I’ve got about a 310w FTP (I have no clue how long I can hold this, but that’s the setting which makes sweet spot workouts feel as they should). How should I train if I want to complete a workout like Phoenix +2 or Polar Bear +1? Ideally, I want to hold 300w for 90 minutes.
I would give sustained power plan a try, also work on your fueling as this will probably play biggest role in this. Ideally you want to up your ftp a little so 300 is lower end SS at that point 90 min wont seem impossible.
That seems an awfully specific target! Are you targeting a 60km TT or something?
If you haven’t been doing structured training then to be honest I would be inclined to do 12 weeks of Sweet Spot Base. That’s going to improve both your FTP (meaning 300W is a lower % of your threshold) as well as increasing how long you can sustain efforts at high % of FTP.
If you wanted to make it a bit more specific to your goal, then you could swap out one of the workouts each week and do a Phoenix progression from the -3 version to the +2 version.
Honestly I wouldn’t over think it. Try the minus versions of the workouts, starting wherever you feel comfortable and work your way up. As an ex-rower, you’ll no doubt be a complete beast within 6 months!
Probably just by doing anything your FTP soon will be 400W or something like that there is no possibility that someone with rowing experience will not be a beast on the bike.