Fitbit and the Modern Negro
January 25, 2015 5:35 PM
Do wrist-based optical heart rate monitors work on dark skin?
All the cool wearable fitness googads (such as, for example, the Apple Watch, Fitbit Charge HR and Fitbit Surge) seem to use an optical heart rate monitor that uses "LED lights [that] reflect onto the skin to detect blood volume changes." (source)
Nifty! It's like we live in the future!
But I can't seem to find any information on whether this technology actually works for black folks. I've seen a couple mentions of how the technology *might* have trouble with darker skin, but nothing about how dark, and no real discussion by actually black people about how well it works for them.
I'm more a Michelle than a Barack and I'd really love to have accurate heart rate readings from a device on my wrist (as opposed to the chest based ones which work fine for me, but ugh). Can I?
All the cool wearable fitness googads (such as, for example, the Apple Watch, Fitbit Charge HR and Fitbit Surge) seem to use an optical heart rate monitor that uses "LED lights [that] reflect onto the skin to detect blood volume changes." (source)
Nifty! It's like we live in the future!
But I can't seem to find any information on whether this technology actually works for black folks. I've seen a couple mentions of how the technology *might* have trouble with darker skin, but nothing about how dark, and no real discussion by actually black people about how well it works for them.
I'm more a Michelle than a Barack and I'd really love to have accurate heart rate readings from a device on my wrist (as opposed to the chest based ones which work fine for me, but ugh). Can I?
Pulse oximetry is a similar technology used in hospitals and other medical settings, so if skin tone interfered with its operation presumably it would be easy to find warnings and protocols about that.
posted by XMLicious at 5:52 PM on January 25, 2015
posted by XMLicious at 5:52 PM on January 25, 2015
Marques Brownlee is a black dude who reviews this kind of stuff on his youtube channel MKBHD. He's done one of the fitbit models, and many other wearable armbands/watches/etc like the moto 360 with these type of heart rate monitors.
He's never, ever mentioned any issues like this. And he LOVES to point out flaws in stuff that other people gloss over or don't mention.
If this was A Thing, i'm sure he would have been one of the first to talk about it, and complain about products that did it in comparison with ones that didn't(he's done this type of thing with features that don't work on several models of smartphone, etc).
I actually thought of this a couple months back, and my next thought was "if it was a problem, he totally would have talked about it".
posted by emptythought at 10:48 PM on January 25, 2015
He's never, ever mentioned any issues like this. And he LOVES to point out flaws in stuff that other people gloss over or don't mention.
If this was A Thing, i'm sure he would have been one of the first to talk about it, and complain about products that did it in comparison with ones that didn't(he's done this type of thing with features that don't work on several models of smartphone, etc).
I actually thought of this a couple months back, and my next thought was "if it was a problem, he totally would have talked about it".
posted by emptythought at 10:48 PM on January 25, 2015
I read a few comments on dcrainmaker.com about this where it is said that dark skin can cause problems. See for example here: We have performed tests with darker/black skinned people. While the Alpha and Link both work in many instances, there are some cases where very dark pigmentation can cause issues with the optical sensors being unable to properly read the blood flow directly beneath the surface of the skin. What we would recommend, if possible, is to check out the Alpha at a local retailer near you. and from another review: Now, you might have noticed it has three LED’s – and you might have also noticed that two are green and one is yellow-ish. This is different than most other products on the market that use just a pair of green LED’s. In talking with the engineers they added the yellow LED because it tends to get better readings on those with darker skin. By using all three LED’s together they can increase accuracy across a broader range of individuals.
In general, from what I have read, optical heart rate monitoring is not super reliable yet regardless of skin color, especially while exercising.
posted by blub at 1:52 AM on January 26, 2015
In general, from what I have read, optical heart rate monitoring is not super reliable yet regardless of skin color, especially while exercising.
posted by blub at 1:52 AM on January 26, 2015
As an aside, your question reminded me of this fantastic Better Off Ted bit.
posted by TonyRobots at 9:10 AM on January 26, 2015
posted by TonyRobots at 9:10 AM on January 26, 2015
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Long answer: Skin color is caused by melanin. Melanin's absorption curve indicates that it is mostly effective at absorbing light of wavelength shorter than 600 nm (roughly orangey-yellow). Based on this whitepaper from Texas Instruments about the design of an optical heart rate monitor, they use infrared and red LEDs. At those wavelengths, melanin is not a very effective absorber, so there should be very little signal loss. Looks like you're good to go!
posted by Maecenas at 5:48 PM on January 25, 2015