in a rehabilitation clinic, over four days.

Interventions: The accelerometer data were analysed using a MATLABÒ program that allowed trunk and thigh threshold angles to be set to distinguish between sitting, standing, lying and moving. Two different approaches to setting these thresholds were investigated: (1) using a midpoint tolerance value of 458 and (2) using a `best estimate' tolerance value. The analysis program generates a summary of activities, which is then compared line-by-line with the manual summary created by the observer. The result was a hit/miss ratio representative of the system's accuracy.

Results: The detection accuracies for sitting and lying using a mid-point tolerance value were poor, with an average detection accuracy of 75% obtained. The `best estimate' approach improved the detection accuracies for sitting and lying by approximately 18% to an average value of 93%.

Conclusion: In a population of older adults, the static activities of sitting, standing and lying and dynamic activities can be distinguished using the technique and threshold values outlined here to a degree of accuracy of 92% and higher.

Validation and User Evaluation of a Sensor-Based Method for Detecting Mobility-Related Activities in Older Adults

Regular physical activity is essential for older adults to stay healthy and independent. However, daily physical activity is generally low among older adults and mainly consists of activities such as standing and shuffling around indoors. Accurate measurement of this low-energy expenditure daily physical activity is crucial for stimulation of activity. The objective of this study was to assess the validity of a necklace-worn sensor-based method for detecting time-on-legs and daily life mobility related postures in older adults. In addition user opinion about the practical use of the sensor was evaluated. Twenty frail and non-frail older adults performed a standardized and free movement protocol in their own home. Results of the sensor-based method were compared to video observation. Sensitivity, specificity and overall agreement of sensor outcomes compared to video observation were calculated. Mobility was assessed based on time-on-legs. Further assessment included the categories standing, sitting, walking and lying. Time-on-legs based sensitivity, specificity and percentage agreement were good to excellent and comparable to laboratory outcomes in other studies. Category-based sensitivity, specificity and overall agreement were moderate to excellent. The necklace-worn sensor is considered an acceptable valid instrument for assessing home-based physical activity based upon time-on-legs in frail and non-frail older adults, but category-based assessment of gait and postures could be further developed.

Extracting Fundamental Periods to Segment Biomedical Signals

We address the problem of segmenting nearly periodic time series into period-like segments. We introduce a definition of nearly periodic time series via triplets 〈 basic shape, shape transformation, time scaling 〉 that covers a wide range of time series. To split the time series into periods, we select a pair of principal components of the Hankel matrix. We then cut the trajectory of the selected principal components by its symmetry axis and, thus, obtaining half-periods that are merged into segments. We describe a method of automatic selection of periodic pairs of principal components, corresponding to the fundamental periodicity. We demonstrate the application of the proposed method to the problem of period extraction for accelerometric time series of human gait. We see the automatic segmentation into periods as a problem of major importance for human activity recognition problem, since it allows to obtain interpretable segments: each extracted period can be seen as an ultimate entity of gait. The method we propose is more general compared to the application specific methods and can be used for any nearly periodical time series. We compare its performance to classical mathematical methods of period extraction and find that it is not only comparable to the alternatives, but in some cases performs better.

Validity of the Acti4 method for detection of physical activity types in free-living settings: comparison with video analysis

This study examined the ability of the Acti4 software for identifying physical activity types from accelerometers during free-living with different levels of movement complexity compared with video observations. Nineteen aircraft cabin cleaners with ActiGraph GT3X+ accelerometer at the thigh and hip performed one semi-standardised and two non-standardised sessions (outside and inside aircraft) with different levels of movement complexity during working hours. The sensitivity for identifying different activity types was 75.4-99.4% for the semi-standardised session, 54.6-98.5% outside the aircraft and 49.9-90.2% inside the aircraft. The specificity was above 90% for all activities, except 'moving' inside the aircraft. These findings indicate that Acti4 provides good estimates of time spent in different activity types during semi-standardised conditions, and for sitting, standing and walking during non-standardised conditions with normal level of movement complexity. The Acti4 software may be a useful tool for researchers and practitioners in the field of ergonomics, occupational and public health. Practitioner Summary: Being inexpensive, small, water-resistant and without wires, the ActiGraph GT3X+ by applying the Acti4 software may be a useful tool for long-term field measurements of physical activity types for researchers and practitioners in the field of ergonomics, occupational and public health.

