It's just 10 minutes into her Tabata class and Michelle Solberg's short hair is plastered to her brow, her cheeks flushed as she gulps deep breaths and shakes her arms and legs for a 10-second rest.

Then she plunges in for another 20-second burst of squats and jumps as fast as she can with nine other students at the Andover YMCA.

And that's the goal: Get sweaty, exhausted and gasping for air, and do it as hard and fast as possible with all-out, high-intensity interval training for four minutes, rest a minute, then blast into a different four-minute full-boogie exercise.

It's called Tabata, a 30-minute training technique developed for Japanese Olympic speed-skaters in the 1990s and studied by researcher scientist Izumi Tabata. Its popularity has exploded in the past five years.

"We've used interval training before, but we started offering Tabata classes in January because we were getting so many requests," said Sean Levesque, group fitness manager for all 22 Twin Cities YMCA locations. Each week those centers offer a total of 100 free drop-in classes to 1,500 to 2,000 members.

Tabata (pronounced tah-BAH-tah) is designed as a faster, more efficient way than traditional training programs to build muscle and endurance and blow off fat. Recent research has confirmed its effectiveness.

Adherents use four or five different exercises during a workout, and often different ones during the next one. Often included are pushups, situps, squats, chin pulls, punches, kicks, sprinting in place, riding stationary bikes and lifting weights.

The interval-training technique of Tabata -- intense exertion broken by intervals of rest -- can be applied to swimming, running, boxing, speed-walking or any other exercise. Typically, those doing a Tabata sequence score themselves by adding up the lowest number of reps in each set of pushups, situps and other exercises. Keeping score during each session enables them to chart their progress over time.

"My arms were shaking halfway through," said Solberg, 34, of Andover, who for eight months has been taking the 30-minute Tabata course right after a 45-minute cycle program twice a week at the Andover Y. "But I love it. I need the discipline of a class and instructor to stick with it."

A mother of two, Solberg said she's lost weight, toned up and "I feel stronger, more energetic. Better emotionally, too."

Going all out while hurt

Tabata came to the Twin Cities about four years ago as a core part of CrossFit gyms, which have sprung up statewide. The exercise also is popping up at LA Fitness, Lifetime Fitness and other centers.

It's also part of many fitness routines sold on DVDs or for streaming online through infomercials touting high-intensity fitness workouts.

Solberg and her husband, Garett, have bought and occasionally use the Insanity and P90X DVD programs at home. She's about to ramp up her home use of Tabata, however. After being laid off nine months ago, she started work this week as an executive assistant at the Federal Reserve Bank of Minneapolis and no longer will have time for daytime classes at the Y.

What drew her to attend the class in the first place was having an instructor who could help adjust her workouts to accommodate past knee and wrist injuries and avoid new injury -- an approach endorsed by many instructors and researchers. A concern of some critics has been rooted in stories about uncoached devotees who push too hard and vomit, pass out, damage joints or tear muscles -- sometimes with pride in their intensity.

"Most people listen to their body pretty well, but sometimes people just want to bust through those barriers -- and sometimes they ought to push through slowly," said instructor Rick Santiago at the Andover Y. "I can give them permission to go all out, but sensibly."

Burning fat, lowering sugar

Tabata, the Japanese researcher, studied the exercise protocol with a group of male college athletes. Using interval sprints for 30 minutes on stationary bikes five days a week for six weeks, they boosted their aerobic fitness by 14 percent, compared with 10 percent for the control group using a moderate pace for 60 minutes each session. Similar results were found in a Canadian study with women this year.

Researchers also found that the intense bursts of exercise and short rest periods extend the fat-burning metabolic process and lower blood sugar -- benefits to diabetics and others who need to lose weight.

The exercise tends to draw students who want to look better, get stronger or build endurance "and who want both the exercise and the results fast," Santiago said. "I've got to say, I've done a number of programs like this, but Tabata is the best for speed and results."

Solberg, who also does yoga weekly, concurs: "Being with other students helped keep me going, but in the end, you get a buzz when you realize, 'Hey, I can really kick it. I'm tougher than I thought.'"

Warren Wolfe • 612-673-7253