Calories burned on stationary cycles

Since it’s winter and I can’t (or at least don’t want to) go cycling after work (in the dark and probable rain), I go to the club and spend time on the stationary cycle. Now the cycle has a number of readouts, but I generally only pay attention to the elapsed time and RPM. But every once in a while I notice the calories burned number. After an hour, it usually reads somewhere around 900 calories.

My queston is: How accurate is this number? Especially for someone who’s in much better shape than the average user.

Does the bike have a console where you input your weight and/or BFP and/or age? If it doesn’t, then it’ll be pretty inaccurate. If it does, it will be somewhat less inaccurate.

I’m not arguing, just asking, but does height/weight even matter? I ask because isn’t it simply that the bike measures how many times a wheel of a certain (effective) mass and radius turns, and how rapidly, and uses that info to calculate the energy that must have been expended?

Of course, the weight of the person doing the exercising would matter if the bike was moving, but in this situation it’s stationary.

Weight matters. You’re correct that the shape of the person doesn’t alter the instantaeous power or the total energy that was *delivered to the pedals *to achieve *X *RPM for *Y *time against *Z *resistance.

But the amount of human energy expended delivering that pedal energy also includes moving those legs. And that chest. And maybe those arms.

Legs wrapped in 100 lbs of fat will be harder to move than legs w/o that fat.

You can also use height vs weight vs sex as a rough proxy for state of conditioning. Which affects the average conversion efficincy from calorie to motion.
I’m not suggesting that each exercise machine maker has perfectly captured all the nuances in their calcs. But I am suggesting they’re not selling pure snake oil when they try.

Here’s a table that suggests 900 kcal/hr is plausible though on the high end of what a heavy person would expend on a stationary bicycle.

The readouts are very inaccurate, and in general should never be counted on, especially if the machine doesn’t ask for weight input. For instance, say a bike’s default is 150 pounds. If a 250 pound guy gets on the bike for an hour at, say, moderate resistance, he will burn much more then the 150 pound person, therefore, the readout will read low. Conversely, if a small, 100 pound person got on the bike for an hour, again at the same intensity of the 250 pound guy, that person’s actual calories burned are much less then both the 250 pound guy and the 150 pound default.

I teach on Kaiser M3 bikes which have computers, including calories burned. Folks are often upset when I tell them that they didn’t actually burn 600 calories because the bikes are calibrated to 160 pounds - on the other hand, the bigger guys love this!

Hmm. That chart jibes pretty well with what the bike (which does not ask for my weight) reads when I’m done riding it. Then again, I would not say I am “much better shape than the average user.” Also, if the bike is anything like the elliptical (which does ask my information), it defaults to something like 30 year old male, 150 lbs.

The bike does have the option to enter my age/weight, but I usually don’t bother. I never thought about that modifying the calories burned amount. I figured it was just for the heart rate calcs.

But since I weigh more than the default 150 lbs (I think) for the machine, then my actual calories burned will be even higher. But according to that table Xema linked to, that’s still not beyond the plausible. I’ll try inputting my weight next time and seeing what it says. This won’t happen until tomorrow, since I ride outside on weekends. I’ll let you know what it says.

Don’t know if anyone’s interested, but what the hell…

I finally got back on my usual (favorite) stationary bike for a full hour tonight. Various things (other users, mostly) had interfered with my using it for a full hour earlier in the week. The result was that I burned about the same number of calories (900 +/- 20) as when I didn’t enter my weight. So apparently that machine is not adjusting its calculations based on the rider’s weight. Damn if I know what it does with that datum, then.

But anyway, part of why I asked this question had already been answered by the table Xema posted. Whenever we get a thread about weight loss, someone usually posts the fact that one can’t burn more than about 500 calories an hour. I had my doubts, and that table confirmed them. I’d been wondering if the calories reported by the cycle were off by a factor of 2, but obviously not.

So what are you doing to burn so many calories an hour then? Are you very large or are you a world class cyclist?

For average effort and average weight, this sounds about right. But if you’re heavy and/or exercising vigorously, you can get to 1000 calories/hour. A 45-minute run for me, at 165lb 8 minutes/mile, burns off around 700 calories.

900 calories per hour on a stationary bike sounds like a lot to me, but if you’re well over 200 lbs and putting in a decent amount of effort, it’s certainly plausible. My only experience with stationary bikes is that they seem to severely overestimate calories burned, but this was on an cheap stationary bike my father has, so perhaps the current models are more accurate at estimating calories burned.

Yes, but my impression (and I’ll admit I could have gotten the wrong one) was that they were saying no one could burn more than 500 calories.

I’m not that heavy – just under 200 lbs. But as I said above, the bike I’m using doesn’t seem to use the input weight in the calorie-burn calcs. I’m definitely putting out a lot of effort, though. Most of the time I’m doing about 100 RPM.

I suspect that this bike is overestimating as well, but it’s hard to say by how much. I may email the company and get their opinion.

You may be putting out 100 RPM but at what type of resistance? The better number to report would be your watts, if it displays such. Try and see what your average watts are, or a good estimate. Watts are how much work you’re doing and it’s easier to verify the calculation using your weight and watts.

As for the 500 calories an hour maximum thing, I’m sure that’s not true. I’m a 140 lb. female and I burn around 600 calories an hour just running.

By the way, if you can post what brand of bike you are using, I may already have information on it (I teach spin on a wide variety of bikes).

The brand is Precor. I don’t think it has a readout for watts, but I’ll double check next time I’m on it. The older Precors they have at the club do have a watts readout, IIRC. I don’t use those much, because they’re harder to spin, which means they are probably overdue for servicing. They’re also not very well situated for watching the TVs.

If you keep track of heart rate, you can square your results against the heart rate calculator here and see if it’s reasonably close.