How skin tone impacts smartwatch accuracy\u00a0<\/h2>Smartwatches use optical heart-rate sensors. Steve Sayers \/ Our Media <\/span><\/figcaption><\/figure>As is common in sport, wrist-based heart-rate sensor technology was first seen in the medical and therapeutic arena and has been adapted for performance purposes. EPO (erythropoietin) is another example of this. It was created for severe anaemics and has been used by the likes of Lance Armstrong.\u00a0<\/p>
But whereas studies into EPO show a consistent, significant (illegal) boost to performance, the same can\u2019t be said of these optical measurements, with a key inaccuracy reported to be skin colour.<\/p>
Pilar Martin-Escudero of Madrid University is an expert in this area and says: \u201cYes, one primary inaccuracy source is skin pigmentation.<\/p>
\u201cThey 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.\u201d<\/p>
Martin-Escudero says this also applies to the accuracy of sports watches that measure oxygen saturation. But is this the experience of those in the commercial business?\u00a0<\/p>
Well, yes. In fact, leading lights such as Garmin are pretty honest about the effectiveness or otherwise of wrist-based optics.\u00a0<\/p>![\"Coros](\"https:\/\/c02.purpledshub.com\/uploads\/sites\/39\/2024\/08\/RussellBurton_20231025_2DX1286-scaled.jpg\")
Skin tone impacts the accuracy of optical heart-rate monitors. Russell Burton \/ Our Media <\/span><\/figcaption><\/figure>Rich Robinson, senior product manager at Garmin UK, says: \u201cGarmin 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.\u201d<\/p>
Robinson suggests the battery takes the hit rather than the readings, but your skin tone impacts performance. This covers tattoos, too, because the ink pattern and saturation of colour can block the light from reaching the sensor.<\/p>
There is good news regarding your erratic epidermis, however, especially for those of us for whom the years are mounting. No matter how expensive your moisturiser is, your skin changes with age.\u00a0<\/p>
According to researcher Hsuh-Wen Chow of National Cheng Kung University, that means \u201cfine wrinkles, roughness, mottled hyperpigmentation, dilated blood vessels and loss of skin tone\u201d.<\/p>
In addition to age-related changes such as arterial stiffness, Chow and colleagues hypothesised that heart-rate readings would be inaccurate. However, after testing 20 adults over 65 years old and 20 between 20 and 26, they reported readings were \u201cgenerally accurate\u201d irrespective of age.<\/p>
So you can age with impunity. Just do so by avoiding smart training in the kitchen. Well, not too close to your appliances anyway.\u00a0<\/p>
\u201cMove away from sources that can interfere with your heart-rate monitor,\u201d says Garmin. \u201cSources of interference may include strong electromagnetic fields, some 2.4 GHz wireless sensors, high-voltage power lines, electric motors, ovens, microwave ovens, 2.4 GHz cordless phones and wireless LAN access points.\u201d<\/p>
Harder, stronger, less accurate?<\/h2>![\"Oscar](\"https:\/\/c02.purpledshub.com\/uploads\/sites\/39\/2023\/12\/RussellBurton202310252DX1096-85455dd.jpg\")
Martin-Escudero tested whether the harder you exercise, the less accurate a watch’s heart-rate readings become. Russell Burton \/ Our Media<\/span><\/figcaption><\/figure>Accuracy isn\u2019t solely about your skin, of course, with one of Martin-Escudero\u2019s studies examining another anecdotal issue: the harder you exercise, the less accurate the results.\u00a0<\/p>
The Spanish academic had subjects run on a treadmill or ride on a cycling ergometer wearing watches from either Apple, Fitbit, TomTom or Samsung. They were tested at increasing intensity against the gold-standard ECG (electrocardiogram).<\/p>
\u201cThe four devices were reasonably accurate at the lowest level,\u201d she says. \u201cHowever, at higher levels of exercise intensity, the Fitbit and Samsung tended to underestimate heart-rate values, while the TomTom and Apple Watch were fairly reliable.\u201d<\/p>
When it came to comparisons between cycling and running, and using the TomTom as an example, it proved more accurate on two wheels than two feet, with treadmill skews kicking in from 150bpm compared to around 128bpm.\u00a0<\/p>
The reason for this comes down to something Martin-Escudero calls \u2018motion artefacts\u2019. When running, you\u2019re not as fixed as on the bike. As you run harder, the watch can move, which lets light in and can impact results.<\/p>
Robinson tells us that Garmin\u2019s models are equally accurate on the bike and while running if the watch stays in the same position, which, of course, isn\u2019t always possible \u2013 unless you want to wear a tourniquet on your forearm.\u00a0<\/p>![\"Ineos-Grenadiers](\"https:\/\/c02.purpledshub.com\/uploads\/sites\/39\/2023\/08\/GettyImages-1303626789-1-31d1605.jpg\")
