June 3, 2005 -- If you don't exercise because it takes too long, find another excuse.
Just six minutes of intense exercise a week can keep people as fit as three hour-long jogs, Canadian researchers report in the June issue of the Journal of Applied Physiology.
Is there a catch? Of course. Those six minutes come from four 30-second bursts of all-out effort with four-minute rests in between each sprint. This "sprint interval training" adds up to three 20-minute sessions a week, says Martin J. Gibala, PhD, associate professor of kinesiology at McMaster University in Hamilton, Ontario.
"Interval-type training is effective for improving health and fitness in a relatively short period of time," Gibala tells WebMD. "Whether you are already active or just getting into it, you can benefit. People can choose whether they want to exercise faster or exercise longer."
If you're thinking of trying this, Gibala says, first check with your doctor. But he adds that with proper medical supervision, all kinds of people -- even those with heart disease -- can benefit from this approach.
The researchers were testing improvements in cardiovascular fitness. This type of exercise would not be appropriate for someone trying to lose weight. Aerobic exercise, such as jogging or bicycling, continuously for 30 minutes burns significantly more fat and would be a more effective weight loss strategy in combination with diet.
Elite Athletes' Secret
The idea of sprint interval training is at least 70 years old. Elite athletes often train this way. But this elite training technique has only recently come under scientific scrutiny. How well can it work? Gibala and colleagues looked at the effect of just a few training sessions.
They enrolled 18 college students in their study. All were "recreationally active," although none of these 21- to 27-year-old students was engaged in any kind of structured athletic training. All the students practiced using a special stationary bicycle used to test fitness capacity.
After the practice sessions, half the students got two weeks off. The other half did six sessions of sprint interval training over the same two weeks. What happened?
Those who didn't train didn't improve. But just those six sessions of sprint interval training increased the students' endurance capacity by 100%. And tests showed that their muscles were burning oxygen much more efficiently.
In later studies, Gibala's team compared a modified version with traditional endurance training more suitable to what a person could do without sophisticated equipment. These studies, he plans to report later this month at the 2005 Canadian Federation for Biological Sciences (CFBS) meeting, show that interval training gets the same results as traditional endurance training -- in a fraction of the time.
"The average person can benefit from interval type training and experience improvements in their fitness in a relatively short period of time," he says. "There is evidence that people are willing to trade off volume of exercise for intensity of exercise -- if they can get off with spending less time on exercise."
Can You Do It Yourself?
The findings really are exciting, says Edward F. Coyle, PhD, director of the human performance laboratory at the University of Texas, Austin. Coyle has worked with Tour de France champion Lance Armstrong and with the San Antonio Spurs professional basketball team. His editorial comments accompany the Gibala team's study.
"This is the first report that you can show large increases in muscle endurance within just two weeks," Coyle tells WebMD. "In today's society, people spend so much time in front of the TV or video screen. It is rare we exercise either intensely or for very long times. Since some people are devoting so little time to exercise, this reminds us how effective or efficient even short amounts of exercise are if performed very intensely."
If this sounds too good to be true, remember there's a catch.
"The exercise, although only 30 seconds for each of the four bouts, is as hard as you can go," Coyle says. "So the first 15 seconds feel not so bad, and the last 15 seconds are hell."
If you're going to try this technique, remember that it's important to consult your doctor before beginning any kind of exercise. Coyle says it's probably best to use a high-quality stationary bicycle -- such as the Lifecycle -- at your local gym. Or join an indoor cycling class. There's no better motivator than a trainer yelling at you to go faster and faster.
"As you fatigue during this kind of exercise, you wind up not being able to move your legs as fast -- so a higher-quality bicycle ergometer will make it less likely you'll fall or pull a muscle," he says. "Set the power output to a level where you feel OK for 15 seconds and you barely can finish the last 15 seconds. For most people that would be between 150 and 350 watts, depending on your size, age, and level of motivation."