Training for my first ultra was quite a challenge. It wasn't really the distance that was tough (although it was), but it was the setbacks that were hard to work around. 11 weeks before my race, I ended up with a possible hairline fracture on one of my left foot metatarsals. I had stepped on a sharp rock and continue to run. Long story short, it swelled up and bruised on both sides of the foot so I had to take a month off. Weirdly enough, I had hurt my right ankle in a softball game that same week so for about a week I was having trouble walking. Of course I played off the ankle because I didn't want to look like I hurt both feet: no wheelchair for me - thank you!
For that month, I didn't do any running and I took off about a week altogether. I did use the elliptical and some swimming (without kicking).
After my left foot started to feel better, I still ended up not running for another week because my right ankle still hurt.
When I was OK to run, I didn't want to over train so I employed a mix of running and elliptical. I kept the weekly running mileage low but supplemented with elliptical days. For the long run, I would spend an hour on the elliptical followed by a long run, and finish with more elliptical. I figured if I couldn't get the mileage in, I could at least get the amount of time in. When using the elliptical, I made sure to stay at a high cadence to mimic my running cadence.
Above is my training schedule. While I stuck with most of it, there are a few days that I didn't get to fit it in.
The single numbers are in miles; cross = Pilates (most of the time but occasionally weights at the gym); "E" = elliptical