A continuous patient activity monitor: validation and relation to disability

Wearable IMU for Shoulder Injury Prevention in Overhead Sports

Body-worn inertial sensors have enabled motion capture outside of the laboratory setting. In this work, an inertial measurement unit was attached to the upper arm to track and discriminate between shoulder motion gestures in order to help prevent shoulder over-use injuries in athletics through real-time preventative feedback. We present a detection and classification approach that can be used to count the number of times certain motion gestures occur. The application presented involves tracking baseball throws and volleyball serves, which are common overhead movements that can lead to shoulder and elbow overuse injuries. Eleven subjects are recruited to collect training, testing, and randomized validation data, which include throws, serves, and seven other exercises that serve as a large null class of similar movements, which is analogous to a realistic usage scenario and requires a robust estimator.

A miniature, wearable activity/fall monitor to assess the efficacy of mobility therapy for children with cerebral palsy during everyday living

Children with cerebral palsy may have difficulty walking and may fall frequently, resulting in a decrease in their participation in school and community activities. It is desirable to assess the effectiveness of mobility therapies for these children on their functioning during everyday living. Over 50 hours of tri-axial accelerometer and digital video recordings from 35 children with cerebral palsy and 51 typically-developing children were analyzed to develop algorithms for automatic real-time processing of the accelerometer signals to monitor a child's level of activity and to detect falls. The present fall-detection algorithm has 100% specificity and a sensitivity of 100% for falls involving trunk rotation. Sensitivities for drops to the knees and to the bottom are 72% and 78%, respectively. The activity and fall-detection algorithms were implemented in a miniature, battery-powered microcontroller-based activity/fall monitor that the child wears in a small fanny pack during everyday living. The monitor continuously logs 1-min. activity levels and the occurrence and characteristics of each fall for two-week recording sessions. Pre-therapy and post-therapy recordings from these monitors will be used to assess the efficacies of alternative treatments for gait abnormalities.

Validation of a novel physical activity assessment device in morbidly obese females

Assessment of physical activity in morbidly obese subjects is important especially in bariatric surgery. We examined the validity of Intelligent Device for Energy Expenditure and Activity (IDEEA) for measuring physical activity and sedentary behavior in morbidly obese women. Activity types, gait counts, and speed detected by the IDEEA monitor were compared to those reported by an observer. The IDEEA monitor detected activity types and gait counts with relatively high accuracy, although slightly lower in extremely obese women than in normal weight controls. The IDEEA monitor accurately estimated gait speeds in both groups. Since gait speed predicts energy expenditure more accurately than gait counts, it is of greater clinical relevance. Reliability of the IDEEA monitor was excellent. The IDEEA monitor is a valid instrument for measuring physical activity and sedentary behavior in extremely obese women, and therefore has potential applications in bariatric surgery both in preoperative evaluation and long-term follow-up.

Are fibromyalgia patients as inactive as they say they are?

Both fibromyalgia and rheumatoid arthritis (RA) patients self-report similar disability. These diseases are viewed differently by the medical profession as one has ample evidence of tissue damage and inflammation and the other does not. We were interested to see if an objective measure produced similar results. Twelve patients with RA were matched with 12 fibromyalgia patients by sex, age, and Health Assessment Questionnaire (HAQ) score. The 24-h ambulatory activity of these patients was recorded using the Numact monitor. Statistical analysis was performed using independent group t test for the ambulatory activity data and Spearman's correlation coefficients for HAQ and total energy. There were no significant differences found between the two groups in terms of total activity. Other compared analyses for activity included the number of steps taken, vigor of steps, and time spent standing, which were not statistically different. The correlation coefficients of HAQ and total ambulatory activity for the fibromyalgia group were rho = -0.638 (p = 0.026). Patients with RA and fibromyalgia displaying similar levels of self-reported disability have objective evidence of similar levels of total ambulatory activity. There is a statistically significant correlation between self-reported and objective measurements of disability for the fibromyalgia patients. Either of these measures merits further study as outcome measures for fibromyalgia.

Evaluation of an accelerometer for at-home monitoring of spontaneous activity in dogs

OBJECTIVE

To determine the correlation between activity as measured by an accelerometer and videographic measurements of movement and mobility in healthy dogs.

ANIMALS

4 healthy dogs.

