What is HIIT (High Intensity Interval Training)?

What is HIIT (High Intensity Interval Training)?

High-intensity interval training, more commonly known as HIIT is now widely recognised as a very effective and time efficient method for boosting cardiovascular fitness in both complete beginners and in trained athletes.  Results from studies all over the world have shown statistically significant benefits to cardiovascular fitness and muscle development, which is why top athletes of all disciplines now include HIIT in their programs.

So what is it, how does it work and how do I do it?


High-intensity interval training (HIIT), also called High-Intensity Intermittent Exercise (HIIE) or sprint interval training (SIT), is an enhanced form of interval training, an exercise strategy alternating periods of short intense anaerobic exercise with less-intense recovery periods. HIIT is a form of cardiovascular exercise. A single HIIT session can vary from 4–30 minutes.


Previously, long aerobic workouts have been promoted as the best method to reduce fat, as it is popularly believed that fatty acid utilization usually occurs after at least 30 minutes of training.

HIIT is somewhat counterintuitive in this regard, but has nonetheless been shown to burn fat more effectively.

High-intensity training, pushes the body to maximum effort to achieve muscle fatigue and maximum oxygen use in a quick burst. The harder muscles work, the more oxygen they require. This is measured relative to a persons VO2 max, which is the highest amount of oxygen your body consumes during exercise. Working your body close to its VO2 max triggers the afterburn effect, where the body continues to consume oxygen (and burn calories) up to 48 hours after the workout (it takes approximately five calories to consume one liter of oxygen). 

HIIT session

HIIT the afterburn harder

HIIT taxes and maximizes both aerobic and anaerobic fitness, while cardio addresses aerobic only. Aerobic respiration requires oxygen to generate energy in the form of ATP, while anaerobic respiration does not. HIIT affects muscle tissue at the cellular level, actually changing mitochondrial activity in the muscles themselves. Studies indicate as little as 27 minutes of HIIT three times per week produces the same anaerobic and aerobic improvement as 60 minutes of steady state cardio five times per week.

However it is also worth noting that this does not mean that any steady state cardio is worthless. Exercise is about fun and enjoyment as much as results, so if you would rather do a 2 hour bike ride along some country roads, then go for it. Keeping variety will keep motivation and that is when lifestyle changes happen.


In short, there are unlimited options for undertaking HIIT sessions.  The concept is based upon raising your heart rate towards maximum levels and then resting before taking it up again.  With so many ways to do this, it is difficult to know where to start.  Here are three of the most common protocols for HIIT:

The Tabata Method

Developed in 1996 by Dr. Izumi Tabata of Japan. It involves high-intensity spurts at 170% of one’s VO2 max. The workouts total four minutes and involve 20 seconds of high intensity followed by 10 seconds of rest for eight cycles. The recommended frequency of Tabata workouts is between two and four times per week. Tabata is best for those who are already fit and are looking for a workout that requires very little time. The Tabata Method can also be performed with strength training movements.

Example session:

Start with a three-minute warm-up, then sprint for 20 seconds. Rest (walk) for 10 seconds, then repeat the sprint/walk cycle for a total of eight cycles.

The Little Method

Developed by Drs. Johnathan Little and Martin Gibala in 2009. It involves high-intensity workouts at 95% of your VO2 max – that is to the point where catching your breath is hard! It entails completing 60 seconds of high intensity followed by 75 seconds of low intensity. Repeat for a total of 12 cycles (totaling 27 minutes) recommended for up to three times per week.

Example session:

Start with a three-minute warm-up. Cycle for 60 seconds quickly and with max resistance. Follow that with 75 seconds of slow cycling at low resistance, and repeat the fast/slow cycle for a total of 27 minutes. This is best for those at an intermediate fitness level who have 30 minutes to spare.

Turbulence training

Developed by exercise physiology researcher Craig Ballantyne. It involves eight-rep weight training sets alternated with one to two-minute cardio sets. The protocol alternates high-weight/low-rep strength training with high-intensity cardio. The maximum 45-minute workouts combine strength training with cardio, and the recommended frequency is three times per week.

Example session

Start with a five-minute warm-up. Perform an eight-rep set of body weight exercises (eg press ups or tricep dips) followed by one minute of mountain climbers. Repeat through a full-body routine for 45 minutes. Turbulence Training is great for all fitness levels and will help to build strength and develop muscle tone.

For an additional fat burning 20 minute blast try out this session from Dan

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