Heart Rate at the Limit: Validating the Samsung Galaxy Watch 6 for Maximal Exercise

As wearable technology becomes a staple in both fitness and clinical monitoring, the demand for high-accuracy heart rate (HR) tracking continues to grow. While most smartwatches perform well at rest, the real challenge lies in maximal-intensity exercise, where heavy movement and physiological stress can interfere with optical sensors.

Marcelo Rodrigues dos Santos, PhD, and his research team at the Health Data Lab (Sidia Institute of Science and Technology), recently tackled this challenge. In a new study published in JMIR Cardio, they evaluated how well the Samsung Galaxy Watch 6 (GW6) holds up during a grueling, maximal cardiopulmonary exercise test (CPET).

Testing the U-Shaped Pattern of Accuracy

The study involved 55 healthy adults performing a ramp protocol on a treadmill, pushing their bodies to volitional exhaustion. Researchers compared the wrist-worn Galaxy Watch 6 against a Polar H10 chest strap, which is widely recognized as the reference standard for non-invasive heart rate monitoring.

The team analyzed the data across five distinct intensity zones, ranging from 50% to 100% of the participants' maximum heart rate. Interestingly, the study observed a U-shaped pattern in reliability:

• Low to Moderate Intensity: The watch showed moderate to good agreement.

• Vigorous Intensity (70%–90%): Reliability dipped slightly, likely due to mechanical "noise" from increased arm swinging and movement artifacts.

• Maximal Intensity (90%–100%): Accuracy recovered to good-to-excellent levels, as movement often becomes more rhythmic and constrained at peak effort.

Key Findings for Clinicians and Athletes

The findings offer a balanced view for those relying on wrist-based data. While the Galaxy Watch 6 consistently provided low absolute error, meaning the point-wise accuracy was high, it also showed a consistent underestimation of heart rate by an average of about 2.67 beats per minute.

Furthermore, the team noted a 22% device failure rate, where usable data wasn't generated. This serves as a practical reminder that while these devices are excellent for tracking trends and group-level data, they may not yet be a total replacement for ECG-based tools in critical diagnostic settings where every beat counts.

Dr. Santos and the Sidia Institute team chose to publish their findings in JMIR Cardio. For researchers working at the intersection of cardiology and technology, the journal’s rigorous peer-review process and strong editorial reputation ensure that validation studies reach the practitioners and policymakers who can implement them in real-world clinical settings.

Expanding the Horizon: More on Wearable Validation from JMIR

The validation of consumer wearables is a cornerstone of the digital health revolution. For those looking to compare technologies or explore clinical applications, we recommend these recent studies in the JMIR Publications network:

• Falter et al. (2019) on the accuracy of the Apple Watch for patients with cardiovascular disease.

• Nissen et al. (2022) evaluating the Fitbit Charge 4 alongside the Samsung Galaxy Watch Active2.

• Webster et al. (2021) on using smartphone snapshots for VO2max measurement in diverse populations.

Curious to see how the latest smartwatch technology performs under extreme physiological stress? Watch the video featuring Marcelo Rodrigues dos Santos, PhD, and read the full research article to explore the detailed statistical analysis and intensity zone breakdown behind the Galaxy Watch 6 validation.

Please cite as:
Inoue A, Soares J, Antunes-Santos F, Ferreira A, Gonçalves A, Alcântara J, dos Santos M
Heart Rate Estimation Using the Galaxy Watch During Maximal Cardiopulmonary Exercise Testing: Cross-Sectional Validation Study
JMIR Cardio 2026;10:e81917
URL: https://cardio.jmir.org/2026/1/e81917
DOI: 10.2196/81917