Fitness Tracker Research for Heart Rate & Training

Wearable Fitness Tracker Monitoring: Insights from Real-World Research

Monitoring heart rate and activity data from wearable devices is a foundational practice for endurance and Zone 2 training. A 2026 pilot study from the University of Manchester offers one of the most direct evaluations of how these devices perform over time, providing evidence for their application in metabolic and endurance fitness.

Samsung Galaxy Watch Led in Long-Term Data Completeness for Heart Rate

Researchers from Manchester and King’s College London evaluated 105 participants who used either a Fitbit Charge 5, Samsung Galaxy Watch 5, or Apple Watch SE for up to 20 weeks. Their primary measure was data “completeness”—the number of valid days each device recorded step count, heart rate, and sleep. The team found smartwatches outperformed the fitness band for the most critical metric for athletes: continuous heart rate data.

While step count data was reliably captured by all devices, heart rate monitoring proved more fragile. For consistent weekly heart rate data—defined as at least three valid days per week—the Samsung Galaxy Watch was superior. A larger proportion of its users maintained this stream of data over the full 20-week follow-up period compared to the other devices. The Fitbit Charge 5, in contrast, showed a steeper decline in data completeness as the study progressed. This suggests that for endurance athletes relying on continuous heart rate to stay in Zone 2, device choice and wear consistency directly impact data reliability.

Device Acceptability is the Engine of Consistent Monitoring

The study’s design allowed participants to choose their preferred device, mirroring real consumer behavior. The Samsung Galaxy Watch was the most frequently selected option, chosen by 43.8% of participants. After three months of use, participants rated their device’s acceptability through a structured questionnaire.

This self-reported satisfaction correlated with the objective data findings. Higher acceptability scores were linked to more consistent use and, consequently, more complete long-term data sets. The research team, led by Bladon and Bucci, concluded that a device’s technical capability is only valuable if the user finds it comfortable, intuitive, and non-burdensome to wear daily. For fitness tracking, a disliked device will end up in a drawer, breaking the data chain needed to monitor training adaptations or metabolic improvements over time.

Applying Clinical-Grade Monitoring Insights to Endurance Training

This research was conducted within the CONNECT study, which focuses on remote monitoring for mental health. However, its methodology and findings translate directly to the demands of metabolic and endurance fitness. The study treated data as a clinical outcome, applying rigorous standards for what constitutes a “valid day” of heart rate or step data. Athletes can adopt a similar mindset: sporadic data has limited value for tracking Zone 2 training for weight loss and metabolic health.

The need for troubleshooting also emerged as a key factor. Participants using devices that required more technical support had more data gaps. This highlights that a wearable is part of a larger ecosystem including phone apps and user knowledge. To effectively use heart rate variability (HRV) or resting heart rate trends—metrics linked to mitochondrial health and recovery—athletes must ensure they understand their device’s data export and syncing processes.

Practical Steps for Better Wearable Data in Your Training

First, prioritize comfort and battery life over marginal gains in sensor accuracy. A device you wear 24/7 will always provide better insights than a more accurate one you remove frequently. The study’s data shows gaps are inevitable, but consistent wear minimizes them.

Second, treat heart rate data with more scrutiny than step count. The research confirms heart rate sensors are more prone to missing data, often due to loose wrist fit or poor sensor contact during activity. For Zone 2 training, ensure your watch is snug and positioned correctly. Consider cross-referencing watch data with perceived exertion to stay in the correct intensity zone.

Finally, use the data trends, not just daily numbers. The study’s analysis focused on patterns over weeks and months. Look at your weekly average resting heart rate or HRV, not daily fluctuations. This longitudinal view is more useful for assessing how your cardiorespiratory fitness is developing and whether your training load is appropriate.

Frequently Asked Questions

Are smartwatches really better for fitness tracking than basic fitness bands?

For consistent, long-term heart rate monitoring, this study suggests they can be. The Samsung Galaxy Watch demonstrated better data completeness over 20 weeks than the Fitbit Charge 5, likely due to higher user acceptability and engagement with a multi-function device.

Why does my watch sometimes show no heart rate data during a workout?

This is a common data gap identified in the research. It is often caused by poor sensor contact with the skin. Ensure the device is worn snugly, slightly higher on the wrist, and that the sensor area is clean and dry for the most reliable readings.

How can I use wearable data to improve my Zone 2 training?

Focus on trends rather than single readings. Monitor your average workout heart rate over weeks to see if you can maintain the same pace at a lower heart rate—a sign of improved efficiency. Also, track resting heart rate and HRV trends to gauge recovery and avoid overtraining.

Sources:
https://pubmed.ncbi.nlm.nih.gov/42413039/
https://pubmed.ncbi.nlm.nih.gov/42412242/
https://pubmed.ncbi.nlm.nih.gov/42308476/