Followby Menno Henselmans
When you’re trained as an economist, you look at the world differently.
I’ve been getting a lot of questions about the benefits of circuit training, and people generally get annoyed with my answers. I can’t help it. I like the truth, which means I give them a careful cost-benefit analysis.
Some people say, “There’s no room for discussion with you.” Not true, I love talking about fitness, so let’s talk about whether or not you should ‘invest’ your time and effort in circuit training.
Circuit training: a product of science.
Many training techniques were ‘developed’ when some bro stumbled upon it, and then popularized when a celebrity picked up on it. Think bicep curl 21s. If Arnold Schwarzenegger hadn’t done them, nobody would have heard of them. (If you don’t know what they are, you’re not missing out.)
Not so with circuit training. Circuit training was carefully designed by R. E. Morgan and G.T. Anderson at the University of Leeds in 1953.1 During a traditional set scheme, you perform a set of an exercise, rest, perform a set again and rest again etc., until you’ve completed all your sets for that exercise.
In a circuit, you perform several exercises in a sequence and only rest once you’ve completed a set of all of them. Then you rest, perform the circuit again and rest again etc., until you’ve completed the desired number of circuits.
In the original version of circuit training, you select a group of 9-12 exercises that trains the entire body with minimal overlap between exercises. When one muscle is worked, the others can rest. This makes optimal use of your rest periods, so it’s very time efficient. Ok, aside from the obvious, how does circuit training compare to traditional sets?
Is circuit training better for weight loss?
An often heard benefit of circuit training is that you burn more calories or fat than during traditional training. This is true relative to the amount of time spent training, but not for total energy expenditure.2 The total amount of calories burned is the same for training sessions with the same total volume.
It doesn’t matter if you perform the exercises in a circuit or in any other order. In physics, energy is measured as work. Work is equal to the product of force and displacement (W = f * d). Basically, the number of calories you burn is determined by how hard you push something, and how far you push it. It doesn’t matter how long you train. You’re lifting the same weights in the same manner for the same distance. Thus, you burn the same amount of energy.
In fact, circuit training can decrease work capacity and therefore how many calories you burn. If your cardiovascular system can’t keep up with the lack of rest in between exercises, you won’t be able to perform as many reps as you would in a traditional training. This is especially true if you’re an advanced athlete.
The stronger you are, the more rest you need between sets to maintain your work capacity.3-5 Beginners can often get away with very short rest periods and bounce from exercise to exercise with unfaltering enthusiasm. But if you have become strong enough to squat about 1.5 times your bodyweight as a man or your bodyweight as a woman, you’ve probably noticed this is no longer the case. A set 10 reps of squats at your 10 rep max now leaves you gassed.
This is because the absolute load determines the amount of work. The weight that you couldn’t even lift before may now be just 75% of your max, but it’s still the same weight and it still requires the same force to move it. You’ve just become capable of producing that force. The energy it takes is the same as before. So the saying “It never gets easier. You just get stronger,” is true.
Why the “afterburn effect” from circuit training is overrated.
Even though circuit training does not increase total energy expenditure during exercise, it does increase the amount of energy you burn after training.2
Excess post-exercise energy consumption (EPOC), or the number of calories you burn after a workout, increases as a result of the increased cardiovascular stimulation of not resting in between exercises. In general, your body requires more energy to return to its resting state after short and vigorous exercise than longer and less intense exercise. How much more?
Take a look at the following graphs. They demonstrate the difference in energy expenditure during a full-body workout with traditional sets (right) and without rest between exercise pairs (left).6
Calorie burn of circuit training (black bars) versus traditional strength training (grey bars).
Seems impressive, right? The differences were statistically significant too. However, statistical significance is not the same as “meaningful,” which also requires taking effect size into account. Basically, the results might be different, but not large enough to have a noticeable effect in the real world. (Read this if you don’t know the difference and want to improve your ability to interpret fitness research).
In this case, the graphs can be deceiving, because they plot energy expenditure in joules instead of calories and in the left graph energy is expressed relative to time. If you calculate the increase in total energy expenditure due to not resting between exercises, it’s a meager 18 calories (kcal).
EPOC in general is overrated. A recent review of the literature found that EPOC ranged from a negligible 4.1 kcal to an unimpressive 114 kcal.7 The highest values of 113 and 114 kcal were found for weightlifting sessions of 60 and 50 sets. Unless you train with a volume that would make Schwarzenegger’s routines look like HIT, it’s safe to say EPOC for you amounts to less than a hundred calories per workout.
A 2-in-1 short circuit.
So will circuit training just provide the same benefits as traditional sets in less time?
Several studies show that circuit training and traditional training are equally effective at developing strength, speed, power, and muscular hypertrophy. When it comes to developing endurance, circuit training is considerably better.8-10
However, these studies were all done on untrained subjects and the longest study only lasted 12 weeks. They hadn’t developed the strength that comes with the aforementioned decreased tolerance for not resting between exercises.
