On most of the cardio exercise equipment at my gym, the built-in display somehow keeps track of calories burned during your workout session. How accurate are these displays?
I’m mainly interested in the elliptical machines, as that’s what I normally use. Like this one for example. I enter my weight (275 lbs), select the program I want (manual), the amount of time I want (20-35 minutes, depending on my energy level and what else I plan on doing for my workout that day), and the resistence level (17, with 20 being the maximum). I then work out at around 70-75 RPM. According to the machine, my heart rate stays in the 165-175 range, right at the top of my ‘theoretical maximum’, and I burn somewhere in the neighborhood of 850 calories in 30 minutes. It’s a good heart-pumping workout, but still, that number seems rather high. (a full meal’s worth of calories burned in 30 minutes?).
The answers are all over the map. You may find, as I did, that the calorie figure stays the same when you turn up the resistance, or that the number seems absurdly high or low. Heart rates on several machines are pretty accurate, but I wouldn’t count on the calorie count.
Some wearable heart rate monitors only work if you temporarily stand still.
if l recall physics correctly calorie expenditure is a SImple calculation. wouldn’t it take a specific amount of energy to move the machine? that would mean that the calorie counter is correct?
Well, since F = ma, and W(ork) = Force x Distance, the Work done (which I would assume correlates with calories since both measure energy) is proportional to mass and acceleration, as well as distance moved. That means that even if the machine can measure the distance you’ve moved and the acceleration, it still has to know your mass (“weight”) to figure out how many calories you’ve expended. If the machine doesn’t know your weight, it doesn’t have a hope in hell.
The question then becomes, for those machines that do ask your weight, how accurate are they?
That’s what I remember from the last thread on this topic. The upshot was that someone who’s in better shape has a more efficient cardiovascular system and will burn fewer calories than someone who is less fit.
You can’t just use W=F*d because this neglects the inefficiency of the human body, which is a (the?) major factor.
So the good news is that you are actually burning more calories for the same type of exercise. The bad new is, you feel it.
I wouldn’t trust the calorie readout because I highly doubt that it’s calibrated in any meaningful way. FWIW, though, the heart rate monitor on every machine I’ve used matches the Polar Heart Rate Monitor on my wrist pretty closely.
Exactly. If the machine was set up to actually measure the energy expended (power * time) then you could use that data, otherwise, meh.
As a rule of thumb, running burns about 100 calories a mile. So if you run a four minute mile that’s 100 calories/minute. A four minute mile is pretty brisk though I’d say normal usage of cardio equipment won’t get you near even half that. To get near 850 calories in 30 minutes (if I got my sums right) you’d have to be working at roughly 4 minute mile rate for the duration. Maybe Lance Armstrong could keep that up but I think it’s very unrealistic for us normal folk.
FWIW I completely ignore the calorie counter on my stationary bike, I just work at the highest effort I can keep up for the duration (usually 1 hour+). Proof that calories are in fact being burned are: Bike flywheel gets too hot to touch: Every week trousers get looser (last years strides are now unwearable 'coz they look like clown pants)
First off, I just want to give you a big HIGH FIVE for doing that workout. I’m sure that’s really tough to do. Keep it up.
Second, the 100 calories per mile is very dependent on how much the runner weighs. That’s the rate if the runner weighs about 150 pounds. A 275 pound person would use about 180 calories per mile. Your 850 calorie workout would be similar to running for almost 5 milies.
That said, the machines are usually inacurate for determining how many calories you use during the exercise. They’ll give you a rough idea, but you have a certain efficiency that determines how many calories you need to burn to produce a given amount of energy. That efficiency is different for different people, and even your own value will change the more you work out. Plus, who knows how the manufacturer calibrated the machine.
One thing I do like to use the calorie display for is a guage of how hard I worked out and use that to compare to past workouts. If I worked out harder, the calories will be greater. If I worked out easier, the calories will be less. As long as your elliptical machine ties the calories to the actual amount of work done, you can use that as a difficulty guage.
One other consideration for the amount of calories burned with that workout–your Post Exercise Caloric Expenditure. The PECE is the amount of extra calories that your body burns after the exercise session to recover. If the session was strenuous, over the next 24 hours you can burn an additional 50% of the calories used during the exercise. The less strenuous the activity, the smaller that percentage will be. So a leisurely walk for 30 minutes might have no PECE. But the session you describe sounds pretty strenuous, so I would guess your body is burning several hundred extra calories more after your workout is complete.
very much so. A 260 lb woman with 60% bodyfat and a 260 man with 10% bodyfat will have the same readings even though the man may use 2-3x as many calories for the same activity.
I would say breathing rate and CO2 output rate is a better measure but I don’t know how you can measure that.
Oxygen uptake is the gold standard for exertion measurements, but it’s tough to measure. It correlates pretty well with heart rate, though, so at least there’s something.
You know I have used an elipticle machine. Most of my body mass does not move when I am using it. So I am not sure where my wieght comes into the equation.
Thanks for all the replys. A bit more information I can add for my specific situation:
I can do 30-35 minutes on the eliptical machine at the resistence level described in my OP without much trouble. I might stop in the middle of the workout once or twice, usually just to get a drink of water or occasionally to slow my heart rate down a little bit.
If the calorie meter on the machine can be believed, I burn somewhere between 25-28 calories/minute during my eliptical workout.
Someone mentioned the comparison to running. Well, I can run about 3 miles without stopping, usually in about 30 minutes. However, I usually feel A LOT more tired after running then I do after an eliptical workout; although I think that might be partially related to the extra stress it puts on my knees.
That’s 1500-1700 calories an hour. At that rate, you should be dropping a pound every 4-6 workouts. Are you?
On or off a treadmill? The latter involves actually propelling yourself rather than just moving your legs, which could definitely acount for the extra tiredness.
I generally weigh myself after my workout. My weight stays fairly constant (I probably eat more junk food then I should), but it can vary plus or minus 3-4 lbs day-to-day, depending on any number of factors (how big my lunch was, how much water I drank during the workout, the last time I used the restroom, etc). Generally, if I work out 4 days in a row, at the end of the 4th day I’ll be about 3 lbs lighter then I was after the first day. Of course, then I take 2-3 days off and I’m back where I started.
But that’s nothing. Back when I was doing 2-a-day practices for college football, they’d make us weigh ourselves before and after each practice, to make sure we weren’t getting too dehydrated or failing to gain back all the water weight that we sweated off. My record was, IIRC 15.4 pounds lost in a single 2.5 hour practice.
I only run on a treadmill if I have absolutely no other option available; I can’t stand treadmill running. I can pretty much recover from a 30-minute eliptical workout with a few stretches and 10 minutes in the hot tub. After a run, I’m usually exhausted for an hour or so, and basically tired for the rest of the day.
But, if I remember from the last time I did a treadmill run, the calorie counts were pretty close what the elliptical machine says. I think the treadmill count may have been 10% lower.
I’d say normal usage of cardio equipment won’t get you near even half that. To get near 850 calories in 30 minutes (if I got my sums right) you’d have to be working at roughly 4 minute mile rate for the duration. Maybe Lance Armstrong could keep that up but I think it’s very unrealistic for us normal folk.