When you select BPP (Base-Build-Peak) the first 45 days are all endurance as the Focus target.
Many riders prefer to stick entirely with endurance level rides during Base phase.
You can eliminate signature decay during that period by changing Decay Method to None under Profile Settings.
Change back to Optimal during Build phase.
This assumes your signature is already dialed in before you change the decay setting.
In your case you want to reset your signature first.
At any time – during any phase – you can test yourself and validate your signature by trying for a Breakthrough (BT).
You’ll notice on the Training page a warning icon appears when your signature has become stale –
Indoors you can select one of the fitness test workouts like this one.
Ride the workout entirely in Slope mode using gears/cadence to hit targets or exceed them. Smash your pedals on the two short sprints (stand if you want) plus make sure to ride to complete failure on the last longer interval.
Click HERE for details on all the fitness test workouts. You’ll likely find a favorite over time.
Performing a fitness test will reset your signature if decay has lowered values during an extended period of LIT.
You can then set Decay Method to None and changes in signature will reflect changes in Training Load alone. Or leave at Optimal and periodically test yourself on a HIT day when you’re feeling especially fresh and ready for a few maximal efforts.
When you reach Build-Peak phases decay is offset by the HIT activities you’ll be doing but you can always test yourself when you feel up for it. 