There are various treadmills available in the fitness machine industry, and most, if not all, have a built in "calories burned" counter. The one I use in my gym is pretty advanced, and it asks for weight, sex, and age input, prior to the workout. The more basic, entry-level machines don't even ask for these inputs.

What I'd like to know is, how accurate are these calorie counters? I know for sure that it's not 100% accurate. I'm more inclined to believe they're accurate to about 90%. Does that seem like a reasonable estimate? i.e., if it shows 600 cals burned at the end of my session, it's probably more like 550 or so.

70-90% Who knows? Nearly everything is an estimate with many variables in the human body.

Try this for running only:

Relative Oxygen Uptake = (0.2 * speed in metres per minute) + (1.8 * speed in metres per minute * percentage gradient) + 3.5

Then to get your absolute oxygen uptake per minute, times the relative by your weight in kg.

1.0 litres per minute oxygen uptake = 5kcals burnt
So divide your absolute oxygen uptake by 1000 to get litres, and then times by 5 to get kcals burnt per minute, then multiply by how long you ran.
Then see how that value compares to the treadmills

If it's asking for your age and sex, it's just making you feel good. I'm not aware of any computations that say you'll burn a different amount of calories on the treadmill just because it's the day after your birthday instead of the day before, and while sex can factor into your basal metabolic rate, it doesn't alter the laws of thermodynamics that govern calories expended when exercising.

The variables that do matter are too many for any machine to track, ranging from your height, the length of your stride, the relative temperature of the room, whether you are holding onto the rails or not, etc. However, a good ballpark can be estimated by taking the distance, time, and your weight.

These counters will get you in the ballpark, but they're more useful as a tool for progress. In other words, if it says 1,000 calories, don't think that's a license to go out and eat 1,000 because neither side of that equation is accurate (you can't accurately track the calories you take in, either, it's just a ballpark). But what you CAN be sure of is if you burn 400 this week on a specific machine, then you burn 410 next week, you are improving in some way. That's where the calories burned are useful - to gauge your progress. They don't translate, however, I've run the exact same routine on three different treadmills and had them report up to 300 calories difference in what I supposedly burned.

Jeremy

There are various treadmills available in the fitness machine industry, and most, if not all, have a built in "calories burned" counter. The one I use in my gym is pretty advanced, and it asks for weight, sex, and age input, prior to the workout. The more basic, entry-level machines don't even ask for these inputs.

What I'd like to know is, how accurate are these calorie counters? I know for sure that it's not 100% accurate. I'm more inclined to believe they're accurate to about 90%. Does that seem like a reasonable estimate? i.e., if it shows 600 cals burned at the end of my session, it's probably more like 550 or so.

If it's asking for your age and sex, it's just making you feel good.

Could also be calculating heart-rate ranges if it's one of those machines with a built-in HR monitor and induction plates. If you run on the "Aerobic" or "Cardio" programs it'll adjust the resistance/pace/incline to try and keep you in the appropriate HR range.

Unfortunately, I've found most of the built-in HRM's to be horrifically inaccurate (and, for some reason, always innacurate on the high-side so that you're seeing sparks in front of your eyes and your pulse is around 185 when the machine reads 130 and is still piling on resistance). Best fitness investment I've made so far has been a personal HRM.

M@

Could also be calculating heart-rate ranges if it's one of those machines with a built-in HR monitor and induction plates. If you run on the "Aerobic" or "Cardio" programs it'll adjust the resistance/pace/incline to try and keep you in the appropriate HR range.

Unfortunately, I've found most of the built-in HRM's to be horrifically inaccurate (and, for some reason, always innacurate on the high-side so that you're seeing sparks in front of your eyes and your pulse is around 185 when the machine reads 130 and is still piling on resistance). Best fitness investment I've made so far has been a personal HRM.

