Circuit training is an interval-based workout program. You complete several different exercises in rapid succession, with short rests in between. Generally, you'll perform each exercise at a high intensity for a set period of time, such as 30 to 60 seconds. After doing one series of exercises, or completing one "circuit," you'll start at the beginning again and complete the circuit one more time. There are various kinds of circuit training. Intervals can be done with weights or weight machines, or they can include cardio -- such as sprinting -- and plyometrics.
Circuit and interval-based workouts hold a number of advantages over traditional exercise sessions. They burn more calories in the same or shorter periods of time, they help you boost your aerobic capacity and they provide a healthy dose of variety that can keep you motivated and interested in your fitness routine. A study by Kirsten A. Burgomaster, et al, published in the Feb. 1, 2005 issue of "Journal of Applied Physiology," also demonstrated that interval workouts increase endurance levels, when six of eight subjects doubled their endurance after just two weeks of the training.
Beginners may be overwhelmed with the effort required to complete a circuit workout, so it's wise to start slowly and allow adequate rest time -- such as 30 to 45 seconds -- between exercises and stations. Weight intervals are usually done with light to moderate weights. The intensity comes from the number of reps and from the short rest periods between intervals. If you're an advanced exerciser, you may not need to rest for more than 5 or 10 seconds before moving on to the next movement. Plan to recover for up to 60 seconds if you are using heavier weights, so that you can retain enough energy to maintain proper form and complete the next interval effectively.
An excellent circuit training workout will combine flexibility, aerobics and strength training, all elements that the American Council on Exercise recommends for a complete and effective routine. Begin with some light cardio work, such as gentle jogging or jumping rope, and a selection of dynamic stretches for major muscle groups. Your circuit exercises could include squats, lunges, push-ups, dumbbell presses, bicep curls, short sprints, calisthenic exercises or core work such as crunches. Select six to eight exercises that you enjoy, perform each for about 30 seconds, rest, move on to the next, and complete the circuit once or twice more. If you choose to do repetitions rather than time bursts, aim for eight to 12 repetitions of each exercise; if using dumbbells, choose weights that fatigue your muscles after about 12 repetitions but don't cause your form to suffer.
Before you try a circuit training workout, consider your fitness level. Interval sessions, especially if they are performed at high intensity levels, are not for everyone and may be harmful for people who are not used to exercising or who have chronic health conditions. You run the risk of straining or injuring your bones, muscles or joints if you try exercises that are too strenuous, so to stay safe, begin with moves that are comfortable and gradually progress to more challenging routines. Finally, speak with your doctor before beginning any circuit workout.