Speedplay

Fartlek, which means "speed play" in Swedish, is a training method that blends continuous training with interval training. Fartlek runs are a very simple form of a long distance run. Fartlek training “is simply defined as periods of fast running intermixed with periods of slower running." For some people, this could be a mix of jogging and sprinting, but for beginners it could be walking with jogging sections added in when possible. A simple example of what a runner would do during a fartlek run is “sprint all out from one light pole to the next, jog to the corner, give a medium effort for a couple of blocks, jog between four light poles and sprint to a stop sign, and so on, for a set total time or distance." The variable intensity and continuous nature of the exercise places stress on both the aerobic and anaerobic systems. It differs from traditional interval training in that it is unstructured; intensity and/or speed varies, as the athlete wishes. Fartlek training is generally associated with running, but can include almost any kind of exercise.

Swedish coach Gösta Holmér developed fartlek in 1937, and, since then, many physiologists have adopted it. It was designed for the downtrodden Swedish cross country running teams that had been beaten throughout the 1920s by Paavo Nurmi and the Finns. Holmér's plan used a faster-than-race pace and concentrated on both speed and endurance training.

This is the first session that was designed by Gösta Holmér for a cross country (multi-terrain) runner. This is also an example of what a fartlek session might look like, but fartlek sessions should be designed for an athlete's own event or sport, as well as catering to their individual needs. Sessions should be at an intensity that causes the athlete to work at 60% to 80% of his or her maximum heart rate. This should mean that the body will not experience too much discomfort while exercising. An athlete should also include a good warm up at the beginning of the session, and a cool down at the end of the session, to improve performance, minimize post-workout muscle soreness, to decrease the chances of injury and for other reasons.

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Wikipedia