High-intensity interval training, or HIIT, is trendy in fitness right now.
Circuit training is a little more old-fashioned.
But does this mean one is better than the other? These two types of workouts have more in common than you may realize. And, while HIIT may give you a more intense workout, circuit training also supplies a challenging and effective session.
Which workout you choose for a client on a particular day will depend on a number of factors, but most importantly you need to understand the workouts themselves: what each type really entails, what situations they're best for, and how they can be effective for specific fitness goals.
The concept of circuit training is pretty simple: Move from one exercise to the next, spending 30 seconds to a couple of minutes on each one. A set of five to ten different exercises make up a circuit, and you may complete just one circuit for a workout or do multiple circuits, depending on how much time you want to work out.
This leaves a lot of room for flexibility. You can do all cardio exercises, all strength training, or alternate between cardio and strength. A circuit may focus on upper body, core, or lower body, or you can set it up to move from one muscle group to the next within one circuit. The possibilities with circuit training are nearly endless.
While circuit training is an old standby in the gym, HIIT is a newer phenomenon that has become very popular. HIIT is all about varying the intensity of a workout, so as with circuit training the actual exercise type varies. However, it is generally used with cardio exercises.
The idea is to cycle through several rounds of a short burst of high-intensity effort followed by a slightly longer recovery period at a lower effort level. For instance, a running HIIT workout might include one minute of running at an exertion level of 7 to 9, followed by two minutes at an exertion of 5 or 6. The recovery periods allow you to rest so that you can really push it during the high-intensity periods.
A subset of HIIT is known as Tabata, named for a Japanese researcher. A true Tabata workout is just over four minutes long. It alternates between 20 seconds of all-out effort and ten seconds of recovery. This is challenging, although it is so short overall.
In deciding which workout type is better, perhaps it makes more sense to compare and contrast them. Both are workouts that help people get fit and support weight loss or maintenance, so the real debate is which type to use when. Understanding some of the ways they are similar and different will help you match the workout to the client and their unique needs and goals.
A major issue people run into when trying to make regular fitness a priority is boredom. Working out can be boring. What each of these kinds of workouts can do is provide a little more variety and even some excitement.
It's hard to get bored when you're changing the exercise every 30 seconds or so in a circuit. And the alternation between difficult, intense bouts and recovery periods in a HIIT workout similarly keeps things interesting.
All good trainers know their clients need both cardio workouts and strength training. HIIT is more suited to cardio workouts. You certainly can use weights and do strength training during a HIIT workout. For high intensity, expect to use bigger weights and to move fast.
Circuit training has the advantage of flexibility. You can design a circuit focused on either cardio or strength, but you can also easily alternate between lifting and cardio within the same circuit.
Studies have shown that HIIT workouts produce a higher calorie burn compared to steady cardio workouts at a medium effort level (1). Alternating intense bouts of exercise with a short recovery period is an effective and efficient way to burn calories, which is good for both clients with limited time and those with weight loss goals.
There are fewer studies that compare HIIT directly to circuit training to determine which offers the greatest energy expenditure. But, one did just that and found speed-based HIIT workouts result in a much higher excess post-exercise oxygen consumption, and therefore a higher calorie burn for the rest of the day when compared to circuit workouts (2).
Check out this ISSA post to get the truth about cardio, fat loss, and the best way to lose weight.
When it comes to improving overall fitness, the type of workout you choose is less important than exercising regularly with a combination of strength and cardio. What circuit training and HIIT have in common is that doing either one is better for fitness than doing nothing. Both will make you fitter and improve your health.
HIIT is very good for burning calories, both during the workout and after as it raises your metabolic rate for hours. It is also a good way to build cardiovascular fitness. Circuit training has a lot more variety, so the exact fitness benefits you'll get from it depend on the exercises, pace, and effort. Potentially, circuit training can build cardio fitness, strength, and agility.
The original researchers who developed the Tabata type of HIIT workout found that it improves both aerobic and anaerobic fitness. Compared to a standard HIIT workout, participants who did Tabata workouts saw bigger increases in each type of fitness, especially anaerobic (3).
Any kind of workout comes with risks, especially if they are not done correctly. As a trainer, you plan and guide workouts to keep clients as safe as possible. However, between these two types, HIIT is naturally riskier. There is the risk of overtraining, for instance. And when performing at high-intensity, people are more likely to overdo it or to trigger an injury.
Of course, there is no final, definitive answer as to whether or not one of these styles of workout is better. And that's because it depends. It depends on the individual, abilities, fitness goals, and even personal preference.
You have to match the workout type to each client: know their goals, understand their limitations, and get to know what motivates them and what kinds of workouts they are most likely to stick with over time.
This is how we work with clients, but in general, it's always a great idea to vary your workouts, both for overall fitness and to keep things interesting. Using some circuit training and some HIIT is great for adding variety.
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Falcone, P.H., Tai, C.Y., Carson, L.R., Joy, J.M., Mosman, M.M., McCann, T.R., Crona, K.P., Kim, M.P. and Moon, J.R. (2015, March). Caloric Expenditure of Aerobic, Resistance, or Combined High-Intensity Interval Training Using a Hydraulic Resistance System in Healthy Men. J. Strength. Cond. Res.29(3), 779-85. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/25162652
Schleppenbach, L.N., Ezer, A.B., Gronemus, S.A., Widenski, K.R., Braun, S.I. and Janot, J.M. (2017). Speed- and Circuit-Based High-Intensity Interval Training on Recovery Oxygen Consumption. Int. J. Exercise Sci.10(7), 942-53. Retrieved from https://digitalcommons.wku.edu/cgi/viewcontent.cgi?article=1918&context=ijes
Tabata, I., Nishimura, K., Kouzaki, M., Hirai, Y., Ogita, F., Miyachi, M. and Yamamoto, K. (1996, October). Effects of Moderate-Intensity Endurance and High-Intensity Intermittent Training on Anaerobic Capacity and VO2max. Med. Sci. Sports Exerc. 28(10), 1327-30. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/8897392