Last year I wasn't quite sure what running to do in the seven weeks between the Fling and the WHW race - I settled for a 30+ mile run, a few 15-ish mile hill runs and a bunch of easy runs. So some long slow stuff but nothing fast. This year we have eight weeks to fill and my plan is a couple of 30+ mile runs (though that might have to change since 7 miles into the first of these today I twisted my ankle coming down Conic Hill after trying to run too quick down one of the rocky sections - I should perhaps of written "don't be a dick" on my hand to help me concentrate as I have a bit of form for twisting my ankle trying to run too fast down rock hills), and one or two interval sessions per week.
This year I've been doing far more interval sessions than previously. Though calling them interval sessions is a perhaps misleading as there is none of this 5 x 1 miles with a 2 min recovery type stuff - I prefer a continuous run with some fast bits and some slow bits, aka fartlek. I guess there has been a bit of debate around why an ultrarunner would do intervals since during a race they'll not typically be running at a fast pace. My feeling is that intervals are one of the best ways to improve running efficiency (especially if they are up and down hills), and also doing fartlek and running the slow bits at ultra pace makes said pace seem somehow easier.
I have two favourite sessions which I thought I would share just in case you are looking for something different to try on a run:
1. Reducing time intervals - for this one, you need find a nice lap of between 1.5 and 3 miles that you are happy to run round a few times. I've got a nice 1.5 mile loop around the local woods that is half uphill and half downhill, and is all on good trails. Then, you set off round the loop at an easy pace. After the first lap, the aim is to do the second lap about 10 to 15 seconds per mile quicker than the first. Then on the third lap, run 10 to 15 seconds per mile quicker than the second lap, and so on until you have done 5 laps, with the fifth lap being maybe two to three minutes quicker than the first one. The idea is to get used to running strongly at the end of a run, and to focus on good running form, when you've got tired legs.
2. Zapping - I once heard this called zapping so that's what I call it. The idea is run fast for a minute, then slow for a minute (or if you prefer fast for 30 seconds, slow for 30 seconds) and repeat until you've been running for about 30 to 40 minutes. It's a good one to really get your legs moving and again I think is a good one for running form and efficiency (especially if some of it is downhill since running fast downhill you have to concentrate on just touching the ground lightly with your feet, there's no time for plodding). As for what pace to run the fast ones, what I aim for is to run at the pace that I would run at if I was running for my life (I find watching The Descent and then doing this run in the dark helps to get my mind in the right place for this).
So the plan is to keep doing intervals over the next 8 weeks, and hopefully my ankle will have recovered well enough soon that I can be running round the local woods late at night imaging I'm being chased by a bunch of carnivorous cavemen.