Turbo Trainer Noob - Why is distance shorter on Watch compared to Apps

I’m brand new to the world of Indoor Smart Trainers. I have a loan of a Tacx Satori. I have a Fenix 6s Pro.

When recording an indoor bike activity on the watch the distance and speed recorded is approximately 60% of that recorded on the Tacx app or Zwift.

The power graphs are similar enough in both the watch and app activities, but the distances differ dramatically. from a quick test tonight:

activity 1: Watch - 0.61miles , Tacx - 1.03 miles

activity 2: Watch - 2.42miles, Zwift - 3.88 miles

I don’t think there was any significant downhills or drafting on Zwift, and definitely none on Tacx.

Additionally, with Zwift now giving Training Load figures, the Zwift activity showed 107, benefit Anaerobic Capacity, as opposed to the watch showing 45, benefit Recovery. I was sweating and above my FTP in watts so it definitely wasn’t recovery.

I’ve tried with changing the settings for wheel size from auto to entering a circumference (on the watch) but it hasn’t seemed to make any difference.

Any ideas welcome .

0 PaulDN81 over 3 years ago

Zwift distance is based on power while the watch's distance is based on wheel revolutions: zwiftinsider.com/.../

0 Spiffman over 3 years ago in reply to PaulDN81

Cheers for the link and the info. That doesn’t explain the Training Load part of this however, as surely Garmin calculates this based heavily on HR, and Zwifts estimation seems more likely for this activity (similarly with a tacx workout I did last week)

0 mcalista over 3 years ago in reply to Spiffman

Spiffman said:
That doesn’t explain the Training Load part of this however, as surely Garmin calculates this based heavily on HR, and Zwifts estimation seems more likely for this activity (similarly with a tacx workout I did last week)

Training Load uses power rather than HR.

Although I've gotta question "sweating and above FTP" if you went 3.88 miles in Zwift.

0 Spiffman over 3 years ago in reply to mcalista

no open window, no fan (yet) adding to sweat, Power zones 3,4 and 5 in the main for the 12 mins.

But putting that aside, the Garmin watch activity and the Zwift Activity both received the same Power data and have come to significantly different Load values.