ClassPass 101: Everything You Need to Know About HIIT Class

High-intensity interval training (HIIT) has been gaining popularity in the last several years, thanks to programs like P90X and Insanity. Personal trainers have long touted this approach to fitness because it’s efficient (a 15-minute workout can often yield the same calorie burn as a 45-minute run), uses multiple muscle groups at once, and primes the body to conserve and burn fuel economically.

Many studios will offer these types of classes in addition to other styles of class: Look for classes with the words HIIT, high intensity, intervals or metabolic conditioning in the title. These are good signs that the class will employ principles of HIIT — working all-out for a period, then resting for a period.

Whether you’re looking to build muscle, sculpt and tone, or improve your endurance, HIIT workouts are a fast-paced way to get a lot out of your gym time. Find out what you should expect the first few times you go.

What to bring
You will be sweating, so bring along a towel and enough water to get you through the workout, and maybe a little extra for afterward to rehydrate. A heart rate tracking monitor, if you regularly use one, can be a fun addition to class, as they provide a clear picture of how hard you’re working and how quickly your heart rate comes back to a normal tempo during recovery periods. The faster you recover, the better.

For outdoor HIIT classes, a yoga mat or gloves can be helpful, just in case you find yourself on pavement.

What to wear
Dress in workout gear you can move and sweat in. Nothing kills a tough interval like having to stop to hike up your pants or pull down your shirt. Supportive waistbands are key, as is fabric that wicks sweat away from the body to keep you cool.

When it comes to footwear, some HIIT classes are taught barefoot, but usually only if the floor is padded. Typically, a structured sneaker or a flatter CrossFit shoe works well. Just remember that your knees may be taking some impact and you may need to move quickly. Whatever is comfortable and supportive for your feet is perfect.

What to expect
HIIT classes are generally 45-60 minutes, depending on the studio you visit. Classes can range from as few as two people to as many as 40, and your interaction with the instructor will vary at each.

Classes generally start with a warm-up. In my experience, they throw you right in with running, jump squats and push-ups, because why waste precious HIIT minutes? The idea is to prime your body as quickly as possible for the workout to come, and an intense warm-up can do wonders for the brain and the body.

HIIT is designed to work the entire body in short, intense blasts, building rest into the workout to improve recovery time and allow the body to more easily access its fuel for the next round. It’s tremendously effective because it keeps the body guessing. “When is the next time I’m going to have to kick it into high gear?” Fuel reserves remain more readily available during and after HIIT (in many situations, for up to eight hours afterward) and your metabolism stays stoked.

In order to work the body in its entirety, HIIT relies on moves that recruit multiple muscle groups, often incorporating plyometrics and isometrics in addition to bursts of hiit cardio. Think jumping switch lunges, plyometric push-ups, high-knee runs, and everyone’s favorite, the burpee. Depending on the studio, you may also use equipment in your HIIT class, alternating between kettlebells, jump ropes, free weights and boxes or steps. Part of the reason HIIT is so effective is its built-in variety!

The structure of HIIT classes is as varied as the moves. From day to day, the structure at the same gym may change, or you may sign up for HIIT at two studios and have remarkably different experiences. In general, expect a period of work followed by a period of rest, repeated across multiple sets with different moves for the duration of your workout.

One of the most common HIIT formats is Tabata — or 20 seconds work, 10 seconds rest, usually performed in sets of eight (so, four minutes).

Expect to jump or be provided with modifications if jumping isn’t your thing. Using your whole body, including your upward power, activates more muscles, so moves like these are common in HIIT.

Expect to be out of breath. The high-intensity piece is not a joke. You want to push yourself so your heart rate reaches 90%+.

Expect to sweat. HIIT is an awesome way to quickly and efficiently detox your blood (and provide it with a brand new batch of oxygen), in addition to your muscle cells, which will be able to regenerate and rebuild more effectively with a regular HIIT routine.

How to stretch
Ensure you include at least five minutes of whole-body stretching following a HIIT workout. Aim to work some length and some oxygen into your legs, back, abs, shoulders and arms, as well as circling out your head, neck, wrists and ankles.

When to go back
Because HIIT is so varied, you could technically take a HIIT class every day and cover your fitness bases in terms of cardio, strength and balance. The only thing lacking is steady-state endurance, although your whole system will build endurance from the sheer intensity of these workouts. Mix in HIIT a couple of times a week with yoga or a run, and take at least one day off to maximize recovery. Remember that recovery is integral to HIIT’s efficacy and taking time off — during and between workouts — is important.