The true measure of calorie burn is how much oxygen you are consuming. Unfortunately, this is hard to measure outside of a lab. While heart rate normally increases in line with oxygen consumption (and HRM's use this assumption to estimate calories), there are factors that can cause this relationship to break down - high blood pressure and some medications are just of the more common causes.
The limiting factor of calorie burn is how fast your lungs can deliver oxygen to the muscles. Most people burn 350-600 calories per hour working out. Someone who is fit and working out vigorously can push this to 700-800. Figures above 800 should be regarded with a great deal of skepticism. As far over 1000 calories? Pah!!
Also, with an elliptical, it doesn't really matter what your heart rate is - it takes a fixed amount of work to overcome the resistance of the machine. Two people using the same settings on an elliptical will burn about the same number of calories, even if their HRM's produce different results.
Heart rate monitors can only measure steady state work such as steady state running, cycling (mobile or fixed) or even jumping rope. Any variation in the speed at which you are doing an exercise will cause them to misread for example going from jumping jacks to squats or squat thrusts in a bodyweight workout. Since workouts such as Tae Bo, kickboxing or Zumbea are constantly changing tempo I doubt that any reading taken during that form of exercise would be anywhere close to accurate.
I would go with what your HRM says. The machines are NOT accurate at all. They don't know how high or low your heart rate it. Your HRM does. 500 sounds pretty reasonable for a 40 minute interval workout. Last night in Zumba i burned 1005 calories. SO yeah, it's possible.
Fitness Minutes: (36,520)
2,235 7/23/13 2:30 P
500 is a very high estimate of calories burned. I would just log it in SP and take the calorie estimate SP gives you. It is unlikely you could have burned that much in 40 minutes, especially on an elliptical machine.
Oh and I will echo and reprint what M@L said because it is so true: "As a reality check, most people burn between 6 and 10 calories per minute working out, which seems consistent with your elliptical. Figures of 12 calories per minute are possible, but it requires a fit person working pretty hard to sustain this rate. If you feel this applies to you, then you might go with the 500 figure, but otherwise I would recommend sticking with the more conservative estimate."
As Motivated said, the output from any heart rate monitor is basically a SWAG (Scientific Wild Ass Guess) for the majority of any given population. It is easier and more accurate to monitor and track calories in than it is to trust to a device or table based on algorithms based on population estimates.
Unless you have a medical condition or take medication/supplements that raises your heart rate- I would use the HRM figures. The machine is calibrated to the average size/weight man. If you use a machine that can take height/weight inputs, those machine estimate would be closer to your HRM.
HRM estimates are based on broad population averages, and like most statistics, they are a good predictor for about 1/3 of the population, somewhat useful for another 1/3, and a less useful predictor for the remaining 1/3. High blood pressure and some medications can lead to a faster heart rate (and thus a higher calorie estimate) than the exercise actually warrants.
As a reality check, most people burn between 6 and 10 calories per minute working out, which seems consistent with your elliptical. Figures of 12 calories per minute are possible, but it requires a fit person working pretty hard to sustain this rate. If you feel this applies to you, then you might go with the 500 figure, but otherwise I would recommend sticking with the more conservative estimate.
HRMs can only really be accurate on the estimated calorie count when you're exercising in the "target heart range." If you were substantially under or over that (it's easy to go over with intervals) you may get an inaccurate result.
I would repeat the experiment, paying close attention to your actual heart rate itself, if your HRM doesn't give you a chart. It could be that your HRM was reading heart rate "spikes" that didn't really occur. That sometimes happens when the band slips, or if it doesn't get a good reading from the band. I've seen my heart rate jump up to 200 when the band doesn't fit properly (and I KNOW I'm not working THAT hard! lol) Watch your watch, and if you see crazy numbers you know there's a problem.
On the other hand, I've had near 500-calorie workouts when running intervals, so it could be that you worked harder than you thought. ;) 40 minutes is a long time, and if your intervals were really intense, you could have burned that number honestly.
I did intervals on the elliptical for 40 minutes yesterday. The machine said I burned around 360 calories, while my HRM said I burned 500! I know that the machines are usually wrong, but I wasn't expecting my HRM to be that much higher! I should definitely trust my HRM, right? (It has my weight, sex, and all that stuff in there and the machine didn't)
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