There are generally two schools of thought on how to approach a training cycle, the Pyramid or the Diamond...
In contrast, the Diamond model focuses on improving all aspects of performance at the same time. You should begin progressing all areas of training from the level you are at currently, and continue progressing every area throughout the training cycle so that each component is at its highest level of development for the race.
Among its chief proponents is Scott Simmons, a several-time National Cross Country Coach of the Year and coach to several top post-collegiate athletes. Simmons details much of his belief in the Diamond model in his book Take the Lead: A Revolutionary Approach to Coaching Cross Country, which he co-wrote with Will Freeman.
Simmons believes that "we do not have to train [the aerobic and anaerobic systems] exclusive of each other, or in separate phases as the pyramid model suggests," but rather should train them simultaneously as the body adapts and progresses in fitness.
So which approach is the best? Like anything, there are arguments to be made either way. I believe, though, that the Diamond model offers several specific advantages:
- Less risk of injury: Progressing each component of training simultaneously reduces injury-risk by not shocking the body with a new stimulus as can happen when transitioning between phases in the pyramid model
- Race ready: The diamond model, I believe, leaves you more ready to race throughout the training cycle, rather than just at the end
- Variety: Mixing in and progressing different aspects of your training throughout the cycle makes training more varied and fun, and in my experience leaves my athletes feeling more fresh and excited about running
Also, I would encourage anyone interested in this topic to check out Scott Simmons' book, which is available at Amazon.