{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,23]],"date-time":"2026-10-23T21:13:32Z","timestamp":1792790012704,"version":"4.5.0"},"reference-count":35,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2025,5,6]],"date-time":"2025-05-06T00:00:00Z","timestamp":1746489600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"New Frontiers in Research","award":["NFRFR-2021-00247"],"award-info":[{"award-number":["NFRFR-2021-00247"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Consumer-grade wrist-based wearable devices have grown in popularity among researchers to continuously collect metrics such as physical activity and heart rate. However, manufacturers rarely disclose the preprocessing sensor data algorithms, and user-generated data are typically shared leading to data governance issues. Open-source technology may address these limitations. This study evaluates the validity of the Bangle.js2 for step counting and heart rate during lab-based validation and agreement with other wearable devices (steps: Fitbit Charge 5; heart rate: Polar H10) in free-living conditions. A custom open-source application was developed to capture the sensor data from the Bangle.js2. Participants (n = 47; 25 males; 27 \u00b1 11 years) were asked to complete a lab-based treadmill validation (3 min stages at 2, 3, 4, and 5 mph) and stair climbing procedure followed by a 24 h free-living period. The Bangle.js2 demonstrated systematic undercounting of steps at slower walking speeds with acceptable error achieved at 5 km\/h. During free-living conditions, the Bangle.js2 demonstrated strong agreement with the Fitbit Charge 5 for per-minute step counting (CCC = 0.90) and total steps over 24 h (CCC = 0.96). Additionally, the Bangle.js2 demonstrated strong agreement with the Polar H10 for minute-averaged heart rate (CCC = 0.78). In conclusion, the Bangle.js2 is a valid open-source hardware and software solution for researchers interested in step counting and heart rate monitoring in free-living conditions.<\/jats:p>","DOI":"10.3390\/s25092926","type":"journal-article","created":{"date-parts":[[2025,5,6]],"date-time":"2025-05-06T09:08:56Z","timestamp":1746522536000},"page":"2926","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":13,"title":["Validation of an Open-Source Smartwatch for Continuous Monitoring of Physical Activity and Heart Rate in Adults"],"prefix":"10.3390","volume":"25","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-4894-9552","authenticated-orcid":false,"given":"Nicholas","family":"Ravanelli","sequence":"first","affiliation":[{"name":"Heat Resilience & Performance Centre, Yong Loo Lin School of Medicine, National University of Singapore, 27 Medical Drive, #03-01, Singapore 117510, Singapore"},{"name":"Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117593, Singapore"},{"name":"Human Potential Translational Research Programme, National University of Singapore, Singapore 117597, Singapore"},{"name":"School of Kinesiology, Lakehead University, Thunder Bay, ON P7B 5E1, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"KarLee","family":"Lefebvre","sequence":"additional","affiliation":[{"name":"School of Kinesiology, Lakehead University, Thunder Bay, ON P7B 5E1, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Amy","family":"Brough","sequence":"additional","affiliation":[{"name":"School of Kinesiology, Lakehead University, Thunder Bay, ON P7B 5E1, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Simon","family":"Paquette","sequence":"additional","affiliation":[{"name":"School of Kinesiology, Lakehead University, Thunder Bay, ON P7B 5E1, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Wei","family":"Lin","sequence":"additional","affiliation":[{"name":"Heat Resilience & Performance Centre, Yong Loo Lin School of Medicine, National University of Singapore, 27 Medical Drive, #03-01, Singapore 117510, Singapore"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,5,6]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"e110","DOI":"10.2196\/jmir.9157","article-title":"Using Fitness Trackers and Smartwatches to Measure Physical Activity in Research: Analysis of Consumer Wrist-Worn Wearables","volume":"20","author":"Henriksen","year":"2018","journal-title":"J. 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