Make sure that 12 days isn’t completely devoid of activity, otherwise you will see a small performance loss. The days T-minus-12 to T-minus-6 days should still have some decent workouts, just shorter in duration and a little less in intensity, i.e. pick something for every other day (if you’re doing that sort of pattern) and ride it at 85-90% (you can adjust on the screen while riding). T-minus-5 to T-minus-1 days is where you want to ideally get that rest, which is where I would schedule in the easy 1 to 1.5hr session three days out just to spin up the legs.
I would certainly choose the low volume General Power - do the week rides on the trainer (Tues / Thurs) and then you do your MTB outdoor rides on the weekend. Maybe earlier on when you are not doing large distances on the MTB (you’ll need to be able to handle 50-60km for a ride, so around 4hrs of ride time, eventually), you can always fill the Wednesday with a 45min session on TR or a nice easy recovery ride around the block.
Traditional build is exactly that - ride a lot…and ride reasonable easy. It’s the old-school way of the roadie. The SSB is better in terms of it being a time-crunched-cyclist program. You’ll get your results faster with SSB, purely because there is less time involved and it is more targeted. There is nothing stopping you from adding an extra week of the SSB plan using the calendar feature - just repeat one of the third or second to last week of the SSB plan or something like that. What ever tickles your fancy.
But always listen to your body. If you are struggling to finish sessions, say like three or four in a row, then that is a good sign that you are too fatigued. Just rest up a bit, cut the riding back, and maybe only do one ride for one week, then come back fresh and re-motivated.
Nutrition is key on the longer rides. The best habit I can suggest is getting used to eating something every half hour - I find aiming for every 20-mins difficult when it comes to mountainbiking as you don’t really get the breaks to fosick around in your back pockets or shuttle pack coughfanny packcough. But do get into the habit. I tend to alternate gel then bar then gel then bar etc. SIS does the perfect size bar at 40gm - takes two bites and you’re good to go. I also use their caffeine shots (little bottles) at the 3hr mark on 4-ish hour rides. Just gives a little lift for the last half hour or so of riding. Banana’s are great too! Just tape one to your frame, and chow down at any time that is appropriate.
For real food you’ll want some good carb intake, eg from vegetables. Swear off the white bread (full of sugar and other crap). If you want some good eating ideas, check out diabetic magazines for recipes. Diabetic recipes will have good carbs in them. Otherwise, troll through the Ask A Cycling Coach Podcasts, especially the ones around Nate doing Leadville 100. Some good discussions on prep, carbs, etc.
