For years, perhaps even six years, I have wanted to do the marathon specific intensive workout, all the way to at least 21k, and Saturday, September 14th, 2013, I did. For some background, Renato Canova is a really good distance running coach, specifically for the marathon. I know this because back in 2007, until about 2010, Nate Jenkins, a 2:14 marathon runner and blogger in Massachusetts weekly blogged his training and training theory which was almost entirely based on the Italian school of marathoning, best communicated and advertised through the coach Renato Canova, although others like Gigliotti are or were just as good, Canova took to the serious runner message boards to explain and wrote a book. Now he is the go to guy even though others have the same skill.
The marathon specific intensive idea is to alternate kilometers, you could do miles or half miles or two kilometers, but kilometers for me always resonated best. Alternate a fast one, with one just slightly slower. I've done this workout a number of times, when preparing for a 10k or a half marathon or marathon. The gold standard for me has always been to hit the goal pace and run a full half marathon. Saturday I ran a half marathon over hilly terrain in 1:14:54 alternating fast and slow kilometers, an average kilometer pace of 3:33. Plus I finished strong! This is the last workout that Abel Kirui ran before winning the world championships in 2011 and Moses Mosop ran before running the fastest debut marathon at 2:03:06 in Boston in 2011.
Canova writes this workout either at hard at 103% of marathon pace and moderate at 97% of marathon pace sometimes, but in Kirui and Mosop's training it was basically 104%/90%, so I targeted mine at current PR paces of 104%/98% or ideal goal paces of 100%/94%, either way the goal is to get really comfortable recovering at a relatively fast pace. The first time I did over 10k was in 2013 this spring. This workout was nearly double I had ever done before, although paces were slower to be specific to the marathon.
At the faster paces you work your aerobic capacity and to a small extent the lactic threshold. The slower paces teach your body to really recover. When the easiest part of the workout is 5:55 pace the body learns to rest and take in oxygen and use more fat because it fears the 5:30 pace about to be placed on it.
I like these workouts because they increase lactic threshold and increase aerobic endurance. To run this workout for any length of distance, say more than 7k, maybe even more than 5k, one must run the slow portions aerobically. The faster one can aerobically run and recover from a harder aerobic pace or anaerobic pace the faster one can run a marathon. My moderate kilometers were around 3:40 pace, the best guys in the world run 3:18-3:20 at altitude on dirt, including hills, after fast kilometers in 2:50.
In short, for people training for sub 2:40 type marathons, simply running 20 miles once a week and doing 6 x mile intervals or 10 mile tempos eventually becomes not enough to reach one's potential. One of the workouts that gets a person to the next level in the marathon is the marathon specific intensive workout. Another one, for another day is the marathon specific extensive workout, such as 4x6k or 6x5k or 8x3k, all with 1k recovery, honestly, I still haven't done one of these yet. Of course there are the 15 miles at 98%, 20 miles at 95% or 25 miles at 92% to round out the marathon specific tempos. Basically those three styles of pure tempos, specific intensive, and specific extensive are the five workouts that take your marathon performance to the next level. Plus a special block, which is about 2/3rds of one of the above five workouts twice in one day. It's not Yasso 800s, or cruise intervals, or a 20 minute tempo or a conversational long run that take one's marathon performance to the next level, it is the long hard close-to-marathon-pace workout that leaves you in tears wanting a nice warm bed that ups the game.