Heart rate

Heart rate measurements from the back of the watch on your wrist are fairly accurate, especially at rest. In most everyday situations and sports with steady intensity, such as jogging or cycling, modern wearables provide a trustworthy picture, differing by just a few beats per minute from an ECG chest strap. The challenge arises during rapid intensity changes (for example, interval training) or sports with lots of wrist movement (such as tennis, basketball, or strength training). In those conditions, the sensor often cannot keep up with fast changes in blood flow, leading to larger errors. For the most precise measurement during intense sports, a chest strap therefore remains superior (Chevance et al., 2022).

Location

GPS‑based location tracking in sports watches is very accurate, often down to just a few meters. Modern watches use multiple satellite systems simultaneously, which significantly improves reliability. Accuracy can temporarily decrease in environments with poor signal, such as dense urban areas with tall buildings, in forests, or during very cloudy weather. Overall, however, you can trust that the recorded distance is a good reflection of reality.

Conclusion

For athletes, wearing wearables carries a double risk. The basic measurements—heart rate, nighttime HRV, sleep duration—are quite reliable. However, the composite “recovery” or “readiness” scores that many athletes use to plan their training and/or day are far less dependable. The algorithms that companies like Garmin or Apple use to derive these scores are largely secret, poorly validated, and often create a false sense of (in)security (Doherty et al., 2025).

The consequence is that athletes may start ignoring their own bodily sensations. Research shows that athletes sometimes skip a workout because their wearable shows “red,” even though they actually feel fine—and the reverse also happens (Lundstrom et al., 2024; Ibrahim et al., 2024). This can undermine the intrinsic self‑regulation that is essential in elite sport.

The solution is simple: treat your wearable as a signal, not as a command. Trust the raw data (heart rate, sleep, activity), but never use recovery scores as the sole basis for training decisions. The combination of objective data, subjective feeling, and a solid training plan remains invaluable. If you find yourself being overly influenced by recovery scores or similar composite metrics, you can usually switch these off easily in the device’s settings.

Personal note

If you are curious about how I use my Garmin watch (Forerunner 165, €155), the answer is very straightforward. I use it for displaying my heart rate in combination with a chest strap, for GPS, and for the step counter. My VO2max was determined through a labtest and manually entered into my smartwatch, so that I can also achieve accurate training goals with it, such as training in zone ‘X’, for example.For everything else, I rely on my own feelings and intuition. Garmin also offers many more expensive models, some well over €1000. It is very tempting to buy one of those because they look fancy. The same goes for more “exotic” wearables such as a Whoop band or an Oura ring.

And that is exactly where it gets tricky. People are always searching for something new, something sexy, something that captures the imagination. You see this not only in the purchase of such gadgets, but also in other areas such as specific training methods or new diets. However, it is crucial to keep distinguishing what is meaningful from what is not. Often these things work suboptimally (or simply not at all), and if you had stuck with the basics you would have achieved the same—or even better—results.

Roeg Kuijpers

Nutritonist, pro athlete coach and personal trainer