Interval training
Interval training is broadly defined as repetitions of high-speed/intensity work followed by periods of rest or low activity.
This training technique is often practiced by long distance runners (800 metres and above) although some sprinters are known to train using this technique as well.
Distance runners often practice intervals on tracks, running hard at a certain pace for a specified distance (or, less often, time) and jogging, walking, or resting between (for a set distance/time.) An example could be 12 repetitions of 400 meters with a 200-meter jog between each. Distances can also vary; one example would be a "ladder" workout consisting of a 1600-meter, two 1200-meter, three 800-meter, and four 400-meter repetitions, each at an appropriate speed and with an appropriate amount of recovery.
Interval training is a favorite of coaches because of its effectiveness in cardiovascular buildup and also its ability to make more well-rounded runners.
More generally, it can refer to any cardiovascular workout (e.g. stationary biking, running, rowing, etc.) that involves brief bouts at near-maximum exertion interspersed with periods of lower-intensity activity. One popular workout that incorporates this methodology is so-called "walk-back sprinting," in which one sprints a short distance (anywhere from 100 to 800 meters), then changes directions and walks back to the starting point (the recovery period) to do it again. To add challenge to the workout, each of these sprints may start at a predetermined time interval, e.g. 200 meter sprint, walk back, and sprint again every 3 minutes. The time interval provides just enough recovery.
It is believed by many in the fitness industry that this method of training is more effective at inducing fat loss than simply training at a moderate intensity level for the same duration. This has been confirmed in at least two studies.[1] [2]
Swedes came up with a term for a type of training that lies in between interval training and plain distance training: fartlek, which means speed play, and consists of distance running "anywhere" with bursts of harder running at more irregular points, lengths, and speeds compared with interval training. Not only is it an efficient training method, fartlek training can help one avoid injuries that often accompany non-stop, repetitive activity, and provides the opportunity to increase one's intensity without burning oneself out in a matter of minutes.[citation needed]