Circuit training involves workouts in which you do multiple different strength-training exercises in a row, with a minimal break in between. These exercises help build muscles, and quickly transitioning from one to the next keeps your heart rate high. In addition to providing a cardiovascular workout, circuit training can also help increase your muscle endurance.
One of the first circuit-training regimens had participants perform 15 to 18 repetitions of 10 different exercises, such as inclined situps, arm curls and leg presses, with 15 seconds of rest in between. This type of workout works well for building muscle endurance because programs designed to improve muscle endurance often call for exercise sets of 12 to 25 repetitions. The idea is that doing more repetitions at a lower weight will help build up slow-twitch muscle fibers, which help increase the endurance of muscles. Circuit training has the added benefit of keeping your heart rate high, improving your overall endurance.