Activity classification in users of ankle foot orthoses

A framework for activity classification using inertial sensors mounted on ankle foot orthoses (AFOs) is presented. A decision tree-nearest neighbor algorithm classifies activities using subject-specific training. Eight volunteer subjects wore modified bilateral AFOs with shank and foot mounted triaxial accelerometers and gyroscopes. The AFOs were fitted with hardware to induce different gait perturbations: free rotation of the ankle, plantarflexion or "equinus" gait, and locked ankle joint. For each condition, the subject performed eight gait activities at varied slopes and standing, sitting, and lying postures. Using video for ground truth, the algorithm had an overall mean sensitivity of 95% using 50% of the data (≈ 140 s) for training and demonstrated upwards of 90% sensitivity with 25% of the data (≈ 70 s) for training. High sensitivities (≥ 87%) and PPV (≥ 90%) were achieved for all annotated gait patterns for all perturbations, excluding stair climbing (63%, 77%) and descending (80%, 78%). Postures were classified with less sensitivity and PPV than gait activities: lying (98%, 93%), standing (80%, 84%) and sitting (64%, 75%). Non-annotated walking (68%) and standing (73%) were classified with less sensitivity than were corresponding annotated events. Our results indicate that AFOs are a suitable sensor platform for future research in activity classification and gait monitoring in AFO users with perturbed gait using limited training data.

Inhibitory deficits in euthymic bipolar disorder patients assessed in the human behavioral pattern monitor

BACKGROUND

Bipolar disorder (BD) is associated with inhibitory deficits characterized by a reduced ability to control inappropriate actions or thoughts. While aspects of inhibition such as exaggerated novelty-seeking and perseveration are quantified in rodent exploration of novel environments, similar models are rarely applied in humans. The human Behavioral Pattern Monitor (hBPM), a cross-species exploratory paradigm, has identified a pattern of impaired inhibitory function in manic BD participants, but this phenotype has not been examined across different BD phases. The objective of this study was to determine if euthymic BD individuals demonstrate inhibitory deficits in the hBPM, supporting disinhibition as an endophenotype for the disorder.

METHODS

25 euthymic BD outpatients and 51 healthy comparison subjects were assessed in the hBPM, where activity was recorded by a concealed videocamera and an ambulatory monitoring sensor.

RESULTS

Euthymic BD individuals, similar to manic subjects, demonstrated increased motor activity, greater interaction with novel objects, and more frequent perseverative behavior relative to comparison participants. The quantity of locomotion was also reduced in BD individuals treated with mood stabilizers compared to other patients.

LIMITATIONS

Low sample size for treatment subgroups limits the evaluation of specific medication regimens.

CONCLUSIONS

Our results suggest that BD is distinguished by both trait- and state-dependent inhibitory deficits optimally assessed with sophisticated multivariate measures. These data support the use of the hBPM as a tool to elucidate the effects of BD across various illness states, facilitate the development of BD animal models, and advance our understanding of the neurobiology underlying the disorder.

Improved physical activity in patients treated for chronic pain by spinal cord stimulation

The objective of this study was to objectively assess the physical activity of daily living in chronic pain patients treated with spinal cord stimulation (SCS). Changes in pain and spontaneous physical activity following SCS were evaluated under real life conditions. Five series of measurements were performed before the implant (baseline) and at one, three, six, and 12 months after the implantation of an SCS system. Compared to baseline values, physical activity increased consistently during the entire follow-up period. The time spent walking and standing was statistically increased after six months (p < 0.01) and the time spent lying decreased significantly (p < 0.001) at the same time. The average total walking distance increased up to 389% at 12 months, reaching statistical significance (p < 0.05) after three months. The stride length and the speed increased (p < 0.01) at all times. We conclude that the reduction in pain intensity due to SCS is associated with a progressive and sustained improvement in physical activity. j.

Physical functioning four years after total hip and knee arthroplasty

Our previous study showed that 6 months after total hip arthroplasty (THA) or total knee arthroplasty (TKA), patients reported having less difficulty with daily activities, showed better functional capacity, and performed activities in their natural environment faster compared to preoperatively. However, their actual daily activity level was not significantly improved. Six months is a rather short follow-up period and the discrepancy in recovery among different aspects of functioning might be explained by this limited duration of follow-up. The objective of the present study was to examine the recovery of different aspects of physical functioning at a follow-up nearly 4 years after THA/TKA. Special attention was given to the actual daily activity level, and whether it had increased 4 years after THA/TKA compared to 6 months postoperatively. Seventy-seven (35 hip, 42 knee) patients who were measured preoperatively and postoperatively (6 months after surgery) in a previous study were invited to participate; 44 patients (23 hip, 21 knee) agreed to participate. The 4-year follow-up data were compared with the preoperative and 6-month postoperative data. The daily activity level after 4 years was found to be actually lower than at 6 months post-surgery (128 min vs. 138 min activity per 24h; p-value 0.48). However, the patients continued to improve in other aspects of physical functioning. In conclusion, 4-year post-surgery patients continued to improve on perceived physical functioning, capacity, and performance of activities in daily life. However, even in this relatively healthy study population, patients did not adopt a more active lifestyle 4 years after surgery.

