• Matthew Thorsen
• Charlene Renee Adams leads a class

It’s a recent Thursday evening in Shelburne, and I’m hanging with a group of teenage girls in a room that has bright orange walls, fluorescent lights and OK Go blasting from the speakers. The place looks like one of those wholesome underage clubs in a mall. Except that, instead of a security guard hovering, there’s Charlene Renee Adams, a personal trainer wearing black capris and holding a stopwatch. And, instead of gabbing about the next episode of “Glee” or “Gossip Girl,” these girls and I are beginning to sweat.

“All right, ladies, ready to get busy?” barks Adams. “Pick up your biceps weights.” With that command, we’re off on a biceps-building, balance-challenging routine that involves curling up the weights while standing on one leg and looking in the mirror as Adams wanders around the room, attempting to throw off our focus.

Welcome to Strength & Stability for Girls Only, a new class at Shelburne Health & Fitness that aims to empower adolescents — physically and mentally. Its approach to exercise goes beyond the typical high-school-sports, one-size-fits-all plan. Reflecting a changing perception of what teens can and cannot do in the gym, the class coincides with a recent study published in the journal Pediatrics that reveals the benefits of strength training for kids. I’m here to discern the heft behind the hype.

When I was growing up, “dumbbell” was a word kids used to pick on each other — not something they picked up in gym class. Most teenagers have been discouraged from weight lifting because of long-held concerns that it might cause injuries and stunt growth without offering many compensating benefits, owing to teens’ lack of testosterone. Those worries are not without basis. In 1979, the United States Consumer Product Safety Commission (USCPSC) reported that half of all weight-lifting injuries requiring emergency treatment involved kids ages 10 to 19.

And, as William J. Kraemer and Steven J. Fleck acknowledge in their 2004 book Strength Training for Youth Athletes, damage to the epiphyseal plates of the long bones can indeed stunt growth. “If not properly treated, damage to the epiphysis could cause it to ossify (become bone) prematurely, stopping limb growth or resulting in limb deformity,” they write. “A few retrospective case reports have noted epiphyseal plate fractures during prepubescence and adolescence.”

But, the authors also note, most of these injuries “were due to improper lifting techniques, maximal lifts, or lack of qualified adult supervision.” The 30-plus-year-old hospital study on damage, moreover, didn’t distinguish between teenagers who were strength training for fitness and those who were attempting to become the next Arnold Schwarzenegger (who, by the way, began weight training at age 15).

Last year, the National Strength and Conditioning Association tossed old statements discouraging kids from participating in strength training and began recommending twice-weekly weight sessions, with professional supervision, for kids as young as 7 or 8.

“There is no real data to suggest that weight lifting and strength training stunts growth,” says Margot Putukian, MD, the director of athletic medicine at Princeton University and former president of the American Medical Society for Sports Medicine. “Most primary-care sports-medicine physicians would tell you that there are benefits to strength training in adolescents.”

These benefits were highlighted in the October 25 Pediatrics report based on a study from German Sport University Cologne. Researchers aggregated the results of 42 earlier studies, involving a total of nearly 1800 children and teens, and found that strength training is an effective regimen for young people. The study’s authors said that the gains of strength training — more bone density, less body fat, better sports performance — outweigh the risks. And the most effective exercises are those with isotonic contractions, such as squats, bench presses and bicep curls.

So, it’s no surprise that squats are part of the hour-long Strength & Stability class at Shelburne Health & Fitness. What is surprising is the degree of variation and attention to detail and safety. I’ve attended fitness classes where we were instructed to do squats until our quads and glutes were shaking, with little notice paid to form — or fun. But Adams mixes it up with one-legged “airplanes” and dips. And when we’re doing regular squats with reasonable weights of 8 to 10 pounds, she reminds us to keep our heels on the ground. That automatically takes the stress off our knees.

There are constant micro-adjustments and words of encouragement. Adams takes a cool-big-sister approach that prevents attention spans from drifting too much — yes, even as she leads triceps-burning exercises called “skull crushers” and emits occasional bursts of “Oh, snap!”

“My philosophy is to keep the girls moving and keep their minds occupied,” Adams tells me later. “They don’t know what to expect next. I’m hoping that they learn to enjoy exercise — it doesn’t have to break your bones or make your muscles hurt.”

Each of the girls has her own reason to attend the class. Fifteen-year-old Leah Epstein of Shelburne is training for Nordic skiing and tennis. Jenny Rehkugler, 16, has free time after school and is looking for a way to stay upbeat through gray November days. “I’m not a very good sports person,” she admits. Natalie Franklin, 13, and Sarah Caffry, 15, are Alpine ski racers.

Shelburne Health & Fitness aims to attract yet more teens. Boys-only classes are in the works, and a new weight-room-training program teaches adolescents how to use equipment safely.

“Strength training can increase or maintain bone density, help hold the skeletal system together better, and can burn more calories and relieve stress while building muscles,” Adams says after the class. “And [strength training] helps self-esteem — when you feel powerful on the inside, the whole body image takes a different shape,” she adds. “You feel wonderful.”