Wrist based HRM vs Chest straps...getting VERY different readings

Dynetha

For example: when wearing the apple watch, I can do 30 minutes on the elliptical and will get a reading of 500 calories burned.

But when I workout with my Polar watch with the chest strap doing the same exact workout, the polar will tell me I've only burned about 300 calories. I mean, the difference between the chest strap and apple watch is always at least several hundred calories, with the wrist base tracker giving me a larger burn. The apple watch does keep up with my heart rate almost to a T because i tested it out but it's just the estimate of calories burned that concerns me.
The longer and more intense my workouts are, the larger the gap gets with apple shooting out huge calorie burn numbers and polar falling behind by several hundred.
I don't mind burning lots of calories BUT I'm trying to lose weight and it would be really helpful to know how hard i'm working or if i'm not working hard enough as far as exercise.
(yes i know nutrition is more important lol)
what do you guys think?

Stockholm_Andy

Is your profile set up correctly on both devices? Current weight, height, age etc?

Both (all) devices use proprietary algorithms to estimate calories burned from HR and your stats. They will all have some variance but 200 odd calories over 30mins seems way too high.

yirara

Well, first of all calorie burn is not related to heartrate. So I would certainly go with the lower number if with anything at all. Secondly, unfortunately optical sensors, like on the watch don't work well with darker skin colours, lots of body hair or very thick skin as those sensors need to 'see' your blood vessels.

rossmonty

I'd take the chest strap any day its more consistent good luck

MeanderingMammal

Dynetha wrote: »

The longer and more intense my workouts are, the larger the gap gets with apple shooting out huge calorie burn numbers and polar falling behind by several hundred.

The issue is not electrical detection of HR vs optical detection of HR, but that the Polar and Apple devices guestimate a calorie expenditure based on HR in different ways, coupled with HR being a poor proxy for calorie expenditure on an elliptical.

Neither of them are correct, I'd suggest that 300 calories in 30 minutes is significantly over-optimistic.

dougii

>Neither of them are correct, I'd suggest that 300 calories in 30 minutes is significantly over-optimistic.<

That is dependent on many factors: body weight, resistance level, steps per minute, etc. When I set the elliptical to a resistance level of 8 or higher and really crank up my steps I have no problem burning ~10 calories a minute. I have others tell me that I am doing more of a strength workout rather than a cardio when I do my version of HITT on the elliptical.

MeanderingMammal

dougii wrote: »

...I have no problem burning ~10 calories a minute.

And how are you measuring that expenditure?

robertw486

Personally I don't put much faith in any device that I can't determine has an accurate way to measure actual power. Even the HR monitors that are "calibrated" to a person via testing and such have the flaw that the major input they rely on is the heart rate rather than the rate of work.

If you tested your devices against something with some science and/or testing to back it up, you might see how close either of them come. If neither one is close, you might be able to find a better way to calculate your calorie burn.

aokoye

I highly doubt the issue in this case is wrist vs chest based HR monitors rather Apple vs Polar. I mean unless there is an actual appreciable difference your heart rate reading (as opposed to calorie estimate). There are definitely areas where wrist based HR monitors are a joke (bikiing outside being a big one) but it isn't clear that that's the issue in your case.

BitofaState

The setting in each may be triggering the differences.

HRM’s use heart rate as a substitute for oxygen expenditure so they need to know or have a good estimate for your max HR and VO2 max. Check that both devices are using the same settings for these. If they have a lower max HR or VO2 max they will give a higher calories consumption.

In Polar at least you then have an adaptive map that requires the appropriate exercise type to be entered as HR is dependant on the muscles being utilised, again if the devices assume you’re doing different things they’ll give different readings.

Ultimately these are estimates and you need to see if over the long term you get the response between the TEE estimate and consumption when tracking using MFP. Without a full lab being able to monitor your VO2 expenditure during exercise or a doubled labelled water study to monitor consumption and expenditure you have to start with the estimates and adjust to get the results you want.

What HRM’s are good for is finding your max HR https://www.polar.com/blog/calculate-maximum-heart-rate-running/ and then making sure you’re working out at an appropriate level based on your goals..

BrianSharpe

Heart rate monitors extrapolate time and heart rate into an estimated calorie burn and given that there's not a correlation between heart rate and calories expended they're not, generally, terribly reliable.

Personally I'd dismiss any device that suggested I was burning 1,000 calories per hour unless I was able to sustain a running speed of 8mph for an hour (I have done 7ish minute miles over a distance of one mile, but not over longer distances).

Each company uses proprietary algorithms for their estimates, if your goal is weight loss I would definitely go with the lower number and monitor my progress. If you're not losing weight (or losing too quickly) go back and re-evaluate.

HoneyBadger302

I use the Polar H10 along with the app. Thus far, the calories burned seems fairly accurate - and by accurate, I essentially eat back my exercise calories, and at a slight deficit from non-exercise needs, am recomping (with a very slow overall weight loss) at a reasonable rate. It also seems pretty on point with what I've historically noticed I seem to burn when I've tracked in the past.

Be sure all your settings are current, and you are choosing the right exercise, and you start and stop it when you start and stop the activity.

Sounds like the watch, however, is way overestimating for you, and I'd definitely go with the lower number.

BitofaState

BrianSharpe wrote: »

Heart rate monitors extrapolate time and heart rate into an estimated calorie burn and given that there's not a correlation between heart rate and calories expended they're not, generally, terribly reliable.

There is a correlation between HR and calorie burn through VO2max, so it's not quite correct to say that HRMs aren't reliable in estimating calorie burn during aerobic exercise. In most cases they will be precise, but may not be accurate (that is give a consistent reading across the same exercise, but that reading may not be the "true" calorie expendature)

https://www.ncbi.nlm.nih.gov/pubmed/15966347

The challenge is getting a reasonable estimate for an individuals VO2max as that varies with training history and genetics. It's possible to have this lab tested if the readings seems way out, but based on the OP's question it's surely best to monitor their net calorie expenditure vs. weight loss over a reasonable period and adjust based on that.

MeanderingMammal

BitofaState wrote: »

BrianSharpe wrote: »

Heart rate monitors extrapolate time and heart rate into an estimated calorie burn and given that there's not a correlation between heart rate and calories expended they're not, generally, terribly reliable.

There is a correlation between HR and calorie burn through VO2max, so it's not quite correct to say that HRMs aren't reliable in estimating calorie burn during aerobic exercise. In most cases they will be precise, but may not be accurate (that is give a consistent reading across the same exercise, but that reading may not be the "true" calorie expendature)

https://www.ncbi.nlm.nih.gov/pubmed/15966347

The challenge is getting a reasonable estimate for an individuals VO2max as that varies with training history and genetics. It's possible to have this lab tested if the readings seems way out, but based on the OP's question it's surely best to monitor their net calorie expenditure vs. weight loss over a reasonable period and adjust based on that.

I think it's worth pointing out that the correlation isn't linear, with two significant inflections. I'd also note that the relationship relies on the metric monitored remaining steady state. As soon as HR starts to vary errors are injected into the extrapolation.

With respect to accuracy cf precision, I'd add the third essential point; repeatability. Using a consumer grade HRM isn't going to offer accuracy or repeatability. The latter being essential for medium term trend based decision making.

_mr_b

You say yourself that both are recording similar HR data ... so the issue isn’t wrist vs strap for measurement it’s Apple v Polar.

I would suggest that Polar would have the upper hand in this as that’s what they do, the Apple Watch being more of a ‘jack of all trades’.
Either way, from a weight loss perspective you would be best taking whatever the lower reading is.

Might be worth checking the setting between the two too.