In Eat & Run (Jurek's book), he talked about, for at least his first WS100 win, doing 10 miles per day on week days on Mt Si, and on weekends he'd to back to back 25 mile long runs, for a total of 100 miles. He would bus it to Mt Si after work, train, then bus it home. He also mentioned doing mile repeats on the track, getting them down to around 5:15 I think. He mentioned other ultra guys didn't do fast stuff like that, but he did, and I think he credited that to getting his course time down on later attempts. He also talks about being more in favour of strengthening than stretching for injury rehab/prehab.