This short workout, designed by Mark Beier, co-director of training at Shred415 in Chicago, maximizes every second, with fast-paced strength moves interspersed with bouts of cardio. “The 1-minute runs, on a treadmill or outside, tap into the aerobic system and challenge the body to use oxygen for energy,” Beier explains. “The end result will be an elevated resting heart rate post-workout and therefore the body will be burning more calories post-workout from fat.”