PROCEDURES

After determination that accelerometers had good agreement, 5 identical accelerometers were used simultaneously to test their output at 8 locations (rotated among collar, vest, and forelimb stocking locations) on each dog. Movement and mobility for each dog were recorded continuously with a computerized videography system for 7-hour sessions on 4 consecutive days. Accelerometer values were combined into 439 fifteen-minute intervals and compared with 3 videographic measurements of movement and mobility (distance traveled, time spent walking > 20 cm/s, and time spent changing position by > 12% of 2-dimensional surface area during 1.5 seconds).

RESULTS

96% of values compared between the most discordant pair of accelerometers were within 2 SDs of the mean value from all 5 accelerometers. All mounting locations provided acceptable correlation with videographic measurements of movement and mobility, and the ventral portion of the collar was determined to be the most convenient location.

CONCLUSIONS AND CLINICAL RELEVANCE

Use of an accelerometer was adequate for at-home activity monitoring, an important end point in clinical trials of treatment for chronic disease, and provided information about daily activity that is unattainable by other methods.

Association of 24-hour activity levels with the clinical severity of chronic venous disease

INTRODUCTION

The pathophysiology underlying the skin changes seen in chronic venous insufficiency (CVI) is multifactorial. Sedentary lifestyle and prolonged sitting and standing at work have been proposed by some authors to be influential in the development of CVI skin changes. This study compared the 24-hour activity profiles in patients with different clinical severities of CVI and normal controls.

METHODS

Patients were classified into groups according to CEAP clinical severity classes: mild (C2&C3), moderate (C4) and severe (C5&C6). Activity profiles were measured in 60 patients and 15 controls using a Newcastle Universities Medical Activity (NUMACT) monitor, which recorded the duration spent in supine, sitting, and standing postures as well as duration spent walking and the walking intensity over a 24-hour period. Analysis was performed by Kruskal-Wallis and Mann-Whitney tests and Spearman correlation.

RESULTS

Walking intensity was significantly different between the controls and patient groups during prolonged walking (P < .001). The controls spent significantly more time standing in a 24-hour period than any of the CVI clinical groups (P = .036), and the percentage time spent sitting was significantly higher in the patient groups (P = .025). No significant differences were found in the total number of steps taken or total duration spent walking in the 24-hour period between any of the groups.

CONCLUSION

This study shows that walking intensity is lower in the more severe clinical groups and may be influenced by the clinical severity of CVI. The study provides evidence that prolonged sitting and reduced standing is associated with increased severity of CVI, which may by an effect of the patient's symptoms rather than a cause of disease progression.

Performance-based methods for measuring the physical function of patients with osteoarthritis of the hip or knee: a systematic review of measurement properties

OBJECTIVE

To systematically review the measurement properties (i.e. internal consistency, reproducibility, validity, responsiveness and interpretability) of all performance-based methods which have been used to measure the physical function of patients with osteoarthritis of the hip or knee.

METHODS

A systematic search was conducted in Medline, CINAHL, PsychINFO and Embase. Standardized criteria were applied to assess the quality of the clinimetric studies and the measurement properties.

RESULTS

Twenty-six performance-based methods were included: 13 walking tests, two stair-climb tests, one chair test and ten multi-item tests. Three out of seven multi-activity tests were tested for internal consistency and two were rated positively. Fourteen tests were tested for reliability and five were rated positively. The absolute measurement error (agreement) was assessed for 10 tests. Only one test received a positive rating. Fourteen tests were tested for construct validity. Only two tests received positive ratings. Responsiveness was assessed for 12 tests, but none of them received a positive rating. A lot of indeterminate ratings were given, mostly for small studies or non-optimal analyses.

CONCLUSION

Many more well-designed studies are needed to assess the measurement properties of performance-based methods. More importantly, however, before one can make a justified choice of a particular performance-based method, consensus is needed on what activities should be included in a performance-based test for patients with hip or knee osteoarthritis and which aspects of function should be measured.

The Technology of Accelerometry-Based Activity Monitors: Current and Future

PURPOSE

This paper reviews accelerometry-based activity monitors, including single-site first-generation devices, emerging technologies, and analytical approaches to predict energy expenditure, with suggestions for further research and development.

