After reading Jason's post - I decided I'd do the same thing: post about how to train for an Ultramarthon. There are bound to be more people like myself who looked for help on how to run an Ultramarathon (any distance over the 26.2 standard marathon).
I hope you don't mind numbers and/or math. I'm an engineer, so be prepared.
For my 1st one back in June 2010 (days before my 39th bday), I had a pretty solid base of running ~25 miles a week for a couple of months. I had been training for a marathon (that got canceled), and then jumped right into 50k training. Those weeks consisted of 3 runs per week, using the FIRST method of "Run Less, Run Faster". One speedwork session (4-7 miles total), one tempo run with total mileage averaging 6-7 miles, and the obligatory long run of 10-15 miles. Remember - I started with nothing just a few years ago...tried to be smarter about my running, got the right shoes fitted, and ran consistently 3-4 days a week for a long time, slowly building mileage and stamina.
I did a somewhat standard 16 week marathon training plan for the 50k, but used basic ratios to up the mileage:
For standard marathons I had run:
Average Mileage per week (16 week training): 30 Miles
Longest Training Run: 20 miles
Maximum Weekly Mileage: 34 Miles
(FYI - My marathon time for this training was 3:53, a PR by 8 minutes 7 months since my last marathon).
With my Longest training run 76% of my marathon goal distance (20/26.2=.76), My longest training run for the 50k should be ~24 miles (~.76*31)
With my Weekly Max equal to 1.3 of my marathon goal distance (34/26.2), My weekly max for 50k training should be ~40 miles (1.3*31).
Over those 16 weeks - I ran 3-4 days a week. 3 of the runs were usually 4-8.5 miles, with the long weekend runs like this: 10(race), 13, 8.4, 17.9, 18, 24, 12.8, 13.1race, 10.3, 23, 18.2(3 runs over 24 hrs),16.2, 21.3, 17, and 9.8 the weekend before the race. All but 3 of these were part of back-to-back runs. The 2nd runs (either the day before or after) were 4.3 miles up to 10.2. Most 2 day total was 30 miles (6+24).
As far as my goals were concerned:
24 mile max distance - Met
Weekly Max: hit my personal max of 47, with 3 other weeks over 40 miles (all three were 44 miles)
Wasn't a goal, but my average mileage over the 16 week 50k training was ~34.
I trained with a camelbak on and ran on trails for just a few of my long runs. I have modified that now and run more trails for my long runs. (Paris Mtn State park in Greenville, SC)
Only real cross-training I did was 30 minutes of Yoga 1-2 times a week.
I got by on a little less sleep, doing all my weekly runs before getting to work at 7am. My weekends runs were also done before the start of the day. I would get my runs out of the way early, getting home around 8am most of the time in order to spend time with my family, including my ~6 month old! (Also to avoid the heat of the south, being in SC, it was often 67° and humid at 5am).
I did run a few races for speed (10 miler PR and 10k PR), but the others just for fun. The long training runs were SLOW, but so very helpful.
The 50k I ran was wonderful. And I am now hooked!
I took photos, enjoyed myself (the views, the experience, the company) but moved forward as much as possible. The aid stations were Heaven (practice eating during runs; I typically have no issues with this). For training runs - my fuel was Gu (1 every 6-7 miles), and I started taking Succeed S-Caps! at that 50k and continue to take them on runs of 20 miles or more, ~ 1/hr).
I drink alot anyway, but hydration is very important. I am never without a water bottle or camelbak. Sometimes both.
Remember - you can do it. There are so many other people who had doubts, but overcame them and finished.
I could go on about what a fantastic, inspiring, kind group of people I have met thru this - but I won't. It doesn't take long to figure that out on your own.