Athletes have long used interval training to amplify performance, but recent research suggests you should crank up the intensity even more. Curious about how to maximize interval training, Jens Bangsbo, a professor at the University of Copenhagen and a former assistant coach with Italy’s dominating Juventus soccer club, has studied interval regimens for the past decade. He even devised one earlier this year that helped runners improve their average 5K times by nearly a minute. All it required was a 30-minute high-intensity workout three times a week for seven weeks.

The key, Bangsbo says, is simply going harder than normal—much harder—and coming as close to your V02 max as possible. By doing so, the body is forced to activate muscle fibers that aren’t normally used, making the muscle stronger overall, which also helps it deal with fatigue better. “For years people have done interval running, but mostly at speeds below maximum oxygen uptake,” says Bangsbo. “This is much more intense and, we believe, can lead to significant improvements.”

THIRTY-MINUTE FIT
Swap these half-hour interval sessions into your normal routine three times a week for seven weeks

Middle-Distance Running
1. One-mile warm-up.
2. Ten seconds of high-intensity running (90 to 95 percent of max), 20 seconds of medium-intensity running (50 to 60 percent of max), and 30 seconds of low-intensity running (25 to 30 percent of max), with two minutes’ rest in between.
3. Repeat five times in 30 minutes.
4. Add one to three repetitions each week for seven weeks.

Marathon-Distance Running and Farther
1. One-mile warm-up.
2. Thirty seconds of high-intensity running (90 to 95 percent of max) followed by three minutes of recovery.
3. Repeat six times.

Cycling
1. Ten-to-15-minute warm-up.
2. Ten seconds of high-intensity cycling (90 to 95 percent of max), 20 seconds of medium-intensity cycling (50 to 60 percent of max), and 30 seconds of low-intensity cycling (25 to 30 percent of max), with two minutes’ rest in between.
3. Repeat five times.

Power Sports
1. Ten-to-15-minute warm-up.
2. Twenty-five to 30 seconds of high-intensity running (90 percent of max) or other exercise like swimming or rowing.
3. Two minutes’ rest.
4. Repeat six to 10 times. Your intensity may flag, but stay as close to your max as possible.