Your smartwatch is lying to you

Summary

The video script discusses the discrepancies in resting heart rate readings among various wearable devices. It highlights the issue of manufacturers using different algorithms, potentially misleading users about their fitness levels. The script compares the resting heart rates measured by Fitbit, Mi Band, and Apple Watch, and explores the possibility that sleeping heart rate could be a more accurate indicator of health. It calls for standardization and transparency in how these devices measure and report resting heart rate.

Takeaways

• 📊 Different wearable devices use various algorithms to measure resting heart rate, leading to inconsistent results.
• 📉 Example: Fitbit measured 53 bpm, Mi Band 51 bpm, and Apple Watch 44 bpm for the same person, illustrating the disparity.
• 🩺 Resting heart rate is typically defined as the heart rate after about 5 minutes of inactivity while awake.
• 🔍 The lack of transparency in manufacturers' algorithms makes it difficult to understand how they calculate resting heart rate.
• 🌙 Some manufacturers, like Garmin, WHOOP, and Oura, calculate resting heart rate based on nighttime measurements.
• 😕 Nighttime heart rate measurements can be misleading, often showing lower values due to physiological changes during sleep.
• 📉 Using lowest nighttime heart rate as resting heart rate can give a false sense of fitness.
• 🤔 There's a correlation between sleeping heart rate and resting heart rate, but they're not perfectly aligned.
• 📚 Current studies indicate sleeping heart rate might be a better health indicator than daytime resting heart rate.
• 📈 Until standardized measurement methods are established, comparing heart rate values across different devices and medical recommendations remains challenging.

Q & A

What problem does the speaker highlight about wearable manufacturers?

The speaker highlights that many wearable manufacturers are providing misleading information about users' resting heart rates.

How do different wearables vary in measuring resting heart rate according to the speaker?

Different wearables use different algorithms to measure resting heart rate, leading to discrepancies in the reported values.

What are the resting heart rates reported by the speaker's Fitbit, Mi Band, and Apple Watch?

The Fitbit reported a resting heart rate of 53 bpm, the Mi Band reported 51 bpm, and the Apple Watch reported 44 bpm.

Why is there a discrepancy in the resting heart rates reported by different devices?

The discrepancy arises because different devices use different algorithms and methods, such as taking a waking measurement or a 24-hour average.

What does Dr. Rohin Francis say about the measurement of resting heart rate?

Dr. Rohin Francis explains that different devices measure heart rate using various algorithms, and earlier devices like the Fitbit used to take a 24-hour average, which could be misleading.

How is resting heart rate typically defined?

Resting heart rate is typically defined as the heart rate measured after at least five minutes of inactivity while the person is awake.

Why might manufacturers prefer to measure resting heart rate during sleep?

Measuring resting heart rate during sleep might provide more consistent and accurate readings because the person is lying still and ambient light levels are low.

What is misleading about the Oura Ring's 'lowest RHR' value?

The 'lowest RHR' value provided by the Oura Ring is misleading because it is the lowest resting heart rate value captured during the night, which may not accurately reflect the true resting heart rate.

Why do some manufacturers choose to report resting heart rate values measured at night?

Manufacturers may choose to report night-time resting heart rate values because these readings are more consistent and might flatter the user by appearing lower, encouraging positive feedback and continued use of the device.

How can users get a true reflection of their overall health regarding resting heart rate?

Users can get a true reflection of their overall health by measuring their heart rate after sitting still for five minutes, rather than relying on the resting heart rate values provided by wearables.

What does the speaker conclude about the comparison between sleeping and resting heart rate?

The speaker concludes that while sleeping heart rate might still be a good measure of health, it is currently hard to compare with traditional resting heart rate measurements due to a lack of standardization and comprehensive studies.

Outlines

00:00

🤔 Discrepancies in Wearable Resting Heart Rate Measurements

This paragraph discusses the inconsistency in resting heart rate readings from various wearable devices. The narrator highlights their personal experience with three different devices—Fitbit, Mi Band, and Apple Watch—yielding different results, raising the question of accuracy. It is explained that these devices use different algorithms, and some, like Fitbit, may take a 24-hour average, which can be misleading. The paragraph also introduces Dr. Rohin Francis, a heart specialist, who clarifies that resting heart rate should be measured while awake and inactive for at least five minutes. The lack of transparency in the algorithms used by manufacturers is criticized, and an attempt is made to understand how different devices calculate resting heart rate by comparing them to all-day heart rate measurements from a Polar H10 chest strap, which is considered a more accurate measure.