Assessment of physical activity by movement registration systems in chronic pain: methodological considerations

OBJECTIVES

Physical activity assessments in chronic pain research have mostly been based on self-report. However, earlier research indicated that chronic pain patients have difficulties in estimating their own daily life activity level. Movement registration systems have been introduced to overcome the limitations of self-reported measures. However, no uniform guidelines for researchers on how to analyze and interpret movement registration data in chronic pain exist. The aim of the study was to provide recommendations for physical activity assessment based on movement registration in patients with chronic pain.

METHODS

First, a systematic review of the procedures and data processing techniques used in movement registration for chronic pain patients will be performed. Second, it will be discussed whether the recommendations for physical activity assessment in healthy individuals are applied in chronic pain research. Last, recommendations regarding assessment procedure and data processing for using movement registration systems in future research in patients with chronic pain will be given.

RESULTS

In chronic pain literature, 27 articles on movement registration were identified. According to the recommendations for activity assessment in healthy individuals, the various descriptions of the assessment procedures in these articles were mostly limited. Especially, information regarding the minimal requirements for the assessment period and the method used for calculation of the final outcome variable were often lacking.

DISCUSSION

It is recommended that studies in chronic pain research explicitly apply and report the criteria that have been used to define an assessment day, the total assessment time, and the method for calculating the final test outcome.

Barcoding human physical activity to assess chronic pain conditions

BACKGROUND

Modern theories define chronic pain as a multidimensional experience - the result of complex interplay between physiological and psychological factors with significant impact on patients' physical, emotional and social functioning. The development of reliable assessment tools capable of capturing the multidimensional impact of chronic pain has challenged the medical community for decades. A number of validated tools are currently used in clinical practice however they all rely on self-reporting and are therefore inherently subjective. In this study we show that a comprehensive analysis of physical activity (PA) under real life conditions may capture behavioral aspects that may reflect physical and emotional functioning.

METHODOLOGY

PA was monitored during five consecutive days in 60 chronic pain patients and 15 pain-free healthy subjects. To analyze the various aspects of pain-related activity behaviors we defined the concept of PA 'barcoding'. The main idea was to combine different features of PA (type, intensity, duration) to define various PA states. The temporal sequence of different states was visualized as a 'barcode' which indicated that significant information about daily activity can be contained in the amount and variety of PA states, and in the temporal structure of sequence. This information was quantified using complementary measures such as structural complexity metrics (information and sample entropy, Lempel-Ziv complexity), time spent in PA states, and two composite scores, which integrate all measures. The reliability of these measures to characterize chronic pain conditions was assessed by comparing groups of subjects with clinically different pain intensity.

CONCLUSION

The defined measures of PA showed good discriminative features. The results suggest that significant information about pain-related functional limitations is captured by the structural complexity of PA barcodes, which decreases when the intensity of pain increases. We conclude that a comprehensive analysis of daily-life PA can provide an objective appraisal of the intensity of pain.

Upper limb activity over time in complex regional pain syndrome type 1 as objectively measured with an upper limb-activity monitor: An explorative multiple case study

BACKGROUND

An upper limb-activity monitor (ULAM) has been developed to determine activity limitations in complex regional pain syndrome type 1 (CRPS1). The ULAM is based on 24h ambulatory monitoring of body segment accelerations and enables valid and objective quantification of mobility and upper limb activity in transversal studies.

AIMS

To explore upper limb activity over time in acute upper limb CRPS1 as measured with the ULAM in a longitudinal study, and to compare this to time courses of other outcome measures for activity limitations and impairments.

METHODS

Four subjects were measured four times during a treatment protocol. Several ULAM outcome measures related to upper limb usage and mobility, three questionnaires (RASQ, DASH, RAND36), and six impairment outcome indicators (VAS-momentary pain, VAS-pain resulting from effort, volume, temperature, active range of motion, strength) were used.

