Circuit training is any workout structured as a series of brief exercises or activities. Different muscle groups are usually worked sequentially, alternating with brief intervals of aerobic activity or rest. The circuit may be repeated one or more times, typically for a total training time of about 30–45 minutes.
Circuit training can be a particularly efficient workout, combining strength and endurance or cardiorespiratory training. Each short burst of resistance exercise, with moderate weights and frequent repetitions, can target a different muscle group, resulting in a total body workout in a short period of time. By working different muscle groups sequentially, circuit training allows the muscles to recover so they can be worked longer and harder, which tones and firms them. Circuit training burns calories and can help with weight loss by building muscle mass since muscle burns more calories than fat tissue, even when at rest. Muscle mass also helps cushion joints against injury.
Circuit training can be adapted for people of any fitness level, from those with physical limitations and disabilities to elite athletes. Circuit training is popular with those who have little time to exercise or who work out during lunch breaks, since one circuit can be completed in as few as ten minutes. Weight-training circuits have become popular among women in recent years since women tend to lose about 1% of their muscle mass each year, beginning in their late thirties, and lost muscle is often replaced with fat. Weight-training circuits also can help protect against osteoporosis. Many athletes use circuit training to keep in shape during the off-season and to work up to more rigorous training during the early preseason. Well-designed circuits can help athletes overcome biomechanical imbalances that are inevitable when training for a single sport. Circuit training also can be sport-specific.
Many people find circuit training easier to stick with than some other exercise routines. It can be easily performed at home with minimal or no equipment and the choices of exercises are almost unlimited. The variety inherent in circuit training can be a welcome relief from more monotonous workouts, such as running or cycling, and exercises are readily replaced if they become too easy or boring. Those that are too hard or too strenuous can be omitted. The amount of exertion and timing of rest intervals can be varied. Aerobic intervals can be increased by shortening or eliminating rest periods.
Circuit training can take many different forms, with various combinations of exercises that can change over time. Circuit training often mixes strength or resistance training with cardiorespiratory activities of varying intensities. The latter can be as simple as jogging in place between weight-training stations. Circuits range from four to about 15 exercises, usually performed for 30–90 seconds each, sometimes with 30–90-second rest intervals in between. Sometimes exercises are repeated a specified number of times without timing or the times are varied depending on the exercise. As fitness improves, station times can increase or rest intervals can decrease or be eliminated. Another variation is to simply move on to the next exercise when fatigue sets in, to give the worked muscles a rest. Usually one to three circuits are completed, often with two to three minutes of rest between circuits.
A very demanding total-body circuit might involve 30–60 minutes of 3-minute high-intensity exercises, with 30-second rest intervals. The workouts may change weekly, with a less-intense recovery week after the first month, followed by very intense and longer workouts for the second month.
Specific types of circuit-training regimens include:
At-home training can follow or adapt one of the many circuits available in books or online. DVDs are also available. Alternatively, anyone can design their own circuit. No equipment is necessary other than a carpeted floor or exercise mat. Toning rings, resistance bands, jump ropes, hand weights, or a stability ball or medicine ball can be used. Gallon milk jugs filled with water or sand can substitute for hand weights. A treadmill, stationary bike, box or aerobic step, or other home-exercise equipment can be incorporated into the circuit.
Home circuit training for both increasing muscle mass and working aerobically might include the following exercises for 45 seconds each, without rest intervals except for moving from standing to the floor and back:
Gyms and weight rooms often arrange their machines in a circuit, so that different muscle groups are worked sequentially. Some commercial franchises specialize in 30-minute circuit training for women and/ or men, especially those who are overweight or out of shape. These establishments typically have 15 machines with resistances that adjust automatically. Thirty seconds on each machine and 30 seconds jogging on a pad between machines allows for two circuits to be completed in 30 minutes. A signal indicates when it is time to change stations or jog between stations. Heart rate checks are performed every ten minutes.
Circuit training in gyms often combines traditional floor and standing exercises with cardio and weight machines. Beginners might start with 5-lb. (2.3-kg) weights and work up to heavier weights. Rest intervals may be simply moving from one station to the next. A typical gym circuit might consist of:
Sport-specific circuit training generally employs fewer exercise stations than general-fitness circuits, with exercises that incorporate movements used in the particular sport. Endurance circuit training, for sports such as distance running, cycling, or rowing, generally incorporates only very light weights or other resistance. The warm-up and cool down are significantly longer, and much more time is spent at each station, Rest intervals are eliminated. Runners may alternate exercises with running various distances.
At the other extreme are circuit-training programs designed by physical therapists for the elderly or disabled or for clients recovering from injuries. Such circuits may focus on accomplishing daily household tasks, such as dressing, making the bed, folding towels, setting the table, and sweeping. As mobility improves, tasks are accomplished without rest intervals and more demanding tasks are added.
Circuit training at home has the advantages of being free and convenient. However, any at-home exercise program requires dedication and self-discipline. Some people have trouble staying motivated and undistracted when they are exercising at home, although varying the exercises in the circuit can help.
Thirty minutes of even daily circuit training may not be enough to maintain weight and physical fitness over the course of a lifetime, although three 30-minute circuit-training sessions every week is an excellent starting point for the physically inactive. However, even well-designed, total-body circuits do not necessarily incorporate all of the exercises that are required for strength, endurance, cardiorespiratory or aerobic fitness, flexibility, and balance. Although circuit training can improve cardiorespiratory fitness, especially in beginners, it is not as effective as aerobic endurance training.
An exercise or circuit should be stopped immediately if it becomes painful or if a “pop” is heard or felt. This is particularly important for young people whose bones, joints, and tendons are still growing and developing. It is easy for children and teens to overdo exercises, causing strains or even permanent damage.
Anyone just starting to exercise—especially those with chronic medical conditions such as heart disease—should consult their physician before undertaking circuit training. People with medical concerns, obesity, or physical limitations should seek qualified help for formulating an appropriate circuit-training program. A circuit-training workout should always begin with a warm-up, such as five minutes of fast walking, to raise the heart rate. Beginners, in particular, can benefit from circuit-training machines in gyms and an instructor or trainer to demonstrate their correct use. No one should use exercise equipment or machines without proper instruction.
Circuit-training workouts should conclude with a five- to ten-minute cool down and stretching routine. Most people should avoid circuit training on consecutive days.
Circuit training has the potential to cause injuries, especially when people jump into intense new exercises without working up to them. Shoulder damage, such as torn rotator cuffs, is a particular concern.
Circuit training has been shown to be an effective and efficient means of losing weight, maintaining weight loss, and improving physical fitness. Studies have indicated that circuit training, such as alternating weight exercises with jogging, improves both cardiorespiratory fitness and strength more than a weight routine alone.
Studies have shown that moderate strength or resistance circuit training can lead to significant improvements in the metabolism of cholesterol, reducing triglycerides, and raising high-density lipoprotein (HDL, “good cholesterol”) levels in the blood. Circuit-training machines, available in most gyms, are often recommended as the most beneficial exercise for patients with heart disease, especially those who are just starting to exercise.
See also Cardiorespiratory fitness tests ; Warmup and cool down .
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Margaret Alic, PhD