There are several schools of thought here.
A. Make a HV plan easier
- Use an easier version of a workout progression if you find it too much. I wouldn’t expect to use an easier version one week and the planned version the next week unless there was some extenuating circumstance (i.e. sick kid cut your normal sleep in half).
- Skip the extra endurance portions at the end of some of the rides if you’re totally cooked.
- Skip an endurance day entirely if you’re really spent.
B. Make a MV plan harder
- Use harder versions of a workout progression.
- Add endurance at the end of existing workouts (i.e. extend the cooldown, ride at 65-75%).
- Add endurance rides on some normally scheduled off days (i.e. Pettit, Fletcher, etc).
FWIW, I did Short Power Build High Volume (SPB-HV), Sweet Spot Base Mid Volume (SSB-MV) but modified it to four weeks, and am in the last block of Sustained Power Build High Volume (SusPB-HV). In hindsight I probably should have done SSB-HV and followed some of my own advice from step A above since SSB-MV still has a lot of intensity at and above threshold, and I’m getting mentally and physically tired of doing hard intervals three times a week.
Whatever you decide, listen to your body - aches, pains, fatigue, tired, grumpy, etc. If they persist more than 1-2 days beyond a particularly tough workout then you’re probably ramping up too quickly and need to dial back.