Instead of asking how much exercise we need, some scientists are looking into how little we can do and still get maximal health and fitness benefits.

The answer appears to be a lot less than most of us think — provided we’re willing to put in some effort. That’s the secret behind high-intensity interval training, or HIIT, an approach to training that compresses all of your exercise into only a few minutes — and the subject of our first Phys Ed video, “The 20-Minute Workout,” part of a new series that will be appearing regularly on Well.

I introduce you to the work of scientists at McMaster University in Ontario who have been at the forefront of HIIT research, studying what the training can do for us and how we can do it in a manageable, practical way. I’ve written about HIIT before: “How 1-Minute Intervals Can Improve Our Health” and “Can You Get Fit in Six Minutes a Week?” Now you can go behind the scenes to see the scientists at work.

There are many good reasons for taking exercise. As well as improving fitness, there are long term health benefits in reducing risk factors associated with cancer, diabetes and cardiovascular disease and you may even feel better. The problem is that most people don’t follow the NHS/government advice to do several hours of exercise 5 times a week.

The reason may be because substantial amounts of physical activity has always been associated with work or survival, not leisure or enjoyment. But it is lack of time which is the most common reason people give for not doing any organised physical activity. But an ever increasing body of research is showing that with far less time commitment, it is possible to get many of the benefits you get from traditional time-consuming aerobic training.

Imagine cycling as hard as possible on an exercise bike for 20-30 seconds, resting then doing the same twice more over a period of a few minutes. At our university laboratories in the UK and Canada, hundreds of volunteers have been performing that routine three times a week during the past 8 years. Medical tests have shown that those three minutes of exercise a week have delivered, on average, improvements in line with the benefits of several hours of conventional exercise such as walking or cycling a week.

These are measured in terms of improved endurance fitness, improved aerobic capacity (a measure of the maximal capacity of your heart, lungs and muscles) and an improvement in the body’s response to insulin which is need to control your blood sugar during eating. Most importantly these findings have been emerging from independent studies in several countries, notably by Professors Martin Gibala at McMaster University in Canada, Niels Vollaard at the University of Bath and Ulrik Wisloff in Norway.

So why is it working? The truthful answer is we do not fully understand why so little time is required. But part of the explanation is (probably) that High Intensity Training (HIT) uses far more of our muscle tissue than classic aerobic exercise. HIT cycling really vigorously uses not just the leg muscles, but also the upper body including arms and shoulders so that 80% of the body’s muscle cells can be activated, compared to 20-40% for walking or moderate intensity jogging or cycling.

Activating the muscle cells breakdown much of the stored glycogen (meaning the body is “primed” to respond to insulin, and this is one of the responses that fails in type II diabetes. This explanation fits with decades of muscle biochemistry and in many ways is not so surprising to exercise scientists.

It is more difficult to explain why HIT also produces large improvements in aerobic capacity and endurance performance. But a growing body of independent research shows this is the case and that the text book explanation of the science of exercise require revision. While more research to do to understand the mechanisms, an explanation is not needed to enjoy the benefits from HIT already. So where is the catch? For some people at risk of having vascular disease, any stress might be a problem, but there is no compelling data that HIT is any more dangerous that normal exercise and it has been used in patients with metabolic and cardiovascular disease.

Indeed, statistically these patients are more likely to die in their sleep. Like any exercise programme, you should ideally talk to your cardiologist first, if you have any concerns. They can confirm if you are potentially at risk. Your GP may also be able to advise you, although traditionally they are not qualified in exercise science. Muscle inactivity can also have other negative consequences. Our bones and muscles become weaker more rapidly in old age if we are inactive, leaving us more likely to have falls and fractures.

For those able to do intensive exercise, HIT may build muscle and so combat aspects of human ageing. It is well established that intense muscle contractions are the best way of building muscle tissue. Many athletes exploit this by using exercise training that activates large amounts of muscle cells, like HIT, to build muscle.

So why is HIT not already part of current public health advice? Although the weight of evidence is building up, conventional wisdom takes time to overturn and longer term studies are needed. In addition, as well as ‘fitness’, public health advice also reflects concerns about obesity. Hours of aerobic exercise a week can “burn” 2000-4000 K-calories helping, it is argued, to battle against obesity.

The trouble is spending more time exercising means you also eat more, as your body strives to promote “energy balance”. To lose weight you must eat less calories than you consume during exercise. We think HIT will not stimulate appetite, while stimulating your basal metabolism (as you build some new muscle), stimulating fat break-down and burning a few K-calories into the bargain. We are now testing this idea across 6 international research centres in a new study funded by the European Union.

The new study is called Metapredict www.metapredict.eu and you can follow our project on the web or via updates on Twitter at ♯metapredict during the next 3 years.

So is the butterfly the best single exercise that there is? Well, no. The butterfly “would probably get my vote for the worst” exercise, said Greg Whyte, a professor of sport and exercise science at Liverpool John Moores University in England and a past Olympian in the modern pentathlon, known for his swimming. The butterfly, he said, is “miserable, isolating, painful.” It requires a coach, a pool and ideally supplemental weight and flexibility training to reduce the high risk of injury.

