Page last updated: 15th November 2022

What Is HIIT | Health Benefits | Other Benefits

HIIT training is a firm favourite in the workout routines of fitness fans and training beginners alike, and and with good reason. The health and wellbeing benefits of HIIT training are huge, all in a fitness format that is highly flexible and incredibly convenient, making it more accessible for some people than other types of workouts.

What is HIIT?

HIIT stands for High Intensity Interval Training. This is a style of training which can include all kinds of different exercises, and is typically defined by the workout format. HIIT workouts are generally shorter workout sessions, which involve a blend of brief higher intensity bursts of activity, followed by recovery periods.

For example, a 15 minute HIIT workout might be: 

• 40 seconds of burpees, followed by 20 seconds rest
• 40 seconds of squats, followed by 20 seconds rest
• 40 seconds of running on the spot, followed by 20 seconds rest
• 40 seconds of jumping jacks, followed by 20 seconds rest
• 40 seconds of lunges, followed by 20 seconds rest
• Repeat the above through three more times

There are many different styles of HIIT workout. Tabata (20 seconds of intense activity, 10 seconds rest) is often considered to be one of the more effective, but challenging forms of HIIT, but there are multiple ways to format a HIIT session. You can learn more about Tabata with our guide.  

We've also written about treadmill HIIT workouts, HIIT workouts for beginners, running HIIT workouts and HIIT workouts you can do at home, so check those out for more inspiration too.

What are the health benefits of HIIT training?

So why is HIIT such a popular style of training? Well, to start with, it's incredibly good for you. Whether you're working on boosting your fitness or you want to improve your mental health, HIIT is a great form of exercise. Physiologically, the benefits of HIIT training include: 

1. Fat burning

HIIT workouts have been shown in several studies (see examples here from 2010 and 2018) to burn more fat than traditional cardio or steady-state workouts. Using bursts of high energy movement can boost your metabolic rate and the energy burned by your body for hours, as shown in this study by the National Library of Medicine (NLM). This triggers the body to burn more fat during and, brilliantly, after you've been working out, so a 15 minute HIIT workout will keep burning calories even when you're relaxing on the sofa an hour later.

2. Increased VO2 max

Your VO2 max is the amount of oxygen your body is able to use during exercise (i.e. your aerobic capacity). The greater your VO2 max, the more effectively your body is able to use oxygen to generate energy and power. A higher VO2 max also helps the body to be more efficient at removing lactic acid from the blood, as your muscles get more efficient in extracting and using the oxygen. Essentially, the better your VO2 max, the better you'll be at working out and exercising. This translates across to daily activity too, so you should find walking up the stairs or running for the bus much easier.

Several studies (such as this from the National Library of Medicine)  have shown HIIT to boost VO2 max and, in most cases, this happens more effectively than regular endurance or moderate level training. According to research from the Journal of Science and Medicine in Sport, if you're looking to boost your VO2 max then any kind of HIIT training will have a positive effect. However, they noted that the best kind of HIIT you can do is long-interval (so longer than two minute intervals), high-volume (a workout of longer than 15 minutes) over a moderate to long term period of time (4 - 12 weeks). That said, any form of HIIT will improve your VO2 max so if you find longer intervals of high intensity too hard right away, start with what you can manage and build your way up.

3. An increase in overall fitness and endurance

So as we can see from the improvements to VO2 max levels, HIIT has been proven to have a fantastic effect on aerobic capacity, but the fitness benefits don't end there. HIIT has also been proven to boost performance and endurance across the board, which means adding HIIT workouts to your routine should improve your performance in your other workouts. In one study of rowers, not only did HIIT training boost their oxygen levels, but also produced higher improvements in power output. So it made participants stronger, fitter and more effective in a shorter amount of workout time. HIIT can also help to build muscle, making it an excellent all-rounder. 

4. Improved heart health

HIIT has been proven to reduce heart rate and blood pressure, particularly for obese or overweight people or those at risk of developing hypertension. One study showed that a group who did HIIT training three times a week for 20 minutes a day saw the same benefits to their blood pressure as a group who completed endurance training for four days a week and 30 minutes a day, despite spending half as much time exercising than the endurance training group. Other studies have also shown a huge beneficial impact to sufferers of chronic heart diseases and heart failure, thanks to the incredible benefits of improved VO2 max.  

Discover more about how exercise can improve heart health. 

5. Great for mental health

The mental health benefits of all types of exercise are well documented. From helping to release happy hormones, improve sleep, boost confidence, build resilience and even battle depression, exercising is one of the best organic ways to improve mental health. And HIIT is no different: several studies have highlighted  a reduction in depression severity, and improvements to mental wellbeing in people who suffer with schizophrenia-spectrum disorders as a direct result of HIIT training. While the benefits are similar to those seen through other forms of exercise, the nature of HIIT workouts mean these can be enjoyed in a shorter amount of training time.

What are the other benefits of HIIT-style workouts?

It's hard to argue with the incredible health benefits of HIIT, but there are plenty of other reasons why you might want to try this style of exercise. The overriding benefit of choosing HIIT over other styles of workouts is convenience. For example:

1. Time efficient

The main benefit of HIIT is that it's incredibly easy to fit an efficient and effective workout into just 15 to 20 minutes. This makes HIIT workouts much easier to slot into your day than other workouts, such as an hour of strength training or 45 minutes on the treadmill. That isn't to say those training formats don't have their own incredible benefits of course (check out why we love strength training and treadmill running here), but for those who are time poor, it is much easier to fit in a HIIT workout.

2. Burn more calories in a shorter amount of time

Despite working out for a much shorter amount of time, HIIT allows you to burn a higher number of calories than other types of workouts. One study compared 30 minutes of weight training, running, cycling and HIIT and discovered that HIIT burned around 25%-30% more calories. For those looking to increase their calorie expenditure and control their weight HIIT can allow you to burn more calories without spending hours at the gym, making it much easier to include in your daily routines.

3. Can be equipment free

Another boost to the convenience of HIIT is that you don't necessarily need any equipment to take part. While there are definitely added benefits of including weights in your workout, you can also train in one of many equipment-free styles, such as bodyweight workouts or interval running, if you are unable to access any equipment. Essentially, if you have the space, you can do HIIT, whether that's in your living room, hotel room, a park or at the gym.

4. Flexible formats

There are so many ways you can integrate HIIT into your workouts, which makes HIIT an accessible workout to almost everyone. Whatever style of workout you prefer, it's incredibly likely you can include high intensity training within it. Love running but are tight on time? You could try a treadmill HIIT workout and know that you're gaining fantastic results in just 15 minutes.  Likewise, there are a range of fantastic options for everyone from beginners to seniors to cyclists and more - check out our The Best HIIT Workout for You guide for more. 

5. More likely to stick to it

One of the most important things when looking to improve your health and fitness is ensuring you can sustain any changes you make. Studies have found that people are more likely to enjoy and continue with a HIIT workout program, compared to continuous moderate energy training styles. And it's easy to see why: HIIT is a flexible and effective workout with tonnes of benefits, which can be completed in a short amount of time. It almost sounds too good to be true!

There are benefits to all forms of exercises; where possible, including a range of different training styles in your weekly workout routines will have the most impact on your health. Adding in a weekly HIIT session will provide a huge number of benefits to your health and wellbeing without the need to sacrifice huge amounts of time. You can also increase the challenge and the benefits from your workout by adding weights such as dumbbells, kettlebells or barbells - learn more with our HIIT workouts with weights guide.

For more fitness inspiration, check out the Workout Exercises and Routines section of our blog. Are you ready to get started on your fitness journey? Then find a gym near you and get started today.