RESULTS

Objectively measured upper limb activity frequently improved; improvements of >5% were found for 63% of the ULAM outcome measures at final assessment. The ULAM outcome measures had a time course more similar to the body-part and CRPS1 specific questionnaire RASQ than the other questionnaires. The time course of impaired temperature was most often in accordance with the ULAM, and both VAS scores showed least accordance.

CONCLUSIONS

Clear changes in upper limb activity over time were frequently found as objectively measured with the ULAM, and relationships among the time courses of the ULAM and other outcome measures were largely explainable. The ULAM can validly assess upper limb activity over time in CRPS1, but between-measurement variability needs careful consideration.

Accelerometer use with children, older adults, and adults with functional limitations

Accurately assessing physical activity behavior in children, older adults, and adults with functional limitations is essential to further our understanding of determinants of physical activity behavior in these populations and to design, implement, and evaluate interventions designed to increase physical activity participation. Objective methods to assess physical activity behavior, owing to improvements in accuracy and precision over self-report measures, have become common in research and practice settings. This article reviews the current use of objective methods to assess physical activity in observational, determinant, and intervention studies for children, older adults, and adults with functional limitations. Important considerations are presented when adopting prediction algorithms developed on one population, and using in another population that is markedly different in age, health, and functional status. Best practices are presented, along with future recommendations for research to advance this area of scientific inquiry.

Assessment of Physical Activity in Older People With and Without Cognitive Impairment

The purpose of this study was to validate a new interview-administered physical activity questionnaire (Assessment of Physical Activity in Frail Older People; APAFOP) in older people with and without cognitive impairment. The authors assessed feasibility, validity, and test–retest reliability in 168 people (n= 78 with,n= 88 without cognitive impairment). Concurrent validity was assessed against an inertia-based motion sensor and an established questionnaire. Sensitivity to change was tested in an ongoing study in patients with mild to moderate dementia (n= 81). Assessment of physical activity by the APAFOP and the motion sensor correlated well in the total sample (TS; p= .705), as well as in the subsamples with cognitive impairment (CI;p= .585) and without CI (p= .787). Excellent feasibility with an acceptance rate of 100%, test–retest reliability (intraclass correlation coefficients ranging from .973 (TS) to .975 (CI) to .966 (no CI), and sensitivity to change (effect sizes: 0.35–1.47) were found in both subsamples.

Review of accelerometry for determining daily activity among elderly patients

OBJECTIVES

To review studies that used accelerometers to classify human movements and to appraise their potential to determine the activities of older patients in hospital settings.

DATA SOURCES

MEDLINE, CINAHL, and Web of Science electronic databases. A search constraint of articles published in English language between January 1980 and March 2010 was applied.

STUDY SELECTION

All studies that validated the use of accelerometers to classify human postural movements and mobility were included. Studies included participants from any age group. All types of accelerometers were included. Outcome measures criteria explored within the studies were comparisons of derived classifications of postural movements and mobility against those made by using observations. Based on these criteria, 54 studies were selected for detailed review from 526 initially identified studies.

DATA EXTRACTION

Data were extracted by the first author and included characteristics of study participants, accelerometers used, body positions of device attachment, study setting, duration, methods, results, and limitations of the validation studies.

DATA SYNTHESIS

The accelerometer-based monitoring technique was investigated predominantly on a small sample of healthy adult participants in a laboratory setting. Most studies applied multiple accelerometers on the sternum, wrists, thighs, and shanks of participants. Most studies collected validation data while participants performed a predefined standardized activity protocol.

CONCLUSIONS

Accelerometer devices have the potential to monitor human movements continuously to determine postural movements and mobility for the assessment of functional ability. Future studies should focus on long-term monitoring of free daily activity of a large sample of mobility-impaired or older hospitalized patients, who are at risk for functional decline. Use of a single waist-mounted triaxial accelerometer would be the most practical and useful option.

Advances in physical activity monitoring and lifestyle interventions in obesity: a review

Obesity represents a strong risk factor for developing chronic diseases. Strategies for disease prevention often promote lifestyle changes encouraging participation in physical activity. However, determining what amount of physical activity is necessary for achieving specific health benefits has been hampered by the lack of accurate instruments for monitoring physical activity and the related physiological outcomes. This review aims at presenting recent advances in activity-monitoring technology and their application to support interventions for health promotion. Activity monitors have evolved from step counters and measuring devices of physical activity duration and intensity to more advanced systems providing quantitative and qualitative information on the individuals' activity behavior. Correspondingly, methods to predict activity-related energy expenditure using bodily acceleration and subjects characteristics have advanced from linear regression to innovative algorithms capable of determining physical activity types and the related metabolic costs. These novel techniques can monitor modes of sedentary behavior as well as the engagement in specific activity types that helps to evaluate the effectiveness of lifestyle interventions. In conclusion, advances in activity monitoring have the potential to support the design of response-dependent physical activity recommendations that are needed to generate effective and personalized lifestyle interventions for health promotion.