05:02

🏋️‍♂️ The Impact of Device Algorithms on Resting Heart Rate Perception

The second paragraph delves into how different wearable manufacturers calculate and report resting heart rates, with a focus on those that use sleeping heart rate as a proxy, which can be misleading. The Oura Ring is specifically called out for providing a 'lowest RHR' value based on sleep data, which may not accurately reflect the user's true resting heart rate. The paragraph also touches on the potential reasons why manufacturers might opt for nighttime readings, such as increased accuracy due to stillness and lower ambient light, and the possibility of enhancing user satisfaction by providing flatteringly low heart rate numbers. The narrator shares their own experience with a cardiologist regarding their low overnight heart rate and emphasizes the difficulty of comparing these readings to the standard medical range of 60 to 100 bpm. The paragraph concludes by suggesting that users should manually measure their resting heart rate for a more accurate assessment of their health and fitness.

Keywords

💡Wearables

Wearables are electronic devices that can be worn on the body, often used for tracking health and fitness metrics. In the video, the speaker mentions his interest in wearables and uses different devices to measure his heart rate.

💡Resting Heart Rate

Resting heart rate (RHR) is the number of heartbeats per minute when a person is at rest. It's a key metric for assessing cardiovascular fitness. The video discusses discrepancies in RHR measurements across different wearable devices and emphasizes its importance for users.

💡Algorithms

Algorithms in this context refer to the computational methods used by wearable devices to calculate heart rate. The video highlights how different algorithms lead to varying RHR readings, which can be misleading for users.

💡Fitbit

Fitbit is a brand of wearable fitness trackers. The video compares the RHR readings from a Fitbit device to other brands, showing a reading of 53 beats per minute and discussing the potential inaccuracies due to different measurement algorithms.

💡Apple Watch

The Apple Watch is a popular smartwatch known for its health and fitness tracking capabilities. In the video, the speaker notes an unusually low RHR of 44 bpm from the Apple Watch, questioning the accuracy of its measurements.

💡Mi Band

Mi Band is a line of wearable fitness trackers by Xiaomi. The video reports a resting heart rate of 51 bpm from the Mi Band, which is compared to other devices to illustrate differences in heart rate measurement.

💡Heart Rate Measurement

Heart rate measurement refers to the process of determining the number of heartbeats per minute. The video explains that different wearables use varying methods to measure heart rate, affecting the accuracy of the data they provide.

💡Dr. Rohin Francis

Dr. Rohin Francis is a heart specialist and YouTube creator mentioned in the video. He provides expert insights into how different devices measure heart rate and the potential inaccuracies involved.

💡Sleeping Heart Rate

Sleeping heart rate is the heart rate measured while a person is asleep. The video discusses how some wearables use sleeping heart rate to report RHR, which can be misleading since it doesn't align with the conventional definition of RHR.

💡Polar H10 Chest Strap

The Polar H10 chest strap is a device used to measure heart rate accurately during activities. The video uses data from this chest strap as a benchmark to compare the accuracy of heart rate measurements from different wearables.

Highlights

Wearable manufacturers may be providing misleading resting heart rate data to users.

Different wearable devices use different algorithms to determine resting heart rate.

Resting heart rate is typically defined as the heart rate at rest, usually after at least 5 minutes of inactivity while awake.

Some devices may be using a 24-hour average to determine resting heart rate, which can be misleading.

Algorithms behind wearable devices are not public, making it difficult to understand how they calculate resting heart rate.

Comparisons of wearable devices' resting heart rate measurements to all-day heart rate measurements can provide insights into their methodologies.

Some manufacturers, like Garmin, WHOOP, and Oura, calculate resting heart rate based on readings taken while the user is asleep.

The Oura Ring's 'lowest RHR' feature may mislead users into thinking they have a lower resting heart rate than they actually do.

Low resting heart rates recorded during sleep can be misleading, as physiological changes during sleep phases can cause heart rate to slow significantly.

Manufacturers might report resting heart rate at night to make users feel healthier or to encourage subscription retention.

Overnight heart rate measurements can be more accurate and consistent than daytime readings due to the user being still and ambient light levels being low.

The lack of standardization in resting heart rate measurement makes it difficult to compare data between different wearable devices.

Resting heart rate values from wearables may not align with the standard medical range of 60 to 100 bpm, leading to potential misunderstandings about health.

Sleeping heart rate might be a good measure of overall health and fitness, but more research is needed to establish its validity.

One study suggests that sleeping heart rate could be a more accurate predictor of risk of death and heart disease than daytime resting heart rate.

The advent of wearable technology allows for continuous heart rate monitoring, which could lead to new insights through future studies.

Until a standard for heart rate measurement is established, device manufacturers may be confusing or misleading customers with their readings.

