Your Complete Guide to Interval Training

HIIT isn't the only type of interval training that should be in your rotation. Learn all about the different types of interval workouts and the benefits they offer.

Interval Training
Stocksy.

Whether you're exhausted from the work day or distracted by the chaos of the crowded gym, it can be tough to stay laser-focused — and avoid skimping on your reps or going easy on your speed — during your strength workouts and cardio sessions. Enter: interval training, a workout style that can help you stay on track while you exercise and continue progressing in your fitness, no matter your goals and preferred level of intensity.

Ahead, fitness experts spell out everything you need to know about interval training, including what it entails, the different types, and the key benefits the workout style offers. Plus, you'll find a round-up of interval training workouts to try when you're ready to give the method a shot.

What Is Interval Training?

Simply put, interval training is a style of workout that involves alternating between fixed periods of activity — whether it be running, cycling, swimming, boxing, or strength training — and recovery, says Kenta Seki, a certified personal trainer and the lead trainer at FitOn. You can flip-flop between your work and rest intervals for a set amount of time (think: 30 minutes) or a distance (e.g. a mile), adds Mechelle Freeman, a former Team USA Olympic Sprinter, founder of Track Girlz, and a Life Time Ultra Fit trainer. 

A classic example of interval training is switching between periods of walking and jogging, says Freeman. Say you decide to hop on the treadmill for 10 minutes. If you’re just easing yourself into running, you might jog for two minutes straight, then immediately slow your pace and walk for two minutes, continuing this pattern for your entire treadmill workout, she explains.

The Main Types of Interval Training

High-intensity interval training (aka HIIT) may be the most well-known type of interval workout, but it's not the only one that should be on your radar. Here, a breakdown of the common styles of interval training.

High-Intensity Interval Training

As you can probably guess from its name, high-intensity interval training involves alternating between bursts of vigorous exercise (think: burpees, squat jumps, punches) and recovery. It’s common for HIIT workouts to have a 1:3 activity-to-recovery ratio; you might work for 20 seconds at a high intensity, then you’ll have 60 seconds of recovery, says Seki. And these vigorous periods are no joke: You’ll be training anywhere from 85 to 100 percent of your maximum heart rate (the greatest number of beats per minute that your heart can pump under maximal stress), says Seki. Under these conditions, expect to feel like you can barely talk during the activity periods, according to the National Academy of Sports Medicine (NASM).

“Interval training can happen within any variations of intensity, and HIIT is the one that takes you to pretty much the peak of heart rate training zones,” he says. “It’s also the style that's focused more on the people that are intermediate to advanced level because you're taking them up to a higher level of their heart-rate reserve.”

Tabata

A subset of HIIT, Tabata workouts involve switching between 20-second periods of resistance-focused or cardio activities (think: thrusters, mountain climbers) and 10-second periods of rest, which you'll repeat eight times to create a four-minute workout, Danyele Wilson, a NASM-certified personal trainer, HIIT master trainer, and EvolveYou coach, previously told Shape. Since those 10 seconds aren’t long enough to allow you to fully recover, you’ll feel totally winded after those four minutes are up — and that’s why it’s often considered a higher-intensity form of high-intensity interval training, said Wilson.

Sprint Interval Training

Just like HIIT, sprint interval training is pretty high-intensity, and you’ll be training at a level in which your heart rate is at 80 to 90 percent of your maximum, says Freeman. But instead of strength- or power-building exercises, you’ll focus all your work periods on running as fast as possible. Because of the effort involved, the activity-to-recovery ratio is 1:3, so if you dash down the track for a minute straight, you’ll spend three minutes recovering, she explains. 

Fartlek Runs

Fartlek runs are another way to use interval training to structure your cardio workouts. This method, also known as unstructured speed work, is less rigid than other types of intervals, says Freeman. “You might say, ‘Okay, I'm gonna run to the tree, and that tree might be about 100 meters away,’” she explains. “It just gives you some goal where you may pick up the pace and then you dial back the pace. It's not prescribed, set interval times, but it gives you chance to go back and forth in between your intensities.” 

Low-Intensity Interval Training

Interval training doesn’t always have to involve working so hard that you feel nearly breathless. Low-intensity interval training involves performing cardio or strength activities while keeping your heart rate within training zone two, says Seki, so your workout feels challenging and it’s a bit difficult for you to talk while working, according to NASM. Since the intensity is a bit lower, your body won’t need as much time to recover before tackling your next activity period. So, you may opt to have a 1:1 or 1:2 work-to-rest ratio, says Freeman. 

The Benefits of Interval Training

Using intervals to structure your workouts comes with plenty of benefits. Below, the experts explain the key perks of the training style.

Gives Your Workouts Structure

If you have no clue how to structure your workouts, interval training can be your best friend. “Most people go into workouts confused, but if you already have some type of template that you can plug your exercises or activities into and follow those guidelines, [you can go in] with a plan,” says Seki. Instead of winging your recovery breaks and your treadmill sprints, for example, you'll know exactly how long you should be spending on each period. Plus, interval training can help you stay on task if you tend to get distracted mid-workout. Thanks to those set-in-stone work and rest periods, you won’t end up accidentally scrolling through TikTok for five minutes in between sets. 

Helps You Track Progress

If you stick with the same interval training program for a few weeks, you’ll be able to see how your fitness — whether it be your pace, the reps you completed, or the weight you used — has improved over time. Then, you can tweak your workouts as necessary to continue progressing, says Seki. “You can start to see that, ‘Okay, I've done this particular workout before and I've done this many reps of an exercise in this amount of time — can I beat that next time?’” he explains. “If you're just going into [your workouts] without knowing what your previous work level was, then you can't really track your progress.”

Increases Calories Burned

Of course, burning a high number of calories does not have to be a goal of your workout — there are plenty of other perks that come with strength training and cardio work, after all. But if that’s an important metric to you, know that higher-intensity interval training can burn more calories than steady-state exercise by increasing excess post-exercise oxygen consumption, or EPOC, says Seki. 

After a tough workout, you’ll use up more oxygen to help return your body to its normal, resting level of metabolic function (aka homeostasis), according to the American Council on Exercise (ACE). This oxygen helps replenish the ATP (aka adenosine triphosphate, the fuel used for muscular activity) utilized during exercise, partners with protein to repair muscle tissue, and brings your body temperature down to resting levels, according to ACE. As you take in this oxygen, you’ll expend calories (about 5 calories per 1 liter of oxygen). And since the extent and duration of EPOC depend on your workout intensity, a HIIT session will also burn more post-workout calories than its low-intensity cousin.

The Best Interval Training Workouts

Ready to give interval training a shot? Try any of the interval workouts below to get a taste for the workout style. Regardless of your preferred methods of moving, there’s sure to be a workout that feels right for you.

Before starting any interval training workout, though, remember to do a proper warm-up to prime your body for the upcoming high-intensity activity, suggests Seki. During the workout itself, try your best to stick with the predetermined intervals in order to get the most benefit, adds Freeman. “When it's time to go again after you recover, just start moving again,” even if you can’t get up to the desired intensity, she says. “If it was a run, and maybe you can just start walking and then [ease]  into the run. At least start to train yourself to stick to the structure.”

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