And who has time for all that?
So, about sixty years ago, circuits were invented. It was shown that you could perform weight training exercises in a continuous circuit for 2-3 total sets and get both a cardiovascular and strength benefit. But, how much benefit do you actually get?
The original circuits, done in the fifties and published in the book Circuit Training, by R.E. Morgan and G.T. Adamson, utilized such exercises as burpees, rope swings, clean and presses, barbell squats, wheelbarrow lifts, dips, pullups, and a few that I didn't recognize, but looked like fun like arm jumps across a ladder. These circuits would vary in length from 10 to 25 minutes and although they were meant to strengthen, their main effect was cardiovascular.
For years, circuits have been used with calisthenics, light implements, and bodyweight only exercises. Circuit weight training is a familiar sight in commercial gyms and health centers around the country using the machines that isolate a body part and take balance, core strength, and natural movement completely out of the picture.
About twenty years ago, bodybuilders started using supersets, or short circuits with much heavier weights meant to stimulate hypertrophy and strength while keeping the heart rate up. And then a number of popular fitness trends began to incorporate high intensity circuits with heavier weights that were supposed to make us stronger, bigger, and more conditioned. However, until recently, it hadn't actually been proven.
What do you mean it hadn't been proven?
Well, I mean no one had actually done any appropriate controlled study to see if the observed training effect was the result of the training or other factors.
A paper published in the Journal of Strength and Conditioning Research in 2008 by Alcarez, et al demonstrated that when comparing a mini-circuit of bench press, leg extension, and ankle extension using 6 rep max loads and 35 second rests to a 6 rep max load bench press with 3 minute passive rest between sets, there was no difference between the bench press efforts and bar velocity. As an added bonus, the average heart rate was approximately 70% HRmax while performing the circuit.
What did I just say?
Basically, they demonstrated that performing exercises instead of resting did not affect the individual’s ability to bench press a load known to induce strength and hypertrophy. And, it provided a good cardiovascular stimulus. A consequent follow-up study by another group, Deminice, et al, looked at 3 different paired sets of exercises using a 10 rep max load. This study showed similar results and lower oxidative stress biomarkers than traditional weight training with longer rest intervals.
Pretty impressive, eh?
So, this would imply that we could get all our work done in less time AND get stronger and bigger all at the same time.
But, that would be basing a whole lot of assumptions off of two papers with no long term results and the added bonus of having used machine based exercises. (I'm being sarcastic, this is not a bonus.)
To get the whole story, we have to take into account the whole picture. Exercise physiologists have been saying (and they’re right) that to continue getting strong, especially for athletes, we need to train at or above 80% of our 1 rep max. Willardson and Burkett did a study in 2008 as well, but they tested rest periods and intensity of the squat. They found that resting less than two minutes diminished the intensity at which the participants could reach and that this minimum 80% could not be reached with less than two minutes rest.
I find this study a bit more useful because unlike the machine based tests, the squat utilizes more of the body’s muscles, including the core and is a more natural movement, ie one we use in athletics and everyday life. The Willardson study did not test a circuit, but it did test a specific recovery period.
So, how do we use this information?
To use this information properly, one cannot assume anything not stated in any of these three studies. However, the sky is the limit in how you can use this in your own workouts. The idea behind circuit training is to keep your heart rate elevated throughout the workout so that you simultaneously get a strength and cardiovascular benefit. If relative strength is an important factor in your workouts, maybe experiment using simple calisthenic or basic cardio exercises such as jumping jacks, jump rope, or rowing between sets to keep your heart rate up, but not stimulate those fast twitch muscles you are trying to rest. Or use an exercises that use different mucle groups such as a pull-up and a squat or a deadlift and an overhead press. Documenting your training and your results will tell you if what you are doing is working or not.
**You will not significantly increase limit strength with circuit workouts unless you are a complete novice for whom anything works for a little while.
In the end, it all comes down to specificity. Untrained folks are much easier to train than trained folks. What I mean by this is I can take a couch potato and have him stack cinder blocks for two hours every day and he will get stronger, have more endurance, and probably lose a little weight. But as he becomes more fit, I have to get smarter with his workouts. I could probably throw him into some bodyweight only circuits and have him work all of his joints through a full range of motion and that will continue to improve him for some time as well. I would then need to perhaps introduce the heavier weight circuits and some additional assistance training. Eventually, if he wanted to get really strong, we’d have to hit the weight room, lift heavy and rest between sets. But, even then to keep progressing, I'd have to keep changing his routine so probably a mixture of all four techniques might be good for him. (Although stacking cinder blocks could perhaps be replaced with something more useful or fun.)
Doing the same thing for too long will always result in plateaus, so mixing things up is good as well. Using a mix of circuits, high intensity interval training, and traditional weight training in an undulating periodized program is a good way to keep things fresh and stimulating and will enable you to keep getting results. But, there must be a plan and an attention to detail because if you miss the plateau, you won’t know when to change. This is why a training log is your best tool in your personal fitness goals. Being able to recognize when you have stopped making progress is vital to your ability to keep moving forward, avoid overtraining, and avoid injury. Regularly test yourself on both strength and endurance to see if you are, in fact progressing, maintaining, or backsliding.
There is no “one way” to train. If anyone tells you otherwise, they’re trying to sell you something.
Alcaraz, Pedro, Jorge Sanches-Lorente, and Anthony Blazevich. "Physical Performance and Cardiovascular Responses to an Acute Bout of Heavy Resistance Circuit Training versus Traditional Strength Training." Journal of Strength and Conditioning Research, 2008: 667-671.
Deiminice, Rafael, Tiago Sicchieri, Mirele Mialichi, Francine Miliani, Paula Ovidio, and Alceu Jordao. "Oxidative Stress Biomarker Responses to an Acute Sessio of Hypertrophy-Resistance Traditional Interval Training and Circuit Training." Journal of Strength and Conditioning Research, 2010: 1-7.
Willardson, Jeffrey, and Lee Burkett. "The Effect of Different Rest Intervals Between Sets on Volume Components and Strength Gains." Journal of Strength and Conditioning Research, 2008: 146-153.