What is HIIT and why does it work?

Published on February 28, 2021

HIIT — meaning High-Intensity Interval Training — is a workout concept that gained popularity in the past years. In the year 2020, healthcare professionals and fitness experts voted HIIT as the trendiest fitness regimen in a survey conducted by the American College of Sports Medicine.

The prospect that you can scale the workouts based on your fitness level and that you can do these workouts anywhere with the equipment you've got — There is a reason behind the success of HIIT.

This article looks at what HIIT is, the potential benefits, and how to get started with HIIT workouts.

What is HIIT?

HIIT is a form of physical activity that involves intense physical activity done within a short period. These short bursts of activity are alternated with periods of rest and repeated for several rounds.

The key to success with HIIT is to find your perfect balance of work intervals and rest intervals. The right balance depends not only on your workout but also on the current fitness level, so while one interval setup might work for one person, the same might be too hard or too weak for another.

However, research to determine the optimal timing of intervals and breaks in HIIT revealed that HIIT workouts with a 60s load and 60s rest split were more effective than a 30s/120s split. You can use this as a base when you try to figure out what your perfect balance is.

If you start with HIIT and are not used to the intensity, avoid having longer breaks after each workout period. Instead, keep your workout periods smaller and opt for a shorter workout in total. If you try a 30s interval, go for something like 30-40s of a break. And then choose like 5-6 rounds instead of 7-8.

Most interesting is that HIIT is an efficient way to exercise that doesn't eat into your time (45). Since HIIT workouts can be as short as 15-20 minutes but provide a wide range of benefits, they can be a very effective choice for everyone with difficulties committing to long sessions at a gym.

HIIT also requires no equipment or gym membership, so people can do it anywhere at a time that suits them.

Benefits of HIIT

HIIT helps you to burn calories quickly (910).

A particular study examined the number of calories burned during a 30-minute bout of HIIT involving biking, running, and weight training. The study showed that HIIT increased the number of calories burnt by 25-30% compared to other forms of physical activity (9).

HIIT improves the burning of fat

A review examined 13 studies and 424 obese and overweight adults. According to the review, both regular moderate-intensity exercise and HIIT can reduce waist circumference and body fat (15).

Another study found that three weekly HIIT sessions at 20 minutes per session caused the participants to lose 2kgs or 4.4 pounds of body fat within 12 weeks – all with no changes to the diet (16). These sessions also reduced their visceral fat by 17%.

Other studies have shown that HIIT can help reduce body fat, the low time commitment notwithstanding (171819). But then, like other exercises, the effectiveness of HIIT may be more pronounced in obese or overweight people (2021).

Your metabolic rate increases for hours after exercise

It is important to note that the burning of calories from HIIT occurs after the exercise itself. Studies have shown that HIIT can boost your body's metabolism after a workout (111213). According to documented studies, your body's metabolic rate after a HIIT session is far higher than what it is after weight training and jogging (11).

The same study found that HIIT caused the body's metabolism to shift towards fat utilization for energy instead of carbs. Another study demonstrated that engaging in HIIT for just two minutes increased the body's metabolism over 24 hours, equivalent to 30 minutes of running (14).

How-To start with HIIT

As mentioned earlier, to get the maximum from your HIIT workouts, you need to find the balance between your workout and resting periods. Start with shorter intervals and then build your way up by increasing both periods at the same time.

It is essential that your resting periods also grow with the workouts. HIIT workouts with long intensity intervals but short rest periods are more likely to lead to burnout and not get the desired effects.

Example intervals could be

  • 10s work and 30s rest (1:3 ratio)
  • 20s work and 40s rest (1:2 ratio)
  • 30s work and 30s rest (1:1 ratio)

Now, that's not to say you can't do other intervals like 20s of work followed by 80s of rest. If you do that, make sure that your work has more complex and challenging exercise (using dumbbells and kettlebells, for example).

How long should a HIIT workout be?

The main benefit of HIIT is that the workouts are short. But what does that mean? Everyone's sweet spot will be different based on their body type, training experience, and fitness level. It also depends on how often you are going to work out.

With the work and rest intervals set, one more aspect defines the length of your workout. How many rounds should you do?

The answer is simple: If your work intervals' performance drops, it is time to finish the workout. Usually, HIIT workouts are around 6-8 rounds, but depending on the exercises, this number can go as low as 4-5 rounds or as high as 9-10 rounds.

How to do a HIIT workout?

Keeping the above information about timing and intervals in mind, the first thing you need to do is to select your exercises. Choose exercises that you can push yourself. If you want to run, the extreme version would be sprinting. If you cycle, you should be able to cycle against resistance (or uphill)

Some exercise ideas (there are so many more)

  • Sprint
  • Bike
  • Rowing
  • Burpees
  • Kettlebell swings
  • Jump rope
  • Lunges (with dumbbells)
  • Dumbbell or Kettlebell Cleans
  • Dumbbell or Kettlebell Thrusters
  • Dumbbell or Kettlebell Snatches
  • Med ball slams
  • Jump Squats

Now, all you need to do is assembling all the workout parts: Exercises, intervals, and rounds. That's your workout.

Now go out and train

You have now all the information to understand how HIIT works. We've explained why High-Intensity Interval Training is effective, the benefits and how you can start to do HIIT. Remember that the central aspect is to have a decent intensity throughout your entire workout, accompanied by a proper resting period.

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Photo by Meghan Holmes on Unsplash