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!
Chapter 3
What Are the Health Benefits of HIIT?
HIIT is an approach to exercise training that provides many health and fitness benefits in a notably time-efficient manner. Numerous studies have been conducted and published about the effects of this unique form of training on different populations, such as athletes, healthy men and women enthusiasts, obese people, and individuals with disease. In this section I am going to highlight HIIT research as it relates to cardiorespiratory fitness, cholesterol levels, blood pressure, and weight management. Things get a bit technical in this part of this book, but bear with me. I really want you to realize how healthy this exercise program may be for you!
How Much Can HIIT Improve Cardiorespiratory Fitness?
Cardiorespiratory fitness, also called aerobic fitness, refers to the ability of the heart, blood vessels, and lungs to supply oxygen-rich blood to exercising muscle tissues and the ability of the muscles to use the supplied oxygen to produce energy for a workout. That’s a lot to absorb in one sentence, so let’s break it down: cardiorespiratory fitness is a measure of your ability to consume oxygen, deliver it to your exercising muscles, and take and use the oxygen for energy production. Hopefully this makes better sense.
When it comes to improving cardiorespiratory fitness, HIIT is a marvel. In a comprehensive 2011 review in the Journal of Obesity, it was reported that healthy young and older adult men and women can improve their cardiorespiratory fitness up to 46% after 8 to 15 weeks of HIIT training. For the record, that is a staggering improvement in a relatively short period of time. Of course, the degree of improvement a person will actually achieve is directly related to her/his fitness level. For instance, the lower a person’s baseline fitness level, the greater the gains she/he will potentially make in cardiorespiratory fitness. Thus, individuals who lead sedentary lifestyles and then begin an exercise program will likely see the largest gains in cardiorespiratory fitness with a progressive and consistent training program. Conversely, people who have been regularly training for years will have smaller, incremental gains that are clearly not as large as those made by their sedentary counterparts.
According to current scientific research, this impressively swift increase in cardiorespiratory fitness is due to a major improvement in the heart’s blood pumping capacity, referred to as “stroke volume.” Stroke volume is the amount of blood pumped by the heart each heartbeat. Your heart, which is the size of your fist, pumps blood through its heart chambers in a way similar to how you quickly clench and open your fist. And, as the heart gets stronger, it pumps stronger, ejecting more blood (i.e., stroke volume) with each heartbeat.
Your ability to sustain aerobic exercise depends on your heart’s ability to continually pump