Circuit training is a popular form of fitness session used by the army, navy, sports teams, squads of athletes/swimmers as well in health clubs and fitness centers. It is generally assumed that a course of circuit training will improve both aerobic fitness and strength, thus making it a very useful conditioning method.

The type of circuit used in the studies involved weight training exercises, typically 10-12 weights exercises for both the upper and lower body. Subjects performed 15 reps or 30 seconds worth of each exercise in rotation. 15-30 seconds rest between exercises was taken and three circuits were performed. This kind of workout takes around 30 minutes to complete.

The loads for each weight exercise were normally 40-50% of 1 RM, which is half the maximum possible load the subject could lift on each exercise. Sessions were completed three times a week for 8-12 weeks. The reason weights exercises were used as opposed to bodyweight exercises, which are common in many circuit-training routines, was to enable the researchers to control the loading levels. In these studies all subjects lifted the same relative load and completed the same amount of work, so they could be compared fairly.

Aerobics Fitness Improvements

Research has shown that continuous running, cycling or rowing at around 75% of max heart rate for 20-30 minutes, three times a week for 8-12 weeks will lift V02max by around 20%

Circuit-Training Routines

In a circuit weight training session, heart rates average around 80% of max, but oxygen consumption only 40% of V02max, which is the minimum level for aerobic fitness improvements. The energy cost of a circuit training session of this kind has been shown to be 6-9 kcal/min depending on bodyweight.Thus circuit weight training routines should be considered a low to moderate form of aerobic training, with the benefits being much less than with traditional training.

Circuit training sessions with rest periods of 60 seconds have shown no improvement in V02max, so keeping the rest periods minimal is important for an aerobic-training stimulus. Alternating between upper and lower-body exercises, so that while the arms are recovering the legs are working and the heart rate is kept going can do this continuously.

The V02max of the women pre-training is much lower than the men's: 35.5 ml/kg/min as opposed to 47 ml/kg/min. This suggests that a higher level of initial fitness may mean a higher intensity of aerobic effort is needed for further improvement. Thus the moderate gain in aerobic fitness shown in the studies, around 5% uplift in V02max, may not occur in fitter individuals.Studies have also shown that blood lactate levels increase dramatically with circuit work, suggesting a high anaerobic content to the training. This would be expected since weight-training exercises are of high intensity and require anaerobic glycolysis. Thus circuit training may be more beneficial in developing anaerobic endurance than aerobic fitness - specifically, the ability to tolerate and buffer elevated lactate levels will be improved.

Circuit training could be seen as a form of interval training; high-intensity anaerobic bouts of weight training exercises with low-intensity aerobic recovery periods. Circuit training may thus be considered useful for some.athletes as an alternative form of anaerobic conditioning training. Trainers should remember that beginners may find circuit training difficult, not because it is tough on the aerobic system but because lactate levels rise above threshold levels.




Circuit training which used loads of 40-50% of 1 RM show improvements on upper- and lower-body tests of 10-30%. This compares favorably with studies using traditional training methods, e.g., three sets of 6-10 reps per exercise.

However, general opinion is that traditional training methods are the best. Traditional strength training uses higher intensity loads with longer rest periods, usually 60- 90% of 1 RM with 1-4 mintues rest, and thus greater strength can be developed. In my experience, most athletes from strength and power sports always use traditional training methods in pre-season and competition periods as their priority method for improving strength and power.



However, endurance athletes and games players may choose to use circuit weight training routines to build/maintain moderate strength while at the same time benefiting from its interval-type content which develops anaerobic endurance.

Change in Body Composition

The research studies consistently show that lean body mass increases with a course of circuit training. A 1-3.2 kg gain in lean body mass can be expected with a consequent decrease in relative fat mass of 1-3%, total weight remaining unchanged. This is a major benefit of circuit training, especially for those who want to get in shape and tone up their muscles.

With traditional aerobic training, a decrease in relative fat mass has led to a decrease in total weight with little change in lean body mass. The resistance work involved in the circuits encourages muscle-mass development, and thus any fat loss is replaced equally by muscle gain. This makes it easier to maintain the lower body fat or reduce body fat even further because the increase in lean body mass pushes up basal metabolic rate and overall calorie expenditure.
These body-composition changes would support the use of circuit weight training routines in a health and fitness setting where toning up, but not losing weight, were the major goals.