HIIT is a trendy workout, but with all the purported and proven benefits, it’s not likely to fade away any time soon. If you are a trainer or a fitness enthusiast, you need to know about HIIT, what it is, how to do it safely, and why you and your clients should.
HIIT sounds technical, but it’s really a simple type of workout. It stands for high intensity interval training. If you understand cardio fitness, you know there are two basic ways to do it:
Steady-State. Steady-state cardiovascular training is when your workout occurs at a fairly continuous level of effort during which your heartrate remains mostly constant. An easy run at a steady pace is a good example of this. Steady-state workouts are usually at a lower effort and last longer.
Intervals. Interval training is when you change your effort level and heart rate throughout the workout. For instance, if you go to the track and do sprints followed by recovery jogs, you’re doing an interval workout. Intervals are usually a more difficult effort level and are done for a shorter period of time.
A HIIT workout is a type of interval training that maximizes effort and intensity. During a HIIT session, you alternate short, very intense bursts of exercise with rest or recovery periods at a low intensity. The intense intervals are typically done at 80% to 95% of an individual’s maximum heart rate.
A classic example is the track workout runners often include in training. Sprint hard for a short period of time or a short distance and jog it out for recovery before repeating the pattern. You can do HIIT exercise with any cardiovascular activity, including cycling, swimming, and elliptical.
HIIT isn’t new, but it has become more popular in recent years for many reasons. What most people love about HIIT workouts is that they take a lot less time than steady-state training. If you don’t have time for 45 minutes on the stair climber, you can do 20 minutes of HIIT and get many of the same benefits and then some.
High intensity interval training is a unique type of cardio workout that has all the benefits of cardiovascular fitness plus others:
Being able to save time on a workout is a major benefit of HIIT, but you don’t want to sacrifice the calorie burn. It turns out that HIIT workouts burn more calories per unit of time than steady-state cardio. So, you can torch the same number of calories in less time–a great option for clients with a weight loss goal.
One study of calories burned compared 30 minutes of steady-state cycling and running with 30 minutes of HIIT. The researchers found that the HIIT participants burned up to 30% more calories (1).
Studies also show that the calorie burn extends well beyond the actual HIIT workout. This style of training seems to rev up metabolism so that you keep burning more calories than you otherwise would, long after the workout is done.
HIIT boosts your metabolic rate, but it might also shift your metabolism toward using fat as energy and away from using carbs. Studies indicate that HIIT is a powerful fat-burning workout, likely for this reason and because of the increase in metabolism generally.
While losing fat, HIIT can also help you build lean muscle (2). For both of these effects, but especially muscle-building, it’s important to understand that the effects are mostly seen in people who are overweight, obese, and largely sedentary. For already well-trained individuals, HIIT is a great workout, but the fat loss and muscle gain will be less.
Anyone can benefit from HIIT workouts for improved cardiovascular health. Stead-state workouts are good too, but the high intensity periods seem to have a greater effect on things like blood pressure and resting heart rate (3). Again, the effect is more pronounced in people who are overweight or have cardiovascular health issues. Try swapping in a HIIT cardio workout on your next cardio exercise day.
For fit individuals and athletes in training, HIIT is highly effective for boosting oxygen consumption. This is the ability of the muscles in your body to use oxygen for energy and it improves athletic performance. Endurance, steady-state cardio has traditionally been the workout of choice for increasing oxygen consumption. Now, experts know that HIIT does it better and in less time.
HIIT is great for most people, but to get the benefits, you have to do it right. It’s easy to overdo HIIT and end up with injuries. Starting out small and building up to longer, more intense workouts is essential. It’s also important to limit the frequency of HIIT sessions. This is not a workout for every single day.
One of the many great things about HIIT is that you can tailor it to just any individual and their goals. When planning HIIT workouts, consider the five elements that you can vary for each client:
Intensity and recovery duration. For a beginner, start with short burst intensity periods and longer recoveries, for instance 30 seconds on and 30 seconds off. As someone gets fitter and adjusts to this tough workout, plan longer intense periods and a shorter rest period.
Intensity level. Intensity should be around 80% to 95% of maximum heart rate, which looks different depending on an individual’s current fitness. You can use fitness watches or perceived exertion to vary intensity.