Transcripts

As you can see, I like my wearables (this one’s  just a wedding ring by the way), but I was shocked  

to find out that many wearable manufacturers are  outright lying to users. And most frustratingly,  

it’s about one of the most important numbers  that these devices give you: resting heart rate.

The best way to illustrate the problem  is to look at my resting heart rate as  

measured three watches I wore for a week  when I was testing their performance.

Fitbit: 53 beats per minute.  Nice. Mi Band: 51 bpm. That’ll do.  

Apple Watch: 44 bpm. Hang on…what?!

So who’s right? Am I reasonably fit,  with a resting heart rate in the low 50s,  

or a full-on athlete, at 44 bpm? I mean, it’s  the former, obviously. But what’s going on here?  

The problem is that different devices  use different algorithms to determine  

your resting heart rate. Over to Dr Rohin Francis,  

heart specialist, and who you might know from  his excellent YouTube channel, Medlife Crisis.

There are different algorithms for a lot of  how the different devices measure heart rate,  

and I think nowadays most of them will take  a waking measurement. But certainly an early  

Fitbit that I had seemed to just take a 24-hour  average, which gave me a very misleading figure,  

way lower than what I was measuring my  resting heart rate to be in the daytime.

The key thing here is how resting  heart rate is usually defined:  

as we found out in the last video…

This is your heart rate at rest. So that  typically means when you're not doing  

anything for at least a few minutes,  so about 5 minutes of inactivity while  

you're awake. \[comedy echo\] …while you’re  awake…while you’re awake…while you’re awake…

And what’s frustrating is that the algorithms  behind these devices aren’t public so,  

while they’re no longer quite as  stupid as just taking a 24-hour  

average, we still don’t know exactly  what the manufacturers are doing here.

We can try to work out how different manufacturers  pick the resting heart rate by comparing them to  

my all-day heart rate measurements. These are  all the readings of my heart rate on a day when  

I was testing out a few different devices, ranging  from just below 40 bpm at the low end to 160-odd  

bpm at the fastest while I was exercising. These  values from a Polar H10 chest strap, so they’re  

the closest we can get to my true heart rate, to  compare with an Apple Watch, Fitbit and Mi Band.  

We can split these up into the times  when I was active, resting or asleep,  

and then overlay the watches’ estimates of resting  heart rate, like this. The Fitbit and the Mi  

Band both seem to choose a value close to the  bottom of the heart rates when I wasn’t moving,  

which makes sense. But it’s hard to know what  Apple is doing here: it looks like maybe they’re  

basing it on values while I’m asleep, but their  website is pretty vague about how it works.

Some manufacturers are a bit more explicit  about what’s going on – but three big ones  

I found information for, Garmin, WHOOP and  Oura, all specifically and proudly explain  

that they calculate your resting  heart rate while you’re asleep!

The Oura Ring is particularly misleading,  giving you one value called ‘lowest RHR’,  

which they define as ‘Your lowest resting  heart rate value captured during the night’.

My resting heart rate on the night I was  deepest sleep was 34, which again very,  

very low. If I look at that, if  that's what my Oura Ring had told  

me my resting heart rate was, I  would think, man, I am super fit.

Yeah, you’re Tour de France level.

Exactly. And yet, clearly that is not the  case. You know, just just just look at me.

Oh, harsh.

That just bears no resemblance.

Noooo, that’s very misleading.  And you'll see often people slow,  

profoundly in sleep. So I have tried this  on myself and I was hitting sort of 30,  

I was hitting 28 …when I was a bit fitter than  I am now!… but very transiently, you know,  

there are physiological changes depending on which  phase of sleep you're in, and in some of them  

you can go really slow. So that would be really  misleading to say that’s your resting heart rate.

Some of you in the comments on the second  video in this series were concerned about  

my low overnight heart rate, and  suggested I should see a doctor.  

So, first, thank you for your concern – but then  I did check with a cardiologist, and his response  

was … to show off that his used to be even  lower. Which means, I guess I’m probably OK?

But why do so many manufacturers report  resting heart rate at night when that’s not  

the conventional definition? Well, let’s  start with the possible cynical reason:  

if your Oura Ring flatters you by telling you  that your resting heart rate is super-low, you  

can brag about it to your friends at the gym and  post screenshots from the app on your Instagram,  

and you might be more likely to be happy with your  Oura Ring and maybe keep paying the subscription?

There is a potentially less cynical reason  too: as we saw in that earlier video,  

heart rate measurements taken overnight, when  you’re lying nice and still and ambient light  

levels are low, are often more accurate than  the daytime ones, sometimes substantially so,  

so readings will probably be more consistent  than measurements taken during the day.

