As I mentioned in the introduction, this book is not meant to be a review of research studies on the benefits of high-intensity training (HIT). I want you to jump in, start training, and get the results you are looking for. However, it's always good to understand the thinking and mechanisms behind any training plan you engage in. First, getting insight into the thought process behind the workout plan is a great way to gauge whether this is the right training program for your goals.
Second, when you are in the middle of a tough set, your lungs burning, sweat pouring off your forehead, and having that occasional what have I gotten myself into moment of self-doubt, you will, in the back of your mind, have an understanding of why you are doing what you are doing and why it is so effective. This should serve as motivation to keep on going. Now let's get into the three big concepts that make up the rationale behind high-intensity workouts.
WHAT IS INTENSITY?
Most people think of intensity in the gym setting as the amount of effort you are putting into a workout. A slow walk on the treadmill while reading the morning paper is a low-intensity workout, while an all-out, sweat-pouring-off-your-forehead, heart-about-to-jump-out-of-your-chest circuit is high intensity. This is intensity of effort, the type of intensity you should be focusing on when completing chapters such as 40 Toughest Workouts, Last (Wo)Man Standing, and Ultimate Fat Loss. But intensity of effort is only one of the definitions of intensity that will be used in this book.
When it comes to official training lingo, intensity represents a specific percentage of your 1-repetition maximum (the maximum amount of weight you can lift for exactly 1 rep, or 1RM), or how much weight is on the bar relative to how much weight you can actually use if you were going all out. This becomes critical when trying to build strength during the workouts in the chapter Getting Stronger. Finally, there is muscular intensity, or how much localized muscle fatigue you are incurring during your workout. A workout that blasts your biceps with several back-to-back exercises as you might find in Targeted Muscle Builders would fall into this category.
So, let's review. Intensity of effort is how hard you perceive yourself to be working, intensity of load is how much weight you are lifting relative to the maximum you are capable of lifting (e.g., 85 percent of your 1RM), and muscular intensity involves repeatedly working a specific muscle to a level of exhaustion. It is important to get a grasp of what type of intensity you are trying to focus on during any given workout.
THE SCIENCE BEHIND HIGH-INTENSITY TRAINING
Along with the performance and aesthetic benefits that people gain from high-intensity training come the scientifically researched mechanisms that cause these desired adaptations. And although the science can get complicated and expansive, it is worth understanding some key concepts and mechanisms behind why HIT is so effective. Following are three key principles as to why HIT is an efficient and results-driven approach to training.
CONCEPT 1: EPOC
The biggest concept to wrap your head around when it comes to the benefits of high-intensity training is something called excessive postexercise oxygen consumption (EPOC). After either resistance training or cardiorespiratory training (or a combination of both), the body continues to need oxygen at a higher rate than before exercise began. This occurs so the body can get back to homeostasis, or its typical resting metabolic rate. Repaying the oxygen debt caused by training requires additional energy expenditure. What this means, in a nutshell, is that you will continue to utilize energy (in the form of burning calories) well after your exercise session is over. High-intensity workouts drive up the effect of EPOC even more because you create a larger oxygen deficiency during the intensified effort of this type of training.
The bottom line? The greater the intensity of the workout, the greater the EPOC and, therefore, the greater the energy expenditure (calories burned) both during and after the workout. This afterburn can last for 36 hours postworkout, so don't underestimate just how powerful it is. Now, not every workout here tries to cash in on the EPOC effect. Many workouts focus more on building strength or gaining muscle mass - which leads perfectly into our next concept.