I just joined xert and synced all my rides from strava since March of this yea. The threshold power is going up and down plenty but looking at the training load and xss, they seem consistent. It shows, for example, a big dip in September, but when looking at the training logs for that month, they dont look much different than other months.
any ideas on what might be causing this?
Looks like the biggest dip in your FTP (start September) is linked to a ‘near breakthrough’ (the large white circle), which Xert seems to consider a loss of fitness. It is possible to flag individual workouts to remove them from this calculation, might be worth trying in this case.
First thing to be aware of is signature decay - so your threshold will go down even if you maintain training load if you don’t have breakthrough efforts. It also goes down as training load drops, which happened during the August break. You overall had a break plus some long gaps between breakthroughs.
Second is that the system is always looking for breakthroughs from every ride, and it doesn’t know if you did a true max effort, but is just checking whether each effort is consistent with your (potentially heavily decayed) signature. So some (or many) of those breakthrough circles may not be reflecting your true fitness. Worth checking whether those efforts in September were in fact all-out efforts vs just hard training rides. That could have caused a fakethrough as @rp86 said as well.
First thing I’d do is try and get a BT to ensure your current signature is correct, and go from there.
As a new user, it’s worth doing some reading of their blog and support articles, and listening to their podcasts as there’s a bit of a learning curve.