Repeats Repeats are essentially multiple tempo runs combined into an interval training format. The key differences between repeats and intervals lie in the recovery time and the interval pace. Repeats utilize long rest periods during which the runner is allowed to recover fully before doing another fast run. The rest periods often use walking for the intermediate activity. The fast run pace for repeats is usually a function of race pace or race pace goal rather than aerobic potential as are the interval workouts.
Repeats are very useful to runners with good mileage bases training for shorter races.
Fartlek Fartlek is an unstructured form of speedwork often done on varied or cross country terrain. During a moderately paced run, the runner varies his speed by periodically accelerating to harder paces and then slowing back down to the moderate pace. Fartlek is a very effective simulation of passing and surging in shorter races and is useful in building aerobic power and speed especially when done on hilly terrain. It provides a pleasant alternative to structured track interval workouts and provides the extra benefits of running hills and utilizing different muscle groups. Your training runs should be tailored to simulate as closely as possible the terrain, the surface and environment in which you expect to race.