Professional cyclists use heart-rate straps for accuracy. Tim de Waele \/ Getty Images<\/span><\/figcaption><\/figure>He also highlights that Garmin is now on its fifth generation of sensors. Garmin doesn\u2019t expand too much on the engineering behind this but, broadly, more LEDs and \u2018better\u2019 algorithms to iron out the data means greater accuracy. However, like many of their contemporaries, Robinson recommends a heart-rate strap for the \u201cbest accuracy possible\u201d.<\/p>
As is common in sport, wrist-based heart-rate sensor technology was first seen in the medical and therapeutic arena and has been adapted for performance purposes. EPO (erythropoietin) is another example of this. It was created for severe anaemics and has been used by the likes of Lance Armstrong.\u00a0<\/p>
But whereas studies into EPO show a consistent, significant (illegal) boost to performance, the same can\u2019t be said of these optical measurements, with a key inaccuracy reported to be skin colour.<\/p>
Pilar Martin-Escudero of Madrid University is an expert in this area and says: \u201cYes, one primary inaccuracy source is skin pigmentation.<\/p>
\u201cThey 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.\u201d<\/p>
Martin-Escudero says this also applies to the accuracy of sports watches that measure oxygen saturation. But is this the experience of those in the commercial business?\u00a0<\/p>
Well, yes. In fact, leading lights such as Garmin are pretty honest about the effectiveness or otherwise of wrist-based optics.\u00a0<\/p> Rich Robinson, senior product manager at Garmin UK, says: \u201cGarmin 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.\u201d<\/p> Robinson suggests the battery takes the hit rather than the readings, but your skin tone impacts performance. This covers tattoos, too, because the ink pattern and saturation of colour can block the light from reaching the sensor.<\/p> There is good news regarding your erratic epidermis, however, especially for those of us for whom the years are mounting. No matter how expensive your moisturiser is, your skin changes with age.\u00a0<\/p> According to researcher Hsuh-Wen Chow of National Cheng Kung University, that means \u201cfine wrinkles, roughness, mottled hyperpigmentation, dilated blood vessels and loss of skin tone\u201d.<\/p> In addition to age-related changes such as arterial stiffness, Chow and colleagues hypothesised that heart-rate readings would be inaccurate. However, after testing 20 adults over 65 years old and 20 between 20 and 26, they reported readings were \u201cgenerally accurate\u201d irrespective of age.<\/p> So you can age with impunity. Just do so by avoiding smart training in the kitchen. Well, not too close to your appliances anyway.\u00a0<\/p> \u201cMove away from sources that can interfere with your heart-rate monitor,\u201d says Garmin. \u201cSources of interference may include strong electromagnetic fields, some 2.4 GHz wireless sensors, high-voltage power lines, electric motors, ovens, microwave ovens, 2.4 GHz cordless phones and wireless LAN access points.\u201d<\/p> Accuracy isn\u2019t solely about your skin, of course, with one of Martin-Escudero\u2019s studies examining another anecdotal issue: the harder you exercise, the less accurate the results.\u00a0<\/p> The Spanish academic had subjects run on a treadmill or ride on a cycling ergometer wearing watches from either Apple, Fitbit, TomTom or Samsung. They were tested at increasing intensity against the gold-standard ECG (electrocardiogram).<\/p> \u201cThe four devices were reasonably accurate at the lowest level,\u201d she says. \u201cHowever, at higher levels of exercise intensity, the Fitbit and Samsung tended to underestimate heart-rate values, while the TomTom and Apple Watch were fairly reliable.\u201d<\/p> When it came to comparisons between cycling and running, and using the TomTom as an example, it proved more accurate on two wheels than two feet, with treadmill skews kicking in from 150bpm compared to around 128bpm.\u00a0<\/p> The reason for this comes down to something Martin-Escudero calls \u2018motion artefacts\u2019. When running, you\u2019re not as fixed as on the bike. As you run harder, the watch can move, which lets light in and can impact results.<\/p> Robinson tells us that Garmin\u2019s models are equally accurate on the bike and while running if the watch stays in the same position, which, of course, isn\u2019t always possible \u2013 unless you want to wear a tourniquet on your forearm.\u00a0<\/p> He also highlights that Garmin is now on its fifth generation of sensors. Garmin doesn\u2019t expand too much on the engineering behind this but, broadly, more LEDs and \u2018better\u2019 algorithms to iron out the data means greater accuracy. However, like many of their contemporaries, Robinson recommends a heart-rate strap for the \u201cbest accuracy possible\u201d.<\/p>Harder, stronger, less accurate?<\/h2>