These are times of media distrust, and we are sad to report that our brethren in the fitness press have provided one more reason to question the credibility of the news. Happily, the Moving Crew Truth Squad is here to clear things up.

To cut to the chase: Despite what you may have heard elsewhere in media outlets that shall remain nameless, six minutes of sprinting per week does not provide as much benefit as longer, regular, traditional cardiovascular exercise sessions.

The study that begat this mischief is interesting and worth knowing about, however. Researchers at McMaster University in Hamilton, Ontario, looked at 14 men and two women of average fitness, ages 20 to 27. Eight of the participants did a series of 30-second sprints on exercise cycles, with four-minute rest periods between sprints, three days a week. Their sprints totaled between two and four minutes per session, and they kept it up for two weeks. The other eight comprised the control group and simply continued mild recreational pursuits.

The results: The sprint-and-recover group increased their endurance -- i.e., time to exhaustion -- by almost 100 percent, from 26 minutes at the beginning to 51 minutes two weeks later. The control group saw no change.

"We are not saying people should go out and do six minutes of exercise a week and end there," said lead investigator Martin Gibala, associate professor of kinesiology at McMaster. For one thing, the sessions that included the sprints were a total of 18 to 36 minutes long, when you include recovery periods. For another, the sprints used in the study were punishing, far more than most non-athletes would be likely to subject themselves to.

But, Gibala added, the study verifies that all healthy populations can benefit from adding bursts of higher-intensity work to their routines, a process known as interval training. Even people who get all of their cardio exercise from walking "should try to do intervals -- one minute hard [exertion], one minute easy -- for 20 minutes three times a week."

While the study gave the participants four minutes' recovery for every 30 seconds of sprinting, Gibala's recommended ratio of one-minute bursts followed by one-minute recovery is more standard. Or shoot for a 30-second sprint and a 30- or 60-second recovery.

A "sprint" means exercising so your heart beats at 85 to 95 percent of your maximum heart rate. If you are not using a heart rate monitor or counting beats, Gibala said, you'll know if you're working at the right pace if you feel "some discomfort [either muscle fatigue or high heart rate], but not necessarily your all-out maximum, like you were running to save your child from an oncoming car."

The study's major contribution to exercise science, Gibala said, is that it shows how interval training improves endurance so dramatically and quickly. Previous studies measured benefits after six or eight weeks; this was the first to show a big payoff in two weeks.

Ed Coyle, director of the Human Performance Laboratory at the University of Texas at Austin, who wrote an editorial that accompanies the study this month in the Journal of Applied Physiology, said deconditioned people might benefit more from interval training than those who are already in shape.

"The lower you are [fitness-wise], the more you stand to gain," Coyle told us. Also, he said, the physical gains could fuel a psychological boost. "When the couch potato has to rush up a flight of stairs, he won't feel so bad [as he would without interval training] and will think more positively of [himself] . . . and maybe take more stairs."

Anyone other than a well-conditioned athlete should check with their doctor before incorporating very intense intervals into a routine.

No chat this week; back online next Thursday, June 30, at 11 a.m. E-mail: move@washpost.com.

-- John Briley

Adding sprints to a workout has many benefits. Skipping other cardio sessions is not among them.