LEXINGTON, Ky. — The 15 women and one man are all steadily focused on the task at hand: survival in a high-intensity training

“I’ve taken a lot of classes, I’ve run in a mini-marathon and HIT is probably the hardest class I have ever been to,” said Allison Justice at FIT Studio in Lexington. A school psychologist, Justice is taking fitness classes at three gyms and is also running. But, initially, she swore she wouldn’t take a second high-intensity training class.

“After the first one we were all like, ‘I am never going to do that again,’ ” she said. “But when you leave and you think, ‘I have just made it through the hardest hour of my life,’ you feel really good about it and you want to go back and try it again.

“You can start seeing changes in your body,” she said. She’s lost 30 pounds since the spring.

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While the idea of extreme fitness has been around for several years, it’s recently come into more public view nationally. Even the most slacking couch jockey is aware of the movement thanks to a seemingly never-ending techno beat of late-night commercials touting DVDs for such intense workouts as P90X and Insanity.

P90X, which a promotional website describes as “sweat-inducing, muscle-pumping exercises designed to transform your body from regular to ripped,” includes a 12-disc program and nutrition advice. The Insanity program is described at its home page, BeachBody.com, as “the world’s most insanely tough work out.”

All the programs work on the same general principle, said Angie Green, a certified trainer for Beach Body, the company behind the programs. The idea is that extremely intense, short workouts focus specifically on different muscles for several minutes followed by a shorter break.

“Extreme fitness is no joke,” said Green, the trainer of trainers who stresses modified ways to do the same move to match various fitness levels. “You have to learn to listen to your body and go at your own pace,” she said.

Anyone who has underlying health conditions such as diabetes or high blood pressure should check with a physician before attempting any strenuous work out effort, said Dr. Scott Black, who specializes in sports medicine at the University of Kentucky. And even if you were once an awesome athlete, if you have been out of the game for 20 years, “Don’t jump into a super intense workout,” he said.

Black, a runner himself, said people need to think about what they want to achieve from an exercise routine. These are not one-size-fit-all programs. And, he said, if you start exercising after a long absence, a monitored or organized program might be better than sweating alone in your basement to a DVD.

High-intensity training, he said, can raise the risk of injury, so people need to pay attention to their limits. Strains and sprains are the most common injuries, he said, but muscle soreness the next day is almost guaranteed. He said the American College of Sports Medicine(acsm.org) is a good source of information on fitness.

Green said she always encourages newcomers to come to class with a friend and introduce themselves to the instructor so they can help modify exercises to suit their fitness levels.

For tips on when to see a doctor before beginning an exercise routine see a fact sheet from the American College of Sports Medicine at http://bit.ly/15JThcF