Validation of the Physical Activity Scale for individuals with physical disabilities

OBJECTIVE

To determine the criterion validity of the Physical Activity Scale for Individuals With Physical Disabilities (PASIPD) by means of daily physical activity levels measured by using a validated accelerometry-based activity monitor in a large group of persons with a physical disability.

DESIGN

Cross-sectional.

SETTING

Participants' home environment.

PARTICIPANTS

Ambulatory and nonambulatory persons with cerebral palsy, meningomyelocele, or spinal cord injury (N=124).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Self-reported physical activity level measured by using the PASIPD, a 2-day recall questionnaire, was correlated to objectively measured physical activity level measured by using a validated accelerometry-based activity monitor.

RESULTS

Significant Spearman correlation coefficients between the PASIPD and activity monitor outcome measures ranged from .22 to .37. The PASIPD overestimated the duration of physical activity measured by using the activity monitor (mean ± SD, 3.9±2.9 vs 1.5±0.9h/d; P<.01). Significant correlation (ρ=-.74; P<.01) was found between average number of hours of physical activity per day measured by using the 2 methods and difference in hours between methods. This indicates larger overestimation for persons with higher activity levels.

CONCLUSIONS

The PASIPD correlated poorly with objective measurements using an accelerometry-based activity monitor in people with a physical disability. However, similar low correlations between objective and subjective activity measurements have been found in the general population. Users of the PASIPD should be cautious about overestimating physical activity levels.

Evaluation of a body-worn sensor system to measure physical activity in older people with impaired function

BACKGROUND

There is limited information on reliable and valid measures of physical activity in older people with impaired function.

OBJECTIVE

This study was conducted to compare the accuracy of single-axis accelerometers in recognizing postures and transitions and step counting with the accuracy of video recordings in people with stroke (n=14), older inpatients (n=14), people with hip fracture (n=8), and a reference group of 10 adults who were healthy.

DESIGN

This was a cross-sectional study, evaluating the concurrent validity of small body-worn accelerometers against video observations as the criterion measure.

METHODS

Activity data were collected from 3 sensors (activPAL) attached to the thighs and the sternum and from registration of the same activities from video recordings. Participants performed a test protocol of in-bed, transfer, and walking activities.

RESULTS

The sensor system was highly accurate in classifying lying, sitting, and standing positions (100%) and in recognizing transitions from lying to sitting positions and from sitting to standing positions (100%). Placement of a sensor on the nonaffected leg resulted in less underestimation of step counts than placement on the affected leg. Still, the sensor system underestimated step counts during walking, especially at slow walking speeds (≤0.47 m/s) (limits of agreement=-2.01 to 16.54, absolute percent error=40.31).

LIMITATIONS

The study was performed in a controlled setting and not during the natural performance of activities.

CONCLUSIONS

The activPAL sensor system provides valid measures of postures and transitions in older people with impaired walking ability. Step counting needs to be improved for the sensor system to be acceptable for this population, especially at slow walking speeds.

How reproducible is home-based 24-hour ambulatory monitoring of motor activity in patients with multiple sclerosis?

OBJECTIVE

To determine the reproducibility of 24-hour monitoring of motor activity in patients with multiple sclerosis (MS).

DESIGN

Test-retest design; 6 research assistants visited the participants twice within 1 week in the home situation.

SETTING

General community.

PARTICIPANTS

A convenience sample of ambulatory patients (N=43; mean age ± SD, 48.7±7.0y; 30 women; median Expanded Disability Status Scale scores, 3.5; interquartile range, 2.5) were recruited from the outpatient clinic of a university medical center.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Dynamic activity and static activity parameters were recorded by using a portable data logger and classified continuously for 24 hours. Reproducibility was determined by calculating intraclass correlation coefficients (ICCs) for test-retest reliability and by applying the Bland-Altman method for agreement between the 2 measurements. The smallest detectable change (SDC) was calculated based on the standard error of measurement.

