Many runners rely on smartwatches for training, using them to track pace, distance and heart rate. They can also be used to monitor your overall health and determine how much recovery you need, thanks to metrics such as heart rate variability (HRV). Some studies over the past few years have exposed accuracy issues with modern watches, cautioning runners not to trust everything their watch tells them, but the technology has been improving. We spoke to representatives from Coros and Garmin about how far running watch tech has come and the areas it can still be improved.
GPS tracking
Distance tracking has come a long way in the past five years. New smartwatches feature dual-band and Global Navigation Satellite System (GNSS) capabilities, delivering more accurate tracking in challenging environments (such as city centres that tall buildings, for example). This technology reduces tracking errors caused by signals reflecting off buildings, rocks or trees. It’s thanks to improvements in tracking accuracy that people can create Strava art in cities using their GPS.
Photo: Peter GPS Artist/Strava
Coros’s head of product marketing, Darian Allberry, commended the rapid advancement in GPS technology across all brands. “In GPS tests five-plus years ago, it was common to see watches have an error margin of five per cent or more in challenging environments,” he says. “Now, when you look to compare accuracy across any device, you’re typically going to be looking at a difference of 200 to 600m over the course of an entire marathon.”
Natalie Miller of Garmin International is quick to point out that tracking is improving beyond just dual-band and GNSS. “We often make improvements in antenna performance and power efficiency,” she says, “layered on top of the basic GNSS technology from the chipset vendors.”
Heart rate
Heart rate tracking has been one of the most heavily critiqued components of modern smartwatches. Although advances in modern heart rate sensors have made activities such as general fitness and easy runs straightforward to monitor, you still need to be cautious about what your heart rate indicates during higher-intensity workouts.
“The sensors have limitations,” Allberry says. “They measure blood flow via light, so factors such as cadence lock (where the watch mistakes your step rate for your heart rate), cold weather (which reduces blood flow to the extremities) or vibration (from running on an uneven surface) can cause accuracy problems.”
If you require a more accurate reading, a dedicated chest strap heart rate monitor is still more accurate than wrist-based HR tracking, though it can be uncomfortable during longer activities. Coros recommends its HRM arm band, which functions like a smartwatch but has the accuracy of a chest strap. “As you move closer to the heart (i.e. upper bicep), you get less noise in the data and more reactive readings,” Allberry says. “From an internal test we conducted, the accuracy of our HRM is 98 per cent to 99 per cent–the same as a chest strap.”
Sleep
Watches’ shut-eye tracking may be improving, but that does not mean you should rely on it completely. Sleep tracking on most watches estimates duration by monitoring HRV, heart rate and movement, all of which are useful for understanding your recovery. “Consumers should view sleep stages (i.e., deep, REM, light) as high-level estimates, rather than medical-grade data,” he adds.
If you have extended sleep issues, it’s best to consult a sleep lab that can measure brain activity and provide the most precise single-night breakdown. “We encourage users to focus on long-term trends, such as a consistent drop in deep sleep or a rise in resting heart rate,” Alberry says. “These are more reliable indicators of recovery and overtraining.”
For sleep, smartwatches are better suited to helping you understand your recovery and training readiness. “Wearables estimate sleep stages with a fair level of accuracy,” Miller says, “which is valuable to view trends for optimal personal recovery.”