High Intensity Interval Training (HIIT) is in absolutely every gym and training facility these days, but because you use the term, doesn’t mean you are doing it correctly. So let’s take a moment to learn what HIIT really is, its benefits, and 3 myths surrounding this training phenomenon.
Before zooming in on HIIT, it’s important to have a brief understanding of resting heart rate (RHR), predicted maximum heart rate and aerobic versus anaerobic exercise. RHR is the number of heart beats per minute you have at rest. If your heart is stronger, it can pump more blood per beat so it doesn’t have to beat as fast. If it’s not beating as fast, your resting heart rate will be lower. Therefore you can often use RHR as an indicator of general cardiovascular health; the lower it is, the healthier your heart. Most adults will have a RHR of 60-80 beats per minute. Well-conditioned individuals may be as low as the 40s and if your RHR is in the 90s, it’s time to discuss your cardiovascular health with your doctor.
Predicted maximum heart rate is the number of beats per minute of the heart when it’s working at its maximum. In a generally healthy person, as your fitness level increases you can work at a higher heart rate more comfortably. There have been numerous equations over the years to determine your predicted maximum heart rate, which in turn will allow you to figure out your heart rate intervals for HIIT. It’s important to note that any equation is just a prediction and you may end up 10-20 beats off your true maximum heart rate. So why do we use an equation if it may end up being inaccurate? The truth, which even scientists agree to, is that it’s better than using nothing at all. One of the most current equations for predicting your max heart rate is 211 – (age x .64).
Besides knowing your RHR and predicted maximum heart rate, it’s important to know the difference between aerobic and anaerobic exercise so you can set up appropriate intervals for your HIIT program. The American College of Sports Medicine defines anaerobic exercise as “intense physical activity of very short duration, fueled by the energy sources within the contracting muscles and independent of the use of inhaled oxygen as an energy source.” Anaerobic exercise is typically thought of as being 80-90% of your predicted maximum heart rate but may get closer to 100% as you become more fit. Short, all-out sprinting would be an example of anaerobic exercise.
Aerobic exercise, as defined by The American College of Sports Medicine, is “any activity that uses large muscle groups, can be maintained continuously and is rhythmic in nature.” Typically aerobic exercise is 60-80% of your predicted maximum heart rate and a fast walk is an example of aerobic exercise.
What is HIIT, really?
Simply put, HIIT is a series of workout intervals that toggle between a high, near-maximum heart rate work interval (anaerobic) and a low to moderate heart rate resting interval (aerobic). An example of a work to rest interval would be 20 seconds work at 80-90% to 40 seconds rest at 60-80%. Another common example is the intense, Tabata style interval of 20 seconds work to 10 seconds rest. But realize that there is an infinite number of ways to set up your interval and your heart rate percentage is your primary concern. There is also an infinite number of exercises you can do for a HIIT workout–anything from running to walking outside to strength training circuits in your gym as long as you are getting your heart rate into the interval you are trying to achieve.
With all of the possibilities of equations, numbers and percentages, it’s often easier and safer to perform HIIT with the use of a heart rate monitoring system. If you are truly interested in HIIT, it’s best to find a system that uses a chest strap, which will perform more closely to that of an EKG, versus a wrist tracker, which uses blood flow technology. A chest strap monitoring system has more accuracy as your heart rate increases than a wrist tracker and while you are in that high heart rate zone, accuracy is important. Examples of monitoring systems with chest straps are MyZone, Polar and Garmin. Heart rate monitoring systems using blood flow technology are FitBit, Jawbone and Mio.
What are the benefits of HIIT?
It can burn a lot of calories in a short period of time. Is it the “I just burned 1000 calories in this simple 15 minute workout” teaser that you see all over the internet? NO, it’s not; nothing is. But on a per-minute basis, you will use more calories a minute in HIIT than traditional aerobic exercise, you just can’t do it as long as aerobic exercise or you aren’t doing it correctly.
It can increase your metabolism for hours after a workout. This is the one that everyone loves. Many recent studies have also found that this increase in metabolism is often accompanied by a shift to calorie usage from fat stores instead of carbohydrate or muscle stores. Pair HIIT with proper post-workout nutrition and it will keep you feeling good and going strong for hours after the workout.
More and more benefits are being found every day. Everything from improved blood sugar regulation to reduced blood pressure and better oxygen consumption. But I feel that more research needs to be done or we fall into the trap of the trend that didn’t really pan out. Remember how fat-free foods were going to make us all skinny?? Enough said.
Since we are all human and humans are considered “wanting animals,” we all want HIIT to be the one and only exercise we should all do and we will all be perfectly fit. Unfortunately that’s just not going to happen.
Here are a few myths we need to dispel related to High Intensity Interval Training:
- I can do HIIT every day. Sorry, nope. You should only perform HIIT 2-3 times a week with a recovery day in between to let your body’s energy systems restore themselves. Plus, if you can perform 5, 6, or 7 days of HIIT, you probably are doing it wrong and not setting up an appropriate interval. Good HIIT workouts are challenging for even the healthiest individuals.
- HIIT will decrease my RHR so I’m healthier. When you do aerobic exercise you get that heart pumping. Since your heart is like any other muscle and gets stronger with use, aerobic exercise helps to decrease your RHR. Recent studies are actually finding that since your heart is beating so fast that your ventricles are not able to fully empty, your heart is not necessarily getting stronger. This will then cause an increase in RHR. If you begin to see an increase of about 10 beats per minute of your RHR it’s best to discontinue HIIT, go back to more aerobic exercise and possibly check with your doctor.
- Anyone can do HIIT. Unfortunately, it’s not for everyone. Have a cardiovascular condition already, not a good idea. Have a RHR over 65 beats per minute, not a good idea either. If you would like to try HIIT and are free of cardiovascular disease and are in generally good health, but your RHR is a little high, work on your aerobic fitness first. Get that resting heart rate down and then work with a qualified trainer using a heart rate monitoring system to take you through a safe HIIT workout.
High Intensity Interval Training