Everything You Need to Know About HIIT Workouts

Everything You Need to Know About HIIT Workouts

The fitness world is prone to trends and buzzwords, the most fashionable of which in recent years is probably “HIIT,” short for high-intensity interval training.

But the concepts behind HIIT aren’t particularly new or trendy. They’re grounded in science and research, and they were around long before the fashionable acronym.

That’s why they’re found in so many programs on Beachbody On Demand like P90X, INSANITY, 21 Day FixLIIFT4, and Transform 20.

LIIFT4 workouts

What Is HIIT?

Simply put, HIIT is characterized by short bursts of intense work interspersed with brief moments of rest. You should follow a program developed by fitness professionals and you’ll definitely need to be willing to step outside of your comfort zone.

“Intense” is relative to each person’s fitness level, but you should be working at a pace that doesn’t feel sustainable for very long; if you can speak even in short sentences during a high-intensity interval, you need to ramp it up.

There’s no standard time associated with HIIT workouts, but most work intervals range from 10 seconds to a couple of minutes. Rest intervals also vary in length and type.

Some workouts prescribe complete inactivity between work sets, while others call for low-intensity exercise or active recovery, like walking, stepping in place, or light jogging.

The rest period is typically just long enough to allow for partial recovery, but not long enough to allow your heart rate to return to its resting state.

“There’s no ‘best’ formula for HIIT,” says Trevor Thieme, Beachbody’s senior manager of fitness and nutrition content. “The work-to-rest ratio depends on the activity, your fitness level, and your fitness goals.”

There are dozens of HIIT variations, but the variation most people are familiar with is Tabata, a 4-minute workout that includes eight consecutive rounds of 20 seconds of work followed by 10 seconds of rest.

EMOM, another formula that’s popular among trainers and group fitness instructors, calls for a specified number of reps “every minute on the minute,” with the rest encompassing however many seconds of each minute remain.

And if you’re grinding through an AMRAP, your goal is to complete “as many reps as possible” within a specified amount of time to complete a “round,” resting as little as possible between rounds.

All of these templates can be applied to almost any type of exercise, including cycling, running, rowing, and resistance training.

LIIFT4 workout

7 Benefits of HIIT Workouts

Whether your goal is to lose weight, get healthy, or simply shake up your exercise routine, HIIT can be a game-changer for the following seven reasons.

1. They burn crazy calories

According to Thieme, you’ll burn tons of calories both during and after you work out — for up to 48 hours. Sometimes referred to by trainers as the “afterburn effect.” This phenomenon is known as “excess post-exercise oxygen consumption,” or EPOC.

To investigate the effects of EPOC, a team of researchers from East Tennessee State University studied two groups of clinically obese women. Both groups exercised on treadmills — one did “low-intensity steady state” running (aka jogging) while the other did high-intensity interval training.

While neither group experienced a reduction in body weight during the eight-week study, the high-intensity group ended up slimmer.

That’s important because it means the women in the HIIT group changed their body composition, losing significant amounts of fat while gaining enough muscle (which weighs more than fat by volume) to keep their scale weight steady.

Much of that fat loss likely came from the effect of HIIT on their resting metabolic rates: After each workout, the metabolisms of the women who performed HIIT were nearly four times higher than those who did lower-intensity exercise — and they remained higher for up to 24 hours.

2. They save time

Time, or lack thereof, is one of the most commonly cited obstacles to starting and maintaining an exercise routine.

Between family and work obligations, the average person struggles to find an hour for the gym. But 30 minutes of HIIT a few times a week is much more feasible.

3. Cardiovascular strength

According to the Centers for Disease Control and Prevention (CDC), that half hour of HIIT is not only efficient, but it also offers the same health benefits as an hour of cardio performed at a slower rate.

The CDC’s guidelines recommend that all adults accumulate at least 150 minutes of moderate-intensity exercise every week.

But you can trim that down to 75 minutes if you bump up the effort to “vigorous-intensity” exercise. You’ll receive all the same health benefits — including a stronger cardiovascular system — but in half the time.

4. Improved VO2 max

VO2 max is the maximum amount of oxygen your body is capable of consuming during high-intensity exercise. It’s a helpful measurement for athletes in training, but it’s also a good indicator of general fitness.

HIIT has been shown to help increase VO2 max by pushing your body to work at full capacity for short intervals.

5. Muscle gain

Because most people are tight on time, they may find themselves choosing to do either cardio or resistance training, but not both. Inevitably, their goals for muscular development or cardiovascular health and endurance suffer.

Because you can add resistance to HIIT — whether that’s through free weights or body weight — you can derive both cardiovascular and muscle-building benefits from one workout.

