Often athletes believe base development is all about going low & easy, and the build phase is about working hard with high intensity. I would prefer to look at it as a general & specific phase in order to be more precise.
- Base (General) – Developing your chronic training load (CTL) or fitness to a level that is appropriate to your goal race.
- Build (Specific) – Executing specific training that simulates race intensities, requirements, and conditions.
The Specificity Principle is a principle that states that exercising a certain body part, component of the body, or particular skill primarily develops that part or skill.
Each event that an athlete trains for has specific intensity, duration, and skill requirements. Assuming a well developed base has been developed during the general phase, each athlete should turn to executing race simulation workouts each week when approx. 8-10 weeks away from their goal race. Specific workouts should become the predominant focus.
This means that during the specific phase, long course athletes will tend to execute longer lower intensity workouts, while short course athletes will focus on higher intensity workouts. General development for these two types of athletes could be quite similar in structure, but the annual training plans will diverge as each athlete enters the specific phase of their annual training progression.
Simulate your race by executing workouts on terrain that matches or is more difficult than your goal race, practicing your race nutrition, and pacing at the intensity you intend to execute for your race.
Another way to to think about specificity: There are no miracles on race day, just execution of what you have already practiced and experienced in training.