Circuit Training

Circuit training is classified as a style of exercise that benefits muscular strength, muscular endurance, cardiovascular endurance, total body flexibility, and stability if necessary. This entry discusses what constitutes a circuit training program, the variables in circuit training, and why it is important to use circuit training in a periodized training regime.

Circuit training was devised in 1959 at Leeds University in England by Morgan and Adamson as a way to improve overall fitness. Since then, circuit training has been used by athletes in all sports at some point in their training. Circuit training routines are composed of a multitude of exercises from resistance training to cardiovascular exercise, and it may use a variety of tools, including medicine balls and Kettlebells, body weight, and resistance training machines.

Program Design

The program design of circuit training will significantly alter the performance outcome. The major variables of the program design are exercise type, the amount of rest between exercises, and the number of exercises in each circuit.

Exercise Type

In determining the type of exercises for the circuit training program, it is important to factor in the individual's level of fitness, existing injuries, and current phase of training. With novice exercisers, the program is usually designed with very basic exercises. Using a resistance training machine is often the exercise of choice with novice exercisers because of the ease of use of a single plane of motion. However, the use of body weight and multiplanar exercises are also excellent and necessary for the novice exerciser, primarily to increase proprioception and functional strength for daily activities.

Many fitness centers have resistance training machines set up in a circuit as a feature for people who are new to fitness centers. The circuits alternate between upper body and lower body exercises, allowing for one part of the body to recover while the other performs. A well-known example of this type of fitness center is Curves, a women's-only fitness center. Although an excellent concept for novice exercisers and women who may be intimidated by the coed fitness centers, extended training with the same circuits or programs will not produce the same positive adaptations from training as it did in the first 6 to 8 weeks. As per the principle of Specific Adaptations to Imposed Demands (the SAID principle), it is prudent to subtly modify the circuit's exercise structure at least every 8 weeks. Modifications can be made by changing the intensity, volume, and tempo and, more important, the plane of motion of movement and demand for stability and application to an athlete or individual's weakest link. An individual's [Page 289][Page 290]functional weakest link is not his or her mobility or stability, rather it is his or her strength or cardiovascular endurance. Exercises in circuits providing improvement in functional mobility or stability for an individual are paramount in circuit training program design.

Table 1 Sample Circuit Training Program for a Novice Exerciser/Athlete

Notes: RM = repetition maximum. a. Rest prior to executing the next exercise. b. Rest prior to repeating the circuit.

Table 1 Sample Circuit Training Program for an Experienced Exerciser/Athlete

Notes: RM = repetition maximum; DB = dumbbell. a. Rest prior to executing the next exercise. b. Rest prior to repeating the circuit.

Rest Intervals

The durations of rest between circuit exercises and rest between repetitions of the entire circuit drastically change the ratios of the energy system's utilization. The three major energy systems used during exercise are the (1) phosphagen system, (2) glycolytic system, and (3) oxidative system. Depending primarily on the intensity of exercise, then secondarily on the duration of exercise and the rest between bouts of exercise in a circuit, one of the three aforementioned systems will be used more than the others. For example, if the work-to-rest ratios between exercises within a circuit is 4:1 (60 seconds of work and 15 seconds of rest), the primary energy system would be the glycolytic system (fast glycolysis and oxidative), which automatically becomes the primary energy system for any exercise lasting more than 10 seconds and less than 3 minutes.

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