Читать книгу HIIT Your Limit - Len Kravitz - Страница 10

I am regularly invited to fitness conferences around the world to discuss the physiological merits of HIIT workouts and how to design HIIT programs. It is a big focus of my professional life, so I’d like to take this opportunity to explain it to you in more detail.

HIIT is a system of cardiovascular training that involves alternating between high- and light- intensity intervals of exercise of varying lengths of time. The high-intensity intervals (often referred to as work periods) may range from 5 seconds to 8 minutes long, and are performed at a self-regulated intensity ranging from comfortable-but-challenging to more challenging. The light-intensity intervals, called the recovery periods, are self-paced periods of exercise at a light-to-moderate intensity. When we speak of intensity, we are talking about the level of exercise exertion, or how hard you exercise. Each workout begins with a gradual warm-up that prepares the body for the following workout. This continues into the HIIT part of the workout, where alternating work and recovery intervals total a combined 10 to 20 minutes—or longer, if you are endurance-trained. Every HIIT workout concludes with a total body cooldown to return the body’s heart rate, breathing rate, blood flow, and temperature back to a pre-exercise level.

In the book introduction I stated that true HIIT workouts are cardiovascular workouts. All of the wonderful health, disease prevention, and fat loss benefits are based on these types of workouts. Plus, all of the workouts in this book are adapted from actual studies that show these fabulous outcomes. Please note that the word “high-intensity” is a buzzword in the fitness industry for any workout that is very challenging. There are countless high-intensity workouts in the fitness industry (such as boot camp and body blast), however not all of them are actual HIIT programs.

Why Is HIIT so Popular?

Recently, interest in HIIT has grown enormously due to the widespread popularity of exercise programs, including P90X, Insanity, and CrossFit, all of which include aspects of HIIT. Millions of exercise buffs have found that alternating hard-intensity intervals of exercise with light-­intensity intervals of recovery leads to enjoyable fitness gains in less time. In fact, in a 12-week 2017 study published in the Journal of Diabetes Research, it took obese sedentary women half the time to lose the same amount of body fat through HIIT training as it took them to lose it through traditional aerobic exercise. Another advantage of HIIT is the ease with which it can be modified for people of all fitness levels and health conditions. HIIT has generated a great deal of support with special populations, such as overweight individuals and those with clinical conditions like type 2 diabetes and cardiovascular disease. HIIT workouts can be performed with every kind of exercise modality, including cycling, walking, swimming, aqua training, elliptical striding, and in many group exercise classes. Also, HIIT workouts provide similar, and perhaps better, fitness benefits than continuous moderate-intensity aerobic workouts—what we call “steady-state workouts”—but in shorter periods of time.

Even more appealingly, HIIT workouts tend to burn more calories than traditional workouts, particularly after the workout; yes, that is correct—after the workout. Let me explain further. During the time period immediately following a workout, the body experiences an exercise “afterburn,” or excess post-exercise oxygen consumption (EPOC) in exercise science terms. That’s a mouthful, so let me put it in plain words. After every workout, your body’s muscles and major systems, such as cardiovascular and respiratory, are still revved up. As a result, it takes energy to recover from exercise, and EPOC represents the energy expenditure you utilize to restore your body after your workout. So as you gradually slow down your muscles and return your body systems to pre-exercise levels, you continue to burn additional calories. This EPOC period tends to peak for about a 2-hour period after an exercise workout, though it may last up to 14 hours or longer. That means your metabolism is actually boosted for 2 or more hours after your workout.

Harder intensity workouts lead to longer EPOC periods. That’s the impressive news about HIIT and EPOC, and why I wanted to highlight it here. Because of the dynamic nature of HIIT workouts, the EPOC periods tend to be longer than they are with traditional steady-state workouts. Therefore, HIIT workouts enable you to burn more calories. This additional calorie burn helps you achieve your weight management goals, which is another benefit of HIIT training highly praised by exercise aficionados.

Interestingly—and quite satisfyingly—during EPOC the body uses primarily fat to restore the body. So, a longer EPOC means the body is burning more fat after the workout, which is another plus from your HIIT workouts.

How Are HIIT Programs Developed?

