slow interval training

Slow interval training is a method of physical conditioning that involves alternating periods of exercise with periods of rest. In this approach, the exercise intervals are performed at a specified level, slightly below an athlete's best effort, and the rest intervals are controlled to allow the heart rate to return to near normal before the next exercise period begins.1

Specifically in slow interval training, the rest period is always shorter than the time it takes to complete the prescribed swimming distance. This method is primarily used to develop an athlete's endurance. It contrasts with fast interval training, which focuses on speed by allowing longer rest periods for near-complete recovery. Interval training, in general, can work both the aerobic and anaerobic systems, utilizing stored muscle energy for short bursts of activity.23