When efficiency and safety are top priorities for you when crafting a fitness program, you might be on the hunt for a single exercise that has three key qualities: It must build strength, challenge your cardiovascular system, and avoid putting a lot of stress on your joints. Sounds too good to be true, right? But surprisingly, there's one move that fits all three criteria: the kettlebell swing, a full-body exercise that requires one simple piece of equipment and can be tailored to meet your fitness level.