Be honest. You probably thought I skimped on the last few explanations of the other training runs. It's because most ultrarunners don't do them. They spend most of their tie and energy focusing on the centerpiece of every training plan- the log run.
Well, except for Crossfit Endurance. If that was your training run selection, go ahead and skip this part. Just don't bitch to me after your 50 miler when your ass crack gets severely chafed, then the cheeks fuse together as they heal.
Okay, where was I? Oh yeah, the long run. The long run serves two purposes:
First, trains your body to deal with the rigors of running long distances. You accomplish this by increasing your long run distance gradually over time. It strengthens your muscles, tendons, ligaments, bones, endocrine system, and any other bodily system that's stressed over long distances.
Second, it allows you to experiment in conditions that are at least somewhat similar to race conditions. How is that water bottle going to feel after 24 miles? Will those packets of spaghetti-flavored Gu still taste good after eight hours of running? Can you bend over to tie your shoes after 32 miles? How about needing to squat to drop a deuce? You can't test these variables without the long run.
Long runs can take on a few different flavors. You could do one single long, continuous run. You could do two shorter runs over two days. You could do five or six shorter runs over the course of one day. Different plans will use one of the different flavors. Personally I like to do all three, though I use the first more than the last two.
When I design my own plans, I like to schedule a run that is long enough for me to develop an “ultra hurt.” I want to experience the point where the pain starts getting annoying; the point where I have to start actively dealing with it. This usually comes at about the 25-30 mile distance.
The longest training run I've ever done is the infamous Kal-Haven double crossing in SW Michigan. Jesse Scott, Mark Robillard, and I set out on a 68 mile out-and-back on a 34 mile rails-to-trails path. It sucked. We had a friend, Tony Schaub, riding a bike to carry some of our gear, but it did little to dampen the extreme beating our bodies took. It definitely crossed the “this run is too long to produce a positive training effect, and will likely just hurt us” threshold. I ran a 100 miler three weeks later and definitely suffered more than I should have. It set me up for a serious case of overtraining that shelved me for months.
The morale of the story- long training runs are important learning tools. REALLY long training runs are stupid.