6. They’re cheap

Most HIIT workouts can be performed with little to no equipment, which means you don’t have to pay for a gym membership or empty your checking account outfitting a home gym.

While a few kettlebells or dumbbells will definitely expand the number of exercises available to you, your body weight alone provides incredibly effective resistance.

A simple, fast-paced circuit of push-ups, lunges, squats, and sit-ups will get your heart pumping in a matter of minutes.

7. You can do them anywhere

Since there are so many bodyweight HIIT options, you can stick to your training plan even when you’re on vacation or traveling for work.

If your hotel doesn’t have a gym, head outside or clear a small patch of hotel room floor, set the timer, and get to work.

Who Should Do HIIT?

If you’re just beginning your fitness journey, or it’s been a while since you worked out with any regularity, you should work up to HIIT.

“If you jump into HIIT without first building a solid foundation in fitness, you increase your risk of overtraining, which can hamper your progress and even sideline you with an injury,” says Thieme.

A personal trainer can put you on the right track, designing programs that are appropriate for your current fitness level.

Over time, you can progress through increasingly intense programs until you’re ready for HIIT.

LIIFT4 workout

How to Get Started Doing HIIT Workouts

With HIIT, it’s easy to get too much of a good thing — even if you’re ready for it — because the workouts are intended to push the limits of your strength, stamina, and grit.

“That’s why if you’re new to HIIT, you might want to consider first doing a program that contains HIIT workouts but doesn’t focus on HIIT exclusively,” says Thieme.

In LIIFT4, because you’re only working out four days a week, Super Trainer Joel Freeman makes every second count during each workout; they’re structured to keep you lifting on pace and constantly moving, while timed rest periods allow you to catch your breath before attacking each set.

Joel believes if you train smart, you’ll never overtrain. Three recovery days a week give muscles time to repair so you can push harder, lift heavier, and get better results faster.

There are two phases for maximum results: For the first six weeks, you’ll build, cut, and define your body, followed by two weeks to burn through calories and fat, revealing your ultimate physique.

How Often Should You Do HIIT?

Once you’re ready for a dedicated HIIT program, start slowly. “Don’t go all-in right away — ease into it by keeping your intensity dialed back for the first few workouts to avoid overreaching, overtraining, and/or experiencing excessive exercise-induced muscle soreness,” says Thieme.

“But if you’re following a smart workout program designed by a smart trainer who knows how to push your limits without compromising your safety and recovery, you can perform HIIT multiple times a week,” he adds.

Advanced HIIT Workouts

For veteran exercisers looking to bust through a fat-loss plateau or simply shake up their existing routine, HIIT can bring your fitness game to a whole new level.

Beachbody’s CORE DE FORCE is an MMA training-inspired program that takes its cues from the cage, pushing you through 3-minute rounds of all-out kicking, punching, and blocking combinations.

Designed by trainers Joel Freeman and Jericho McMatthews, the 30-day program requires no equipment and includes a customizable eating plan for optimum results.

And if you’re already in killer shape, check out Shaun T’s INSANITY series, which includes some of the toughest programs in the entire Beachbody catalog, says Thieme.

INSANITY promises to deliver “a year’s worth of results in just 60 days” by hammering you with an interval after relentless interval in every workout.

The workouts range in duration from 40 to 60 minutes and incorporate cardio, plyometrics, and bodyweight movements like planks, squats, and push-ups.

Individual progress is measured with periodic “fit tests” that assess your strength and endurance.

If you’re short on time, you’ll like INSANITY MAX:30, which also uses a 60-day calendar, but caps each session at 30 minutes.

This program introduces 150 new movements and offers modifications for each. You’ll push yourself hard in month 1, and even harder in month 2 when the work intervals become longer, and the rest periods remain the same.

And each Friday, you’ll be reminded why we included this program in our INSANITY series when you perform the “Friday Fight” workout, which has been described as a “fight between you and your mind.”

HIIT Workouts on Beachbody On Demand

Beachbody offers a number of high-intensity interval training programs, as well as individual workouts within other programs that are based on HIIT protocols.

Beachbody HIIT Programs


Fitness level: Intermediate-Advanced

Program length: 30 days

Boxing, kickboxing, and muay Thai combos mix with cardio and bodyweight moves in this series of MMA-inspired workouts. CORE DE FORCE’s 27- to 47-minute routines consist of three-minute “rounds” of kicks, punches, jumps, and more that target the entire body — especially the core.