RESULTS

Test-retest reliability expressed by the ICC(agreement) was .72 for dynamic activity, .74 for transitions, .77 for walking, .71 for static activity, .67 for sitting, .62 for standing, and .55 for lying. Bland and Altman analysis indicated no systematic differences between the first and second assessment for dynamic and static activity. Measurement error expressed by the SDC was 1.23 for dynamic activity, 66 for transitions, .99 for walking, 1.52 for static activity, 4.68 for lying, 3.95 for sitting, and 3.34 for standing.

CONCLUSIONS

The current study shows that with 24-hour monitoring, a reproducible estimate of physical activity can be obtained in ambulatory patients with MS.

Functional capacity and actual daily activity do not contribute to patient satisfaction after total knee arthroplasty

BACKGROUND

After total knee arthroplasty (TKA) only 75-89% of patients are satisfied. Because patient satisfaction is a prime goal of all orthopaedic procedures, optimization of patient satisfaction is of major importance. Factors related to patient satisfaction after TKA have been explored, but no studies have included two potentially relevant factors, i.e. the functional capacity of daily activities and actual daily activity. This present prospective study examines whether functional capacity and actual daily activity (in addition to an extensive set of potential factors) contribute to patient satisfaction six months after TKA.

METHODS

A total of 44 patients were extensively examined preoperatively and six months post surgery. Functional capacity was measured with three capacity tests, focusing on walking, stair climbing, and chair rising. Actual daily activity was measured in the patient's home situation by means of a 48-hour measurement with an Activity Monitor. To establish which factors were related to patient satisfaction six months post surgery, logistic regression analyses were used to calculate odds ratios.

RESULTS

Preoperative and postoperative functional capacity and actual daily activity had no relation with patient satisfaction. Preoperatively, only self-reported mental functioning was positively related to patient satisfaction. Postoperatively, based on multivariate analysis, only fulfilled expectations regarding pain and experienced pain six months post surgery were related to patient satisfaction.

CONCLUSIONS

Functional capacity and actual daily activity do not contribute to patient satisfaction after TKA. Patients with a better preoperative self-reported mental functioning, and patients who experienced less pain and had fulfilled expectations regarding pain postoperatively, were more often satisfied.

Day-to-Day Variability of Physical Activity of Older Adults Living in the Community

The purpose of the study was to investigate whether a 24-hr recording period is sufficient to describe physical activity (PA) of 1 week for intraindividual comparison in older adults. Furthermore, the authors analyzed whether physical performance can be used as a surrogate marker of PA. PA was captured on 7 consecutive days by a body-fixed sensor in 44 community-dwelling older adults (80.75 ± 4.05 yr). Mean times of walking and of “time on feet” of the group were 10.2 hr (± 3.5) and 35.1 hr (± 9.43), respectively. Intraindividual variabilities of walking and of time on feet were 31.9% ± 10.79% and 19.4% ± 8.76%, respectively. Accumulated time of variables of PA showed no differences between weekdays, with variabilities of 3.8% and 1.8% for walking and time on feet, respectively. Association between Short Physical Performance Battery and PA was limited (walkingr= .397, time on feetr= .41).

The quantitative assessment of motor activity in mania and schizophrenia

BACKGROUND

Increased motor activity is a cardinal feature of the mania of Bipolar Disorder (BD), and is thought to reflect dopaminergic dysregulation. Motor activity in BD has been studied almost exclusively with self-report and observer-rated scales, limiting the ability to objectively quantify this behavior. We used an ambulatory monitoring device to quantify motor activity in BD and schizophrenia (SCZ) patients in a novel exploratory paradigm, the human Behavioral Pattern Monitor (BPM).

METHOD

28 patients in the manic phase of BD, 17 SCZ patients, and 21 nonpatient (NC) subjects were tested in the BPM, an unfamiliar room containing novel objects. Motor activity was measured with a wearable ambulatory monitoring device (LifeShirt).

RESULTS

Manic BD patients exhibited higher levels of motor activity when exploring the novel environment than SCZ and NC groups. Motor activity showed some modest relationships with symptom ratings of mania and psychosis and was not related to smoking or body mass index.

LIMITATIONS

Although motor activity did not appear to be impacted significantly by antipsychotic or mood-stabilizing medications, this was a naturalistic study and medications were not controlled, thus limiting conclusions about potential medication effects on motor activity.

CONCLUSION

Manic BD patients exhibit a unique signature of motoric overactivity in a novel exploratory environment. The use of an objective method to quantify exploration and motor activity may help characterize the unique aspects of BD and, because it is amenable to translational research, may further the study of the biological and genetic bases of the disease.

