@article{neudorfer_validation_2025,
 abstract = {The Polar Fitness Test (PFT) estimates maximal oxygen consumption (V̇O2max) under resting conditions using heart rate data from the manufacturer’s 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 V̇O2max based on the 6-min walk test (6MWT). Twenty-four participants (9 female; age 57.4 ± 10.2 years) undergoing medically supervised exercise training—including seven individuals on heart rate-limiting medication—completed the PFT, 6MWT, and cardiopulmonary exercise testing (CPET), which served as the criterion V̇O2max 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 −1.0 mL/min/kg, and limits of agreement (LoA) of ±11.4 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 ± 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 V̇O2max 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.},
 author = {Neudorfer, Michael and Ötzlinger, Lukas and Kumar, Devender and Niebauer, Josef and Smeddinck, Jan David and Sareban, Mahdi and Treff, Gunnar},
 copyright = {http://creativecommons.org/licenses/by/3.0/},
 doi = {10.3390/s25185649},
 issn = {1424-8220},
 journal = {Sensors},
 keywords = {telemedicine, photoplethysmography, wearables, mHealth, prevention, cardiac rehabilitation},
 language = {en},
 note = {Publisher: Multidisciplinary Digital Publishing Institute},
 number = {18},
 pages = {5649},
 shorttitle = {Validation of the Polar Fitness Test for Estimation of Maximal Oxygen Consumption at Rest in Medically Supervised Exercise Training},
 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},
 url = {https://www.mdpi.com/1424-8220/25/18/5649},
 urldate = {2025-10-02},
 volume = {25},
 year = {2025}
}