SPRINT

Sprinting simply involves running as fast as you can for a specified distance (such as the 40-yard dash) or for a specified time (such as 30 seconds). Doing all-out sprints from 30 seconds and resting for anywhere from one minute to four minutes between sprints is a great form of HIIT. In fact, one study showed that those running 4-6 all-out 30-second sprints with 4 minutes of rest between sprints, just 3 times a week lost twice as much body fat over 6 weeks as those running at a steady state for 30-60 minutes three times a week. The sprinters also gained one pound of lean muscle mass over the 6 weeks and the slow and steady runners did not.