Gait posture estimation using wearable acceleration and gyro sensors

A method for gait analysis using wearable acceleration sensors and gyro sensors is proposed in this work. The volunteers wore sensor units that included a tri-axis acceleration sensor and three single axis gyro sensors. The angular velocity data measured by the gyro sensors were used to estimate the translational acceleration in the gait analysis. The translational acceleration was then subtracted from the acceleration sensor measurements to obtain the gravitational acceleration, giving the orientation of the lower limb segments. Segment orientation along with body measurements were used to obtain the positions of hip, knee, and ankle joints to create stick figure models of the volunteers. This method can measure the three-dimensional positions of joint centers of the hip, knee, and ankle during movement. Experiments were carried out on the normal gait of three healthy volunteers. As a result, the flexion-extension (F-E) and the adduction-abduction (A-A) joint angles of the hips and the flexion-extension (F-E) joint angles of the knees were calculated and compared with a camera motion capture system. The correlation coefficients were above 0.88 for the hip F-E, higher than 0.72 for the hip A-A, better than 0.92 for the knee F-E. A moving stick figure model of each volunteer was created to visually confirm the walking posture. Further, the knee and ankle joint trajectories in the horizontal plane showed that the left and right legs were bilaterally symmetric.

Everyday physical activity and community participation of adults with hemiplegic Cerebral Palsy

PURPOSE

To assess the level and potential determinants of everyday physical activity and participation in various life areas of adults with hemiplegic cerebral palsy (CP) in comparison with healthy subjects.

METHOD

In a cross-sectional study everyday physical activity was measured (Activity Monitor) in 16 adults with CP, aged 28 (3) years, and 16 age/gender matched healthy volunteers, aged 29 (3) years. Participation was assessed by means of validated questionnaires. Age, gender, body fat (skinfold thickness), muscle tone (Ashworth Scale), functional level and participation were assessed as potential determinants of everyday physical activity.

RESULTS

In adults with CP mean (SD) duration of dynamic activities during a day (10.6 [3.5]%) was comparable to healthy subjects (11.2 4%) (p = 0.66). In most life areas the level of participation was comparable for both groups, although adults with CP spent more time on non-intensive leisure activities. Participation in sports appeared to be a determinant of everyday physical activity in both groups.

CONCLUSIONS

The results indicate that the levels of everyday physical activity and community participation in adults with hemiplegic CP are comparable to levels in healthy comparison subjects.

Activity identification using body-mounted sensors--a review of classification techniques

With the advent of miniaturized sensing technology, which can be body-worn, it is now possible to collect and store data on different aspects of human movement under the conditions of free living. This technology has the potential to be used in automated activity profiling systems which produce a continuous record of activity patterns over extended periods of time. Such activity profiling systems are dependent on classification algorithms which can effectively interpret body-worn sensor data and identify different activities. This article reviews the different techniques which have been used to classify normal activities and/or identify falls from body-worn sensor data. The review is structured according to the different analytical techniques and illustrates the variety of approaches which have previously been applied in this field. Although significant progress has been made in this important area, there is still significant scope for further work, particularly in the application of advanced classification techniques to problems involving many different activities.

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.

A comparison of feature extraction methods for the classification of dynamic activities from accelerometer data

Driven by the demands on healthcare resulting from the shift toward more sedentary lifestyles, considerable effort has been devoted to the monitoring and classification of human activity. In previous studies, various classification schemes and feature extraction methods have been used to identify different activities from a range of different datasets. In this paper, we present a comparison of 14 methods to extract classification features from accelerometer signals. These are based on the wavelet transform and other well-known time- and frequency-domain signal characteristics. To allow an objective comparison between the different features, we used two datasets of activities collected from 20 subjects. The first set comprised three commonly used activities, namely, level walking, stair ascent, and stair descent, and the second a total of eight activities. Furthermore, we compared the classification accuracy for each feature set across different combinations of three different accelerometer placements. The classification analysis has been performed with robust subject-based cross-validation methods using a nearest-neighbor classifier. The findings show that, although the wavelet transform approach can be used to characterize nonstationary signals, it does not perform as accurately as frequency-based features when classifying dynamic activities performed by healthy subjects. Overall, the best feature sets achieved over 95% intersubject classification accuracy.

