ArticlePloS one2023
How many days are needed? Measurement reliability of wearable device data to assess physical activity.
Article in PloS one, 2023. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 24 papers, 2 of them syntheses that pooled it.
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The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
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Who cites it
24 citing papers in PubMed, 2 syntheses or guidelines pooled it.
- Adherence to Actigraphic Devices in Elementary School-Aged Children: Systematic Review and Meta-Analysis.Journal of medical Internet research · 2025Pooled it
- DE-PASS best evidence statement (BESt): determinants of adolescents' device-based physical activity and sedentary behaviour in settings: a systematic review and meta-analysis.BMC public health · 2024Pooled it
- Isolating the role of researcher observation on reactivity to the measurement of physical activity.Applied psychology. Health and well-being · 2025Trial
- Hawthorne Effect in Screening Ambulatory Activity Status Using Wearable Pedometers Varies Across Age Groups.AJPM focus · 2026Article
- Objective Smartphone Screen Time Monitoring Among Caregivers of Preschool-Aged Children: Reliability Study of Monitoring Duration.JMIR mHealth and uHealth · 2026Article
- Intensive Longitudinal Data Collection Methods in Health Research: Tutorial for Selecting Measures and Designing a Sampling Protocol.JMIR mHealth and uHealth · 2026Article
- Reliability and Validity of a Novel, Portable Thermal Grill Illusion Apparatus Using Two Graphene Probes: An Initial Psychophysical Validation Study.European journal of pain (London, England) · 2026Observational
- Association of genetic risk and physical activity with incident type 2 diabetes.The Journal of clinical endocrinology and metabolism · 2026Article
- Do adults with cardiovascular disease risk show meaningful reactivity to physical activity measurement? Coordinated analysis across six studies.British journal of health psychology · 2026Article
- Concurrent associations between visit-to-visit changes in actigraphy-based physical activity and cognitive aging in older adults.Neurobiology of aging · 2026Article
- Article
- Accelerometer-based assessment of occupational standing time and its association with venous disorders - results of a cross-sectional field study.Scientific reports · 2026Article
- Enhancing Caregivers' Quality of Life Through a Web-Based Person-Centered Solution (TechQoL4Carers): Protocol for a Mixed Methods Pilot Trial.JMIR research protocols · 2026Article
- 11 million days of longitudinal wearable data reveal novel future health insights.medRxiv : the preprint server for health sciences · 2026Article
- Wearable Sensors for the Assessment of Functional Outcome Following Reverse Shoulder Arthroplasty: A Systematic Scoping Review.Journal of clinical medicine · 2025Review
- Validation of the Fitbit Charge 5 for the Detection of Heart Rate and Electrodermal Activity.Psychophysiology · 2025Article
- From Steps to Context: Optimizing Digital Phenotyping for Physical Activity Monitoring in Older Adults by Integrating Wearable Data and Ecological Momentary Assessment.Sensors (Basel, Switzerland) · 2025Article
- Article
- Twenty-four hour physical activity, sedentary behaviour and sleep profiles in adults living with rheumatoid arthritis: a cross-sectional latent class analysis.Journal of activity, sedentary and sleep behaviors · 2024Article
- Missing Data Statistics Provide Causal Insights into Data Loss in Diabetes Health Monitoring by Wearable Sensors.Sensors (Basel, Switzerland) · 2024Article
Corrections and comments
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Authors and funding
5 authors.
Funding
Abstract
introduction/purposePhysical activity studies often utilize wearable devices to measure participants' habitual activity levels by averaging values across several valid observation days. These studies face competing demands-available resources and the burden to study participants must be balanced with the goal to obtain reliable measurements of a person's longer-term average. Information about the number of valid observation days required to reliably measure targeted metrics of habitual activity is required to inform study design.
methodsTo date, the number of days required to achieve a desired level of aggregate long-term reliability (typically 0.80) has often been estimated by applying the Spearman-Brown Prophecy formula to short-term test-retest reliability data from studies with single, relatively brief observation windows. Our work, in contrast, utilizes a resampling-based approach to quantify the long-term test-retest reliability of aggregate measures of activity in a cohort of 79 participants who were asked to wear a FitBit Flex every day for approximately one year.
resultsThe conventional approach can produce reliability estimates that substantially overestimate the actual test-retest reliability. Six or more valid days of observation for each participant appear necessary to obtain 0.80 reliability for the average amount of time spent in light physical activity; 8 and 10 valid days are needed for sedentary time and moderate/vigorous activity respectively.
conclusionProtocols that result in 7-10 valid observation days for each participant may be needed to obtain reliable measurements of key physical activity metrics.
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