There are a lot of misunderstandings about the best way to reshape your body. This is because there are a lot of trainers out there who espouse different fitness philosophies. In general, the various regimens touted all have some merit. In this article, we’ll take a very simple look at various training strategies, bust a myth or two, and explain why interval training (and high intensity interval training, a.k.a HIIT) is the most efficient way to change your fitness level.
What Is Interval Training?
In short, you are interval training any time your workout includes a set wherein you perform at your maximum level, which is then followed by a lower-intensity set, which is then repeated to achieve a cumulative effect. An interval can be a set of curls, a dance move, or anything that tires you out over its given interval of time. The intervals can be short and hard, or long and easy, but they’re all intervals, just so long as there is some cumulative effect (you get more tired as you go). All interval workouts aren’t the same, though; the duration and intensity of the intervals are what define the workout.
Conversely, aerobic training is when you maintain a steady output at a low intensity level over the course of the workout. This type of workout helps your aerobic efficiency but is a very slow way to change your body.
The Myth of the Fat-Burning Zone
It’s impossible to approach this topic without debunking the term “fat-burning zone.” You might hear uninformed trainers recommend that their clients reduce the intensity of their workouts so that their bodies will burn more fat. In reality, all these trainers are doing is lowering the overall effectiveness of their clients’ programs.
Here’s a quick explanation of the fat-burning zone: At an aerobic pace (a steady output at low intensity), your body utilizes stored body fat as fuel to save its preferred fuel (stored blood glycogen) for more pressing matters. It sounds great because you’re burning body fat. And while this is true, you’re burning it at a very slow rate.
During higher intensity work, like high intensity interval training, your body turns to a limited supply of muscle glycogen (often referred to as “blood sugar”) for energy. While your body’s burning glycogen during this more intense period, and not fat, it’s breaking down more body tissue. Breakdown is a bad word for a good thing, because your body produces more hormones and increases its metabolism to repair this breakdown. As the tissue repairs itself, it builds more muscle so that next time you do a stressful workout it won’t be so taxing. This process of adapting to intense exercise is where your body makes rapid change.
Continually building on this process is called progressive overload. By continually adapting to stress and then adding more (either with weight or speed or programs), you increase your body’s fitness so that it’s actually burning body fat for fuel as you rest. Interval training and HIIT workouts should be a key component in every phase of your training.
Interval Training Workouts Explained
Asked what separates serious and recreational athletes, author and fitness trainer Steve Ilg replied, “Intervals.” But since “intervals” is an umbrella term for training that targets many different energy systems, it requires further explanation. It’s also pretty accurate. Recreational athletes tend towards training within comfort zones. Interval training, regardless of the targeted intensity level, and HIIT workouts always forces you out of it. And you must be willing to leave your comfort zone if you want to see significant changes in your fitness level.
Interval levels can vary dramatically. For example, HIIT workouts are short versions of interval training, sometimes only lasting seconds, and often completely anaerobic (thought the workout can be aerobic as the recovery time becomes part of the total load). Distance runners and cyclists often use much longer intervals, spanning one to many minutes, which are obviously somewhat aerobic. The reason for the varying intensity of intervals is to train different systems in the body. These are defined by terms you may have heard of, like AT (anaerobic threshold) and VO2/max, and some you may not have, like phosphagen and glycolytic . For our purposes, you don’t need to know these terms. Here’s the 101 version.
- LSD (Long Slow Distance): Not the hippie drug from the ’60s, but rather long slow distance. This is not an interval; it’s a term you’re likely to hear especially if you know or are a runner or cyclist. Its purpose is for base-level aerobic conditioning. As I said above, it’s not very applicable for making significant body changes, unless you do it for a very long time. Yet many trainers still recommend it. I think this is primarily because their clients won’t complain about doing a 30 minute workout of easy exercise, though it can have some application for very de-conditioned clients and endurance athletes.
- Sports-specific intervals: These target the systems mentioned above. Intervals training exists for all athletic endeavors. Since it’s targeted for sports performance, we won’t discuss it. You’ll learn plenty about it if you join a local group to train for an event though.
- Weight training intervals: All weight training could be considered interval training, since you can’t do it forever. Old school weight training, however, often allowed rest for so long between sets that there was little cumulative effect. If you’ve spent much time at gyms, you’ve probably seen this in play; a set of bench press, a lot of yapping’. Repeat. Speed that up, and take out the yapping, and the weight training workout is generally referred to as circuit training. In circuit training, you move between exercises without much rest so that there is a cumulative cardiovascular effect. What defines these circuits is time, although you’ll usually use a number of repetitions as a time estimate. Short efforts using heavy weight target power (or absolute strength). Medium-timed effort of 12 seconds to a minute targets muscular hypertrophy, or growth. Above one minute, muscular endurance becomes the aim and muscle growth starts to become limited.
- Cardio intervals: These are what most of you probably define as interval training workouts. First, we must define the difference between cardio and aerobic. Cardio means heart, while aerobic means oxygen. Aerobic training is most easily defined by the word “easy.” It’s really defined by training below your anaerobic threshold, which is the point where you feel “pumped”. Cardio, however, is all training that affects the heart. So it can include aerobic training but also all the high-intensity training associated with intervals, and circuit training. High-intensity cardio intervals, like you might do for running, are performed in something we called training zones, targeting the terms mentioned above (glycolytic, etc). Cardio intervals target these zones for various periods of time. To design your own interval workouts, you must do this yourself, so it helps to understand what each is and why you’d want to train it. When you have a trainer, he or she does it for you.
How to Pick Interval Training Workouts
Like every other aspect of fitness, your starting point should be based on your current physical condition. If you aren’t very fit, you’ll want to start with a basic interval program, which will feel plenty hard. If you’re in doubt, start slow. It’s easier to increase your workout’s intensity than to go backward.
You never want to begin with a HIIT workout unless you’ve got a solid fitness base. This style of workout is so intense that you won’t even be able to finish each workout, negating the whole interval aspect. And even if you do finish, training this hard out of the gate increases the risk of injury.
Intervals are the most effective way to see quick results from a workout program. If you’re not doing them, add them right away. If you’re already doing intervals, perhaps it’s time to step up to the next level.