I’ll be honest, I am no champion at sticking to a fixed plan when it comes to cycling.
64, 77kgs (down from 116kgs 4 years ago) ftp 255, ride 300/400km week al year with regular 100km ride in beautiful Normandy France plus outings to grand FONDO events.
My goal is to ride fast(er) for 100km and to also be able to sustain long climbs with good power for the times I get to the mountains.
As I said no man for fixed rigid plans…
I wanted to get opinions on my way forward.
My idea was to ride outdoors as I do with no structured element, that’s 3/4 times a week split longer easier and others faster, but to add 2 hiit sessions per week of say 45 to 60 min.
I’m a big believer in 2 hard workouts a week. The only thing I’d question given your goals are whether your unstructured training is giving you the work you need to do longer sustained power for the climbs and the overall ride length. If it is, I say go for it and see how it goes. If not, you might want to replace one of those HIIT workouts with something focused on extending your time at SweetSpot/Threshold.
I’d just do one interval day that gets you a really solid workout in followed by a short and easy recovery day. Then do all your riding around outside. IMO, many get recover wrong and cannot absorb their intensity days, less is usually more for a recreational rider (like just about everyone on this forum)
The only issue will be going hard when you are riding out side and carrying around a lot of fatigue. Your plan will work if you have the discipline to only ride endurance pace when outside.
Also figure on 3 weeks on 1 week off (easy riding / half volume).