HRM Accuracy

bigblondewolf

I'm posting because I'm wondering if my new HRM is faulty. It's told me I've burned a total of 1,437 calories today between day one of the C25K program I did this morning along with about 45 minutes of weight lifting, and then I took my dog for a hike of just over an hour after. And yes I did stop the monitor after each workout so it's not like I had it running for hours.

I checked and my stats have been programmed into the watch accurately. Female, 25, 156lbs 5 foot 4in just in case it helps. I'm pretty new to both running and weights and I know you burn more cals in the beginning but that number seems nuts.

Also, assuming it is correct. How the heck do I eat back that many calories? My diary is public. I've been trying my best but generally I only eat between 1300-2000 when I'm working out. I've already eaten 1150 today and I don't think I can do the full 1676 it says I have left. Haaaalp!

StraubreyR

Everything is an estimate, even an HRM. It's just a better estimate! Could you burn that many calories? Sure. If I ride my bike for 3 1/2 hours, I can burn 1500 calories. I have switched to the TDEE - 20% method. You base your calorie intake on your weekly activity level including exercise, and don't eat back any exercise calories. I like it better as I eat the same amount of calories each day.

goldmay

That number can be accurate depending on your intensity. Did you re-wet the chest strap in between workouts? If it was dry it could be less accurate. I've also heard it's also only accurate for cardio, not lifting.

RosieWest8

Are you able to look at what your average heart rate was on your HRM? If you can you can use a few other calories-burned-heartrate websites to calculate how many calories were burned and see if the numbers seem more or less close. I'd check that and then if your HRM calculation is way off then there is probably something set wrong or it's got an issue. I always used this site once I did a workout with my HRM:
http://www.shapesense.com/fitness-exercise/calculators/heart-rate-based-calorie-burn-calculator.aspx

Not saying it's exactly accurate but I used this method when I was tracking food/calories burned and I was consistently loosing weight so I guess it was close enough.

As far as eating back those calories...if you're actually burning that much, then I'd try to eat back what I could (and it's fine to try another method as the other person suggested where you don't have 'eat back' calories as long as you know you are getting enough cals during the day). You might need to invest in some calorie dense snacks to keep around like dried fruit or nuts, nut butters, or avocados. Ha, let yourself have more butter/oil if you want.
I used to keep dried cherries and walnuts on hand to munch if I was low on cals....good for you but a good calorie punch. And that way you don't have to eat A LOT of food to get a good amount of calories.

TheWorstHorse

This is a good question. And it comes up a lot on MFP. Here's one thing to read about HRM accuracy:

http://www.myfitnesspal.com/topics/show/1314142-calculating-calories-burned

I know, shameless self-promotion. If you search the forums, you will find lots of other posts on using a HRM to estimate calories burned.

And if you are burning that many calories, the answer to your question depends on how many times a week you work out at that level. If it is once a week, make the calories up over two days. If you are burning this many calories three or four times a week, it gets harder. You just have to eat more to cover the exercise calories. An Olympic-class athlete often needs 6000 or 7000 Kcalories a day; when they aren't working out, they are probably eating.

However you make it up, my suggestion is to eat good quality food like fresh fish and chicken, minimally processed nut butters, and whole grains, and legumes rather than fast food. That way your body is getting all the nutrients (micro and macro) it needs to be healthy.

November_Fire

It will grossly overestimate when you did the lifting, because it only goes off your heart rate, not what you're actually doing. I could wear it while my child has a tantrum, or during a scary movie, and though my heart rate is skyrocketing I'm not actually running a marathon, so I didn't burn 70 cals just listening to a toddler tantrum. I can make my heart rate rise just thinking scary thoughts (try it, it's fun) but it isn't burning. Weights are the same way - your heart rate will be doing one thing, but the calorie burn from weights comes during repair. So don't wear it for that. It gives huge numbers. They monitor steady-state cardio - ie: you're doing the same cardio-ish thing for a period of time. You can google 'heart rate monitor and strength training' for a more sciency answer.

Also ensure you've set it to your own base heart rate. Mine was set at a base of 60 bpm, and told me I burned a bajillion calories during exercise because, to the machine, me going from 60 up to 100 was a leap of 40. However my base rest rate is actually 85-90 - no, I've no idea why - so going up to 100 wasn't really that epic at all. Once I'd set the base rate properly, it gave a lower calorie burn for my cardio, but the numbers all match up for weight loss/gain/maintain so chances are they're correct.

Running and hiking give me dead good numbers. 249 cals this morning doing C25K #2, 350 on an hour's hike, sounds similar to my figures. We're a similar size. So, the lifts aside, it's probably right.

bigblondewolf

I didn't re-wet the strap but I was working out at a pretty serious intensity for myself so the band was soaked in sweat and I didn't take it off between exercises.

