01 HOW ACCURATE IS MY SMARTWATCH?
In 2023, the global wearable technology market was valued at $130 billion. This includes fitness and smartwatches. Seen through a sporting lens, they delver a swathe of fitness metrics including your heart rate. This is useful information to guide your training. But are the results accurate?
Wrist-based heart-rate sensors are a more usable and portable option than the traditional chest-strap option. They’ve evolved over the years but, essentially, they follow the same principle of employing optical heart-rate sensors that measure changes in blood volume in the capillary layer that sits just beneath the epidermis, which is the outermost of the three layers that comprise skin.
As is common in sport, it’s technology first seen in the medical and therapeutic arena that’s been adapted for performance purposes. But whereas studies into the likes of EPO show a consistent, significant (illegal) boost, the same can’t be said of these optical measurements, with a key inaccuracy reported to be skin colour. It’s something we put to Pilar Martin-Escudero of Madrid University, an expert in this area. “One primary inaccuracy source is skin pigmentation,” says Martin-Escudero. “[These devices] operate by shining light through the skin. Melanin, responsible for skin colour, can absorb light at specific wavelengths, complicating readings in individuals with darker skin tones.”
This, says Pilar Martin-Escudero, also applies to the accuracy of watches that measure oxygen saturation. But is this the experience of those in the commercial business? In fact, leading lights such as Garmin are pretty honest with the effectiveness or not of wrist-based optics. Over to Rich Robinson, senior product manager at Garmin UK.
“Garmin watches are designed to work on all skin tones but as the level of melanin increases in the body, the sensor may have to work harder by increasing the light brightness to find a pulse. This can result in the battery level being depleted faster.”