Fitness level: Intermediate to advanced

Program length: 90 days

TurboFire races through one complex move after another for total-body cardio conditioning in each of its 11 different HIIT workouts. It’s the high-energy feel of a group class, six days a week for 12 weeks, en route to greater cardiovascular and muscular fitness, and a more sculpted physique.


Fitness level: Advanced

Program length: 60 days

The Shaun T program that helped popularize HIIT will test the limits of your endurance (and accelerate the pace of your transformation) with extra-long work intervals and extra-short rest periods. Foregoing weights in favor of bodyweight resistance, INSANITY workouts clock in at 40 to 60 minutes.


Fitness level: Advanced

Program length: 60 days

This evolution of INSANITY introduces 150 new moves and limits each workout to 30 minutes. But don’t let that fool you into thinking it’s any easier than the original — you’ll be doing just as much work in half the time. See how long it takes you to “max out” before you find yourself sucking wind in a puddle of your own sweat.


Fitness level: Advanced

Program length: 30 days each

This elite training program is designed for those who are already in excellent shape and want to achieve their full fitness potential.

Body weight won’t be enough here, which is why dumbbells, exercise bands, an agility ladder, and a speed rope are required.

Beachbody Programs That Contain HIIT

Transform :20

Fitness level: advanced

Program length: 6 weeks

Transform :20 a high-intensity, six-week fitness and nutrition program that will help transform your body and mind in just 20 minutes a day.

Shaun T‘s step program that’s nothing like old-school step aerobics. Less dance and more functional, it will help you sculpt your glutes, chisel your abs, strengthen and define your upper body, and burn fat all over.

Shaun T also created weekly behind-the-scenes videos featuring him and the cast as they discuss their own challenges, with the goal of motivating everyone to stay committed and strong.


Fitness level: intermediate to advanced

Program length: 8 weeks

LIIFT4 is an efficient 4 days-a-week workout that combines weightlifting and calorie-burning high-intensity interval training (HIIT). The moves are based on classic lifting techniques that let you isolate, stabilize, and focus each rep on the muscle group you’re working.

Every workout ends with a quick core routine for a full-body build and burn that leaves you shredded.

There are two phases for maximum results: For the first six weeks, you’ll build, cut, and define your body, followed by two weeks to burn through calories and fat, revealing your ultimate physique.

80 Day Obsession

Fitness level: Intermediate-Advanced

Program length: 13 weeks

Workout Duration: Between 27 – 60 minutes

Super Trainer Autumn Calabrese will help you build a strong, lean body — including a firmer butt and more sculpted abs — with 80 unique workouts.

You’ll do six workouts per week, each lasting between 27 and 60 minutes. The workout themes always remain the same (Booty, Total Body Core, AAA, Legs, Cardio Core, and Cardio Flow), but Autumn changes how you perform them each week, so you never do the same workout twice.

If you’re not feeling ready for 80DO, no problem: You can prepare with A Little Obsessed, our five-day precursor program with slightly easier workouts.

And if you can’t get enough of the Obsession, try out A Little More Obsessed — these six additional workouts include new exercises and are a little shorter than 80 Day Obsession workouts, but still high-intensity.

SHIFT SHOP (Speed Workouts)

Fitness level: beginner to intermediate

Program length: 3 weeks

Split into cardio and strength routines that alternate daily, SHIFT SHOP offers Speed :25, Speed :35, Speed :45, and Super Speed :50 workouts that emphasize athletic intervals to improve agility, coordination, stability, and endurance as you burn fat.

The program’s unique ramp-up method increases workout length and complexity over three weeks, helping you reach an all-new level of fitness.

Super Trainer Chris Downing added four more workouts to take the “shift” to a whole new level.

You’ll still use his breakthrough “ramp-up” method of increasing your daily workout by 10 minutes every week, but this time we’ve added a Prep Week and new workouts designed to test your speed and strength as you get faster and stronger.

You’ll start Prep Week with 15-minute Quick Shift workouts that give you a taste of what’s ahead and two Proving Grounds workouts that score your starting performance. Think of it as your baseline week — your goal is to only get better from here.

P90X – Plyometrics

P90X2 – Plyocide

P90X3 – Triometrics

The Master’s Hammer and Chisel – Hammer Plyometrics, Chisel Agility

21 Day Fix EXTREME – Plyo Fix Extreme

ChaLEAN Extreme – Burn It Off!

The Bottom Line

Whether you’re currently crushing HIIT workouts on the regular, or you’ve never exercised in your life and have HIIT on the horizon, there’s a fitness plan for you.

Beachbody On Demand hundreds of world-class workouts of all varieties, lengths, and levels of intensity.

For help choosing the program that best suits your interests and fitness level, reach out to your Beachbody Coach or check out this handy guide.