Examining the Activpal3 monitor in measuring body position and step counts in infants: a validity study
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The ActivPAL physical activity monitor has been previously reported as a reliable and valid tool to measure everyday physical activities. The aim of this study was to examine the reliability and validity of the ActivPAL during typical office-based activities. A convenient sample of 10 adults participated in this study with two ActivPAL units attached to the participant's right thigh. Participants completed 6 minutes of specific office-based tasks such as typing an email, writing on a whiteboard, collecting printing and running a small errand with instructions provided through an audio recording. Each bout was filmed with time of sitting, standing and walking visually assessed using the same categories provided by the ActivPAL analysis. Reliability between ActivPAL recordings was assessed via Wilcoxon comparisons and intraclass correlation coefficients (ICC). Relative error was calculated as the difference between visual observations and ActivPAL recordings. Validity was assessed via Wilcoxon comparisons between ActivPAL recordings and video observations. There were no significant differences between ActivPAL units for sitting (196.2+/-5.0 vs. 195.9+/-5.1 seconds), standing (121.8+/-4.8 vs. 122.3+/-6.9 seconds) or walking (42.0+/-6.1 vs. 41.9+/-7.1 seconds) activities. Significant ICC were detected for sitting (0.928), standing (0.849) and walking (0.849) time. In contrast, the ActivPAL recordings for sitting, standing and walking time were significantly different to visual observations (p 3.8%, >24.5% and >54.1%, respectively. The current study has identified ActivPAL units as reliable tools to document physical activity. However, the ActivPAL underestimated sitting and walking time, and overestimated standing time during office-based tasks.
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Background The activPAL has been identified as an accurate and reliable measure of sedentary behaviour. However, only limited information is available on the accuracy of the activPAL activity count function as a measure of physical activity, while no unit calibration of the activPAL has been completed to date. This study aimed to investigate the criterion validity of the activPAL, examine the concurrent validity of the activPAL, and perform and validate a value calibration of the activPAL in an adolescent female population. The performance of the activPAL in estimating posture was also compared with sedentary thresholds used with the ActiGraph accelerometer. Methodologies Thirty adolescent females (15 developmental; 15 cross-validation) aged 15–18 years performed 5 activities while wearing the activPAL, ActiGraph GT3X, and the Cosmed K4B2. A random coefficient statistics model examined the relationship between metabolic equivalent (MET) values and activPAL counts. Receiver operating characteristic analysis was used to determine activity thresholds and for cross-validation. The random coefficient statistics model showed a concordance correlation coefficient of 0.93 (standard error of the estimate = 1.13). An optimal moderate threshold of 2997 was determined using mixed regression, while an optimal vigorous threshold of 8229 was determined using receiver operating statistics. The activPAL count function demonstrated very high concurrent validity (r = 0.96, p<0.01) with the ActiGraph count function. Levels of agreement for sitting, standing, and stepping between direct observation and the activPAL and ActiGraph were 100%, 98.1%, 99.2% and 100%, 0%, 100%, respectively. Conclusions These findings suggest that the activPAL is a valid, objective measurement tool that can be used for both the measurement of physical activity and sedentary behaviours in an adolescent female population.
Concurrent validity
Sedentary Behavior
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Reported Relationships: M.H. Granat: Intellectual Property; I am co-inventor of the activPAL. Devices like the activPAL and ActiGraph, which collect data from three orthogonal axes of acceleration, are used to distinguish between sedentary and upright activity. However a device worn on the thigh, which uses thigh inclination to distinguish sitting/lying activities from upright activities could also provide information on thigh rotation. In lying, it is usual for the individual to roll over and therefore using other axes from the acceleration data it could be possible to distinguish between sitting and lying. PURPOSE: To develop and pilot test an algorithm that could automatically classify sedentary events into lying events and sitting events using triaxial accelerometer data collected from a single site on the thigh using the activPAL3TM. METHODS: Seven day free-living activity from 14 sedentary workers in the UK was recorded using the activPAL3 monitor. All participants recorded in a diary when they went to bed and when they got up. The “in bed” sedentary events were assumed to be lying and the “not in bed” events as sitting. An algorithm using a threshold of 65° computed from the y-axis was used to detect rotation of the thigh and this threshold was used to classify each sedentary event as either lying or sitting. The classification accuracy of the algorithm was compared to self-reported classification from the diary using sensitivity and specificity analyses. RESULTS: A mean of 6.7 days of valid recording were obtain. The algorithm classified 96.7% of the sedentary time “in bed” (sensitivity) and 92.9% of the time “not in bed” as not lying (specificity). The median time of lying events “in bed” was 5.4hrs. Most “out of bed” sedentary periods, which were classified as lying were long and close to the time the individual reported to have gone to bed, and it is likely that these were actually lying events such as lying on a couch. CONCLUSION: It is possible to use triaxial accelerometer data recorded only from a single site on the thigh to classify sedentary events into the postures of sitting and lying. Future studies using a larger sample size and objective criterion variables like free-living direct observation are required to further refine the algorithm developed in the current study.
