Wearables for Long COVID, ME/CFS and POTS: What the Data Really Shows

Many people living with Long COVID, ME/CFS or POTS now wear a smartwatch or fitness tracker — not as a trend, but because heart rate, heart rate variability (HRV) and activity can be captured objectively. This can help build a clearer picture of personal exertion limits and catch early signs of post-exertional malaise (PEM). At the same time, independent validation studies show that consumer devices have real technical limitations. Understanding those limits makes it possible to use wearable data sensibly rather than trusting it blindly.

What resting heart rate and heart rate can tell you

The Workwell Foundation, which has researched exertion intolerance in ME/CFS for years, recommends heart rate monitoring as a practical pacing aid: the idea is to stay below one's anaerobic threshold as much as possible to avoid triggering PEM. Wearables make this kind of continuous, everyday monitoring practical, where previously only occasional measurements were feasible.

A recent study on wearable-based heart rate variability in Long COVID (medRxiv, 2025) found signs of autonomic dysfunction and described possible thresholds that may relate to the onset of PEM. Work like this is promising, but it is still at an early, unconfirmed research stage — the thresholds discussed there should not be adopted uncritically as individual limits.

A smaller case series on wearable use in Long COVID (PMC, 2024) also suggests that regular feedback on heart rate and activity helped some participants reduce day-to-day symptom severity — though with a limited number of participants and no control group, which limits how broadly the findings can be applied.

Where consumer wearables reach their limits

Optical pulse measurement via light sensor (photoplethysmography) is the most common method in smartwatches — and it is also one of the biggest sources of error. A 2025 validation study of nocturnal resting heart rate and HRV across several popular consumer devices (Physiological Reports) found notable deviations from medical-grade reference measurements, particularly for HRV, a metric that is especially sensitive to noise given its fine resolution. Another study assessing the accuracy of four heart rate wearables (PMC, 2024) found a similar pattern: deviations varied meaningfully by device, activity, and skin tone.

This matters especially for people with POTS, since heart rate can shift quickly and substantially with position changes. Motion artifacts, a loose wrist fit, cold hands, or darker skin pigmentation can further distort optical readings. Step counters, in turn, typically overcount with jerky arm movements and undercount during very slow walking or wheelchair use — an important limitation when exertion capacity fluctuates significantly.

It's also worth noting: consumer wearables are, in general, not medical devices and were not designed or approved to reliably monitor individuals through the course of an illness. Their algorithms are usually proprietary, get changed without notice, and are often calibrated on healthy, younger populations — not on people with autonomic dysfunction.

Avoiding misinterpretation

A single reading — say, an elevated resting heart rate on one morning — says little on its own. Individual trends over days or weeks, compared against one's own usual range, are far more informative. Anyone using a personal rule of thumb such as "try to keep heart rate under X" should treat it as a rough guide rather than an exact physiological limit, especially since measurement accuracy varies with activity.

• Avoid switching devices: different models often produce different absolute values, so comparing across devices is rarely meaningful.
• Consider context: sleep quality, caffeine, stress, menstrual cycle, and ambient temperature all influence resting heart rate and HRV independently of PEM.
• Don't replace subjective symptoms with numbers: wearable data complements how your body feels, it doesn't substitute for it.
• Don't overinterpret one unusual reading: a single outlier rarely justifies an immediate change in behavior — a recurring pattern is more informative.

How to get hold of your own data

None of the above helps much while the numbers stay inside the manufacturer's app. Most providers do offer a full export, and it costs nothing — it is just rarely well signposted.

• Garmin: the full export is called "Export Your Data" and lives in the Garmin account in a browser, not in the Connect app. You request it and receive a ZIP later — heart rate, sleep and activities, going back years. For a single recording, downloading the FIT file from Garmin Connect is enough.
• Apple Watch and iPhone: in the Health app, export all health data from your own profile. The result is a ZIP containing one very large XML file; on older devices this takes a few minutes.
• Whoop: the data export can be requested in the membership account and also arrives as a ZIP.
• ResMed CPAP devices: the raw data sits on the SD card in the device; a smaller extract is available from the myAir app.

mypacing reads these formats automatically. Fitbit, Oura and Withings not yet — you can upload them anyway and we will look at them by hand. The route is described in the guide; uploading happens on the upload page.

One point that belongs to the subject of this article: an export almost always contains a great deal more than the manufacturer's app displays — heart rate minute by minute, for instance, rather than a smoothed daily curve. That resolution is exactly what you need in order to see how long you were above a limit, not merely that you were.

Conclusion

Wearables can be a useful tool for people with Long COVID, ME/CFS and POTS to surface patterns in their own exertion behavior and support pacing decisions. But the available research also makes clear: measurement accuracy varies by device, situation, and individual physical characteristics, and many promising approaches to defining thresholds are still in early stages of scientific validation. Wearable data is most helpful when treated as one input among several — alongside a symptom diary, activity log, and personal experience.

This article is for general information only and does not replace individual medical assessment. mypacing.app is not a medical device.

Last reviewed and extended on 17 August 2026: the section on getting hold of your own data is new. The sources below are unchanged.