HRMs for measuring strength training caloric burn

Bry_Fitness70

I have been using a Heart Rate Monitor (HRM) for nearly several years to calculate my calories burned during exercise. It is a wrist HRM that connects via Bluetooth to a fitness application on my smart phone. The app uses my personal data entered (sex, height, weight, age, etc.) along with the HR data to calculate the number of calories burned during the various workouts that I do.

One guideline that seems to be universally accepted is that HR data is only accurate when it comes to measuring “steady state” exercises, i.e., something like running or cycling. Exercise that entails movement interrupted by breaks, like strength training, cannot be accurately measured with HRMs, so an estimation should be utilized.

I found this curious, because there is residual calorie burn between movements. For example, if I do a set of bench presses, my HR escalates, and my caloric burn increases. I take a break between sets, my HR decreases, and my caloric burn decreases. Given this dynamic, I have used an HRM to measure my calories burned during strength training. If nothing else, using the fitness app captures the exercise, date, time, and duration of my workouts, so is useful for documenting my fitness regiment.

Recently, I downloaded a big block of data from MFP and dumped it into a database for analysis. I filtered my exercise data to display the strength training entries to the period when I began HRM training, and 232 events were displayed. I summed the total calories burned (63,388) and total minutes (9,270). Using these totals, the average calories burned per minute was 6.83. I then went to MFP, added strength training, entered 1 minute of exercise, and the application calculated 7 calories per minute (other sources I have found estimate between 5-9)

So the bottom line is that the HRM calculated burn was 6.83 vs 7.00 for MFP’s guesstimate, a variance of .17 calorie per minute. Taking into account the size of the sample, I think I can reasonably conclude that my HRM provides an acceptable level of accuracy in calculating calories burned.

Spliner1969

I believe my HRM and App combo does a good job. I have been using them for over a year and find them to be accurate on both cardio and other training I do. Weight training, maybe, but I use it to calculate calories burned doing cross fit/cross training in which I have very little rest between exercises and find it to be at least 80% accurate, possibly higher. It all depends, for me anyway, on whether or not I can keep my heart rate above 100bpm. If I can it is pretty accurate, if I can't keep it high enough I will work harder to keep it higher. Works for me anyway. Mine is a Polar H7 chest strap.

NorthCascades

Bry_Lander wrote: »

One guideline that seems to be universally accepted is that HR data is only accurate when it comes to measuring “steady state” exercises, i.e., something like running or cycling. Exercise that entails movement interrupted by breaks, like strength training, cannot be accurately measured with HRMs, so an estimation should be utilized.

...

So the bottom line is that the HRM calculated burn was 6.83 vs 7.00 for MFP’s guesstimate, a variance of .17 calorie per minute. Taking into account the size of the sample, I think I can reasonably conclude that my HRM provides an acceptable level of accuracy in calculating calories burned.

Two comments.

Cycling is often a type of exercise that involves breaks. That's why we use power meters. And freewheels.

You've demonstrated that your HRM comes up with numbers similar to MFP's, but MFP's calorie burn estimates are not highly respected for their accuracy.

Edit to add one more comment: I wear a chest strap when I do strength training but ignore the calorie suggestion. I just want to see/record my body's reaction to the work I'm doing.

Bry_Fitness70

NorthCascades wrote: »

Bry_Lander wrote: »

One guideline that seems to be universally accepted is that HR data is only accurate when it comes to measuring “steady state” exercises, i.e., something like running or cycling. Exercise that entails movement interrupted by breaks, like strength training, cannot be accurately measured with HRMs, so an estimation should be utilized.

...

So the bottom line is that the HRM calculated burn was 6.83 vs 7.00 for MFP’s guesstimate, a variance of .17 calorie per minute. Taking into account the size of the sample, I think I can reasonably conclude that my HRM provides an acceptable level of accuracy in calculating calories burned.

Two comments.

