HRM vs BMR confusion

SDkitty

Hi everyone, I apologize if this has been asked a million times but I am at work and can't search all the threads pertaining to HRMs right now. I feel like this must be a very dumb question but I am confused. I just recently finally purchased a HRM (FT7) and out of curiousity wanted to wear it while I was sleeping to see how accurate my bmr is (1467). I slept for 6 hours and my HRM said I burned 105 calories. Doing the math that would mean that if I did nothing for 24 hours that I would burn 420 calories which is obviously not correct so what does BMR actually factor? I was under the impression that our BMR was literally the amount of calories our body burns just to stay alive? So does this mean that my HRM is not accurate or does it just not work while sleeping?

Like I said, I must be missing something very simple because it sounds stupid when I say it. LOL :flowerforyou:

SDkitty

Wow. Must be a dumber question than I thought if no one at all responds

aprilgicker

I would have to say it slipped. Try wearing it through your waking day that way you can check it every now and then.

Don't worry about the post some just get cycled down without answers.

Captain_Tightpants

Yeah, it probably moved in your sleep. Your BMR is way above 420, unless you're a smurf.

erickirb

HRMs are not accurate when you are not doing steady state cardio. Usually at rest it will over estimate your burn, so my guess is that the sensor was unable to track you HR all night.

What you are trying to do is not how HRMs are designed to work and therefore will not give you what you are looking for.

LorinaLynn

I've heard that HRMs aren't terribly accurate unless you're doing cardio, in terms of them not being accurate to wear during strength training. So, if that's the case, then I wouldn't expect them to be accurate for sedentary "activities" either. There are some that are meant to be worn around the clock but unless yours is one that's marketed as such, I'd say it's not anywhere near accurate for that.

Edit: What Erick just said.

lordbyron46

My BMR is 2600 a day, I'm Male 37yrs old, with exercise Im only eating around 300 a day, BMR means what we would burn if we slept for 24hours and did nothing else. 420 is 100% wrong !!

iKristine

Oh dear.

First off, the HRM are not meant to be used while sleeping. Sure they will produce a number, but they don't report accuracy.

They are to be used during activity of some kind. And now I feel the need to set examples (running, jumprope, elliptical etc)

Besides this your cal burn changes nightly based on the activity prior, and can even change every few hours. Example I burn 1.4 cl minute asleep, sometimes it bumps down to 1.1 or 1.3.

BodyBuggs, MediFit bands record (key word) your cal burns nightly. They are accurate for the most part.

"I was under the impression that our BMR was literally the amount of calories our body burns just to stay alive" -- correct.

SDkitty

My BMR is 2600 a day, I'm Male 37yrs old, with exercise Im only eating around 300 a day, BMR means what we would burn if we slept for 24hours and did nothing else. 420 is 100% wrong !!

I am well aware that 420 was 100% wrong, hence the post and confusion. Thank you everyone for confirming that it is inaccurate while at rest. I had just assumed that it would be accurate for all heart rates *facepalm*. I was mostly just curious how accurate BMR calculators really are :bigsmile:

According to my BMR x 1.2 I burn around 75 calories an hour which seems about right I guess

erickirb

My BMR is 2600 a day, I'm Male 37yrs old, with exercise Im only eating around 300 a day, BMR means what we would burn if we slept for 24hours and did nothing else. 420 is 100% wrong !!

I am well aware that 420 was 100% wrong, hence the post and confusion. Thank you everyone for confirming that it is inaccurate while at rest. I had just assumed that it would be accurate for all heart rates *facepalm*. I was mostly just curious how accurate BMR calculators really are :bigsmile:

According to my BMR x 1.2 I burn around 75 calories an hour which seems about right I guess

The reason why they are not accurate at rest or doing anaerobic (weights/sprints) is that the calculation in the HRM assumes a certain oxygen uptake that happens during cardio. It uses this along with your HR (estimation of intensity) and your age, gender, weight, height to estimate caloric burns. During weights your HR is elevated for a difference reason so the estimated oxygen uptake would be wrong, and during rest your HR is not elevated so again the oxygen uptake portion of the calculation used would be wrong.

lauehorn

Oh dear.

First off, the HRM are not meant to be used while sleeping. Sure they will produce a number, but they don't report accuracy.

They are to be used during activity of some kind. And now I feel the need to set examples (running, jumprope, elliptical etc)

Besides this your cal burn changes nightly based on the activity prior, and can even change every few hours. Example I burn 1.4 cl minute asleep, sometimes it bumps down to 1.1 or 1.3.

BodyBuggs, MediFit bands record (key word) your cal burns nightly. They are accurate for the most part.

"I was under the impression that our BMR was literally the amount of calories our body burns just to stay alive" -- correct.

^^^ This

HRM aren't intended for using all day and all night. They are for cardio activities and most sensors have to stay moist to be effective (ie. while you sweat, this isn't a problem).