Max Quinn is standing with a 65-pound steel bar in his hands, staring into a full-length mirror in a sweaty Winchester gym under the watchful eye of his fitness trainer. Perspiration beads on his forehead as he bends at the knees, grunts softly then lifts the bar.

''Good, good, good," says Max's coach, Tricia Quagrello. ''Back straight, head up."

Back in the day -- say the mid-1990s -- a 12-year-old like Max of Melrose would have been shooting baskets on this crisp winter day in someone's driveway, blowing on his hands to keep them warm and trying to squeeze in one more game before it got too dark. No more.

''That's a high pull S-L-D-L combo," Quagrello explains. ''That stands for 'straight-leg dead lift.' It works everything from the hips, legs, back, lats, triceps and glutes and helps explosive power."

If Max were vying for a spot on the varsity football team, that might seem like an important skill to cultivate, but he's not. All his intense training -- three days a week since shortly after his 10th birthday -- fits under the broad and somewhat nebulous rubric of fitness.

''I guess I want to be stronger," Max says with a touch of uncertainty after the set. ''I've already lost a lot of weight."

Welcome to the new world of youth sports and fitness, increasingly a rarified realm of the highly focused and committed.

It is a place where children as young as 8 compete in an athletic arms race in dozens of state-of-the-art sports centers popping up in affluent suburbs around Greater Boston. Inside, children looking for a competitive advantage are sweating through the same drills, being guided by the same level of coaches, and using the same technology as professional athletes whose livelihood depends on their performance.

With an estimated 20 percent of high school athletes now employing private coaches, area athletic directors say a tipping point has been reached among these youths much as it did a decade ago among SAT takers. The consequence: Thousands of teenage athletes no longer believe that they can compete on their own. The perception has trickled all the way down to noncompetitive athletes like Max.

''It's sort of like keeping up with the Joneses," said Ed Lippie, one of the muscular and deeply committed proprietors of Mike Boyle's Strength and Conditioning, the fitness mecca where Max -- and hundreds of other teens and preteens -- work out year round. ''It's one of our best marketing tools."

Children like Max say they love the exercise and revel in the results (his bench press has increased from 20 pounds to 82 since he started training). Trainers and businessmen like Lippie expound on the benefits of teaching body awareness and setting positive patterns that will serve their clients throughout their lives. But critics point out that at the end of day a lot of adults are getting rich on the backs of stressed-out children. Childhood obesity continues to grow, and participation in organized youth sports programs across the nation continues to decline.

An estimated $4.1 billion a year is spent in the United States on private sport instruction for children, but more than 70 percent of youngsters quit organized sports by age 13, according to the nonprofit National Alliance for Youth Sports. Critics say the professionalization of youth sports is a major factor in driving children off the playing field. But for those who want to compete, parents and athletes argue, the personal attention has become a necessity.

''If other kids are doing it and your kid isn't, how are they going to be able to compete?" says Dan Pellegrino, whose son Mike plays varsity football at Newton South and has had personal coaches for two years. ''Honestly, I wish I had started this five years earlier; it's given him a huge edge."

Among the consequences of that fierce competition is that children are specializing in sports at younger and younger ages. Where that held true for gymnastics and tennis 10 years ago, it's now the norm nearly across the board from baseball to soccer.

The result, says Jim Davis, the athletic director for the Belmont Public Schools, is that the number of multisport athletes has decreased by 30 percent in the last decade.

''A lot of these kids are getting sold a pipe dream," Davis says. ''They think if they do this they will get a Division 1 scholarship, but the fact of the matter is most of them won't. On the other hand you see the kids coming into football in much better shape. We used to have to take the first two weeks of the season to get them in shape; now they're already there and they are bigger, faster, and stronger."

At the end of the day the cycle creates more spectators than athletes and an ever-broader gulf between the haves and the have-nots, argues Jay Coakley, a sports sociologist at the University of Colorado. The children whose parents can afford private training are more likely to make the team, while those who can't are increasingly likely to get cut.

Max Quinn's father, Michael, said his reason for letting his son use a personal trainer relates to the boy's physical development and self-image. For that the training is perfect, he said. ''It's definitely helped his self-esteem," he said.

To fill the ever-deepening demand for private coaching, bigger, shinier, increasingly high-tech gyms are popping up across the country and the region. In Sudbury, 20 miles from where Max works out, a state-of-the-art, 25,000-square-foot Velocity Sports Performance facility opened in November. Three huge banners hanging from the rafters spell out the company's credo: strength, speed, agility.

''It used to be said you can't teach speed," said Jane Taylor, the sports performance director at Velocity. ''Now we know that's not true. You can and we do."

The Atlanta-based company has moved into 17 markets since it started franchising in 2002, and company CEO David Walmsley said it plans to open as many as 50 more facilities next year.

''This is still an embryonic industry," he said last week from his office in Georgia. ''There is tremendous room for growth."

Among Velocity's true believers is 13-year-old Nick Addeo, an eighth-grader from Sudbury who has his mind set on a Division 1 soccer program.

''Soccer is his life," his mother, Jen Addeo, said earlier this month as she watched him run through drills on a 35-yard field of artificial turf.

At Velocity, coaches with professional and college experience pace customers through a series of footwork and stretching drills. They are educated on the finer points of ankle rotation and body-weight distribution to give them an advantage in changing direction. Their 40-yard dash times are measured in increments of 10 yards so coaches can deconstruct their relative acceleration.

''Kids who just play rec leagues don't have that competitive cauldron ," Jen Addeo said. ''If you want to make a serious college team, you're going to have to devote yourself from an early age."

Ron Gilfix, who along with his wife, Suzi, opened the Sudbury facility, said classes are filling up fast enough to predict that he will be running in the black by the end of his first year in business. New classes are always in the offing.

A three-day ''speed camp" last week sought to improve flexibility, speed, agility, power, strength, and balance and teach injury prevention.

''Whether you're trying to turn pro or just want to feel like one, we promise we'll help get you there," the Velocity flier said. Campers starting in the fifth grade were invited. The cost was $90 for three 1-hour sessions.

''For better or worse we live in a sports-obsessed society," said Gilfix, who sold restaurant cleaning supplies and digital television before buying the Velocity franchise. ''We're here to help kids find their inner athlete. That translates in confidence and that translates into success."

Sprinting across the 35-yard field of artificial turf under the watchful eye of his personal coach, Nick appears to be taking that challenge seriously. On his T-shirt, stained in sweat across his chest, is a soccer ball. Above it, six words: ''My goal is to deny yours."

© Copyright 2004 Globe Newspaper Company.