Doctor Says 20-Second Workout Can Make You Slimmer and Healthier

For many of us, exercising can be a chore, but what if your workout could be over in just 20 seconds?

Dr. Michael Mosley believes that three 20-second bursts of high-intensity training, three times per week, can make people skinnier and healthier.

He calls the concept "fast exercise," and describes the approach in his new book, also titled "Fast Exercise."

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It's the latest in the apparent trend of rapid workouts. First, there was the seven-minute workout, then the four-minute plan.

ABC News correspondent Juju Chang met Mosley at Reebok Sports Club in New York to go through the paces of the routine.

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Mosley explained that the key to effective, high intensity workouts are doing short bursts of intense exercise. He said they seem to be much more effective for weight loss as well as for insulin resistance.

Science shows that what's beneficial about exercise is the stress and intensity of the workout, not the duration, Mosley said. The benefits of this type of exercise regimen include reduced risks of cancer and diabetes.

For Mosley, it's personal.

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"Two years ago I discovered I was a diabetic," Mosley said. "I was a bit overweight. That moved me into … fast exercise. And now I'm 20 pounds lighter and my blood sugars are completely normal. I've gone from diabetic to normal."

Mosley is also the bestselling author of "The Fast Diet," which outlines a weight-loss plan in which participants can eat what they want for five days a week, but must fast for two non-consecutive days.

As a guinea pig for his own research, Mosley says he doesn't need a fancy gym, or even gym clothes.

"Stair running is a fabulous form of exercise," he said. "You can do it in any building which has three floors."

But can a few minutes a week really work?

Daniel Rohanna teaches high-intensity workouts at Reebok. He understands that people have a lot going on in their lives.

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"For a lot of people it's 'I've got kids, I've got my job, I've got to get groceries.' It's really nice to get in, get out, hit it hard and I'm done, but I don't think 10 minutes, three times a week is going to be enough," he said.

Mosley said scientists all over the world are finding health benefits from doing better workouts in less time.

Try These Workouts From 'Fast Exercise'

*You should consult your physician before starting this or any exercise routine.

The Bare Minimum. 40 seconds hard exercise (2 x 20 seconds) Total - 4-6 minutes, including recovery.

Unbelievably, there is evidence that just 40 seconds of intense activity can make a difference. In 2011, Dr. Niels Vollaard and colleagues at Bath University did a study in which they asked fifteen healthy but sedentary young men and women to try something they called REHIT (reduced­ exertion high-intensity training) for six weeks.

He started them off in the first week with a couple of minutes of gentle cycling, then one 10-second burst of in­tense cycling followed by a couple of minutes of cool down. In weeks two and three, each exercise session consisted of a warm-up, fifteen seconds of all-out sprinting, a couple of minutes of recovery, another fifteen seconds of all-out sprinting, then the gentle cool down.

For the final three weeks they cranked it up so each ex­ercise session consisted of two 20-second flat-out sprints separated by a couple of minutes of recovery.

Despite the fact that over the six weeks the volunteers had done less than ten minutes of hard exercise, both the men and the women showed significant improvements in their aerobic fitness - with a measure known as VO2max, the maximum volume of oxygen used by the body, up 15% and 12% respec­tively. When it came to insulin sensitivity, there was a gender difference: the men's sensitivity improved by 28% while the women's did not improve.

Vollaard is currently carrying out further studies to see if this gender difference is real and also to see if people with metabolic syndrome and diabetes get similar improvements.

He is also keen to investigate in the future whether a single burst of 20 seconds done three times a week makes a measur­able difference. If you are only doing a few bursts, 20 seconds seems to be the minimum time for a burst that will make a difference.

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The basic principle here is to push yourself in two 20-second bursts. The most obvious activity to choose is cycling, since that was what they did in the trials; if you are doing it indoors, you will need an exercise bike with variable resistance on which you can crank up the intensity mechanically; and, if cycling outside, you will need to find a hill, preferably quite a steep one, and use gravity to increase your workload. But in principle, any of the activities above will work fine. In the case of running, you will need to find some way of cranking up the resistance for your 20-second spurts - either mechanically, on a treadmill in the gym, or by using a hill if you are outside.

- Start off with a couple of minutes of gentle pedaling/running/swimming.

- When you feel ready, speed up and work your body as hard as you can for 20 seconds then slow down.

- Repeat the sprint after you've had a couple of minutes of gentle pedaling/jogging/walking to recover. Recovery time is important.

In total, the bare minimum should take less than ten minutes. Mosely likes to do it on an exercise bike (see box below) and, now that he's more used to it, he does it in less than four minutes by minimizing warm-up and cool down and by cutting his gentle pedaling to about a minute.

