{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T01:44:47Z","timestamp":1760060687711,"version":"build-2065373602"},"reference-count":54,"publisher":"MDPI AG","issue":"18","license":[{"start":{"date-parts":[[2025,9,10]],"date-time":"2025-09-10T00:00:00Z","timestamp":1757462400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The Polar Fitness Test (PFT) estimates maximal oxygen consumption (V\u0307O2max) under resting conditions using heart rate data from the manufacturer\u2019s wearable devices. We aimed to validate the PFT in a population with cardiovascular risk factors and to compare its results with five established equations predicting V\u0307O2max based on the 6-min walk test (6MWT). Twenty-four participants (9 female; age 57.4 \u00b1 10.2 years) undergoing medically supervised exercise training\u2014including seven individuals on heart rate-limiting medication\u2014completed the PFT, 6MWT, and cardiopulmonary exercise testing (CPET), which served as the criterion V\u0307O2max measurement. The PFT showed a mean absolute percent-age error (MAPE) of 13.7%, an intraclass correlation coefficient (ICC) of 0.743, a mean bias of \u22121.0 mL\/min\/kg, and limits of agreement (LoA) of \u00b111.4 mL\/min\/kg compared to CPET. Among the 6MWT-based equations, only the Porcari equation demonstrated similar performance (MAPE 12.6%, ICC 0.725, mean bias 0.2 mL\/min\/kg, LoA \u00b1 9.7 mL\/min\/kg), while other equations showed larger errors and systematic deviations. Our data indicate that the PFT may present an easily accessible option to estimate V\u0307O2max on population level when exercise-based testing is not feasible. However, its variability limits use for individual clinical decisions, reaffirming the relevance of CPET for accurate assessment.<\/jats:p>","DOI":"10.3390\/s25185649","type":"journal-article","created":{"date-parts":[[2025,9,10]],"date-time":"2025-09-10T14:14:55Z","timestamp":1757513695000},"page":"5649","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Validation of the Polar Fitness Test for Estimation of Maximal Oxygen Consumption at Rest in Medically Supervised Exercise Training: Comparison with CPET and the 6-Minute Walk Test"],"prefix":"10.3390","volume":"25","author":[{"given":"Michael","family":"Neudorfer","sequence":"first","affiliation":[{"name":"University Institute of Sports Medicine, Prevention and Rehabilitation, University Hospital Salzburg, Paracelsus Medical University, 5020 Salzburg, Austria"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Lukas","family":"\u00d6tzlinger","sequence":"additional","affiliation":[{"name":"University Institute of Sports Medicine, Prevention and Rehabilitation, University Hospital Salzburg, Paracelsus Medical University, 5020 Salzburg, Austria"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6971-2829","authenticated-orcid":false,"given":"Devender","family":"Kumar","sequence":"additional","affiliation":[{"name":"Ludwig Boltzmann Institute for Digital Health and Prevention, 5020 Salzburg, Austria"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Josef","family":"Niebauer","sequence":"additional","affiliation":[{"name":"University Institute of Sports Medicine, Prevention and Rehabilitation, University Hospital Salzburg, Paracelsus Medical University, 5020 Salzburg, Austria"},{"name":"Ludwig Boltzmann Institute for Digital Health and Prevention, 5020 Salzburg, Austria"},{"name":"Institute of Molecular Sports and Rehabilitation Medicine, Paracelsus Medical University, 5020 Salzburg, Austria"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0562-8473","authenticated-orcid":false,"given":"Jan David","family":"Smeddinck","sequence":"additional","affiliation":[{"name":"Ludwig Boltzmann Institute for Digital Health and Prevention, 5020 Salzburg, Austria"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mahdi","family":"Sareban","sequence":"additional","affiliation":[{"name":"University Institute of Sports Medicine, Prevention and Rehabilitation, University Hospital Salzburg, Paracelsus Medical University, 5020 Salzburg, Austria"},{"name":"Ludwig Boltzmann Institute for Digital Health and Prevention, 5020 Salzburg, Austria"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5388-4282","authenticated-orcid":false,"given":"Gunnar","family":"Treff","sequence":"additional","affiliation":[{"name":"Ludwig Boltzmann Institute for Digital Health and Prevention, 5020 Salzburg, Austria"},{"name":"Institute of Molecular Sports and Rehabilitation Medicine, Paracelsus Medical University, 5020 Salzburg, Austria"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2025,9,10]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1362","DOI":"10.1123\/ijspp.2023-0229","article-title":"The V\u0307O2max Legacy of Hill and Lupton (1923)\u2014100 Years On","volume":"18","author":"Millet","year":"2023","journal-title":"Int. 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