Originally Posted by
Carbonfiberboy
My experience was that if I could do a 4-5 hour hilly ride and do a max sustainable effort on every climb, all the way to the finish, I could do well on rides of any length, at least up to 400k. I guess that's the "ability to repeat." Those were about 10-12 hour weeks, often no intensity other than the one weekly long hard ride, where I'd see 45'-60' of Z4 and 5'-20' of Z5. Of course that was in my 60s, so YMMV. Rather a stupid simple training scheme, but it worked, I think because it was reality-based. It took me months of doing that to get that result.
I was thinking more of the affect time v intensity has on shorter, but very hard rides, like sub 2 hours. The interesting thing for me this year is that reducing volume / increasing intensity has actually improved my Zwift racing (higher FTP and VO2 max), but definitely taken the edge off my endurance over 4+ hour hilly rides (more drop off in endurance power >2-3 hours). When I was doing 10+ hour weeks I had better endurance, but was less punchy. Now I'm wondering if I can increase volume at low intensity to regain my endurance without losing power gained at threshold and above. I think it might work if I'm strict with the low intensity and don't cause too much additional fatigue.