If you are very unfit or have never tried HIT before, it may be worth slowly building up the sprints from 2 x 10 seconds to 2 x 20 seconds. Once you have mastered 2 x 20 seconds you may want to add on another 20-second sprint which, along with the recommended recovery period, will add another couple of minutes to your regime.

First find a quiet stairwell in a building with at least four full floors. If you are unfit, you may want to spend a few weeks walking up the four flights before attempting any­thing more adventurous.

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When you feel up to it, try bounding up the stairs for 20 seconds. And I mean bounding. If you are a beginner, this should be long enough to make you breathe heavily and to feel the buildup of fatigue in your thighs. As you get fitter you will find that you need to run for longer, up more stairs, to get the same feeling.

Ideally take the lift down to where you started, or in a tall building just pause for 1-2 minutes to catch your breath before bounding up another few floors.

The 30-Second Sprinter. 2 minutes hard exercise. Total - 16 minutes, including 14 minutes recovery

This is similar to the 20-second sprints that we have just described, except that you will need a longer recovery pe­riod between sprints because going from 20 seconds to 30 seconds of all-out sprinting is much more demanding.

If you are not used to HIT, you should start gradually, preferably by working your way through a 20-second re­gime first, then trying 2 x 30 seconds and building up from there.

Make time to do a couple of minutes of warm-up and en­sure you are mentally ready before starting your first sprint. Between each sprint pedal gently for 3-4 minutes to recover (you will need it).

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This regime is based on the original HIT studies, which were done in Canada and were called SIT (sprint interval training). The Canadians found that doing four 30-second sprints (interspersed with a few minutes of recovery) three times a week led to similar improvements in fitness as run­ning or cycling at a steady speed for many hours a week.

30-second sprint/bike: 4 x 30-second sprints on a bike. Make time to do a couple of minutes warm-up before start­ing your first sprint. Between each sprint take 3-4 minutes to recover by pedaling at a gentle pace (you will need it). Then take at least 2 minutes to cool down.

30-second sprint/run: 4 x 30-second running sprints up a hill. Warm up by running at a gentle pace to your chosen hill. Then sprint for 30 seconds up the hill; walk down or around for a few minutes, then do it again. And again. And again. Finish by jogging slowly home. Stretch if you like.

30-second sprint/swim: If you like swimming, do the first few lengths at a gentle pace. When you are ready, try swim­ming 25 meters flat out (or count to 30 in your head). Take a bit of a breather, then continue gently swimming a couple more lengths. Then do another sprint. Repeat four times. Finish with a very gentle couple of lengths.

The 60-Second Workout

2½ minutes hard exercise, total - 10-11 minutes, including 8 minutes recovery

This is one of my favorite approaches and a format I have used for many years. It's very simple: the basic principle is to alternate 60-second bursts of activity with 90-second recovery periods - for example, 1 minute on, 1½ minutes off. It's wonderfully flexible: it can be done with any of the activities listed above, like cycling, running, swimming, and can be scaled down or up according to what you require.

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You might think that 60 seconds of HIT has to be tougher than 30 seconds, but this version is not. The 60-second work­out evolved out of work done by the sports science team at McMaster University when they were trying to find an ef­fective but "gentler" version of the challenging 30-second Sprinter. The key difference is that you don't push yourself quite as hard. Instead of going flat out, you exercise for a minute at about 90% of your best effort, aiming to push your heart rate up to around 80% of your maximum heart rate (see section on measuring the impact of exercise at the back of the book) by the end of the first minute. (To find out your HR max, see the reference section at the back.)

In the original studies they asked the volunteers to do 10 x 1-minute bursts of HIT with 90 seconds recovery in between each burst. This is what I do. More recently re­searchers from Metapredict (a group of exercise academics) have begun testing a less demanding variant, involving a maximum of 5 x 60-second bursts alternated with 90-second recovery periods.

The less fit should definitely start with three bursts; if you are super keen, and really want to push your limits, you can do the full 10 (this is effectively the Roger Bannister ver­sion, and particularly beneficial if you are preparing for an endurance event). Our recommendation, if you are basically quite fit, is that you aim for a steady five. So:

- Two minutes of warm-up.

- 5 x 60-second bursts of activity, with 90 seconds recovery between each burst.

- One minute of cool down.

The Fat Burner: 8 minutes hard exercise, total - 20 minutes, including 12 minutes recovery

This workout involves a repetitive cycle of eight seconds of intense activity alternated with twelve seconds of recovery, and is only really suitable for an exercise bike. It is based on two key Australian studies by Stephen Boutcher, which showed that HIT could lead to significant fat loss.

After a brief warm-up, you cycle hard against resistance for eight seconds, then gently for twelve, then hard against resistance again for eight seconds, and gently for twelve, and so on.

Copyright 2013 by Parenting Matters Limited and Peta Bee from FASTEXERCISE published by Atria Books, a division of Simon & Schuster, Inc.