Type of recovery. The recovery periods can be slower movement, like jogging after a sprint, or complete rest. The important thing is to get the heart rate down a little before the next intense period.
Number of cycles. For beginners, start out with just a few rounds of alternating high and low intensity. Build up the number of cycles and duration as they get fitter.
Also important to consider is frequency. Doing HIIT too often can actually cause muscle loss. It can also lead to burnout and injuries. For newbies, only do it once per week. Fitter people can safely do two to three sessions per week as long as they have plenty of recovery time.
Need more? Check out ISSA’s HIIT course. You’ll advance your education and earn credits toward your personal trainer recertification!
HIIT is incredibly flexible. Not only can you vary factors to match an individual’s fitness level, but you can also use just about any type of exercise to do HIIT. It is better suited to cardio, though, so you might want to save strength training for its own dedicated workout. For HIIT to be effective, intensity has to be high, and that’s harder to achieve with resistance moves.
Here are some basic workout guidelines for beginners through advanced and highly-trained athletes:
Beginner. Spend just 20 seconds in an all-out period of high intensity, followed by two minutes of light activity. Repeat three to five times or for a total of 10 to 15 minutes.
Intermediate. Increase the intense periods to 30 seconds and reduce the recovery times to just one minute. Do more repetitions or go up to 20 minutes total.
Advanced. For advanced clients, increase the high-intensity intervals to 40 or 60 seconds and take the rest down to 20 or 40 seconds. They can continue for up to 30 minutes.
Extra Advanced. Although designed to be shorter in overall duration, a Tabata workout is even more intense than standard HIIT workouts. The intense periods are absolutely all out and for 20 seconds. The rest periods are only 10 seconds. Repeat the pattern 8 to 10 times. Intensity is the key here. You should be struggling.
As you start to build your own workouts, here are some of the best exercises to include HIIT routines include:
You can also mix and match different exercises during one session to keep things interesting and to hit different muscle groups. Strength training doesn’t always work as well as cardio, but it can if you are able to elevate your heart rate significantly. Try targeting big muscle groups like legs and glutes with exercises like squat variations, jumping squats, or jumping lunges.
Want to start with a bodyweight workout? Try this 25-minute HIIT workout.
If you have access to gym equipment, try this 20-minute HIIT workout:
Plank Hip Extensions - 10 reps each leg
Walking Lunges - 10 reps each leg
Jumping Jacks - 30 seconds
High Knees - 30 seconds
Complete each exercise for 30 seconds and then recover for 15 seconds. To decrease the difficulty, try resting for 30 seconds. To increase the difficulty, increase the work time to 45 seconds.
Kettlebell Clean and Press
Tire Flip to Burpee
Med Ball Jump Squat
Battle Rope Waves
Lat Stretch - 30 seconds
Single-Leg Hamstring Stretch - 30 seconds each leg
Hamstring Foam Roll - 20 seconds
Built a solid foundation for your future fitness career with the ISSA’s Certified Personal Trainer – Self-Guided Study Program. Keep learning about workout trends like HIIT with ISSA specializations and continuing education courses.
Falcone, P. H., Tai, C. Y., Carson, L. R., Joy, J. M., Mosman, M. M., McCann, T. R., Crona, K. P., Kim, M. P., & Moon, J. R. (2015). Caloric expenditure of aerobic, resistance, or combined high-intensity interval training using a hydraulic resistance system in healthy men. Journal of strength and conditioning research, 29(3), 779–785. https://doi.org/10.1519/JSC.0000000000000661
Martins, C., Kazakova, I., Ludviksen, M., Mehus, I., Wisloff, U., Kulseng, B., Morgan, L., & King, N. (2016). High-Intensity Interval Training and Isocaloric Moderate-Intensity Continuous Training Result in Similar Improvements in Body Composition and Fitness in Obese Individuals. International journal of sport nutrition and exercise metabolism, 26(3), 197–204. https://doi.org/10.1123/ijsnem.2015-0078
Skutnik, B. C., Smith, J. R., Johnson, A. M., Kurti, S. P., & Harms, C. A. (2016). The Effect of Low Volume Interval Training on Resting Blood Pressure in Pre-hypertensive Subjects: A Preliminary Study. The Physician and sportsmedicine, 44(2), 177–183. https://doi.org/10.1080/00913847.2016.1159501
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