For years, Michelle Cuellar exercised five days a week. "But you wouldn't have known it by looking at me," says the 33-year-old mother of two. "I felt fit -- but I was still fat."
No matter what Cuellar did -- run on the treadmill for 30 minutes at a time or attend the occasional spinning class or boot camp, her weight rose. By last summer, she carried 176 pounds on her 5-foot-6 frame.
Then, last fall, for the first time in her life, Cuellar started shrinking. She tried on a pair of pants "that hadn't fit since 1998 -- and they fit!" she says. "In eight weeks, 5 inches came off my butt, 2 inches off my stomach. The weight -- 7, 9, 12 pounds -- just started falling off."
Her breakthrough? "I started doing intervals," says the Centennial, Colo., woman.
Intervals -- short bursts of speed mixed into a running, biking, swimming, elliptical, rowing or other aerobic workout -- are nothing new for organized sports, where they've long been a tried-and-true method to build speed and power. What's new is that high-intensity interval training is being discovered by average people, who like the speed but love the side effects even more: weight loss, muscle toning and reduced workout time.
"Interval training is hot right now and getting hotter," says Joseph Grassadonia, publisher of Santa Cruz-based OnFitness magazine, which is targeted at personal trainers. "It's always been there, but we are writing more and more about it because it's simply the fastest way to get clients fit."
Cuellar says she trimmed 10 minutes from her workout time simply by replacing her old steady-state 30-minute, 6-mph treadmill jog with "Sprint 8," a 20-minute aerobic session peppered with eight 30-second, 8-mph sprints so intense that they left her gasping for breath.
Sprint 8, the centerpiece of the book "Ready Set Go! Synergy Fitness," by Phil Campbell, has a growing list of believers. Gary Green, 45, a Web-based businessman from Tustin, says he halved his workout time and cycled off 25 pounds since switching to the program in August. Internet marketer Robert Burns of San Diego, 43, says he lost 25 pounds since May doing three swimming or running Sprint 8 workouts a week. "I feel younger and get faster and faster every day," he said.