Ask a dozen physiologists which exercise is best, and you’ll get a dozen wildly divergent replies. “Trying to choose” a single best exercise is “like trying to condense the entire field” of exercise science, said Martin Gibala, the chairman of the department of kinesiology at McMaster University in Hamilton, Ontario.

But when pressed, he suggested one of the foundations of old-fashioned calisthenics: the burpee, in which you drop to the ground, kick your feet out behind you, pull your feet back in and leap up as high as you can. “It builds muscles. It builds endurance.” He paused. “But it’s hard to imagine most people enjoying” an all-burpees program, “or sticking with it for long.”

And sticking with an exercise is key, even if you don’t spend a lot of time working out. The health benefits of activity follow a breathtakingly steep curve. “The majority of the mortality-related benefits” from exercising are due to the first 30 minutes of exercise, said Timothy Church, M.D., who holds the John S. McIlhenny endowed chair in health wisdom at the Pennington Biomedical Research Center in Baton Rouge, La. A recent meta-analysis of studies about exercise and mortality showed that, in general, a sedentary person’s risk of dying prematurely from any cause plummeted by nearly 20 percent if he or she began brisk walking (or the equivalent) for 30 minutes five times a week. If he or she tripled that amount, for instance, to 90 minutes of exercise four or five times a week, his or her risk of premature death dropped by only another 4 percent. So the one indisputable aspect of the single best exercise is that it be sustainable. From there, though, the debate grows heated.

“I personally think that brisk walking is far and away the single best exercise,” said Michael Joyner, M.D., a professor of anesthesiology at the Mayo Clinic in Rochester, Minn., and a leading researcher in the field of endurance exercise.

As proof, he points to the work of Hiroshi Nose, M.D., Ph.D., a professor of sports medical sciences at Shinshu University Graduate School of Medicine in Japan, who has enrolled thousands of older Japanese citizens in an innovative, five-month-long program of brisk, interval-style walking (three minutes of fast walking, followed by three minutes of slower walking, repeated 10 times). The results have been striking. “Physical fitness — maximal aerobic power and thigh muscle strength — increased by about 20 percent,” Dr. Nose wrote in an e-mail, “which is sure to make you feel about 10 years younger than before training.” The walkers’ “symptoms of lifestyle-related diseases (hypertension, hyperglycemia and obesity) decreased by about 20 percent,” he added, while their depression scores dropped by half.

Walking has also been shown by other researchers to aid materially in weight control. A 15-year study found that middle-aged women who walked for at least an hour a day maintained their weight over the decades. Those who didn’t gained weight. In addition, a recent seminal study found that when older people started a regular program of brisk walking, the volume of their hippocampus, a portion of the brain involved in memory, increased significantly.

But let’s face it, walking holds little appeal — or physiological benefit — for anyone who already exercises. “I nominate the squat,” said Stuart Phillips, Ph.D., a professor of kinesiology at McMaster University and an expert on the effects of resistance training on the human body. The squat “activates the body’s biggest muscles, those in the buttocks, back and legs.” It’s simple. “Just fold your arms across your chest,” he said, “bend your knees and lower your trunk until your thighs are about parallel with the floor. Do that 25 times. It’s a very potent exercise.” Use a barbell once the body-weight squats grow easy.

The squat, and weight training in general, are particularly good at combating sarcopenia, he said, or the inevitable and debilitating loss of muscle mass that accompanies advancing age. “Each of us is experiencing sarcopenia right this minute,” he said. “We just don’t realize it.” Endurance exercise, he added, unlike resistance training, does little to slow the condition.

Resistance training is good for weight control, as well. In studies conducted by other researchers, a regimen of simple weight training by sedentary men and women led to a significant decrease in waist circumference and abdominal fat. It also has been found to lower the risk of developing diabetes and cardiovascular disease. Counterintuitively, weight training may even improve cardiovascular fitness, Phillips said, as measured by changes in a person’s VO2max, or the maximum amount of oxygen that the heart and lungs can deliver to the muscles. Most physiologists believe that only endurance-exercise training can raise someone’s VO2max. But in small experiments, he said, weight training, by itself, effectively increased cardiovascular fitness.

“I used to run marathons,” he said. Now he mostly weight-trains, “and I’m in better shape.”

But there’s something undignified and boring about a squats-only routine. And the science supporting weight training as an all-purpose exercise approach, while provocative, remains inconclusive. Is there a single activity that has proved to be, at once, more strenuous than walking while building power like the squat?

