An article here explains more:
On September 15, 2007, I completed what I am told is the sixth toughest 100-mile run in the world, the Angeles Crest 100 (the Western States 100 doesn’t really even qualify in the top ten). I averaged 6.5 hours of training per week. That includes strength training (almost 3 hours), CrossFit, and speed, interval, and pace work. My body learned to become aerobic at the higher paces, and even during the speed work (see next paragraph on the testing). My one-repetition maximum squat at the beginning of this revamping was 250 pounds. Three weeks before the race I could do 240 pounds for six consecutive reps pretty easily. I didn’t put on a single pound of body weight, and I set personal records at every distance I ran. I showed up to the race in an almost perfect mental state, not overtrained and broken down. I was positive, and I took care of my body pre-race: lots of fluids, clean nutrition, plenty of myofascial release, and stretching. I went in with the expectation of finishing, and I did just that.There is an FAQ on the approach here.
It is an intriguing debate.
Gym Jones' Mark Twight and Mountain Athlete's ROb Shaul have been down this avenue already and concluded that to go long you have to train long too, at least from time to time.
Rob Shaul explains:
In other words, all that endurance training does for you is prepare for the specific endurance sport/activity you train for. But sprint/interval training can help you prepare you for long, slow events, with a fraction of the time investment.
Mark Twight at Gym Jones has found that short, sprint interval and metabolic conditioning, like the way we train at Mountain Athlete, can help prepare you for endurance events, but not more than one or two in a row. You have to train long, to go long.
The point: our training is best for preparing you for all types of eventualities in the mountains, but you need to supplement it with long-slow training on the weekends once every two weeks or so.
Mark Twight's thoughts are here:
Finally, this year marks the return of my endurance. After having built a 20-year base I fell into the trap of thinking there might be a free lunch. I went against everything I had learned over those 20 years because the argument and its presenter was quite convincing, and I was susceptible to the easier way, the cure-in-a-bottle way, and I wanted the experts to be wrong. I went into it headlong, and received enough positive feedback to swallow the hook rather than letting it set in my lip. Emphasis on short-duration, high-intensity work didn’t strip endurance from me right away, rather the opposite occurred in the beginning. However, 18 months of nothing but short, hard efforts did “cure” my endurance. Despite an ability to go hard for durations up to three hours in length, “hard” is a relative term that didn’t equate to fast in my case. I couldn’t recover quickly from such efforts nor did I improve even after I balanced short, high-intensity work with longer, low-intensity training sessions. I realized that if I didn’t spit up the hook I’d be stuck on the low plateau I’d chosen for the rest of my life. While some are content with mediocre performance – especially if someone keeps telling them its “elite” – I expect better of myself and I’m willing to suffer trying to achieve it.
Over one year ago I cut out the hook. I began rebuilding my endurance. It is taking a long time. Every day I cursed myself for having sacrificed it and all of the hours and days and years I had worked to achieve it. I trained 435 hours in 2006 but spent inordinate time in the gym, 57 hours, which I could have spent more wisely doing other work. This year, with slightly more total volume and 50% less time spent in the gym, my benchmark lifts are equal to or heavier than last year. Many of them better than in 2005 when I weighed 5% more and spent over 100 hours in the gym. That said, Dan John reminded me that this year’s performance, as with any other year, does not exist in a vacuum, it sits on the foundation of the previous years. This season my lactate threshold occurs 11 beats per minute higher than in 2005. As a percentage of MVO2 it is within 2-3 beats per minute of the highest levels I achieved in the mid-90s. I can put out a reasonable amount of power for about four hours, and keep going for at least eight. I’m still a bottom-of-the-barrel Cat 5 road racer – where everyone must start – but I as long as I regain and maintain the general fitness required by the sport I can learn its specific technical aspects and continue gaining the experience I need to progress. This year I also learned that at 2-3% body fat my power drops off but at 5-6% I’m still light enough to motor uphill, power output is better, and I recover faster day-to-day.
The crossfit endurance approach is a very interesting one, but I must admit the thinking - and experience - of Mark Twight seems to indicate a need to add some long slow stuff on occasion if this is your aim.
Of course there is a debate as to whether such prolonged endurance exercise is even healthy! but if that is your aim as an athlete.......
UPDATE - it is also worth reading through Lyle McDonald's discussion of intervals. Admittedly most of this is about intervals for fat loss, but it is still an interesting discussion.
Steady state versus interval training: Getting to the point Part 1