fartlek

CONT: Fartlek is the Swedish for ""speed play,"" and that is exactly what this run is all about. Unlike tempo and interval work, fartlek is unstructured and alternates between moderate to hard efforts with easy efforts throughout.
OBS: Fartlek training is generally associated with running, but can include almost any kind of exercise.

CONT: Fartlek significa 'juego de velocidad' en sueco y fue precisamente en este país donde se inventó este útil y popular sistema de entrenamiento.