What is HIIT Exercise?

What is HIIT Exercise 3

This article will provide an insight into the format of exercise known as HIIT, covering what it is and how it works and it’s benefits and disadvantages.

A main principle of HIIT is that it should never be easy, in that workouts are designed to constantly challenge the participant regardless of fitness and physical ability who should be applying maximum effort during each session.

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Intense periods during HIIT training could be 30 seconds of sprinting during a jog or maximum effort during a cycle or a minute of repetitions of an exercise performed at maximum effort in circuit training.

What is HIIT?
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HIIT stands for ‘High Intensity Interval Training’ with the format of workouts combining short intense periods or intervals of exercise performed at maximum effort with longer or equal intervals of moderate to difficult exercise, or small periods of rest or active recovery such as continuous movement like pacing or jogging.


The HIIT principle can be applied to different types of exercise which is why I referred to it as a format. Here are some examples of equipment that can be used and exercises that can be performed as HIIT;

  • Running; Outdoor and Treadmill
  • Cycling; Outdoor, Exercise Bike, Spinning Bike etc
  • Cardiovascular Exercise Equipment
  • Bodyweight exercises
  • Circuit Training
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HIIT is a very time-efficient way to exercise. Workouts generally last around 20-25 minutes but can range from just 4-5 minutes up to 35 minutes. A good general session length would be 20-25 minutes. This allows the intensity to remain as high as possible throughout which is vital for maximum benefit.

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The intensity of a HIIT workout during the short intense periods should be reaching the participants peak physical output levels, at 80-95% of maximum heart rate through maximum effort being applied in what ever the exercise is. A heart rate monitor can be used to good effect with HIIT. If you own a personal fitness tracker it should have one built in.

A good way to monitor your performance without a heart rate monitor is by using a mental scale of 1 to 10 to measure your effort level. Imagine level 1 being sat down relaxing and level 10 literally being unable to exert yourself anymore.

For an effective HIIT session, you’ll need to aim for an effort level of around 9 out of 10 during the high intensity periods. By the time the interval is ending you should feel like you couldn’t have continued any longer at that intensity.

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The Advantages of HIIT

Burn high calories in short amounts of time

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HIIT will burn more calories in a shorter amount of time compared with other formats of exercise. It’s possible to burn around 300 calories for 30 minutes of HIIT training, and more depending on the intensity which is key when HIIT training. In the points below I’ve explained some excellent benefits of HIIT.

Increased metabolic rate after exercise

HIIT training is extremely efficient at burning calories and therefore excess fat in comparison to steady state or continuous exercise. Because of how intense HIIT is, after working out your body will enter a recovery phase of increased metabolic rate in which it will continue to burn calories above its usual rate while you rest. This is known as Excess Post Exercise Oxygen Consumption (EPOC) and has been shown in studies to last for up to 36 hours!

Loose fat…

In addition to this, some studies have shown EPOC not only increasing caloric expenditure but also the body’s ability to burn fat. HIIT has been shown to double the amount of fat burned at the same caloric expenditure as other forms of exercise, so as an example if you use 200 calories weight training, a HIIT workout using the same amount of calories (200) will burn off twice the amount of fat!

…Not muscle

HIIT won’t build significant amounts of muscle in comparison to lifting weights but it will not reduce muscle mass. Individuals with low muscle mass will gain muscle enough to cope with the demands of HIIT. HIIT can help preserve lean muscle mass while burning fat effectively, and will improve cardiovascular fitness and endurance. It also improves the body’s work capacity; it’s ability to work at different intensities and for varying duration.

Improved muscle oxygen consumption

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When we exercise, our muscles consume oxygen to produce energy. HIIT can produce the same improvement in our muscles’ oxygen consumption as traditional endurance training in a shorter amount of time. This has traditionally been achieved through long continuous cardio workouts.