“I think, actually, that you can make a strong case for H.I.T.,” Gibala said. High-intensity interval training, or H.I.T. as it’s familiarly known among physiologists, is essentially all-interval exercise. As studied in Gibala’s lab, it involves grunting through a series of short, strenuous intervals on specialized stationary bicycles, known as Wingate ergometers. In his first experiments, riders completed 30 seconds of cycling at the highest intensity the riders could stand. After resting for four minutes, the volunteers repeated the interval several times, for a total of two to three minutes of extremely intense exercise. After two weeks, the H.I.T. riders, with less than 20 minutes of hard effort behind them, had increased their aerobic capacity as much as riders who had pedaled leisurely for more than 10 hours. Other researchers also have found that H.I.T. reduces blood-sugar levels and diabetes risk, and Gibala anticipates that it will aid in weight control, although he hasn’t studied that topic fully yet.

The approach seems promising, since most of us have minimal time to exercise each week. Gibala last month published a new study of H.I.T., requiring only a stationary bicycle and some degree of grit. In this modified version, you sprint for 60 seconds at a pace that feels unpleasant but sustainable, followed by 60 seconds of pedaling easily, then another 60-second sprint and recovery, 10 times in all. “There’s no particular reason why” H.I.T. shouldn’t be adaptable to almost any sport, Gibala said, as long as you adequately push yourself.

Of course, to be effective, H.I.T. must hurt. But a study published last month found that when a group of recreational runners practiced H.I.T. on the track, they enjoyed the workout more than a second group of runners who jogged continuously for 50 minutes. The H.I.T. runners, the study’s authors suspect, were less bored.

The only glaring inadequacy of H.I.T. is that it builds muscular strength less effectively than, say, the squat. But even that can be partially remedied, Gibala said: “Sprinting up stairs is a power workout and interval session simultaneously.”Meaning that running up steps just might be the single best exercise of all. Great news for those of us who could never master the butterfly.

Published: April 15, 2011, New York Times http://www.nytimes.com/2011/04/17/magazine/mag-17exercise-t.html?pagewanted=2&_r=1

Rather than slaving away for hours in the gym, people should focus their attention on quick “sprints” with each workout lasting just a few minutes.

James Timmons, Heriot-Watt University professor of exercise biology has studied the effects of quick exercise.

He recommends 4 x 30 second sprints on an exercise bike three times a week.

He said people could reduce their risk of diabetes and heart disease substantially with short, intense workouts – with such “time-efficient” exercising appealing to busy workers.

In his study, published in the journal BMC Endocrine Disorders, 16 men exercised for three sessions a week for two weeks.

Each session was made up of 4 x 30 second sprints on an exercise bike.

This involved the men going as fast as they could for 30 seconds and then taking a few minutes of complete rest between each sprint.

After two weeks, Prof Timmons said the results were “substantial”, with a 23% improvement in insulin function.

While his research focused on young men, Prof Timmons said it would work for people of all ages and for both men and women.

He said: “This study looked at the way we break down stores of glycogen.

“Think about diabetes as being glucose circulating in the blood rather than stored in the muscles where it should be.

“If we take out the glycogen from the muscles through exercise, then the muscles draw in that excess glucose from the blood.”

Intense contractions

He added: “If you go for a jog or a run you oxidise glycogen but you are not depleting the glycogen in your muscles.

“The only way to get to this glycogen is through very intense contractions of the muscles.

“If we can get people in their 20s, 30s and 40s doing these exercises twice a week then it could have a very dramatic effect on the future prevalence of diabetes.”

He said the effects were bigger than the traditional “one hour of running per day”.

The exercise routine is known as “high-intensity interval training” or HIT for short.

Prof Timmons said current guidelines on how much exercise people should take may need revising.

Diabetes UK research manager Victoria King said short duration, high-intensity training improved insulin action in young healthy males but the research had only been undertaken in a small group of people without diabetes.

She said: “Whilst the improvement in the control of insulin action in those who undertook the training is interesting, it’s limited at this stage as to what we can learn.”

“Short bouts of very intense exercise improved muscle health and performance comparable to several weeks of traditional endurance training,” said Martin Gibala, an associate professor at Canada’s McMaster University. The research, published in the June edition of the Journal of Applied Physiology, says that repeatedly doing very intense exercise such as sprinting resulted in unique changes in skeletal muscle and endurance capacity, similar to training that requires hours of exercise each week.

Sixteen subjects were used in the test: Eight who performed two weeks of sprinting at intervals, and eight who did no exercise training. The program had in it four and seven 30-second bursts of “all out” cycling followed by four minutes of recovery time, three times a week for two weeks. Researchers found that endurance capacity in the sprint group increased on average from 26 minutes to 51 minutes, whereas the control group showed no change. The muscles of the trained group also showed a significant increase in a chemical known as citrate synthase, an enzyme that is indicative of the tissue’s power to use oxygen.

“Sprint training may offer an option for individuals who cite lack of time as a major impediment to fitness and conditioning,” said Gibala. “This type of training is very demanding and requires a high level of motivation, however less frequent, higher intensity exercise can indeed lead to improvements in health and fitness.”

Extracted from McMaster university journal of Applied Physiology, discovered and published by Martin Gibala.

http://edition.cnn.com/2005/HEALTH/06/06/sprint.training/