Running calories are way off

So I tried my new HRM today. I did 33 minutes on the treadmill (5 minutes warmup, 28 minutes running af 5 mph, then 5.2 mph). I've been using the machine's calorie count. It had me at over 300 calories used. But my HRM said I only used up 276. That's a BIG difference!!! Have I been over estimating my calorie burn? Is this happening on all the exercising that I do? The treadmill was right on target in terms of my heart rate, however. Then how can it be so different? No wonder I've only lost 1 1/2 lbs in the last month!

Anyone else have this problem? pre and post HRM use?

Normal.

I've always heard that machines over estimate cal burned, so I usually take that into account
I have an at home treadmill and burn about 500 cals in 45minutes doing 3, 3 minute sprints ay 7.5 and light jogging/walking..I also pump the incline to 4.0

There was another poster on here (Gosh, I can't remember her name, now) that once stated that in order to get an accurate number on a machine, take the number of calories burned and subtract 10%.

So, if the machine said 300 calories, subtract 30 cal (10%), which would be 270.

It doesn't exactly match, but it may explain the difference.

Does your machine have a HRM in it or does it just estimate based on height/ weight? That may also play a role in the number it displays.

I have a timex HRM and when I got it I compared it to the Precor Treadmill that I walk on. The heart rates tracked pretty evenly, but the Timex HRM calculated the calories as much higher. I actually e-mailed Timex and we did the math, and the HRM was performing to spec, its just their calculation is probably way too generous. If I were a person who ate back their workout calories, I would probably end up gaining weight!!!! I find to this point not eating my workout calories is working for me. If I were eating my workout calories back, I would definitely try to figure out what percentage of these calculated calories I should eat.

All that said, the HRM is a great tool for me to compare the different exercise's effectiveness, and to see the progress I am making in my workouts, such as today's treadmill work out, I burned 50 less calories, and happened to have walked faster than I normally do, so I realize I'm getting more fit by the minute!! Hooray

Whenever I work out on a machine - I enter my weight but take about 15 punds off (I actually weigh 150 so I put in 135) and I read somewhere, that that will give you a better, more accurate calorie count. : ) I'd rather underestimate than embellish.

First of all, heart rate monitors are an estimate of calories expended--they do not measure ANYTHING directly other than heart rate. They assume a relationship between percentage of max heart rate and calorie expenditure, which has it's own built-in error factor.

To say a machine is "way off" because it does not agree with your HRM is a false assumption. There is little or no empirical evidence that would establish that an HRM calorie estimate is more accurate than a machine reading. Both use the same basic idea: test a selective representative group of subjects and use the data to establish algorithms that are extrapolated to the general population, with the inherent accuracy limitations associated with that method.

Treadmills are usually the most consistent, even though they almost certainly overestimate calorie expenditure. That is because there are well-established, well-validated equations for calculating energy expenditure while walking or running on a flat surface or on an incline. These are easy to program into even a cheap treadmill. I know for a fact that my treadmill calorie readout matches the ACSM equations exactly. The overestimation comes from the fact that there is no wind resistance with a treadmill and more "bounce" in the deck, as compared to running/walking on solid ground.

Bikes have pretty well developed equations, too, but you are more dependent on the quality and calibration of the resistance mechanism.

Cross trainers show the greatest variability because there is no set definition of movement or resistance. There is no way to accurately "calculate" calories burned, so manufacturers must do their own studies for each machine. That can be costly and I suspect many lesser-name brands don't bother. I know that Life Fitness, for example, directly tests calorie expenditure on every new piece of cardio equipment they develop.

I have found it difficult to get detailed research information about the accuracy of the Polar HRM calorie calculations. Some studies I have seen indicate that they underestimate calorie expenditure at lower intensity levels and that there is a lot of inter-person variability. It's important to keep in mind that HR response to exercise is not consistent during a workout. If you perform at a fixed intensity, the workload will not change, however heart rate will take several minutes to level off, then, as the workout continues, gradually drift upward. Over, say a 45 min workout, it is not unusual to see a 10-15 bpm increase with no corresponding increase in workload intensity. This is called "cardiovascular drift" and is due primarily to decreased plasma volume (loss of fluid) and increased core body temperature.

So while it is true than many exercise machines overestimate calories burned, HRM are not the "gold standard" of comparison.

Thanks Azdak. That's a lot of information for me to absorb, and I'm still thinking about it. I didn't know about cardiovascular drift, but now that I think back on my runs, that makes a lot of sense. I guess, although the HRM is not a perfect measure, it's the best I can do for now. And if the Polar tends to underestimate calorie burn at lower intensity (which I'm not sure what constitute as low), then at least I won't be over estimating what I'm burning. And at least the HRM takes into account my sex and height (which the treadmill at our gym doesn't). But who knows, maybe they ask for the information and don't actually use it. In any case, I now know I must be more careful in estimating my calorie burns. But how I'm going to do this is another matter. The HRM is all I have at this point.

Thanks everyone for your input.

Certainly not denigrating HRMs--I find it nearly impossible to work out w/out my Polar F11. As a fitness professional, I tend to react to what I perceive are "absolutist" statements and misleading information. And I think that statements like "all machines are way off" and "HRM is the only reliable choice", while well-intentioned, are overly simplistic. I just want to make sure that people have the most accurate information possible. And it's probably better to underestimate than overestimate.

One of the biggest benefits of the HRM is that it is the only device that can give you ANY indication of what you are burning in a cardio workout class, spinning class, etc.

Azdak. I was going to call Polar tomorrow, but maybe you know the answer. Would I be able to wear the HRM in a yoga class where we sometimes lie on our stomachs? I'm not particularly big at 138 lbs, but I'm still a little worried. I did want to see what I was burning in the yoga class, however. That one I think is way off (I've been using the MFP calorie count for yoga and I think it's over estimating for what we do which is more stretching and less holding of difficult positions).

1 thing to keep in mind is that sweat is what maintains the contact between the chest strap and you. I have used my polar during yoga, pilates, and ball workout while lying on the ball and have had no problem........However, I did once try to do strength training before cardio and I noticed at least 3 or 4 times during the 30 mins that my HRM was reading 0--it wasn't making good contact because I wasn't sweaty--especially while doing planks. So I'd recommend keeping an eye on the monitor every once in awhile to make sure it's still getting a reading.