Fitbit Versa vs Polar calorie burn estimate difference

Tanya_Clair

I have been using a Polar chest strap heart rate monitor for a couple of years now and have always considered it to be rather reliable when it comes to calorie burn estimates. However, I got a Fitbit Versa yesterday and decided to wear both today on a 30 minute bike ride to compare the two. The Polar heart rate average was 158, highest heart rate was 181 and calorie burn 357 whereas the Fitbit measured heart rate average was 157, highest heart rate was 181 but with a calorie burn of 445. Both watches are set up with the same personal data and measured the same heart rates, does anyone know why the Fitbit calorie burn is so much higher? I have logged the Polar calorie burn as I considered it to be much more realistic!

Any thoughts?

sijomial

For a female rider both numbers seem remarkably high. Are you a very high standard rider and/or usually tall and strong?

Think you would do well to compare your calorie burn estimates to a more accurate way of estimating calories rather than using HR.

Using a power meter equipped bike or indoor trainer would be ideal.
357 net cals for half an hour would be about 198w average power.
445 net cals for half an hour would be about 245w average power and that would be a truly remarkable level.

A less accurate comparison would be recording your ride on Strava which attempts to estimate your power.

Tanya_Clair

Im about 5 foot 8 so not unusually tall. When i'm at the gym the bike normally estimates around 310 calories for 30 minutes but as far as I know it doesn't measure power,but I will look out for one when I get back to the gym next week. I used Strava today, I can only see speed/distance etc for my ride, is there a specific measurement of power or can I use my speed/distance to work that out? Thanks for your help!

sijomial

Both cals and watts shows on the phone app when you view your ride or if you are looking at your ride on a PC there is a grey box on the right hand side which toggles between "Show More" and "Show Less" - that should reveal the estimate of your calories.



BTW there's a good chance that your Polar, Fitbit and Strava are all giving you estimated gross calories whereas watts to calories formula is for net cals (average watts for an hour X 3.6).
Not that significant for short duration rides though.

Duck_Puddle

Just wanted to add that I’m while I’m not sure I’m your Polar specifically, I know for certain that Fitbit gives total calories burned from the moment you hit start until you hit stop. So that includes calories you would have burned had you been asleep or sitting on the couch PLUS the calories you burned doing the workout. My Fitbit burns are always a bit higher than everything else (and the difference is usually by about the amount I would have burned in that amount of time had I not been working out).

For biking though-power (watts) is the way to go regardless.

But if you do other workouts, you’ll see similar differences.

Tanya_Clair

I will have a look for that on Strava, cheers!


That also makes sense, I will be careful then if I ever use the fitbit instead of the polar for logging exercise!