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Alex Hutchinson draws on the latest research to answer your fitness and workout questions

in this biweekly column on the science of sport.

The question

Can I get fit by exercising just a few minutes a week?

The answer

Breathless claims about exercise regimens that produce near-instant results with minimal effort are generally the domain of late-night infomercials and their ilk.

So it may seem surprising that one of the hot topics at last month's American College of Sports Medicine annual meeting in Indianapolis was research on "high-intensity interval training" (HIT), suggesting that many of the benefits of traditional endurance training can be achieved with a few short bouts of intense exercise totalling as little as seven minutes a week.

The latest research on the topic, from a group at Hamilton's McMaster University, was just published in the online edition of the American Journal of Physiology - Regulatory, Integrative and Comparative Physiology. It shows that that HIT improves the structure and function of key arteries that deliver blood to the muscles and heart, just like typical cardio training.

The McMaster group has produced a series of remarkable studies on HIT over the past few years, led by exercise physiologist Martin Gibala.

Their subjects cycled as hard as they could for 30 seconds, then rested for four minutes, and repeated four to six times. They did this short workout three times a week.

"The gains are quite substantial," Dr. Gibala says. When compared with control subjects who cycled continuously for up to an hour a day, five times a week, the HIT subjects showed similar gains in exercise capacity, muscle metabolism and cardiovascular fitness.

Similar studies by University of Guelph researcher Jason Talanian have found that interval training also increases the body's ability to burn fat, an effect that persists even during lower-intensity activities following the interval training.

The results are no surprise to elite cyclists, runners and swimmers, who have relied on interval training for decades to achieve peak performance. To break the four-minute mile in 1954, Roger Bannister famously relied on interval sessions of 10 60-second sprints separated by two minutes of rest, because his duties as a medical student on clinical rotation limited his training time to half an hour a day at lunch.

Such time constraints are the main reason Dr. Gibala advocates HIT, since studies consistently find that lack of time is the top reason that people don't manage to get the 30 to 60 minutes of daily exercise recommended by public health guidelines.

"We're not saying that it's a panacea that has all the benefits of [traditional]endurance training," he says. "But it's a way that people can get away with less."

High-intensity exercise is generally thought to carry some risks, so sedentary or older people should check with a doctor before trying HIT. Interestingly, though, University of British Columbia researcher Darren Warburton presented results in Indianapolis showing his work with cancer and heart disease patients, demonstrating that these higher-risk populations can also benefit safely from HIT.

There is a catch - the disclaimer at the end of the infomercial, if you will. To cram the benefits of an hour-long workout into a few short minutes, you also have to compress the effort you would have spent.

"That's the trade-off," Dr. Gibala says. "Going all out is uncomfortable. It hurts." But at least with this approach it's over quickly.

Alex Hutchinson is a former member of Canada's long-distance running team and has a PhD

in physics.

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How to take a HIT

The guiding principle of HIT is that the shorter the workout, the higher the intensity you need to reap the benefits. "Basically," McMaster University's Martin Gibala says, "you need to get out of your comfort zone." Start by trying a HIT workout once or twice a week.

The Street-lighter: For a sedentary person who gets winded walking around the block, HIT can be as simple as walking more quickly than usual between two light poles. Then back off, and repeat after you have recovered.

The Bannister: Go hard for one minute, then recover (either

by slowing down or stopping completely) for one to two minutes. Repeat 10 times. This is a staple workout for a wide range of abilities, suitable for any

cardio activity.

The Timesaver: Dr. Gibala's protocol of 30 seconds of all-out cycling four to six times with four minutes rest is the shortest workout shown to be effective. But achieving the necessary intensity outside the lab is extremely challenging, so it's best suited to experts and those capable of extreme self-punishment.

All these workouts should be preceded by a gentle warm-up of at least five to 10 minutes.

Alex Hutchinson

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