A bit confused by all the different training numbers between Garmin, Strava, TP…etc.
Garmin has my Acute Load at 645. Strava has my Fitness at 18. No idea what TP is anymore since I don’t have a paid account anymore, but their fitness/form/fatigue chart seemed to work well for me, but i’m not interested in paying the $$ for the account anymore.
What have you found that works for you when monitoring your “fitness” or training load? (outside of TR progression levels of course 
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I think the Strava Fitness metric is a good indicator of your chronic training load. My understanding is that it is similar to CTL, which you may recall from TP. Don’t know if it’s calculated exactly the same (CTL is an ongoing daily avg of your TSS over 42 days). Though Strava named it “Fitness”, many view it more as a load measure, as many other factors may actually affect your fitness other than cumulative TSS.
If your FTP is not set correctly for each workout on EVERY platform, then your numbers will always be different and inaccurate when comparing platforms. This means every time your FTP changes, you must change it in EVERY platform. If you upload past/historical data, your FTP has to be correct at the time you completed that workout/ride.
Intervals.icu is free and well regarded.
Intervals.icu was mentioned, and I’d throw money Davids way for what he provides, you could use Golden Cheetah if you use a PC.