A study found that eight weeks of HIIT or continuous stationary cycling training increased muscle oxygen consumption by about 25% with almost identical results, however the total time spent exercising to achieve those results from was vastly different between the exercise formats with 120 minutes a week of traditional training needed compared with only 60 minutes a week of HIIT, half the amount of time!

Reduces resting heart rate and blood pressure

Research indicates that HIIT can reduce resting heart rate and blood pressure in overweight individuals, who are particularly susceptible to high blood pressure. A study found that just eight weeks of HIIT stationary cycling training decreased blood pressure as much as traditional endurance training in adults with high blood pressure but in less time, with HIIT requiring 3 x 20 minute sessions a week compared with traditional endurance training requiring 4 x 30 minute sessions a week.

Reduces blood sugar levels

Blood sugar levels can be reduced by HIIT training programs lasting under 12 weeks and not only that, it also improves insulin resistance more than traditional continuous exercise in healthy individuals and has been shown to be particularly effective in reducing blood sugar levels of individuals with type 2 diabetes.


The Disadvantages of HIIT

High amounts of effort required

Compared to the advantages, there aren’t many. Although not entirely a disadvantage, some may prefer other formats of exercise as HIIT requires maximum effort and with the intensity of it being that high, a significant level of motivation is required to complete training sessions to a worthwhile level. So if you’re having an off day and feeling tired or lacking energy, you’re likely to benefit less from the workout.

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Won’t significantly increase strength and power

Another disadvantage is the decrease in your energy output as the training session progresses, so people who are training to increase their physical power and strength may find it’s not the ideal exercise format for them as HIIT best targets and improves our cardiovascular and muscular endurance.

Higher injury risk

HIIT has a relatively high injury risk as it’s one of the most challenging exercise formats around, pushing your body to its limits especially if the training comprises body movements and weights. Surgeons in the UK have said that the number of young people in need of surgery has increased somewhat due to HIIT workouts, such as Cross Fit.

If the exercises in your HIIT routine are completely new to you, it would be a good idea to practice them to become familiar with them and ensure you can perform them to correct form in an environment that is not intense.

Rest assured though as there are plenty of exercises that can be done using the HIIT format like the ones mentioned earlier in this article.

Not suitable for beginners

HIIT is extremely challenging and requires a good level of fitness so it is not ideal for beginners. It would be wise to improve your mobility, strength and cardiovascular fitness levels before taking on a HIIT training routine, however I’m sure there will be some routines that cater for beginners and are designed to progressively improve fitness.

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Can require long recovery times

After HIIT you will need to recover, and due to its intensity your recovery times may need to be longer than those required after other workouts or sports you do. No more than 3 x 30 minute HIIT workouts a week is a sensible amount which will allow you enough time to recover between sessions but be able to steadily and continually improve your fitness levels and complete workouts to the best of your ability.

Avoid HIIT if you have heart problems

In HIIT the aim is to get your heart rate above 80 percent of your maximum heart rate limit and this will not be safe for people with heart disease and/or high blood pressure. If you have heart problems, choose low-intensity workouts, such as jogging, swimming or gentle strength training or yoga.


Time For HIIT?

We have established that HIIT is an excellent way to exercise to burn calories quickly and twice the amount of fat as other forms of exercise as well as increase our metabolic rate for hours after working out, reduce blood sugar levels and our resting heart rate. As well as this it takes a shorter amount of time to achieve the same results compared with other ways of working out so if you want to get fit quick it has to be one of your top choices. Just prepare to move, sweat and get very out of breath!

2 thoughts on “What is HIIT Exercise?

  1. Your posts are informative and educational, especially for me.
    Please put some images regarding your post.
    Like in the word “Cardiovascular”, I have to google it
    what is the meaning, cause I’m not fluent in English.
    Thanks for sharing

    1. Hello and thank you for taking the time to post a comment here. There are now images included 🙂 I’m happy the posts are providing you with educational value and hope you continue to enjoy the website, thankyou.

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