A group gym exercise method in which endurance exercises (those that increase endurance and stamina) are combined with strength exercises (those that develop the size and strength of skeletal muscles) is known as circuit training.

In circuit training, stations are positioned around the facility, with each one focusing on a different exercise -- sit-ups, pushups, resistance training, weight training, and others. Participating individuals are assigned to each station for mini-workouts of 8-20 repetitions each, and rotate to the next station with little or no rest in between those 15-45 second turns.

This goes on until all stations have been tackled by a participant (one complete circuit) or until a pre-specified time period.

The program may consist of exercise machines, calisthenics, elastic resistance, hand-held weights, or a combination of any of these. Between each station, a 30-second to 3-minute aerobics workout is squeezed in to improve the participant's cardiorespiratory endurance.

This program was developed in 1953 by G.T. Anderson and R.E. Morgan in London and originally comprised 9-12 stations. Today, any number of stations can be employed, according to the circuit's design.

This type of workout is preferred by those who want to get an intensive strength and resistance training because the in-between rests are eliminated to take the participant to her maximum target heart rate as well as her maximum physical effort.

Others turn to circuit training simply for the variety.

If you've been solely on the treadmill for months, or have never tried anything other than the stepper, then circuit training can definitely keep you from getting bored with exercising.

Dr. Len Kravitz, a researcher at the University of Mexico and Program Coordinator of Exercise Science, believes that "variety" of the stimulus to muscle is important, and that if these stimuli are not regularly changed, the benefits gained in muscular or strength endurance will eventually plateau.

What are the advantages of circuit training?

• Circuit training is flexible.If you've got time constraints, a total-body workout can be finished in roughly 10 minutes. If more time is available, you can finish up to four circuits, which would total about 45 minutes.

• Circuit training is challenging and can be psychologically rewarding.A study on unfit female college students concluded that those who were involved in circuit training improved in several aspects of body image more than those who only trained aerobically (Anshel, et al., Journal of Sport Behavior, 2006).

• Circuit training involves a very quick pace that is great for fat-burning.

• Circuit training can be fashioned to whatever fitness level you're at -- whether you're an expert or beginner, you can work out at an intensity that suits you.

• Circuit training can be done either at your home or in the gym.