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Abstract Background Accurate measurement of physical activity and sedentary behavior is an important consideration for health care professionals. The activPAL activity monitor has not been validated against a criterion measure for people with rheumatoid arthritis (RA). Objective The objective of this study was to determine the criterion validity of the activPAL activity monitor for measuring step counts, transition counts, and time spent in sedentary, standing, and walking behaviors in people with RA. Design A laboratory-based criterion validation study was conducted. Methods Participants with a confirmed medical diagnosis of RA were recruited from 2 outpatient rheumatology clinics. The testing procedure consisted of standardized testing components and tasks related to activities of daily living. Participants wore an activPAL activity monitor and were video recorded throughout the testing procedure. Direct observation was used as the criterion measure. Data analysis consisted of validation analysis of the activPAL activity monitor data and the criterion measure data. Results Twenty-four people participated in the study. Data from 20 participants were included in the final analysis. The activPAL significantly underestimated step counts by 26% and transition counts by 36%. There was no significant difference between the activPAL activity monitor and the criterion measure for time spent in sedentary, standing or light activity, and walking behaviors. Limitations Validation of activities of daily living in a laboratory environment is a limitation of this study. Conclusions The activPAL activity monitor underestimated step and transition counts and, therefore, is not valid for measuring these outcomes in people with RA. Relative to direct observation, the activPAL activity monitor is valid for measuring time spent in sedentary, standing, and walking behaviors in people with RA.
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The aim of this study was to assess concurrent validity between activPAL and activPAL3 accelerometers in a sample of 53 community-dwelling older adults ≥ 65 years. Physical activity (PA) was measured simultaneously with activPAL and activPAL3 while performing scripted activities. The level of agreement between both devices was calculated for sitting/lying, standing, and walking. In addition, PA was measured over one week using activPAL to estimate the expected agreement with activPAL3 in real life. Overall agreement between activPAL and activPAL3 was 97%. Compared with activPAL, the largest disagreement was seen for standing, with 5% categorized as walking by activPAL3. For walking and sitting/lying, the disagreement was 2%, respectively. The expected daily differences between activPAL3 and activPAL were +15.0 min (95% CI: 11.3ߝ18.8) for walking and +29.5 min (95% CI: 6.2–52.7) for standing. ActivPAL and activPAL3 showed good agreement in older adults. However, if using these devices interchangeably, observed differences might still bias results.
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This study examined (a) the validity of two accelerometers (ActiGraph GT3X [ActiGraph LLC, Pensacola, FL, USA] and activPAL [PAL Technologies Ltd., Glasgow, Scotland]) for the assessment of sedentary behavior; and (b) the variations in assessment accuracy by setting minimum sedentary bout durations against a proxy for direct observation using an automated wearable camera in free-living environments. Time spent in sedentary behavior estimated from the GT3X, with varying identification methods (i.e., a hybrid machine learning algorithm, Sojourn, and activity count thresholds), and the activPAL were compared to the criterion measure with and without applying minimum sedentary bout durations. The activPAL assessed sedentary behavior most accurately followed by GT3X with the Sojourn method. The performance of the GT3X is improved when identifying sedentary bouts ≥ 15 min with the Sojourn method or a threshold of < 150 cpm. The activPAL should be considered for studies focusing on sedentary behavior. The ability of the GT3X to assess sedentary behavior is improved when focusing on sedentary bouts ≥ 15 min using the Sojourn method or the threshold of < 150 cpm.
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The objective of this study was to assess the validity of the step count functions in Actical accelerometers and activPAL inclinometers, compared with pedome-ter-derived step count data. Firstly, directly observed step counts over 3 treadmill speeds were compared with steps collected from 3 pedometers, accelerometers, and inclinometers in 10 adults. Secondly, step count data were derived from 22 participants who wore a pedome-ter, accelerometer, and inclinometer over 48 hours. Agreement between measurement tools was determined. All monitors appropriately measured steps in the labo-ratory conditions. In free living conditions, the mean percentage differences with pedometer-determined step counts were -7.3% and 7.0% for the Actical and ac-tivPAL monitors, respectively. With the exception of slow walking for the Actical units (ICC < 0.001), acceptable reliability was found within units for all treadmill speeds, and across units during the free living condition. The 95% prediction interval ranges were wide, ranging from -68.8% to 54.2% for the Acticals, and from -39.1% to 53.2% for the activPALs. Step counts gathered from Actical and activPAL units should not be used interchangeably with pedometer-derived step count data.
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Background: Our understanding of the amount of time children spend sitting, standing and stepping during a typical school day is limited. The ActivPAL monitor, which can differentiate between sitting and standing, was used in this study to objectively assess free-living activities in children. Aims: The main purpose was to objectively quantify the time children spend sitting, standing and stepping in atypical school day. A secondary purpose was to compare the ActivPAL monitor step counts with those obtained from Actical accelerometers. Study Design:Pilot observational study.
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