High Intensity Interval Training (HIIT)
Whether you are new to the world of fitness or a fitness veteran, you have probably heard of HIIT workouts in some form or another; in some cases, you may not have even realized that was the kind of program you were witnessing or even doing yourself!
HIIT programs have been around for years and it is what certain programs heavily rely on when it comes to weight loss and fat loss: Insanity, Les Mills Combat, Turbo Fire, and even programs based around certain styles of dancing such as Zumba, to name a few. All of these are great, fun options if you are looking for fun HIIT style workouts. Now you may be wondering-how are these examples of HIIT workouts? I will be explaining that shortly, but while you are reading this article, ask yourself this question: will this be a more effective form of cardio when it comes to reaching my goals? I want you to come away with a better understanding of what a HIIT workout is and how it can help you reach your goals. I will try to keep everything as simple as possible and present you with a realistic, easy to understand view of HIIT and how it pertains to your goals. I want to empower you with the knowledge you need to effectively incorporate HIIT workouts (referred to as HIIT from here on out, for the most part) into your training to really maximize your progress. With that being said, let’s get started.
High-intensity interval training (HIIT) is a form of cardio training that involves cycles of high intensity bursts and low to moderate intensity recovery. Usually, a very popular rotation and, arguably, the most effective breakdown for HIIT is a 1:2 ratio. This means that the intensity is usually half the length of the rest or recovery phase; an easy way to remember if you see it written out (by the majority of trainers and coaches) would be: intensity/recovery. Still a little confused? That’s totally ok! Think of this example: you are always riding your bike for cardio and have decided that you want to try out that HIIT workout stuff everyone is talking about. So you decide to pedal as intensely as you can for 30 seconds and then slow it down to a cruising pace for 60 seconds; you repeat this for, in this example, nine more rounds. Congratulations, you have just completed your very first HIIT workout!
As shown in the previous example, HIIT pairs quick bouts of high energy (high intensity) exercise with low-effort rest or recovery intervals. This, however, is not a new concept like many believe because of all the recent hype that certain programs are gaining because of results, advertising, etc. As early as 1912, an Olympic long-distance runner, Hannes Kolehmainen was using interval workouts as part of his training routine. HIIT, in the modern form, is designed for people whose primary concern is to burn fat and increase their overall cardiovascular/respiratory function and endurance while maintaining muscle mass. This is one reason why HIIT are becoming more and more popular in sports such as football and wrestling as well as with physique competitors, models, and others.
So, why is it so effective? The reason HIIT’s are so effective is simple; by turning up the heat in your workouts, you will keep your gym time feeling productive the entire time while speeding up your fat oxidation (burning) all in less time than your typical cardio session. How is this possible? When you perform a HIIT style workout, you are raising your metabolic rate (the rate at which you burn calories), and it stays elevated much longer after you have completed the workout because of the intensity. So you not only burn calories throughout the workout itself, but you burn calories at a higher rate once you are finished as well!
How does your body continue burning calories after you are done exercising? Basically, because of an excess of post exercise oxygen consumption, or EPOC for short. Immediately after a session of exercise, intense exercise in particular, oxygen consumption (and, therefore, caloric expenditure as well) remains elevated as the muscle cells in the areas worked throughout your workout are repairing and restoring the cells to their pre-exercise condition. Throughout this process, the cells are using calories to fuel their repair and restoration, which leads to higher calorie burning for you.
Another hallmark of HIIT that is becoming more apparent in research studies across the world is in the size and number of mitochondria (the energy portion of a cell). Long thought to only occur from long periods of endurance training, it is now being proven that HIIT is actually producing the same kind of results in a shorter amount of time. Mitochondria use oxygen to manufacture high levels of ATP (Adenosine Triphosphate) which transports chemical energy throughout your cells to fuel your metabolism. So, the higher levels of mitochondria, the higher levels of ATP. The higher levels of ATP, the more effective your metabolism can function which translates into more calories consumed and burned up. Since calories are literally energy, you have more energy to use throughout your workout which translates into an athlete running longer at a higher intensity than they could previously.
Many studies have shown that fat oxidation, more commonly referred to as fat burning, was significantly higher and carbohydrate oxidation (burning) was significantly lower in individuals that participated in HIIT’s on a regular basis for six weeks. In a 1996 study conducted at the Baylor College of Medicine in Houston Texas, researchers found that subjects who performed a HIIT workout burned significantly more calories during the 24 hours following the workout than those that did steady rate cardio due to a rise in the HIIT subjects’ resting metabolic rate. Because of the intensity of the HIIT’s, it takes more energy to fuel your cell restoration and since calories are energy, you burn calories!
When East Tennessee State conducted the same study, they found that the subjects that participated in the HIIT burned 100 or more extra calories per day during the 24 hours after exercise. In a totally unrelated study in 2007, reported by the Journal of Applied Physiology, researchers found that young women who completed seven HIIT’s over a two week period experienced a 30% increase in their fat burning and in their level of muscle enzymes that are responsible for enhancing the fat burning process. What do all of these studies and all this research show? Despite that fact that it requires less total time, HIIT cardio is the best way to burn fat and preserve your muscle in ways that steady rate cardio cannot.
Contrary to popular belief, not all forms of cardio are the same! An example is weightlifting- there are various forms and exercises an individual can do to reach their specific goals. Although discussing HIIT, I am also referring to steady state training, a kind of cardio in which your intensity and distance stay the same for a prescribed amount of time. With steady state cardio, low to moderate intensity exercises are done at 60%-70% max heart rate; in contrast, HIIT involves intervals of high intensity exercise at a rate near 90% max heart rate which is then followed by a slower paced active recovery period. Many bodybuilders, physique athletes, and trainers will swear by steady state cardio while just as many will praise HIIT as the most effective way to lose weight and burn fat. Obviously, this comes down to a matter of preference in most cases as the scientific findings (of both) speak for themselves.