_Terrapin_

c25k is a 30 minute program of running and walking; assume you went 2.5 to 2.7 miles, so 250 to 270 calories. The dog walk add 100 calories for each mile, assume 3. So 300 calories. The weight lifting depends on what you did; heavy strenuous compound lifting or what? So far, 550 to 570 calories as estimates. Lifting burns less calories then running, and HRM ought to be used for steady state cardio to provide an estimate. You didn't burn 1400 plus calories.

bigblondewolf

c25k is a 30 minute program of running and walking; assume you went 2.5 to 2.7 miles, so 250 to 270 calories. The dog walk add 100 calories for each mile, assume 3. So 300 calories. The weight lifting depends on what you did; heavy strenuous compound lifting or what? So far, 550 to 570 calories as estimates. Lifting burns less calories then running, and HRM ought to be used for steady state cardio to provide an estimate. You didn't burn 1400 plus calories.

But if this is true than what good is a heart rate monitor? I was under the assumption that a HRM would give me a more accurate picture of what I was burning.

brianpperkins

c25k is a 30 minute program of running and walking; assume you went 2.5 to 2.7 miles, so 250 to 270 calories. The dog walk add 100 calories for each mile, assume 3. So 300 calories. The weight lifting depends on what you did; heavy strenuous compound lifting or what? So far, 550 to 570 calories as estimates. Lifting burns less calories then running, and HRM ought to be used for steady state cardio to provide an estimate. You didn't burn 1400 plus calories.

But if this is true than what good is a heart rate monitor? I was under the assumption that a HRM would give me a more accurate picture of what I was burning.

It is a more accurate picture as long as you use it in the way it is designed. They are programmed for steady state cardio activities ... not intervals which is what C25K really is. They are not programmed for weight lifting.

Basically there is an established relationship between oxygen uptake, heart rate, and calories burned for certain activities based upon lab testing (usually of fit people). When you do any other activity, the math does't apply for caloric burns.

Most HRMs, even cheap ones, are great at tracking heart rate which is its own data point to evaluate and assess over time.

_Terrapin_

c25k is a 30 minute program of running and walking; assume you went 2.5 to 2.7 miles, so 250 to 270 calories. The dog walk add 100 calories for each mile, assume 3. So 300 calories. The weight lifting depends on what you did; heavy strenuous compound lifting or what? So far, 550 to 570 calories as estimates. Lifting burns less calories then running, and HRM ought to be used for steady state cardio to provide an estimate. You didn't burn 1400 plus calories.

But if this is true than what good is a heart rate monitor? I was under the assumption that a HRM would give me a more accurate picture of what I was burning.

Yes, if you do steady state cardio, so 2 of the 3 activities, sure. But an easy average are the ones I provided. And accuracy and estimation go together like oil and water. 50 up or 50 down when you think 1,400 was your burn. . .think about it. And a heart rate monitor is great to now your average heart rate during cardio work. It is a great way to study and understand your how your heart is reacting to being stressed. It is also useful to measure you VO2 max if you have model for it. So, there are many uses for it, not just calories burned. Hope this helps.

MBrothers22

They are not accurate for lifting weights. Only use them for steady cardio like running and biking or whatever else where your heart rate isn't jumping and falling rapidly.

I'd also recommend taking 10% off what it says just to be safe because they aren't 100% accurate, just the closest you can get. It's what I do at least

SKME2013

Apparently there are quite huge differences between heart rate monitors. I don' know which one you have, but mine is pretty accurate. I have the Polar multi sports watch RCX5 with H7 and H2 heart rate straps. What makes it more accurate is that my watch allows me to do a personal fitness test, measuring my resting heart rate, VO2 Max and other parameters.

So it depends on what model you are using.
Stef.

November_Fire

But if this is true than what good is a heart rate monitor? I was under the assumption that a HRM would give me a more accurate picture of what I was burning.

It does, for cardio. No electric doohicky can gauge the calories of strength training. It's why people are still arguing about how much strength training actually burns (some say 'nothing!', others says 'millions!', and others have the data - training done versus weight lost - that shows it's 'quite considerable if you work hard'.)

bigblondewolf

Thanks so much for the explanations everyone. I'll be sure to take my HRM results with a grain of salt from now on lol

cwolfman13

Your HRM isn't going to be of any use for calorie burn during weight training...it is only relatively accurate for a steady state aerobic event. Also, if you are out of shape, your HR is going to be higher than someone who is in shape...most of these are calibrated using statistical averages of fit individuals...so your higher HR is going to artificially inflate your calorie burn. As you get more fit, your monitor will be more accurate. Even then, it's an estimate and you'd at minimum want to knock off your basal calories.

When I was doing the MFP eat back method I knocked off around 20% from whatever my HRM told me for a steady state aerobic event....I never used it for weight training because it is pretty much worthless for that activity as I stated before.

Also, while your number is somewhat inflated, you probably did burn quite a few calories...that's a lot of exercise. You have to begin to understand the relationship between your activity and your calorie requisites. When I'm training for a cycling event for example, I often need around 3,000 calories...and that's to keep my rate of loss at around 0.5 - 1 Lb per week. This is where a lot of people go wrong...they think they have to do all of this exercise and whatnot but don't understand how to properly fuel their bodies.