Cycling is often a type of exercise that involves breaks. That's why we use power meters. And freewheels.

You've demonstrated that your HRM comes up with numbers similar to MFP's, but MFP's calorie burn estimates are not highly respected for their accuracy.

Edit to add one more comment: I wear a chest strap when I do strength training but ignore the calorie suggestion. I just want to see/record my body's reaction to the work I'm doing.

Thanks for the comments

1) Maybe I should have stated "spinning" instead, where the peddling is continuous (or at least it is when I do it).

2) I also stated that other sources estimate strength training caloric burn at 5-9 calories per minute. I didn't list links, but they are easily found by doing an internet search.

My stats, as I interpret them, show consistency, which can be interpreted as having validity. I prefer measuring rather than using general tables figures, and I think that using my methodology is a reasonable way to measure burned calories for strength training.

Sued0nim

@azdac wrote this 6 years ago, still mainly relevant (apart from top end HRMs)

http://www.myfitnesspal.com/blog/Azdak/view/the-real-facts-about-hrms-and-calories-what-you-need-to-know-before-purchasing-an-hrm-or-using-one-21472

BusyRaeNOTBusty

But how long does it take for your heart rate to drop after a set? 30sec, 45? I only rest for a minute or two

Sued0nim wrote: »

@azdac wrote this 6 years ago, still mainly relevant (apart from top end HRMs)

http://www.myfitnesspal.com/blog/Azdak/view/the-real-facts-about-hrms-and-calories-what-you-need-to-know-before-purchasing-an-hrm-or-using-one-21472

Yeah, this is the source I've always referred to.

AnvilHead

Sued0nim wrote: »

@azdac wrote this 6 years ago, still mainly relevant (apart from top end HRMs)

http://www.myfitnesspal.com/blog/Azdak/view/the-real-facts-about-hrms-and-calories-what-you-need-to-know-before-purchasing-an-hrm-or-using-one-21472

Thank you for linking that! I'd been looking for it for a while and wasn't able to dig it up. Bookmarked for future reference.

NorthCascades

Bry_Lander wrote: »

My stats, as I interpret them, show consistency, which can be interpreted as having validity. I prefer measuring rather than using general tables figures, and I think that using my methodology is a reasonable way to measure burned calories for strength training.

If you're satisfied with your methodology and results, it doesn't matter what a bunch of idiots on the internet think.

I agree that it's better to measure than to use generic tables. I personally think strength training is an exception because the way your muscles get the energy they use to lift works differently from the way your muscles get energy for cardio exercises, so the programming assumptions should not pan out. But again, you shouldn't care what I think, especially if your numbers don't bare out what I'm saying.

Bry_Lander wrote: »

1) Maybe I should have stated "spinning" instead, where the peddling is continuous (or at least it is when I do it).

Outdoors, cycling is usually anything but steady. And good HRMs do a good job anyway. Which kind of suggests that you might be on to something.

NorthCascades

Sued0nim wrote: »

@azdac wrote this 6 years ago, still mainly relevant (apart from top end HRMs)

http://www.myfitnesspal.com/blog/Azdak/view/the-real-facts-about-hrms-and-calories-what-you-need-to-know-before-purchasing-an-hrm-or-using-one-21472

I don't understand why "METs" would be involved in any way in this calculation?

For example, we know that 70% of HRmax is equivalent to approx 57% of VO2max. If we know that person's VO2 max is 12 METs and they are working at 70% of HRmax, we can estimate that they are working at (57% x 12 METS) or 6.8 METs. If that person weighs 80 kg, we can estimate that they are burning ~545 Cals/hour (MET value x Body wt in kg).

VO2max is the upper limit to how much oxygen (by volume) a person can use at a particular type of exercise. If we know a person's VO2max, we'll know it as, say, 55 ml/kg/minute.

Also the same individual has different VO2max numbers for different activities. Most people have a higher number for running than for cycling, mine is 6 points higher.