Short Fast Intervals
Similar in form to long intervals, these shorter, faster repeats require you to walk additional intervals at a slightly faster-than-race pace.  Being shorter, these intervals often prove the most fun, at least at the beginning.

Warm up well and keep in mind the same discipline as maintained during the longer repeats.  Each repeat must be consistent in pace. These workouts are actually considered VO₂ Max training and thus improve the body’s oxygen capacity.