If you’re a fitness newcomer, you’ve likely encountered the term “HIIT” written in the description of an online workout or heard trainers briefly mention it, without providing any details, during your in-studio classes. Consequently, you might be feeling completely clueless, wondering what this unfamiliar acronym means and why everyone praises the intense workout style.

To obtain answers to all of your pressing questions, turn to this HIIT workout guide, which explains “what is a HIIT workout?” and breaks down some of the major benefits of HIIT. Additionally, you’ll discover a compilation of some of the finest HIIT workouts, including options that require no equipment and sessions that focus on building strength and inducing sweat that will leave your muscles trembling.

What Is HIIT?

Although the exact definition differs from trainer to trainer, HIIT — which stands for high-intensity interval training — generally pertains to a training style that involves alternating between bursts of vigorous exercise and short periods of active recovery moves or complete rest, says Chris Ryan, C.S.C.S., a certified personal trainer with MIRROR and a lululemon ambassador. “You’re looking at engaging in some form of exercise and then changing it up to maintain a high heart rate,” he explains. “You’re also limiting the duration of the workout itself, so you’re not aiming to work out for two hours.” For instance, you might perform 45 seconds of an intense exercise such as thrusters, followed by 45 seconds of toe-touch jacks (tapping your foot out to your side instead of full jumping jacks) or simply resting, he says. Repeat that circuit three times, replicate the process with two other exercise circuits, and you’ve completed a 15-minute HIIT workout that will make you perspire profusely.

The simplest way to ensure that your HIIT workout is truly high-intensity, as advertised, is to consider your rating of perceived exertion (RPE). Your RPE essentially represents a self-assessed rating of how hard you feel like you’re exerting yourself (based on breathing rate, heart rate, sweat, and muscle fatigue) on a scale of 1 to 10, according to the Centers for Disease Control and Prevention. An RPE of 5 may equate to moderate intensity, while an RPE of 9 may make you feel like you’re exerting maximum effort, adds Ryan.

But if you prefer a more technical approach, examine your heart rate.

For strenuous activity to be considered “vigorous-intensity,” your pulse should be between 77 to 93 percent of your maximum pulse rate, according to the CDC. (To calculate your approximate maximum pulse rate, simply subtract your age from 220.) During a high-intensity interval training (HIIT) workout, your pulse rate might range from approximately 130 to 160 beats per minute, and during particularly challenging sections, it could rise as high as 170 or 180, states Ryan. Perform some mathematical calculations, and that implies a 30-year-old with a pulse rate anywhere from 146 to 177 during a HIIT workout is maximizing their perspiration session. (By the way, the talk test can also aid in comprehending the intensity of your workout.)

The Advantages of High-Intensity Interval Training (HIIT) Workouts

They enhance your cardiovascular well-being and VO2 max.

All the plank jacks, high knees, and butt kicks involved in HIIT workouts can benefit your heart — and assist you in meeting the recommended physical activity guidelines for the week. In case you didn’t know, the U.S. Department of Health and Human Services suggests that adults should engage in at least 150 minutes of physical activity with moderate intensity or 75 minutes of vigorous-intensity activity every week. A single session of moderate-to-vigorous physical activity can lower blood pressure, and individuals who consistently meet the moderate-intensity requirement have a significantly reduced risk of developing cardiovascular disease, as stated by the HHS. Fortunately, HIIT falls under the “vigorous-intensity” category, so you are likely to enjoy these benefits.

Moreover, regularly challenging your body with cardio-heavy workouts like HIIT can make your daily activities less demanding. “The more your heart and your lungs are so-called stressed, the better off you’re going to be walking up a flight of subway stairs or carrying grocery bags,” says Ryan. “Your everyday life is just going to improve because you won’t have to exert yourself as much for an ‘easy’ activity.”

Another cardiovascular advantage of HIIT: Your endurance workouts might feel less strenuous. When compared to long, slow training intensities, research indicates that high-intensity aerobic interval training “significantly increases” VO2 max — the maximum amount of oxygen your body can utilize during intense exercise. According to UC Davis Health, the higher your VO2 max, the more energy your body can use, and the longer you can exercise.

You’ll continue to burn calories even after your workout concludes.

Thanks to excess post-exercise oxygen consumption, or EPOC, your body will continue to expend calories long after you’ve completed your HIIT workout. “It’s the gift that keeps on giving,” says Ryan. After your intense sweat session, your body works diligently to return to homeostasis — its normal, resting metabolic state — and to do so, it requires more oxygen than before you exercised, as mentioned by the University of New Mexico.

Since you’re consuming oxygen at a higher rate to replenish the adenosine triphosphate (ATP) that was utilized as fuel during your workout, reoxygenate your blood, and lower your core temperature, you’re also utilizing more energy (read: torching more calories). And a HIIT workout is essentially a formula for EPOC success: Investigation implies the magnitude of EPOC increases as workout intensity does, and a modest 2019 study discovered that individuals who performed interval exercises had greater EPOC than those who engaged in steady-state exercise.

You’ll experience muscle gains.

Although they may appear to focus on cardiovascular exercise, HIIT workouts can also function as strength training, depending on how they are structured, says Ryan. For instance, you can increase your heart rate and strengthen your arms by incorporating a lightweight dumbbell and performing a press during a standard jumping jack or by holding weights while throwing punches, says Ryan.

Equipment is not necessary.

Even if you are traveling and do not have access to equipment, you can still complete a vigorous workout and reap the health benefits of HIIT. Case in point: a recent study conducted in 2021 discovered that young, healthy adults who engaged in three equipment-free, bodyweight-based HIIT workouts per week enhanced their cardiovascular fitness in just four weeks. However, HIIT workouts are not limited to only bodyweight exercises, and you can incorporate this style of workout into your strength training, cycling, walking, swimming, aqua training, elliptical cross-training, and more, as suggested by the American College of Sports Medicine.

The Top HIIT Workouts

To improve your heart health and muscle gains, consider integrating these top HIIT workouts into your regimen. Whether you are a complete beginner or prefer low-impact exercises, there are options available to you.

Feeling adventurous? Create your own high-intensity workout by selecting a few HIIT exercises recommended by trainers and perform each exercise for 45 seconds, followed by 45 seconds of active recovery or rest, for three rounds. Just be prepared: you will feel sore later today but incredibly strong like a superhero tomorrow.

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