The 15 women and one man are all steadily focused on the task at hand: survival. This HIT - high-intensity training - class at FIT Studio in Lexington, Ky., is part of a national exercise trend.
While the idea of extreme fitness has been around for several years, it's recently come into more public view. 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 works outs 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." Submit a before and after picture to the company and you get a free "Insanity" T-shirt.
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.
"Good, good, good, that stays up, that stays up," said FIT Studio instructor Allison Perry. Members of the HIT class at FIT launch, in one fluid move, from a low lunge to a high kick, then back down slapping one hand on the ground.
Her pleasure at their progress is fleeting. She soon issues another challenge: "How far back can you lunge?"
There are no groans, only measured breathing and thwack of palms on plastic as they push through.
"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. A school psychologist, she is taking classes at three gyms and is also running. But, initially, she swore she wouldn't take a second HIT class. So did nearly everyone else.
"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."
Another pull toward the short-lived torture?
"You can start seeing changes in your body," she said. She's lost 30 pound since the spring.
As the class moves on, even the most hard-core falter slightly. Cold rags are fetched from the lobby, and at least one squeamish-looking HIT-ter makes a quick visit to the restroom.
But they don't stop. Not even after Perry demonstrates near the end of the class a move she calls the Spider-man crawl, which basically involves mimicking the way Spider-man's body moves up a wall without the help of the wall.
The look on the faces of the women, even Justice, who cheerfully grinned pretty much the whole time until now, is just a flicker of disbelief at what Perry is asking.
Then it is on.
"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, medical director of employee health work with sports medicine. 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 work out," 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.
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.
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.
Kellie Dryden said she has been exercising a long time. High-intensity training "really pushes my endurance and everything I am used to doing.
"It is a challenge and that's what I like about it," she said.
"If I get close to throwing up - and I did in this class - I just stop and take a breath and get a drink of water and calm down," she said. "So far I haven't seen anybody throw up yet."
It's not exactly a love/hate relationship she has with the program, but, "This one I have to psych myself up to do," she said. "I really, really have to psych myself up."
Explore further: The latest exercise trend: "Get Fit in 60 Seconds" researchers publish user-friendly how-to guide
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 bit.ly/TpQFNQ