METHODS

The physics and measurement principles of the accelerometer are described, including the sensor properties, data collections, filtering, and integration analyses. The paper also compares these properties in several commonly used single-site accelerometers. The emerging accelerometry technologies introduced include the multisensor arrays and the combination of accelerometers with physiological sensors. The outputs of accelerometers are compared with criterion measures of energy expenditure (indirect calorimeters and double-labeled water) to develop mathematical models (linear, nonlinear, and variability approaches).

RESULTS

The technologies of the sensor and data processing directly influence the results of the outcome measurement (activity counts and energy expenditure predictions). Multisite assessment and combining accelerometers with physiological measures may offer additional advantages. Nonlinear approaches to predict energy expenditure using accelerometer outputs from multiple sites and orientation can enhance accuracy.

CONCLUSIONS

The development of portable accelerometers has made objective assessments of physical activity possible. Future technological improvements will include examining raw acceleration signals and developing advanced models for accurate energy expenditure predictions.

Measuring daily behavior using ambulatory accelerometry: the Activity Monitor

Advanced ambulatory systems that measure aspects of overt human behavior during normal daily life have become feasible, owing to developments in data recording and sensor technology. One such instrument is the Activity Monitor (AM). This paper provides a technical description of the AM and information about its validity and current applications. The AM is based on ambulatory accelerometry, the aim of which is to assess postures and motions for long-term (> 24-h) measurement periods during normal daily life. Accelerometers are attached to the thighs, trunk, and lower arms, and signals are continuously stored in a digital portable recorder. In the postmeasurement analysis, postures and motions are detected by means of custom-made software programs. Validity studies performed on different populations showed high agreement scores between the computerized and automatic AM output and the visually analyzed video recordings. The AM has so far been applied in rehabilitation, psychophysiology, and cardiology but has many possibilities in behavioral research.

Motion pattern and posture: correctly assessed by calibrated accelerometers

Basic motion patterns and posture can be distinguished by multichannel accelerometry, as recently shown. A refinement of this method appeared to be desirable to further increase its effectiveness, especially to distinguish walking and climbing stairs, and body rotation during sleep. Recordings were made of 31 subjects, according to a standard protocol comprising 13 motions and postures. This recording was repeated three times with appropriate permutation. Five uni-axial sensors and three sites of placement (sternum with three axes, right and left thigh) were selected. A hierarchical classification strategy used a standard protocol (i.e., individual reference patterns) to distinguish subtypes of moving behaviors and posture. The analysis method of the actometer signals reliably detected 13 different postural and activity conditions (only 3.2% misclassifications). A minimum set of sensors can be found for a given application; for example, a two-sensor configuration would clearly suffice to differentiate between four basic classes (sitting, standing, lying, moving) in ambulatory monitoring.

Spontaneous ambulatory activity as a quantifiable outcome measure for rheumatoid arthritis

OBJECTIVE

To validate the objective monitoring of ambulatory activity as an outcome measure for rheumatoid arthritis (RA).

METHODS

We have compared ambulatory activity to a range of currently favoured outcome measures, ranging from subjective opinions to X-ray damage, in a population of 93 RA sufferers.

RESULTS

Correlations were stronger with measures of joint damage and disability, and less strong with measures of disease activity. Sensitivity to change was good. Three different interventions were compared for the quantity of the response, and the results agree with clinical experience, with steroid injection of the knee and use of non-steroidal anti-inflammatory drugs (NSAIDs) having a similar response and the provision of surgical shoes producing a more modest increase in ambulation.

CONCLUSION

The measurement of ambulatory activity has validity for RA assessment. It provides different but related data to the currently used measures. It is objective, relevant, quantifiable and of unlimited scale. It could be used to quantify interventions aimed at increasing ambulation, in carefully constructed studies.

Current techniques for assessing physical exposure to work-related musculoskeletal risks, with emphasis on posture-based methods

Physical exposure to risks for potential work-related musculoskeletal injuries has been assessed using a variety of methods, including pen and paper based observation methods, videotaping and computer-aided analysis, direct or instrumental techniques, and various approaches to self-report assessment. These methods are critically reviewed in this paper. The applications of these techniques in ergonomic and epidemiologic studies are considered, and their advantages and shortcomings are highlighted. Finally, a strategy that considers both the ergonomics experts' view and the practitioners' needs for developing a practical exposure assessment tool is then discussed.