Play through the pain. Rub some vile-smelling liniment on that pulled muscle and get back out there. There's no injury that 20 minutes in the whirlpool can't cure.

A generation ago, that gladiatorial credo among high school athletes sometimes meant that health considerations were secondary to victory on the football field, the wrestling mat, the basketball court. Some athletes paid the price later in adulthood, enduring creaky ankles, trick knees or a shoulder that ached for days after a trifling softball game.Today, the macho mystique is being gang-tackled by sports physicians, certified athletic trainers, some enlightened coaches and the Massachusetts Interscholastic Athletic Association. Propelled into adults' consciousness by the fitness boom of the 1970s, sports medicine now occupies a niche in many high school locker rooms.

"A few years ago, there was no such thing as sports medicine," observes William Gaine, assistant executive director of the Massachusetts Interscholastic Athletic Association. "It's just exploded, and now the health and safety of student athletes has become a significant issue."

Roughly 100 of the state's 352 secondary schools have team physicians, whose diagnoses of injury - or recommendations against a student playing a particular sport - can sideline journeyman player and all-star alike.

"The most difficult thing is to have an elite athlete whom you have to take out for a season or tell them they can't continue in their sport," says Dr. John Duff, a Danvers, Mass., orthopedist who treats athletes from North Shore schools. "There's anger, frustration, disappointment, tears - sometimes tears from the parent. But it's reality."

Michael Mulcay met reality on an operating table last summer. A 6-foot-2-inch forward at Danvers High School, Mulcay underwent surgery in August to remove a bone spur that was rubbing against a tendon beneath his left kneecap, similar to the heel problem that recently sidelined Celtics star Larry Bird. Dr. David St. Pierre, Duff's associate and the Danvers High team doctor, performed the surgery.

Now, as practice sessions begin for his final season, Mulcay is undergoing ultrasound treatments as part of follow-up physical therapy. He finds he can jump better than before the surgery, and he has high hopes of going on to play basketball in college. But he is also more aware of the warning signs of injury and the need to monitor his own rehabilitation. "It really concerns me a lot," he says as he ices his knee after practice. He says he asks the doctor "a lot of questions."

Coinciding with the growing clout of sports physicians is the sound of new words being bandied about high school locker rooms - Orthotron, Hydrocollator, Cybex. It's not a list of Arnold Schwarzenegger's screen credits, but a sampling of the rehabilitation machines to be found in training rooms and doctors' offices.

Coupled with such diagnostic techniques as arthroscopy and magnetic resonance imaging, physicians can now "look the athlete in the eye and say, `We'll have you back on the field in four weeks,' " says Dr. R. Scott Oliver, a Duxbury, Mass., orthopedist.

Sports physicians have also added to the athletic roster by stressing injury prevention via year-round conditioning, sound nutritional habits and the comprehensive preseason screening of athletes.

For example, Oliver recently conducted physicals on Plymouth athletes who are going out for winter sports. Under a $5,000 contract with Plymouth for all three sports seasons, Oliver employs a team approach to gauge the readiness of student athletes. Nurses check athletes' vision, hearing and blood pressure; a pediatrician checks the heart, lungs and overall health indicators; and physical therapists check for sprains, flat feet, abnormalities of the neck or spine and other problems.

Then Oliver steps in to examine students found to have problems, occasionally steering a student to a different sport, as in the case of the 16-year-old Plymouth student who opted to play hockey rather than football after developing knee problems, or advising the team trainer how to wrap a player's ankles before each game. Throughout the season, Oliver is available to injured athletes for treatment of injuries ranging from patella tendinitis or "jumper's knee," which plagues many basketball players, to strained ligaments, concussions or separated shoulders.

Resistance to his advice comes not from formerly omnipotent coaches - "They're great; they don't give us any guff at all. They say, `Whatever you say, doc,' " says Oliver - but occasionally from the injured players.

"I've got to be the heavy sometimes, and they don't like it one bit," says Oliver. "They'll try to fight it, but I tell them nobody's going to let them go on the field like that."

While sports medicine's stock may be soaring in many school systems, others are unwilling or unable to make the investment.

"A lot of schools have their head in the sand," contends Dr. Lyle Micheli, director of sports medicine at Children's Hospital in Boston. Micheli says each high school should have both a team doctor and a certified trainer, "but that's very rare, because it costs money." Hiring a trainer would cost a school around $26,000, plus equipment costs, Duff estimates.

"Medical care to young athletes at the high school level is not very systematized, as opposed to college," says Micheli, who is trying to set up a sports clinic for Boston schools. "Often it's assumed that kids are naturally fit and ready to play, and that's not the case."

An additional hurdle is the shortage of qualified athletic trainers, through whom advances in sports medicine techniques filter down to athletes. The state's 160,000 high school athletes are being shortchanged by the "tremendous void" of trainers, maintains Gaine of the MIAA.

Noting that only one-quarter of MIAA member schools have licensed trainers for their athletic teams, Gaine blames fiscal constraints on school systems and a paucity of college programs to train the trainers. Only four Massachusetts colleges offer a curriculum to educate trainers to meet state licensing standards.

The MIAA has endorsed a report released by State Auditor Joseph DeNucci that found high school athletes face a high risk of injury because of the lack of certified trainers. To combat the shortage, the report calls for creation of a provisional athletic trainer license with "realistic and attainable" standards of trainer competency.

On the day before Thanksgiving, trainer Jeff Stone watches the Natick High School varsity football team in a final scrimmage before the season's final game. With a well-equipped training room, the respect of Natick coaches and a team doctor to whom he can refer injured athletes, Stone knows he is in an enviable situation.

He said he hopes the number of trainers will soon multiply, so coaches don't have to guess about whether a player is fit for action.

While many adults pant through punishing exercise regimens to retain a semblance of their younger selves, the average high school student takes a no-sweat approach to fitness, according to physical education teachers in Massachusetts.

Some teachers have sought to reanimate gym class by introducing new sports and different approaches to exercise. But dire dispatches from the gym indicate that fitness still remains near the bottom of a long list of priorities held by their students.

"Your overall high school population is not as physically fit as they were 15 or 20 years ago," says Dennis Azevedo, chairman of the Plymouth High School physical education department.

"In general, the level of fitness is down," concurs George Wheeler, head physical education teacher at Framingham North High School. "I see a lot of injuries that indicate they don't do anything physical anymore."

Nor is the shape of things any better at St. John's Preparatory School in Danvers, where physical education chairman Fred Glatz asserts: "There's no doubt that for the most part the students are less fit than they were 10 or 15 years ago."

Physicians and physical education teachers alike round up the usual suspects when discussing the cause: fast food, TV-fixated passivity, reliance on automobiles, the popularity of such low-exertion after-school diversions as mall-crawling and computer programming.

By now, bemoaning the state of fitness among the nation's youths has become one of America's sturdy traditions, prompting skepticism from some researchers who question whether the standardized tests, which include pull-ups and sit-ups, genuinely test fitness.

Additionally, some specialists warn that a societal preoccupation with fitness can filter down to teen-agers in harmful ways. "I think that kids are subject to cultural pressures around body images" that can lead to such eating disorders as bulimia and anorexia, says Dr. Arthur Barsky, a psychiatrist at Harvard Medical School.