In recent research, it has been shown that the cardiovascular adaptations that occur within HIIT are similar, or in some cases, superior to those that occurs with steady state cardio programs. Steady state cardio can produce weight loss with muscle loss; HIIT appears to limit that muscle loss, yet still allows for weight loss with increased results. To illustrate this point, think about the legs of an Olympic sprinter versus those of an Olympic distance runner. The sprinter, whose program revolves heavily on HIIT, has significantly larger, more muscular thighs than those of the marathon runner. This is due to the fact that too much steady state cardio (usually prescribed in 45-60 minute sessions and done constantly) can actually rob the body of muscle gains whereas HIIT, (usually kept between 20-30 minutes), preserves muscles and can, in fact, help build muscle. HIIT has also been shown to be better at increasing an athlete’s endurance by improving their VO2 max or the bodies upper limit for consuming, distributing and using oxygen for energy production.
So, although you all have found the muscle preservation and growth portion above to be highly interesting, I know the burning question in your minds is: what about burning fat and making me leaner? Well, HIIT is on top in that area again as well! In a recent study conducted at the University of New South Wales (in Australia), it was found that after 15 weeks on a 3 times a week HIIT program, women lost an average of 5.5lbs of body fat which represents, about, an 11.2% decrease. In contrast, those in the control group, who performed three steady state workouts over the same 15 week period, actually saw a slight increase in body fat! The reason, as also noted in other university studies, is because subjects that did HIIT had higher markers for fat oxidation (fat burning) within their muscle fibers than those that stuck strictly to steady state cardio. Another awesome finding was that subjects that suffered from metabolic syndrome (a combination of disorders that increase one’s risk for cardiovascular disease and diabetes) that participated in a 16 week HIIT program experienced a 100% decrease in the fat producing enzyme fatty acid syntheses in comparison to the subjects that followed a steady state program for those 16 weeks. In every study that I have viewed and in all the studies presented so far within this article, HIIT is definitely here to stay as a top training method and is a very scientifically sound program.
So how do you go about implementing HIIT into your training program to maximize your results?
During your first few HIIT sessions, I would recommend simply focusing on determining how intense you can go and where your current abilities are. Do not let your ego get in the way of this-You are in a contest with yourself and no one else! It’s better to complete the workout as planned, all the way to the finish, than to start something that is unrealistic and get discouraged or injured and not finish. If, on the other hand, you complete the workout and think to yourself, “that wasn’t so bad,” then it is time to raise the bar and challenge yourself more. Do this each time you feel it is too easy; no one knows your body better than you do. A trainer’s job is to help, guide, and teach you. Only you know how hard you are truly pushing yourself. Like all other aspects of training, the key is to start slowly and increase the intensity over time to avoid injury and maximize results. To further maximize your results, promote muscle growth, and minimize the risk factors for injury, keep your HIIT sessions within 20-30 minutes and only participate in HIIT cardio three times a week. This will allow you to keep your intensity up every workout and also maximize fat loss when coupled with weight training and a healthy diet.
To really get your results popping and add some more detail to those hams and glutes, consider working hills into your HIIT sessions at least once a week. If you do not have any hills available then adjust the incline of a treadmill to the desired angle to simulate it; be sure to drop the incline to zero for the recovery phases (make sure to allow that in your timing of rest and work intervals). Doing cardio after you are finished lifting weights or early in the morning (on an empty stomach) will burn the largest amount of fat because during both of these times your body is slightly carb depleted which, in turn, makes fat the primary fuel source or energy for exercise. If you choose to do your cardio first thing in the morning, I recommend you have about half a scoop (about 10 grams) of whey protein mixed in water or 6-10 grams of amino acids (BCAA’s) before your session. This will help to ensure that your body draws most of its energy from your fat storage and these fast digesting supplements instead of from your muscles.
As far as the work/rest periods go, try to remember the 1:2 ratio; so, your rest period should be twice the length of your work period on average. Full recovery takes, roughly, four minutes for most individuals but you can shorten the rest interval if your working intervals are also shorter and you haven’t completely exhausted your anaerobic energy system. If your heart rate does not drop down to around 70% of your max heart rate if you are using a monitor to keep track (or if not, then you should be able to speak a short sentence without being totally out of breath), during your recovery/rest interval, then you need to either lengthen your rest interval or shorten the working interval.
Please note-before starting any program or adjusting anything major within your current program, always consult with your physician! If you have a history of cardiovascular problems, respiratory problems or any other health concerns that may limit your exercise at intense levels, or if you are relatively new to aerobic exercises, then HIIT is most likely not for you yet. Remember to start slow and build yourself up in all areas to avoid injury and maximize your results.
Below you will find a sample workout to try if you aren’t quite sure how to go about starting a HIIT routine and would like some additional help.
Please feel free to choose from the list of exercises below or use some other form of cardio or high intensity exercise you enjoy (i.e. dancing, cross country skiing, etc). Also, remember to change up variables in your chosen exercises: incline, height, strokes, anything that you can change to challenge yourself. Do these 3x a week and do a different exercise whenever you feel like it; change it up!
Some popular intervals that are a good place start are 30 second work/60 second recovery, 20 seconds work/40 seconds recovery, 1 minute work/2 minutes recovery. As you progress in your recovery you can decrease your low intensity interval times to make a 1:1 ratio, for example 30 seconds work/30-45 seconds recovery.