The year Teri Smith turned 40, she decided it was time to tackle a nagging urge to get in shape. It was then that she enrolled in her first physical boot camp class.

“I had no energy and could feel my age creeping up,” says a Pembroke Pines, Florida mother of two. Her weight had also increased. Although she was light, the 20 pounds she had added over the years did not feel comfortable on her 5-foot-3 frame.

Smith, a successful graphic designer, had never felt more comfortable in sneakers than she did in front of her Macintosh. “She didn’t have the confidence” to exercise, she says, because she always felt uncoordinated.

But when her stylist suggested she try the boot camp fitness class, she plucked up the courage to do it. And she has never looked back.

“No other workout makes me feel this good. It makes me feel like I really kicked my ass,” says Smith, 42, a faithful boot camper for two and a half years.

She is now one of the fastest runners in the class and is once again happy with her appearance. “It took me 12 weeks, but I lost 25 pounds,” Smith says.

What is a physical boot camp?

Boot Camp exercise classes vary in style, depending on the teacher. But you can generally expect to find yourself outside, rain or shine. You’ll probably spend an hour doing some form of cardio (running, walking, interval training, or obstacle course challenges), along with elements of strength (using dumbbells, exercise bands, or the resistance of your own body weight). You’ll also work on flexibility in a stretching portion of the class, which may incorporate elements of yoga or Pilates.

The fitness boot camp class Smith attends in Weston, Florida, is taught by former college football player and fitness trainer Tom Rayhill. Rayhill Boot Camp is offered three times a day, seven days a week, throughout the year. People can pay daily, weekly or monthly and come as often as they like.

Many other boot camp classes are offered for defined periods of time. California-based John Spencer Ellis’ Orange County Adventure Boot Camp, which has locations in nine countries, is offered to women only at 5:30 a.m., five days a week for one month. Many participants re-enlist one or more times.

Boot Camp fitness classes challenge both mind and body, instructors say.

“We work on technique, form, core training, breathing, relaxation, and a better understanding of how the body moves,” says Ellis. “In four weeks, people will lose 5-6% body fat, lose up to 10 pounds, and cut their mile time by sometimes 2 minutes per mile.”

Often the confidence that boot camp class participants gain helps them take control of other aspects of their lives, Ellis says.

What is a physical boot camp? continued…

“They might say, ‘I’m going back to school. I’m going to get this job. I’m going to start my own company, I’m going to travel,'” he says.

Boot camp became more than just training for Smith when her oldest son was diagnosed with Asperger’s syndrome (a developmental disorder that’s milder than autism) and her husband, an Air Force lieutenant colonel, he had to spend a year in Korea without family.

“It was literally my saving grace,” Smith says. “It was a very stressful time. (Boot Camp) was a way to take care of myself physically and emotionally, it was my social outlet. It kept me sane.”

‘Let me go and give me 50’

Although the name “boot camp” was inspired by military boot camps, none of the instructors who spoke to WebMD use intimidation tactics in their classes.

“If you’re lining people up and yelling at them, that’s not real camaraderie. That’s something you can fake,” says Rayhill. Besides, he says he, it’s not necessary. People push themselves when they are in a group.

“Human nature is to challenge yourself against other humans,” says Rayhill. “Not everyone has the same athletic bent, but when you hang out with those more driven people, you’re naturally going to want to do better,” she says.

Ellis Adventure Boot Camps follow the same philosophy. The boot camp is for the military, he says, and that’s not the people enrolled in Adventure Boot Camp. Its participants are generally moms ages 25 to 50 who may have had C-sections and want to get in shape.

“Negative reinforcement usually only goes so far,” he says. “My choice is to have an empowering environment, one that is nurturing and very challenging. One that is not just about getting fit but about community and nutrition and being better at everything you do.”

Still, he says, it is is a boot camp: “People are expected to show up, shut up, pay attention and give 100%,” he says. “He’s disciplined by nature. He’s intense. He’s not a piece of cake.”

camaraderie is key

So why are boot camp classes suddenly seeming to pop up everywhere?

According to Rayhill, it’s all about peer interaction and encouragement.

“Most of what we do all day is very isolating,” says Rayhill. “We have iPods, cell phones, computers. We’re not connecting with other people.”

The interaction of a boot camp class is not only emotionally satisfying, but it helps people push themselves physically, he says.

“If you’re around other athletic people, they’ll take it out on you,” says Rayhill. “By the time they leave, they’ve already done a lot of positive things that day.

“No computer can make you feel better, not like connecting with other people.”

A cult of personality?

Another powerful draw to boot camp classes, say some participants, is the charisma of the teachers.

A boot camp class, Ellis says, is meant to empower students throughout the day. As a teacher, “at different times, you intersperse powerful thoughts and statements. You are setting the example. You are leading the way.”

Rayhill also tries to be a guiding force for its students. As one of six children, and a 5-foot-8 former college football player (who still holds two Illinois state records), Rayhill says he’s “always been a high achiever.”

His goal as a teacher, he says, is to give the class a different workout every day and encourage them to find what it takes to reach their goals.

“I call myself a catalyst. I know what it takes to get there. I know there’s more than one way to do something. We’re talking about how to make people better,” he says. “Whatever you want from your life, you have to get it. You have to do it for yourself.”