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March 16th, 2010
05:16 PM ET

Study: Working out harder for less time effective

By Matt Sloane
CNN Medical Producer

If you're always complaining that you don't have time to exercise, your excuse-making days may now be over. A new study published in the Journal of Physiology suggests that doing short-duration, high-intensity training sessions may be just as effective as longer duration, less intense exercise. Simply put, you can do your workout in just 20 minutes and still see the benefits.

Researchers from McMaster University in Ontario, Canada, had seven men exercise for just one minute on a stationary bike at the highest intesity they were capable of. This one-minute burst was followed by a minute of rest, another minute of intense exercise, and so on, until partipants reached 20 minutes total – 10 exercising, 10 resting.

Participants were subjected to muscle biopsies before and after training, and specific attention was paid to the number of mitochondria – the tiny powerhouses in each cell.

"People’s risk of type 2 diabetes is inversely related to the amount of mitochondria in cells," said professor Martin Gibala, the study's lead investigator. "After the high-intensity training, the amount of mitochondria went up to levels that we've seen in traditional endurance training, 4-5 hours per week."

Translated: muscle fitness in just 20 minutes.

Of course interval training is nothing new – elite athletes have been training with intervals for years, but Gibala says the goal here was to prove that anybody – not just the finely tuned athletes – could train with intervals.

"We've been doing interval training research for years now, but the model we've used...is not something people can use in everyday life," said Gibala. "In this study, we used a less-extreme model of interval training using a standard stationary bike. It's a safer and more realistic for the everyday person, and still time efficient."

But, exercise experts say the only downside to short bursts of high-intensity training – by itself – can be a lack of muscle endurance.

"It depends on what benefit you're looking for," said Forrest Pecha, director of athletic training services at Emory University Sports Medicine. "If you're looking to build cardiovascular endurance, interval training only works in conjunction with longer, more sustained workouts."

If, however, you're looking to simply get in shape, and time is your enemy, Pecha says, intervals may be right for you.

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