You’re going to get better at threshold by working on threshhold. Threshhold progressions will be more productive I think than more “base.” The key is that you are working at threshhold and not above threshold, so that’s why accurate FTP is important.
To bust out of the plateau you may need to do more.
- Add 2-3 hours to your weekly volume
- Or some strength training if you aren’t already.
- And a VO2 block to shock your system into adapting.
- And eat more. sleep more.
If you are afraid of overtraining, you probably won’t push yourself hard enough to get out of the plateau.