Ever wondered about the watts reading

Options
cragmor
cragmor Posts: 24 Member
in Fitness and Exercise
on exercise equipment? I found how you can take that reading, and determine how many calories you burned during that exercise. Since the wattage is a reading how how intense you are working, it would seem to be that it can create an accurate picture of the calories burned. At least more accurate than some online calculators that just ask for weight, and duration.
Some info on what 1 Watt is equal to:
A) 1 Watt is equal to
1) 0.0143 kcal/min
2) 1 Joule/second
3) 60 Newton meters/min (Nm/min)
4) 6.12 kgm/min
5) 1 kcal = 69.78 Watts
B) 1 Litre of O2 = 5.05 kcal
C) 1 MET = 3.5 mL O2 per Kg body weight per minute
D) 1 pound = 0.454 kg (divide weight in pounds by 2.2 to get kilograms)
This info will be used later for some calculations

Here is what I did. Using a speadsheet application, Google docs in my case, I created a spreadsheet.
First thing is to enter your weight.
If you entered it in lbs, you need to convert it to kg : [weight in kg]=[weight in lbs] / 2.2
Then, enter the watts reading from the equipment
Multiply the watts by 0.0143 to get kcal/min
Divide the kcal/min value by 5.05 to get litres of 02
Multiply litres of 02 by [body weight in kg] to get mL/kg/min
Divide the mL/kg/min by 3.5 to get the MET value of the workout.

Now that you have the MET value, you can calculate calories burned.
Total Calories Burned = Duration (in minutes) x (MET x 3.5 x weight in kg)/200

I am sure that not many people are interested in the nuts and bolts of how it works, but if you want me to send you the spreadsheet I created, just leave your email address.

I am not a scientist etc, just a guy trying to understand how it all works. I gathered this from the net, and it seems credible. I make no guarantees on how accurate it really is.

Replies

  • Pril2000
    Pril2000 Posts: 254 Member
    Options
    So instead of burning 400 calories in a 45 min spin class, I'm only burning 215 because I'm producing only around 60-70 watts? That sucks. I felt like I was working really hard, but I'm only really burning half what I think I am.

    This is definitely useful. Thank you for posting!

    :happy:
  • cragmor
    cragmor Posts: 24 Member
    Options
    I know what you mean. When I first did the math, I could not believe it. Then I considered that what I was doing was working, and I was losing weight, so all is good. I just needed to adjust my perception of how my body of burning calories.
  • mlb929
    mlb929 Posts: 1,974 Member
    Options
    Thank you for this, my elliptical at home has a faulty connection and I can't ever read the calorie output, but I can see the watts. Now I know what to do with them. For example: Mine reads 10 calories instead of 210 :)
  • Pril2000
    Pril2000 Posts: 254 Member
    Options
    Yeah. Perception is key. I get caught up in the numbers. Really, a little over 200 calories a workout is decent when you're already eating at a deficit. I have to think of it that way, so that I don't feel dicouraged. Everyone wants to think they're blasting 500+ calories in an hour, but that is high and not very reasonable when you consider that everyone weighs differently and is working at different intensities.

    Thanks again. As long as I keep up and exercise a little every day, it works for me, so I am happy.

Categories