M@

Yes, and I would like to add that if you want a really good approximation of the number of calories burned when doing cardio, get a personnal heart rate monitor which can also estimate your VO2max. I recommend the Polar F11 (although I had to borrow a RS200 to estimate my max heart rate)

If you enter your information correctly, and do the Fitness Test (the estimation of VO2max), then I'd say it has a +/- 10% margin of error, which is considerably better than machines.

What I'd like to know is, how accurate are these calorie counters?

They aren't that accurate unless your VO2max is close to the rule of thumb they use for the calculation.

Read this:

http://forums.johnstonefitness.com/showthread.php?t=19458

The guy who suggested the heart monitor (Polar F11) has given the simplest way to get pretty accurate calorie counts. It's what I use, even though I cross check it.

I recommend the Polar F11...

Oooh...sexah! That's going on my wishlist ASAP. :tucool:

My current HRM's a Polar but it's pretty basic and the watch, while it's only a couple years old, looks like I got it out of a vending machine.

If it's asking for your age and sex, it's just making you feel good. I'm not aware of any computations that say you'll burn a different amount of calories on the treadmill just because it's the day after your birthday instead of the day before, and while sex can factor into your basal metabolic rate, it doesn't alter the laws of thermodynamics that govern calories expended when exercising.

Age and sex are being asked because they use a formula for maximum heart rate that depends on age. Something like

MHR = 220 - AGE

or

MHR = 207 - 0.7 x AGE

The reason it asks for sex is that there is a big difference in VO2max for men and women. And, if you know age, you can get a more accurate guess for VO2max.

If it asks for weight as well, then it can get even closer by using Cooper's tables; see them here for example:

http://www.brianmac.demon.co.uk/vo2max.htm

But as you can also see from the tables, the variables of age, sex and weight give you good information about average calories burned over a population, but for an individual, there is often variation of 25% - 50% from the average, and sometimes a lot more.

If you are keeping track of the heart rate, the two numbers, MHR and VO2max, are all you need to know to reasonably estimate calories. You do not need to know the stride length, or hair color, because if that person is burning calories on a treadmill, then they are using oxygen to do it, and pumping that oxygen with their heart. This is why you can use heart rate to get reasonably accurate calories - if you have decent MHR and VO2max numbers.

If you want really accurate calories, then you want to hook the person up to measure the gases the inhale and exhale. But still, you only need to look at the oxygen consumption.

Cool info!!! I was thinking of the older models that were using the cal/kg/fudge factor method, I see your point with VO2 ... thanks for the share, it was very informative for me!

Jeremy

Age and sex are being asked because they use a formula for maximum heart rate that depends on age. Something like

MHR = 220 - AGE

or

MHR = 207 - 0.7 x AGE

The reason it asks for sex is that there is a big difference in VO2max for men and women. And, if you know age, you can get a more accurate guess for VO2max.

If it asks for weight as well, then it can get even closer by using Cooper's tables; see them here for example:

http://www.brianmac.demon.co.uk/vo2max.htm

But as you can also see from the tables, the variables of age, sex and weight give you good information about average calories burned over a population, but for an individual, there is often variation of 25% - 50% from the average, and sometimes a lot more.

If you are keeping track of the heart rate, the two numbers, MHR and VO2max, are all you need to know to reasonably estimate calories. You do not need to know the stride length, or hair color, because if that person is burning calories on a treadmill, then they are using oxygen to do it, and pumping that oxygen with their heart. This is why you can use heart rate to get reasonably accurate calories - if you have decent MHR and VO2max numbers.

If you want really accurate calories, then you want to hook the person up to measure the gases the inhale and exhale. But still, you only need to look at the oxygen consumption.

I see your point with VO2 ... thanks for the share, it was very informative for me!

Yeah VO2max is actually my primary goal so I think about calories from a different point of view.

The spread of different exercise machines though, is still pretty wide. If you get a machine that doesn't use heart rate, the calories are very suspect. If it uses heart rate but doesn't ask your age, sex or weight - very suspect.

One of these days I might get one of those mini VO2max things (http://www.thefitnessexpert.com/cardio_coach.html) but I'll be waiting until they come down in price a lot.