It's a new year, but we're carrying one popular 2017 workout straight into 2018. High-intensity interval training—more commonly referred to as HIIT—is No. 1 on the American College of Sport's Medicine fitness list for the second year in a row. Characterized by short bursts of super-intense, heart-pumping movements like sprints, burpees, or jumping jacks, HIIT gained popularity when people discovered that they could get a solid workout in an extraordinarily short amount of time, like 10 or 20 minutes. In an age when we're busier than ever, it makes sense that HIIT is particularly appealing.
HIIT isn't just a timesaver: It also works. "From the heart to the muscles to the metabolic system, all are pushed to the limit, and the body’s response is to function more efficiently," explains Kaiser Permanente's Robert Sallis, M.D.