Small increase of actual physical activity 6 months after total hip or knee arthroplasty

Limitation in daily physical activity is one of the reasons for total hip arthroplasty (THA) or total knee arthroplasty (TKA). However, studies of the effects of THA or TKA generally do not determine actual daily activity as part of physical functioning. We determined the effect of THA or TKA on patients' actual physical activity and body function (pain, stiffness), capacity to perform tasks, and self-reported physical functioning. We also assessed whether there are differences in the effect of the surgery between patients undergoing THA or TKA and whether the improvements vary between these different outcome measures. We recruited patients with long-standing end-stage osteoarthritis of the hip or knee awaiting THA or TKA. Measurements were performed before surgery and 3 and 6 months after surgery. Actual physical activity improved by 0.7%. Patients' body function, capacity, and self-reported physical functioning also improved. The effects of the surgery on these aspects of physical functioning were similar for THA and TKA. The effect on actual physical activity (8%) was smaller than on body function (80%-167%), capacity (19%-36%), and self-reported physical functioning (87%-112%). Therefore, in contrast to the large effect on pain and stiffness, patients' capacity, and their self-reported physical functioning, the improvement in actual physical activity of our patients was less than expected 6 months after surgery.

LEVEL OF EVIDENCE

Level I, prospective study. See the Guidelines for Authors for a complete description of levels of evidence.

Ambulatory measurement of 3D knee joint angle

Three-dimensional measurement of joint motion is a promising tool for clinical evaluation and therapeutic treatment comparisons. Although many devices exist for joints kinematics assessment, there is a need for a system that could be used in routine practice. Such a system should be accurate, ambulatory, and easy to use. The combination of gyroscopes and accelerometers (i.e., inertial measurement unit) has proven to be suitable for unrestrained measurement of orientation during a short period of time (i.e., few minutes). However, due to their inability to detect horizontal reference, inertial-based systems generally fail to measure differential orientation, a prerequisite for computing the three-dimentional knee joint angle recommended by the Internal Society of Biomechanics (ISB). A simple method based on a leg movement is proposed here to align two inertial measurement units fixed on the thigh and shank segments. Based on the combination of the former alignment and a fusion algorithm, the three-dimensional knee joint angle is measured and compared with a magnetic motion capture system during walking. The proposed system is suitable to measure the absolute knee flexion/extension and abduction/adduction angles with mean (SD) offset errors of -1 degree (1 degree ) and 0 degrees (0.6 degrees ) and mean (SD) root mean square (RMS) errors of 1.5 degrees (0.4 degrees ) and 1.7 degrees (0.5 degrees ). The system is also suitable for the relative measurement of knee internal/external rotation (mean (SD) offset error of 3.4 degrees (2.7 degrees )) with a mean (SD) RMS error of 1.6 degrees (0.5 degrees ). The method described in this paper can be easily adapted in order to measure other joint angular displacements such as elbow or ankle.

Comparison of the performance of the activPAL™ Professional physical activity logger to a discrete accelerometer-based activity monitor

The aim of this study was to assess the accuracy of the 'activPAL Professional' physical activity logger by comparing its output to that of a proven discrete accelerometer-based activity monitor during extended measurements on healthy subjects while performing activities of daily living (ADL). Ten healthy adults, with unrestricted mobility, wore both the activPAL and the discrete dual accelerometer (Analog Devices ADXL202)-based activity monitor that recorded in synchronization with each other. The accelerometer derived data were then compared to that generated by the activPAL and a complete statistical and error analysis was performed using a Matlab program. This program determined trunk and thigh inclination angles to distinguish between sitting/lying, standing and stepping for the discrete accelerometer device and amount of time spent on each activity. Analysis was performed on a second-by-second basis and then categorized at 15s intervals in direct comparison with the activPAL generated data. Of the total time monitored (approximately 60 h) the detection accuracies for static and dynamic activities were approximately 98%. In a population of healthy adults, the data obtained from the activPAL Professional physical activity logger for both static and dynamic activities showed a close match to a proven discrete accelerometer data with an offset of approximately 2% between the two systems.

Functional activity monitoring from wearable sensor data

A novel approach is presented for the interpretation and use of EMG and accelerometer data to monitor, identify, and categorize functional motor activities in individuals whose movements are unscripted, unrestrained, and take place in the "real world". Our proposed solution provides a novel and practical way of conceptualizing physical activities that facilitates the deployment of modern signal processing and interpretation techniques to carry out activity monitoring. A hierarchical approach is adopted that is based upon: 1) blackboard and rule-based technology from artificial intelligence to support a process in which coarse-grained activity partitioning forms the context for finer-grained activity partitioning; 2) neural network technology to support initial activity classification; and 3) integrated processing and understanding of signals (IPUS) technology for revising the initial classifications to account for the high degrees of anticipated signal variability and overlap during freeform activity.