Goal: Introduce higher intensity work to develop an aerobic foundation while learning to control energy expenditure.
How: Start in the middle of the blue zone, then go 10 seconds at 70% of your max speed. Recover back down to the middle of the blue zone as quickly as possible for a 60 second active recovery period. Repeat for a total of 10-20 reps.
Exercises: Any cardiovascular exercise, from pedaling on a stationary bike to field work, is effective for this method.