How many calories am I burning?

[V8mate]

When I'm at the gym, I have two sources of calorie-burning information available to me: the aerobic exercise machines (cross trainer, treadmill, bike etc), and one of those wristwatch exercise calculator doofers, which talks to the listening device straped around my chest.

At the end of a 30 minute session on a machine, the two devices are a long way from agreeing, and I wonder which is closer?

Here's what each device knows about me (and what's going on during the exercise):

Exercise machine:
My weight (I type it in at the start)
The speed, resistance etc that the machine is being used at i.e. the work being done)


Sports watch thing:
Age
Height
Weight
Heart rate


Which would you suggest is reporting the calories expended more accurately?

[RizzoTheRat]

Does the watch not also measure the distance travelled on the device?

The machine can measure the actual work you put in to it, but it has to guess at your efficiency, which it does from your age and weight.

The watch measures your heartrate so should have a better idea of your efficiency, but if its not tracking your speed/distance it doesn't know hoe much work you've put in to the system.

[V8mate]

The watch and machine don't communicate with each other, no.

[AngryPartsBloke]

It doesn't matter how man calories you burn during the workout, it matters how many you burn in the 48hr period after**. It's for that reason I wouldn't worry about what either information source is telling you.

• and why they are not an acurate measure

[grumbledoak]

You can look things like that up on the internet for a third opinion. Try e.g. MyFitnessPal or just plain google a routine. I would imagine the exercise machine is closer.

[Digger]

I use my my Polar FT80 calorie readings and plug them in to My fitness Palestinian (MyFitnessPal autocorrected )

I reckon it's pretty accurate, it has to be distinctly more accurate than the standalone machine as it's measuring your actual heart rate and knows your age. What am I missing here? What I do like about it is the %MHR reading, when it tells me I'm at 90%+ MHR, I know I need to back off soon or wake up on the floor.

[V8mate]

swerni said:

Out of interest, what are the two readings

The machine is very linear, so the readings escalate more quickly initially. I guess it's what I'd expect from a machine doing the same 'work'.

On the watch, the rate of calories is clearly linked to heart rate. On a 30 minute session, the watch will start much more slowly and then overtake the machine after about 20 minutes. By the end of the session the watch is c.100 calories ahead of the machine, say, 550 v 450 on the cross trainer, 480 to 420 on the treadmill.

[okgo]

I would imagine the machine too.

[Hoofy]

Divide the lowest by 2 just to be safe.

[anonymous-user]

Isn't the machine just following a logarithm based on your (or anyones) age sex weight etc. If two people of completely different fitness did the same workout and inputed the same info then it would say they've burned the same calories, which is nonsense.

Something measuring your heart rate must be the more accurate indicator assuming you've programmed info like max/min heart rate etc so it can accurately work out your zones and so on.

[okgo]

I was going along the lines of -

I do an hour at x watts (lots of the machines can be selected to show you this) and let's say I burn 1000 calories, it was comfortably tough.

You do an hour at the same watts, you nearly kill yourself, but the same amount of actual work has be done thus calories are the same/very similar

That's how it works with bikes anyway, can't see it being much different here?

So fitness just makes it easier, but you still do the work and burn the calories?

[spikeyhead]

okgo said:

I was going along the lines of -

I do an hour at x watts (lots of the machines can be selected to show you this) and let's say I burn 1000 calories, it was comfortably tough.

You do an hour at the same watts, you nearly kill yourself, but the same amount of actual work has be done thus calories are the same/very similar

That's how it works with bikes anyway, can't see it being much different here?

So fitness just makes it easier, but you still do the work and burn the calories?

Almost, if you are used to an exercise you may well be able to do it more efficiently, thus wasting less energy. Swimming isn't anywhere near as calorific if you're a good swimmer.

[V8mate]

Indeed. As I've got better at doing certain things, the calorie score goes down. The obvious driver is that my heart rate runs lower for the duration as fitness improves.

[fandango_c]

spikeyhead said:

okgo said:

I was going along the lines of -

I do an hour at x watts (lots of the machines can be selected to show you this) and let's say I burn 1000 calories, it was comfortably tough.

You do an hour at the same watts, you nearly kill yourself, but the same amount of actual work has be done thus calories are the same/very similar

That's how it works with bikes anyway, can't see it being much different here?

So fitness just makes it easier, but you still do the work and burn the calories?

Almost, if you are used to an exercise you may well be able to do it more efficiently, thus wasting less energy. Swimming isn't anywhere near as calorific if you're a good swimmer.

Alternatively you could go at a faster speed and use the same energy.

[okgo]

spikeyhead said:

Almost, if you are used to an exercise you may well be able to do it more efficiently, thus wasting less energy. Swimming isn't anywhere near as calorific if you're a good swimmer.

Interesting. I have a powermeter on my bike and it gives a KJ figure at the end of a ride, the KJ (which can easily be converted into calories) figure doesn't change if you get more or less fit so you are still burning that energy whether it feels easy or hard. Wouldn't the machine he's on do similar?

[spikeyhead]

okgo said:

spikeyhead said:

Almost, if you are used to an exercise you may well be able to do it more efficiently, thus wasting less energy. Swimming isn't anywhere near as calorific if you're a good swimmer.

Interesting. I have a powermeter on my bike and it gives a KJ figure at the end of a ride, the KJ (which can easily be converted into calories) figure doesn't change if you get more or less fit so you are still burning that energy whether it feels easy or hard. Wouldn't the machine he's on do similar?

Imagine lifting a weight up from the ground to a roof on a rope. The energy required is very simply the potential energy change. It's very easy to calculate that. If it's lifted up smoothly and slowly then that's about all the energy required. If it's pulled up by a series of jerks then it will accelerate and decelerate and that will use extra energy because it's inefficient. The same thing can happen within your body when exercising.

[V8mate]

spikeyhead said:

okgo said:

spikeyhead said:

Almost, if you are used to an exercise you may well be able to do it more efficiently, thus wasting less energy. Swimming isn't anywhere near as calorific if you're a good swimmer.

Interesting. I have a powermeter on my bike and it gives a KJ figure at the end of a ride, the KJ (which can easily be converted into calories) figure doesn't change if you get more or less fit so you are still burning that energy whether it feels easy or hard. Wouldn't the machine he's on do similar?

Imagine lifting a weight up from the ground to a roof on a rope. The energy required is very simply the potential energy change. It's very easy to calculate that. If it's lifted up smoothly and slowly then that's about all the energy required. If it's pulled up by a series of jerks then it will accelerate and decelerate and that will use extra energy because it's inefficient. The same thing can happen within your body when exercising.

Okgo's not disputing that. He's saying that the machine doesn't know how easy or hard you're finding running at 9 km/h, for example. It just knows that you are.