In studies where circuit training requires a reduction in intensity to maintain the workload, traditional training results in superior strength gains.11 In the only study of somewhat resistance-trained subjects that lasted more than three weeks, there was a consistent albeit non-significant trend for superior power adaptations in the traditional group compared to the circuit training group. Look at the graphs below. The bars represent changes in power and bone strength.
Peak power output on bench press after circuit training or traditional strength training.
Maximal power output for people who did circuit training (left), or traditional strength training (right).
Bone mineral content in people who did circuit training (left), or traditional strength training (right).
More fundamentally, the nature of the stress imposed on your body during circuit training is different from traditional strength training. During circuit training, you place a nearly continuous demand on your cardiovascular system. Circuit training effectively combines cardio and strength training in the same workout. Very efficient, but readers familiar with my stance on cardio should be skeptical.
When you subject your body to two training stresses that are on different points of the strength-endurance continuum, this compromises the adaptation to both. This is called “the interference effect.” It occurs because the adaptations required to optimally adapt to endurance training and strength training are physiologically distinct. For example, after cardiovascular training your body wants to convert its muscle fiber type composition to a slow-twitch dominant profile to increase endurance.
After strength training, it wants to convert muscle fibers to a fast-twitch dominant profile to increase strength.
Will circuit training yield the results you want?
Circuit training works exactly as intended by Morgan & Anderson, the guys who first studied it. It’s a way to perform full-body strength workouts that also serve as cardio in just 20 minutes. It’s easily marketed as ‘holistic’, it can be performed in groups by placing exercise stations in a literal circuit, and it gives people the instantly gratifying endorphin rush.
As such, it is very suitable for the recreational fitness crowd that wants a bit of everything without investing a large amount of time. A circuit is also a great way to structure your training if you don’t have the time for a traditional session.
However, if you train for maximal strength and muscular development, there’s no need to bounce from exercise to exercise. Circuit training isn’t magic. It’s a compromise. So you can take your sweet time.
About the Author
Bayesian bodybuilder, popular science author and online personal trainer, Menno Henselmans helps serious trainees attain their ideal physique using scientific and Bayesian methods. Follow him on Facebook or Twitter and check out his website for more free articles.
References
1. Sorani, R. (1966). Circuit training. Dubuque, IA: Wm. C. Brown.
2. Effects of different strength training methods on postexercise energetic expenditure. Da Silva RL, Brentano MA, Kruel LF. J Strength Cond Res. 2010 Aug;24(8):2255-60.
3. Willardson JM. A brief review: factors affecting the length of the rest interval between resistance exercise sets. J Strength Cond Res. 2006;20(4):978-84.
4. Ratamess NA, Chiarello CM, Sacco AJ, Hoffman JR, Faigenbaum AD, Ross RE, Kang J. The effects of rest interval length on acute bench press performance: the influence of gender and muscle strength. J Strength Cond Res. 2012;26(7):1817-26.
5. Arazi H, Mirzaei B, Sangdevini M, Abadi MRH. An interaction between exercise order and rest interval during lower-body resistance exercise. Baltic J Health Phys Activity. 2012;4(2):77-83.
6. The metabolic costs of reciprocal supersets vs. traditional resistance exercise in young recreationally active adults. Kelleher AR, Hackney KJ, Fairchild TJ, Keslacy S, Ploutz-Snyder LL. J Strength Cond Res. 2010 Apr;24(4):1043-51.
7. Farinatti, P., Castinheiras Neto, A. G., & da Silva, N. L. (2012). Influence of Resistance Training Variables on Excess Postexercise Oxygen Consumption: A Systematic Review. ISRN Physiology, 2013.
8. Similarity in adaptations to high-resistance circuit vs. traditional strength training in resistance-trained men. Alcaraz PE, Perez-Gomez J, Chavarrias M, Blazevich AJ. J Strength Cond Res. 2011 Sep;25(9):2519-27.
9. Alcaraz, P. E., Sánchez-Lorente, J., & Blazevich, A. J. (2008). Physical performance and cardiovascular responses to an acute bout of heavy resistance circuit training versus traditional strength training. The Journal of Strength & Conditioning Research, 22(3), 667-671.
10. Hagerman, F. C., Walsh, S. J., Staron, R. S., Hikida, R. S., Gilders, R. M., Murray, T. F., … & Ragg, K. E. (2000). Effects of high-intensity resistance training on untrained older men. I. Strength, cardiovascular, and metabolic responses. The Journals of Gerontology Series A: Biological Sciences and Medical Sciences, 55(7), B336-B346.
11. Physiological adaptations to strength and circuit training in postmenopausal women with bone loss. Brentano MA, Cadore EL, Da Silva EM, Ambrosini AB, Coertjens M, Petkowicz R, Viero I, Kruel LF. J Strength Cond Res. 2008 Nov;22(6):1816-25.
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