When you develop a HIIT program, you must consider the intensity (how hard you are exercising), the interval time ratio (length of work interval in relation to length of recovery interval), the workout duration (length of workout), and workout frequency (how many times a week). When it comes to deciding on an intensity, I recommend you use a rating system based on your perceived exertion during your workouts. Ratings of perceived exertion is a self-paced way for you to select the appropriate exercise intensity, and it’s scientifically sound. For the work intervals, I encourage you to exercise at an intensity between comfortable-but-challenging and comfortable-but-more-challenging. These distinctions are entirely subjective; your senses will help you accurately and effectively gauge the intensity. You will use perceived exertion to self-monitor your workout intensity, and quite precisely. In fact, exercise enthusiasts, fitness professionals, and scientists have been using the perceived-exertion method to self-monitor exercise intensity for the last fifty years. For your recovery intervals, choose an exertion level that feels like a light-to-moderate intensity. (We’ll discuss the details of the perceived exertion approach more thoroughly in Section 3, prior to starting the HIIT workouts.)

Another rather simple way to monitor your workout intensity is with the talk test. Using the talk test as your guide, a comfortable-but-challenging workout would be one where you are able to carry on a conversation, but have some difficulty speaking. I know it may seem a little bizarre, but there are studies that show the talk test is a very reliable measure of exercise intensity. Using the talk test as a guide, during the recovery intervals you should be able to carry on a conversation with mild to no difficulty.

When it comes to designing HIIT workouts, particularly those created by sports performance coaches, a major consideration is the time ratio between the work and recovery intervals. This time ratio describes the length of the work interval and the length of recovery interval. Essentially, this ratio can be deliberately designed to improve a specific sport performance variable. For instance, with track sprinters, coaches use short powerful work intervals to improve the speed and power of the athletes. Powerful bursts are followed by recovery intervals, which are often two to four times longer, to allow the athlete to fully recover. Many coaches use a specific time ratio of work intervals to recovery intervals to improve a specific energy system (such as the aerobic system) in their athletes. For example, a time ratio of 1 to 1, written 1:1, might be a 3-minute work (or high-intensity) interval followed by a 3-minute recovery (or light-intensity) interval. As you can see, 3 minutes of work and 3 minutes of recovery is a 1:1 ratio. Some of these 1:1 HIIT workouts often incorporate 3-, 4-, or 5-minute work intervals alternately, followed by of recovery intervals of an equal length of time.

These 1:1 time ratio workouts seem to be very good for endurance athletes and help them perform better in their endurance competitions. Here’s another example that illustrates the use of strategically designed intervals. There’s a popular HIIT training protocol called the “sprint interval training method.” With this type of program, the person exercising does up to 30 seconds of sprinting effort for the work intervals, followed by recovery intervals ranging from 30 seconds up to 4.5 minutes. I include several sprint interval workouts in this book.

In regard to workout duration, HIIT workouts may last from 5 minutes to approximately 60 minutes. For those of you using this book, I have designed the HIIT workouts to be from 10–20 minutes as this has been shown to be highly effective and time efficient. The duration of the workout is influenced by a person’s fitness level and goals. When looking at the duration of a HIIT workout, we do not traditionally count the warm-up or cooldown minutes to determine the length of the HIIT workout. So, if you did ten 30-second work intervals alternating with ten recovery intervals, each 30 seconds long, we would just say the entire HIIT workout is 10 minutes.

Frequency of HIIT workouts is our last consideration in designing HIIT workouts. HIIT workouts may be more exhausting than steady-state workouts (which are usually completed at a continuous low-to-moderate intensity during the entire workout), and therefore, a longer period of rest is often needed between them. Perhaps start with two HIIT training workouts a week, with any other aerobic workouts being steady-state workouts, such as brisk walking, cycling, swimming. When you feel ready for a greater challenge, increase your workout frequency by adding a third HIIT workout a week. It is best not to do HIIT workouts on back-to-back days, though. Try to spread your HIIT workouts throughout the week.

Maximize Your Results and Minimize the Risks with HIIT

Most importantly, regardless of your age, gender, and fitness level, safe participation and enjoyment of HIIT workouts (and all exercise programs for that matter) requires that you adjust the intensity of the workout to your preferred challenge level. When it comes to exercise, safety should always be your number one priority. Focus first on finding your own optimal training intensity, not just keeping up with other people. Some fitness leaders promote the idea that you have to exercise at an all-out intensity level for the HIIT workout to be beneficial—this is not correct. In fact, I suggest you avoid exercising at an all-out intensity during your workouts. Pushing yourself to this level may potentially cause bodily harm. In HIIT Your Limit!, the recurring message is that you should exercise at a comfortable-but-challenging to more challenging intensity during your HIIT work intervals. There is a big difference between a healthy challenge workout and one that is too difficult. So, comfortable-but-challenging is your goal when doing the harder (work) intervals in your HIIT workouts. You can do it!