Endurance, the amount of time you can stay active, is a big part of staying in shape. Building your endurance by working out and pushing yourself can put you on a path to health and fitness for the future. Cardio training—whether running, biking, or swimming—is one of the best ways to build endurance and get a great workout. Learn about safety during cardio workouts, as well as how you can make a plan for cardio training—and stick to it!