HIIT training - or High Intensity Interval Training - has long been practised by the experts as the best way to get fit and now it's down to us to try it. Peta Bee introduces the new way to work out

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High intensity interval training has been practised by athletes for years and now it looks like it’s hit the mainstream as the best way to increase fitness levels and burn fat - health writer Peta Bee explains what it is and how it works.

What is High Intensity Interval Training?

From the three minute workout to the seven minute workout and from GRIT training to Tabata, if you haven’t yet heard of High Intensity Interval Training  (or HIIT as it’s known) where have you been hiding? As the biggest fitness trend for years, the appeal is that HIIT workouts - short bursts of all-out effort followed by brief periods of recovery - are condensed into a gut-busting matter of minutes. You work hard, but the session lasts no longer than the time it takes to get changed afterwards. But how does it work and will it get the results you are after? Here is our lowdown on the minimalist workout trend.

Where did the idea come from?

To sports scientists HIIT is not that new, but to the rest of us a workout that lasts only a few minutes is the stuff of futuristic dreams. First murmurings of its benefits came seven years ago when studies at McMaster University in Ontario showed that 30 second bike sprints for a total of three minutes led to the same muscle cell adaptations as two hours of long, steady bike riding.

Since then dozens of research papers have shown that it’s not the duration of a workout that matters, but the gut-busting effort you are prepared to make while doing it. “With exercise, your body responds and adapts to overload,” says John Brewer, professor of sport at the University of Bedfordshire. “So, if you increase the intensity of a workout, then you are overloading the demands on your cardiovascular system in a positive way. The upshot is you can workout for less time and get better results than from a long, slow plod.”

How long should you spend on a HIIT workout?

How long should you grow your hair? Ultimately, the duration of your workout comes down to convenience and choice. Each new scientific paper that emerges claims that the duration used in that particular study is the way to go. Exercise scientists at Abertay University in Dundee reported recently that just sixty seconds of effort - sprint all out for six seconds on a bike then resting for one minute, repeating the cycle 10 times three times a week - is all you need. Seriously.

At Loughborough University, Professor Jamie Timmons and his team plug the three minute approach - a 20 second flat out sprint followed by a 2 minute recovery and repeated three times. Fashionable New Yorkers are currently into the 7-Minute Workout, a bodyweight circuit with 12 exercises including the plank, lunges and pushups that was shown in a study published in the journal of the American College of Sports Medicine to produce results comparable to a run and weights session combined. Or you could try the single four-minute fast run shown in recent Norwegian trials to boost endurance and general fitness. You get the picture. There is no hard and fast rule - a HIIT session generally lasts at least one minute, but no longer than 10.

Can you do it at gyms?

Gyms are jumping on the HIIT bandwagon faster than you could do the workout itself. Fitness First has launched a four minute Tabata class, based on the intermittent training theories of Japanese scientist Professor Izumi Tabata, a former researcher at Japan’s National Institute for Health and Nutrition. Sessions entail performing 20 seconds of an exercise - it can be anything from sprints to lunges, squat jumps to press-ups - followed by a 10 second rest, repeated for four minutes. Other gym classes that promise a HIIT approach include Grit and Puma HIIT, but at 20 and 30 minutes duration, they are considered less authentic versions by aficionados.

What about DIY HIIT at home?

The beauty of HIIT is that you can do it anywhere. Indeed, beginners can start by adding 60 bursts of effort a day to their daily walk or stair-climbing. When a group of women were asked to do just one minute a day of higher intensity activity - and that could mean climbing the stairs or taking a fast walk - they offset the calorie equivalent of 0.41 pounds in weight. That, the University of Utah scientists explained, would mean that a 5’5” tall woman who used the stairs at work would weigh almost half a pound less than a woman who took the lift. As you progress, the variety of HIIT methods - cycling, running, skipping, circuits, swimming - means you are unlikely to get bored. And, of course, it’s a workout for which you will always have time.

What are the benefits?

Steve Mellor , director of Freedom2Train , says that, done correctly and consistently, the minimalist workout approach has huge body benefits. “It is meant to be three or four minutes of tough, gruelling, gut-busting effort but it is worth the hard work,” Mellor says. “Stick at it and you will see a huge improvement in performance after two weeks and dramatic results in the way your body looks and performs after four weeks.”

Tabata, a version of HIIT, has produced significant benefits. One recent study at Auburn University Montgomery Kinesiology Laboratory in the US got participants to perform a four minute Tabata session of body weight squat jumps. On average, they blasted away 13.5 calories per minute and doubled their metabolic rates for at least 30 minutes afterward. "It would take five times the amount of typical cardio exercise to shed the same number of calories you can in a four-minute Tabata," said lead researcher, Dr Michele Olson.

At Loughborough, Professor Timmons has shown HIIT helps to improve insulin sensitivity - important for keeping blood sugar or glucose stable - by up to 24 per cent in two weeks, important in the battle against diabetes. And Dr John Babraj from Abertay University has just submitted for publication a paper on the effects of just two 60-second workouts a week on a group of middle-aged people. His results showed that, on average, people lost 1kg of fat over the two month trial even though they were asked not to change their usual diet or activity habits.

Any downsides?

But what about Andrew Marr? This is the question that most commonly arises from the mouths of HIIT critics ever since the BBC presenter blamed a high intensity rowing session for triggering a stroke. On closer analysis, Marr had an underlying susceptibility that had seen him suffer two previous ‘silent strokes’ that had gone unnoticed. Experts say he would have been at risk whatever the exercise approach he had taken. But in general, the advice is not to start HIIT from scratch, particularly if you haven’t exercised in a while. “You need to build up a decent fitness base to try something this intense,” says Professor Brewer. “It’s not designed to be easy and could be risky to push yourself to those kind of limits if you haven’t worked out for ages.”

Who does it?

Name a celebrity with an impressive physique and the likelihood is they incorporate HIIT methods into their training. Everyone from Jennifer Aniston to Jennifer Lopez has admitted to using high intensity training methods. They are also a favourite with athletes, footballers and sports people who were using interval training long before the rest of us had heard of it.

Not quite ready for a new workout routine just yet? Join us in January as we put HIIT to the test and bring you how-to videos and more on how high intensity training really gets results.