HRM Accuracy?

Typically running burns more calories than riding a bike from what I have read and my own experience, but it depends on how hard you ride the bike. Since the Polar is measuring calories by your heart rate response make note of your pulse riding versus running. If your heart rate is similar then according to Polar calories should be similar. Personally I can get my heart rate to 190 by running and hard to get above 150 when riding but it all depends on the person I guess.

Soooo I use my HRM for all cardio. I've noticed some discrepancies. For instance, when I run, I burn an average of about 100 calories per 10 minutes. I am moving constantly so I don't doubt the accuracy of the HRM. However, I've noticed that when I'm bike riding I burn a very similar amount of calories according to the HRM. I somehow doubt the accuracy because there are multiple periods of time when I'm not pedaling at all (going downhill), and then there are often periods of intense pedaling (uphill). In this way, riding a bike is more like interval training I guess.

The thing is, I am much more spent after a 30 minute run than a 30 minute bike ride, even though the HRM tells me I've burned a comparable amount of calories doing each. I know I may seem nitpicky here, but losing fat is all about math, and I'd like to make sure my math is as close to accurate as possible.

Should I believe the HRM on bike riding and other cardio activity that isn't constant (such as P90X Plyo)?

P.S. - I'm using a Polar FT7

HRM's are widely used by athletes in both activities and I've never seen any discussion of an HRM being less in accurate for one sport than for another.

Both activities have the ability to burn large amount of calories because you're engaging "big muscles" — quads, hammies, and glutes — and both have the potential to elevate the HR significantly so both exercises are a good candidate for getting calorie estimates from an HRM.

An issue that you might want to consider is that your values are just estimates and, you can expect that the estimates are 10 to 20% above or below of the true value.

"I know I may seem nitpicky here, but losing fat is all about math, and I'd like to make sure my math is as close to accurate as possible."
The most accurate estimates that I've been able to find (for less than $1k of hardware and software) is by using FirstBeat Athlete and a high end HRM. FBA is software from FirstBeat.fi (it's about $70) and, when it's coupled with an HRM that does R-R recording, you will get to 5 to 10% inaccurate. The only HRM's that do R-R are the high end Suunto, the Polar 800, and the Garmin 610. The Suunto and the Polar do R-R right out of the box but you have to download a FIT file to the 610 to enable R-R because Garmin does not admit that the 610 even does R-R. If you want help with the 610, contact me off line and I'll walk you through the R-R set up process.

One of the interesting things about FBA is that I analyzes the percentage of fat vs carbs you've burned during a run.

I also want to do some experimentation to see if I can determine if water consumption in the early stages of a long run impacts cardiac drift.

FBA is an interesting piece of software and, coupled with R-R, gives significant insight into what's happening on the inside.

They are all just estimates, treat them as such and move along. No sense worrying about it since there's no way to know how accurate they are in the first place.

Only have to go 9mph (that's only a 6.66 min mile) to burn 976 cals per hour according to the MFP database.

Okay...I don't run, so this situation may not parallel yours. If I do a 60 min. Jazzercise class and do full on high impact, according to my HRM, I burn less than if I do the same class alternating high impact with low impact. I think it is the whole interval thing and it is very effective. I am less tired after a class where I alternate the impact, but have burned more calories.

Okay...I don't run, so this situation may not parallel yours. If I do a 60 min. Jazzercise class and do full on high impact, according to my HRM, I burn less than if I do the same class alternating high impact with low impact. I think it is the whole interval thing and it is very effective. I am less tired after a class where I alternate the impact, but have burned more calories.

HRM's do not work for intervals. unless those intervals are still in the cardio zone, then they do. But if you're sprinting, then walking for example. Don't even both with the HRM, it's number might as well be random.

Maybe what I am describing is not technically interval - wrong term to use. I'm not referring to HIIT. I am definitely in the aerobic zone the whole time I am alternating high impact with low impact for about 3 minute routines each time. My heart rate is probably in the 140-155 bpm for high impact and in the 125-140 range for low impact.

However, now I'm wondering if my HRM is accurate for the whole 60 min. since the last 15 min. of class is strength work. Honestly, I don't think it matters that much because I eat back only 1/2 - 2/3 of my exercise calories in case of errors in HRM accuracy and errors in weighing/measuring, and to cover the few things I don't track like a piece of sf gum, etc.

then sounds like you're doing things properly. and yes, I would consider that accurate reflection of work done and a smart way to go about calories too.

the issue with inaccuracy is that heart rate and calorie burned ONLY have a correlation while you're actively doing cardio. If you take breaks, then your heart rate will stay elevated, but your body is not actually working. thus it's not burning exercise calories. So the heartrate monitor gets a false reading as your heart will still be beating rapidly for a while. Sorta same thing with weights. Your heart rate has 0 correlation on calories for any sort of resistance training as resistance training does not use oxygen to do work. And a HRM is in essence a oxygen correlation tracker. No oxygen, no accurate calorie burn numbers. Same thing with low impact exercises. the lower the impact, the more the fatty acid energy system works to power the muscles. A SUPER energy efficient system that makes a buttload of ATP. And while it does use oxygen, the formula the HRM uses is order of magnitude to high for it to be accurate.