"The key is to get totally winded in 30 seconds or less," he says, "If you're on a treadmill [or an exercise bike], start sprinting as the machine speeds up. When it reaches top speed, go all out for 30 seconds. Then slow it down and go nice and easy for 90 seconds to recover." If you're running outside, try to cover about 200 feet—roughly half a city block—as fast as possible. Walk slowly for 90 seconds to cool down, then repeat your course.