Unfortunately this does mean it’s very hard  to compare between manufacturers. If a Fitbit,  

Apple Watch and Oura Ring user all walk  into a bar, the guy with the Oura Ring  

may emerge the smuggest about his resting  heart rate – the Apple user is obviously  

the smuggest overall – but it might be  that the Fitbit-wearer is actually fitter  

than both of them, despite his watch giving  him a higher value for resting heart rate.

The bigger problem is that all of  this makes it very hard to compare  

with the standard medical range, usually  given as 60 to 100 beats per minute,  

where most of us should probably be aiming for  somewhere toward the lower end of that range.  

These numbers were established in big medical  studies where resting heart rate was measured  

by a doctor or a nurse in a clinic, not by  taking a 24-hour measurement and then trying  

to extract the lowest possible number to make  the user feel good about themselves. If you  

were looking at this graph of heart rate vs risk  of death from the last video and thinking ‘wow,  

my Garmin says I’ve got a resting heart rate of  43 bpm, I’m gonna live forever!’, Well, I’m afraid  

I’ve got some bad news. Which is a shame, because  that’s exactly what my new Garmin is telling me.

These values could make us think that we’re  healthier than we actually are. An Oura Ring  

user thinking their resting heart rate was 60  bpm might think that they’re pretty healthy. But,  

if they’re basing that on their lowest sleeping  heart rate, then that’s very misleading – if  

it’s anything like mine, 20 bpm below their  actual resting heart rate. So, if you do have  

an Apple Watch, Oura Ring, Garmin or WHOOP strap,  don’t rely on the resting heart rate measurement  

values in the app – if you want to compare  yourself to the classic 60–100 bpm range,  

or your gym buddies who use different devices,  then just you’re going to have to sit still for  

five minutes and see where your heart rate ends up  to get a truer reflection of your overall health.

In spite of all this, sleeping heart rate might  still be a good measure. It would definitely  

make sense that people with a lower resting heart  rate during the day had a lower one at night too,  

but sadly the only paper I could find that made  the comparison directly was done in teenage  

athletes, so quite a specific population, and  there were only 11 of them in the study, which  

means it’s not exactly definitive. Do let me know  in the comments if you know of any better ones!

So I decided to take a look at my own data. On  this graph every point is a day, and along the  

bottom is my resting heart rate that day, and up  the side is my sleeping heart rate that night. As  

you can see, there’s a pretty clear relationship.  The points lie fairly close to a straight a line –  

for the nerds, R squared is 0.7, where 0 would be  no correlation and 1 a perfect correlation – and,  

on average, my sleeping heart rate is about 9  beats per minute lower than my resting heart rate.  

So it does seem plausible, given that resting  heart rate is a good measure of overall health  

and fitness, sleeping heart rate could be too. %%r = 0.849, r^2 = 0.72%%

Another study I found correlated sleeping heart  rate and resting heart rate across 600 people,  

and found an R squared of 0.25 – meaning that,  between people (rather than just within me),  

they are related, but not quite as strongly.  But actually, the fact that sleeping and  

resting heart rate aren’t perfectly correlated  might be because sleeping heart rate is better:  

the study found that sleeping heart rate was a  more accurate predictor of risk of death and risk  

of heart disease than the daytime resting heart  rate was. This is just one study, compared to the  

huge weight of evidence for we’ve got for resting  heart rate – but it does seem possible, maybe even  

plausible, that sleeping heart rate could be a  pretty decent measure – and that would be a happy  

coincidence for device manufacturers, who find it  easier to measure your heart rate at that time.

Historically, it’s been very hard to measure  heart rate overnight in a large population,  

because you’d have needed to strap them up with  expensive medical equipment – it was far cheaper  

and easier to take a one-off measurement  sometime during the day. But of course,  

wearable technology now means that we can monitor  heart rates in huge numbers of people 24/7,  

so hopefully new studies will shed some more  light on this – and I wouldn’t be shocked if  

sleeping heart rate did turn out to be better  than conventional waking resting heart rate.

The trouble is, until we have those studies and  we come up with some kind of standard, it’s really  

hard to compare values between manufacturers,  devices and the normal medical recommendations.  

And all that means, for now, many of the leading  device manufacturers are at best confusing,  

and at worst misleading their customers.  

So, share this video with any friends who use one  of these fitness-tracking wearables – especially  

if yours is a Fitbit and theirs is an  Oura Ring. Or Apple Watch. Or Garmin.

Watch more videos from my series  on smartwatches here or, speaking  

of algorithms, the YouTube algorithm  thinks you’ll enjoy this video next!