For student athletes, the beginning of a new school year also marks another annual ritual: the sports physical. But the sudden death last month of a McLean High School football player highlights the limitations of the medical exams that 35 states, including Maryland, Virginia and the District, require.

School sports exams, which certify that student athletes are fit to play, are far from comprehensive, experts say. Although they resemble regular physical exams -- both types of physicals check blood pressure, heart rate, vision and hearing -- sports exams focus primarily on muscles, ligaments and joints and generally do not include blood tests, urinalysis and more sophisticated screening.

In addition, sports physicals are not designed to detect many life-threatening medical problems, such as an enlarged heart, the condition that killed 16-year-old David L. Robinson, the McLean High School student who collapsed and died last month during football practice. Two days before his death, Robinson had been certified as eligible to play by a Fairfax County physician.

Sports exams "are good for picking up high blood pressure, hernias, certain types of heart murmurs and different types of orthopedic injuries that may lead to unstable joints," says Jeffrey L. Tanji, director of the sports medicine program at the University of California at Davis. "But the sports physical is a screening exam," not a diagnostic work-up, which is what doctors say would be necessary to detect problems such as an enlarged heart.

In the past, sports exams were used to bench student athletes with health problems, such as high blood pressure and poor vision. In some cases while taking a medical history, doctors discovered a student athlete had certain conditions including hemophilia, which automatically precluded participation in team sports.

As a result of liberalized recommendations issued in 1988 by the American Academy of Pediatrics that permitted students with hernias and other conditions to play, only 1 to 3 percent of students are sidelined today. Using equipment that offers better protection against injury, even hemophiliacs can now safely participate in all but the most intense contact sports.

Whether sports exams, or for that matter physical exams, need to be conducted annually is a matter of debate among doctors. Many question their value. "Medically, they're not necessary every year," says pediatrician Sally Harris, a member of the Committee on Sports Medicine and Physical Fitness of the American Academy of Pediatrics.

Instead, Harris and others suggest that students be screened less frequently at key milestones: when they start a new sport, enter a higher level of competition or are promoted.

However, school boards continue to require the annual sports exams, which cost $30 to $50 per student, at least in part out of fear of lawsuits by parents.

"A lot of the requirement to do physicals stems from concerns about liability," Harris says. In 1988, state school officials in Maryland polled coaches about conducting the sports exams every other year. "Coaches wanted to have the physicals every year for their own self-assurance," said Edward Sparks, the state's physical education director.

Sports physicals can help prevent injury and detect other kinds of health problems, including exercise-induced asthma, which affects as many as 10 percent of all athletes. They provide a quick check-up for children and adolescents who are rarely sick and may see a physician infrequently. For students from low-income families, such screening may be one of few regular contacts with a physician.

Sports exams are most effective in detecting musculoskeletal problems -- such as a pulled hamstring or an injured knee -- that raise the risk of further injury.

These exams focus on knees, ankles, shoulders and the lower back, areas most prone to injury. At least a third of sports injuries are related "to inadequate rehabilitation from previous injuries," says Albuquerque pediatrician Michael Nelson, chairman of the pediatric academy's committee on sports medicine and physical fitness. By doing the exams four to six weeks before the sports season begins, "we have a chance to identify problems and correct or compensate for them, and that can reduce injuries," he adds.

In addition, Nelson says, "many physicians take advantage of {the exams} to deal with other non-sport issues like sex and drug use as well as other health issues."

But without national standardization for sports physicals, their quality varies. In New York, which has the most stringent state requirements for sports exams, doctors must assess sexual maturity as part of the physical, in order to identify students who may lag behind their peers and could be more easily injured. Most jurisdictions, including the District, Maryland and Virginia, require students to be checked only for general health.

The manner in which sports physicals are performed also varies widely. Many students simply are examined by their family doctor or pediatrician. Some school systems use an assembly-line approach: Athletes line up in the gym and a single doctor walks down the line checking heart rates and other vital signs. This pattern is repeated until the physical is complete. There's no privacy, little opportunity to talk individually to students and a greater chance to miss abnormal heartbeats that might signal a risk.

A more popular approach with doctors and coaches is to screen a group of students using a team of physicians and nurses. Stations manned by specialists are set up in a gym. Height and weight are measured at one station; at another, a cardiologist listens to the heart; at still another, an ophthalmologist examines the eyes. Students move from one station to the next to complete the physical exam.

What's really needed to improve the quality of sports exams, experts say, is a standardized set of guidelines. To do that, four medical organizations, including the American Academy of Pediatrics and the American Academy of Family Physicians, are working to establish national requirements for sports physicals. Their recommendations are expected in the next year.

More than anything else, Harris and others say, the quality of an exam hinges in large part on taking a good history when interviewing students about their health and that of their immediate family. By asking questions such as whether a family member has died of a sudden heart attack or stroke before age 50, whether the student has had heart palpitations or felt faint or dizzy after exercising, doctors can identify as many as 60 percent of youngsters at risk for sudden death in sports, Nelson says.

The physical part of the exam -- checking blood pressure, taking a pulse, listening to the heart -- will identify about 10 to 15 percent of student athletes who need to be referred for follow-up visits for a variety of health problems.

About one in five children will have a suspicious heart murmur -- an abnormal, but usually harmless, sound in the heartbeat. Additional tests, including the non-invasive echocardiogram -- which takes a detailed picture of heart function using sound waves -- may be needed to clear a small percentage of students for playing organized sports.

About 8 percent of students may also need to have a repeat blood pressure check. When blood pressure levels rise above 140/90, doctors recommend at least one additional measurement on another day. But even if hypertension is confirmed, that won't preclude sports since exercise is one of the best ways to lower blood pressure. The occasional exception, says UCLA's Harris, are weightlifters, whose blood pressures can rise dangerously high during lifts.

Sports physicals don't always include blood or urine tests that could screen for kidney disease, high blood cholesterol or anemia, although annual physicals sometimes include those tests. Studies show that these tests "are not cost-effective for children and adolescents," says Gregory L. Landry, staff physician at the University of Wisconsin Hospital's Sports Medicine Clinic. So many incorrect results turn up that they raise anxieties and wind up requiring more tests. "If doctors are not performing those tests," says Landry, "it doesn't mean that they are being less thorough."