Machines are notorious for significantly overestimating calories. However, HRM's are not 100% reliable either - high blood pressure, some medications, etc can cause issues. And given they are based on broad population averages, statistically they are a good predictor for 1/3 of the population, somewhat good predictor for another 1/3, and less useful for the remaining 1/3.
One approach might be to check your HRM walking or running (these are well studied and understood activities, and online estimates are reasonably reliable).
To put things in context, even if the machine were 25% off, and you were burning 300 calories rather than 400, when combined with say, knocking off 500 calories through watching your intake, this gives a calorie deficit of 800 rather than 900 - the impact of the error is not all that significant. (Mis)estimates of calories burned should not prevent you from losing weight.
Not that I have anything against trying to get a more reliable estimate.
Fitness Minutes: (4,545)
925 10/29/12 4:06 P
Yea I was pretty shocked because the one place it was over my HRM the other place WAY WAY under meaning I would basically be starving myself not eating enough calories if I logged what the machines told me (because I can not hold the metal bars the whole time it would drive me insane)
Fitness Minutes: (197,740)
10/29/12 3:58 P
I can't imagine what, if any, my weight loss would be if I went by the machine numbers. It is always inflated by 33-50% over both my HRMs.
Fitness Minutes: (4,545)
925 10/29/12 3:49 P
I've had a couple people message me on how I was liking my HRM even though I am getting a newer one in Nov. Today proved a massive point to me personally about the machines we use and track.
I was sitting at Gym #1 canceling my membership and over heard the PT telling this lady who wants to lose weight that she needs the deficit in calories, OK that is correct. Then he said "You burned 70 calories on that machine in 10 minutes." I know for a fact their machines now are about 7-15 calories off at all times from the HRM. But at least those machines were staying nearly accurate with my transmitter.
Went to my new gym after (which I LOVE) but their machines right off the bat not reading or syncing correctly. I found unless you hold the metal HRM readers at ALL TIMES it is way way off. It was stating at times I had a HR of 139 when I was 155-170, the difference on one machine was over 200 calories less!
The only reason I wanted to share is because all the slow downs I might have had in the past might have been from logging calories off the machines and not using the HRM, meaning my intake for food on SP could be inaccurate as well since I clearly see my fitness calories were wrong a portion of the time. I know a lot of people worry about what SP has for calories (and when I took the info I had it said I burned 300+ more than my HRM which I find hard to believe in most cases)
We all have our own ways of staying accountable side by side with SP but in case anyone was wanting another insight to the HRM's information I am siding now they are much better than relying on the machines.