High-Intensity Interval Training: the what, why and how
What is it?
With roots in military and athletic training, high-intensity interval training (also known by its acronym form: HIIT) is a time-efficient style of training that has become incredibly popular across Australia and the world in the last decade (2). High-intensity interval training – depending on the style or mode will involve an allocated period of time (commonly 30-60 minutes) that begins with a warm-up, followed by alternating periods of high-intensity physical work and recovery, finishing with a cool down. HIIT is broadly accepted to involve relatively intense but submaximal efforts that elicit ≥80% of your maximal heart rate. Cross-fit boxes, functional training gyms, F45 studios, spin classes and boot camps are all examples of high-intensity interval training. Generally, high-intensity interval training can be categorised into two types:
- Body Weight or Resistance HIIT: interval training that uses bodily movements, weighted objects, bars, or devices for high- repetition resistance activities. (e.g. Crossfit & F45)
- Aerobic HIIT: interval training that uses traditional aerobic exercise modalities such as running and cycling (e.g. spin class) (1)
Is Tabata the same as HIIT Training?
Yes! “Tabata training” is a type of HIIT first described by the Japanese scientist Izumi Tabata in 1996. Tabata and his colleagues conducted a study that compared moderate-intensity continuous training at 70% of maximal oxygen consumption (VO2max) for 60 minutes, with HIIT conducted at 170% of VO2max. HIIT consisted of eight, 20-second all-out exercise bouts followed by 10 seconds of rest for a total of 4 minutes of exercise. The study found that HIIT improved aerobic capacity to a similar degree as moderate intensity continuous training, but also resulted in a 28% increase in anaerobic capacity. (7)“Tabata training” is a type of HIIT first described by the Japanese scientist Izumi Tabata in 1996 #physiowithafinishline @pogophysio Click To Tweet
Why do it?
High-intensity interval training is well-researched and has been proven to be beneficial for a variety of key physical and psychological markers of health. Current Australian guidelines suggest accumulating 150 to 300 minutes (2 ½ to 5 hours) of moderate intensity physical activity (effortful but you can still talk whilst doing it) or 75 to 150 minutes (1 ¼ to 2 ½ hours) of vigorous intensity physical activity, or an equivalent combination of both moderate and vigorous activities, each week (3).
The biggest reported barrier to meeting weekly exercise recommendations is a scarcity of time (6). High-intensity interval training allows you to gain all the benefits regular continuous exercise provides in a workout as short as 10 minutes (4).
Advantages of HIIT Vs Moderate-Intensity Training:
- HIIT can simultaneously produce adaptations in both aerobic and anaerobic exercise capacity (6)
- HIIT may be superior in improving cardiovascular and metabolic function (e.g. blood pressure, cardiac contractility, insulin signalling and blood glucose levels) when compared with more traditional training protocols. (4,5)
- In already well-trained individuals, interval training seems to be necessary to provoke additional increases in exercise capacity that cannot be achieved with steady-state training (4)
- HIIT also has been shown to be superior when compared with steady- state training for those attempting to lose weight – as it increases body’s potential to use fat as an energy source more than steady-state aerobic exercise (4,5)
- HIIT has been demonstrated improve selective attention in children when performed in a classroom setting (4)
- HIIT can be more enjoyable than moderate-intensity continuous exercise (6)
How do I do it?
A HIIT workout can be completed almost anywhere, in a brief timeframe that suits you.
The first thing you want to figure out is your Workout:Rest (W:R) ratio – for the less physically active/fit, a W:R ratio of 1:4 can be a safer place to begin (4). For example, with a 1:4 ratio – you could work for 30 seconds intensely with 2 minutes rest. For the more physically fit – the ratio can be upped to 1:2, or the standard 1:1 ratio. Meaning that if you had a work period of 30 seconds, your rest would be 30 or 60 seconds (1:1 and 1:2 respectively). (4)
Once your W:R ratio is decided, you choose the number of work periods you complete, and what type of work will be completed. Below is an example of a HIIT workout template with some example exercises at a W:R ratio of 1:2. A great simple workout to try at home in 30 minutes:
The first thing to be considered before you commence any form of high-intensity interval training is an honest self-assessment of your current cardiorespiratory fitness and cardiovascular health. If you find yourself getting “puffed” easily or just aren’t sure – it’s crucial to consult your GP before commencing training (1,4). When commencing HIIT for the first time – it is a good idea to test the waters with a light workout with a 1:4 work to rest ratio. This can be something a qualified Physiotherapist, Exercise Physiologist or Personal Trainer can guide you with, helping you develop a solid base of fitness before ramping intensity.Click To Tweet
The next important safety consideration for HIIT is overtraining risk (1,4). It’s common to go “too hard – too soon” with HIIT (1,4). If you begin HIIT training, complete it under the guidance of a trained professional (Physiotherapist, Exercise Physiologist or Personal Trainer) and ensure you progress slowly – giving yourself the necessary rest days dispersed through your training schedule. But at the end of the day – I always feel the body knows best, and if we listen closely enough we know when we need more rest time.
HIIT can be a fantastic time-efficient way to meet your weekly physical activity requirements, stay healthy and feel great. However, HIIT isn’t for everyone, and it’s important to get checked by your GP and enlist the help of a qualified exercise professional to safely start training. Get training and let us know how you go!
Oliver Crossley (APAM)
Featured in the Top 50 Physical Therapy Blog
- Kilpatrick, M. W., Jung, M. E., & Little, J. P. (2014). High-intensity interval training: a review of physiological and psychological responses. ACSM’s Health & Fitness Journal, 18(5), 11-16.
- Gillen, J. B., & Gibala, M. J. (2013). Is high-intensity interval training a time-efficient exercise strategy to improve health and fitness?. Applied Physiology, Nutrition, and Metabolism, 39(3), 409-412.
- Schoenfeld, B., & Dawes, J. (2009). High-intensity interval training: Applications for general fitness training. Strength & Conditioning Journal, 31(6), 44-46.
- Gillen, J. B., & Gibala, M. J. (2018). Interval training: a time-efficient exercise strategy to improve cardiometabolic health. Applied Physiology, Nutrition, and Metabolism, 43(10), iii-iv.
- Foster, C., Farland, C. V., Guidotti, F., Harbin, M., Roberts, B., Schuette, J., … & Porcari, J. P. (2015). The effects of high intensity interval training vs steady state training on aerobic and anaerobic capacity. Journal of sports science & medicine, 14(4), 747.
- Emberts, T., Porcari, J., Dobers-Tein, S., Steffen, J., & Foster, C. (2013). Exercise intensity and energy expenditure of a tabata workout. Journal of sports science & medicine, 12(3), 612-3.