fartlek
noun
fart·lek
ˈfärtˌlek
plural -s
: endurance training in which a runner alternates periods of sprinting with periods of jogging
Word History
Etymology
Swedish, from fart speed, pace (from Middle Low German vart journey, pace, alteration of Old Saxon fard; akin to Old English fierd, fyrd military expedition, campaign) + lek play, game, from Old Norse leikr