Interval training: A shorter, more enjoyable workout?

High-intensity interval training (HIIT) is a time-efficient way for people to improve their fitness and cardiovascular health. Even short bursts of high-intensity activity may trigger the release of mood-boosting brain chemicals. Traditionally, HIIT features 30 to 90 seconds of high-intensity effort followed by an equal or longer period of lower-intensity activity or rest. HIIT variations include fartlek (Swedish for “speed play”), which uses environmental cues to set intervals, and Tabata, which features 20-second intervals of intensity followed by 10-second recovery intervals.