Exercise time and distance different in Fitbit and strava

[Redsarahdavies]

This week when I have gone for a run, Fitbit says a different distance and total time to strava. Fitbit showed I had done 3 miles over 30 mins and strava said 2 miles in 20 mins. This is the 3rd time it doesn’t match so I’m very confused.  Any ideas? 

[Ian-J]

I’ve been having the exact problem the last couple of days. Even on the Fitbit activity page overall it says 5 miles for 1 walk but only gives splits for 4.3 miles.

I exported the tcx to Komoot and the distance comes out right.

[Triletics]

@Ian-J Strava does its own data processing when it receives TCX files. There is an agreement between Strava and some companies like Garmin so the incoming data is never touched but I don't think Fitbit cares at all about Strava integration.

Said that, if you closely analyse what Fitbit gives you'll going to see lots of issues with its GPS tracking and inconsistencies. There are a few issues.

The same activity record shows different distances within the Fitbit ecosystem.

As it has been noticed, the web Dashboard and Fitbit app can't agree on what the running distance is. Here's an example:

So 9.16km or 9.25km?

The Fitbit app says 9.16km:

...but is it...?

Let's export the GPS data and see what was the GPS distance:

Now, we have 9.56km! Interesting. It's known that Fitbit doesn't use GPS for running so this could be irrelevant (but isn't but I will go back to it). So why we may have two different distances 9.16km and 9.25km? Let's see at steps:
The activity summary in the web dashboard says 11154:

However, after opening the activity the impact says 11060 steps:

This means, there are also two different records of steps taken during activity 11154 and 11060, a difference of 94 steps. That probably could explain why we have also a difference in distance of 90m (by stride length that difference for me is 104m since the distance isn't measured exactly by stride x steps but is a little more complicated and is quite close to 90m difference). So now we have different 3 different distances, two different step counts and I didn't get yet to the GPS data.

Looking at the Strava Flyby feature, red is Fitbit, and grey is an accurate GPS tracker. The map shows intervals and on top of the hill. Fitbit doesn't seem to get there and always lags slightly behind a different GPS tracker. This tells me, there is a delay in reading the GPS data and/or some data smoothing. When I got to the top of the hill I turned around and that little segment was never captured (there were 8 reps).

The actual distance was 11.04km (by GPS) and 11.03km by foot pod.

Here's what it looks like in motion (it shows single runner wearing two watches during the same run):

Fitbit GPS lags behind and cuts u-turn.

So Strava distance is probably the least of your issues when using Fitbit for running 🤷

[Ian-J]

This is the Fitbit activity data for my walk, in 1 place it says 5miles only gives me data for 4.3miles. If I do a distance correction on Stara it comes out correct.

 

[Triletics]

@Ian-J the point is, whatever issue you have, it's been there for years and unlikely will be fixed so it's something to live with if you want to stick with Fitbit.

[phatbitzr]

@Triletics, I have noticed that a long while ago.  I use to track my rides with Strava, fitbit and bike computer.  When I ride back and forth on a linear path, the fitbit always looks like I turned around slightly earlier.  Doing the flyby and comparing all 3 rides, the fitbit was always seems to be a couple of seconds ahead of Strava.  It seems like fitbit doesn't syncing its clock down to the exact second, thus when recording a session, it arrives at same location while its internal clock is slightly behind, hence, on playback, the fitbit is ahead.

I also noticed when using fitbit when skiing, it doesn't reach the same top speed as Strava or a few other ski tracking apps.  So it must be smoothing the speed data also.

[whizzieg]

I have had the same problem (I think) my fitbit shows me I have run 6km for example but then syncs a shorter distance to Strava. I have recorded using both to make sure my distance was what I thought it was - it seems from comments on this subject that it is a known issue and has been for some time.

I wish I'd read this before buying it as I specifically wanted the Fitbit to record runs/walks etc 😞

It's really annoying!!!