When the budget squeeze hits a school system, physical education is often the first program to go. And the real losers, say many health professionals, are America's children.

"Only one state out of 50 has daily physical education for all students from kindergarten through the 12th grade," notes actor Arnold Schwarzenegger, chairman of the President's Council on Physical Fitness and Sports.

"I wonder about the future," he says, "when 40 percent of all American youngsters between 5 and 8 already show at least one heart disease risk factor: physical inactivity, obesity, elevated cholesterol or high blood pressure."

While there is some controversy over how fit, or unfit, America's children are, most experts agree on two things:

Children today are getting fatter. One in five is obese, says William H. Dietz, an associate professor of pediatrics at Tufts University School of Medicine. Since 1963, the prevalence of obesity has increased 54 percent among children 6 to 11 and 39 percent among those 12 to 17.

Many are less active than is necessary for health. Those between ages 2 and 5 average 25 1/2 hours a week watching television, according to the Physician and Sportsmedicine journal in a special report on Children and Fitness.END NOTES

Last year, Schwarzenegger launched a campaign to visit the governor of every state to advocate daily physical education classes and to show America's out-of-shape youngsters that "It's Hip to Be Fit." This week in San Francisco, he'll address the annual convention of the American Alliance for Health, Physical Education, Recreation and Dance.

Experts say daily gym classes are a start but focusing on the number of classes isn't enough. "Kids come into the world usually feeling good about activity," says exercise physiologist Russell Pate, chairman of the department of exercise science at the University of South Carolina, "but too often physical education programs turn them off by rewarding only top athletes and not encouraging participation by all. We've got to help them learn skills to do activities they can stay with for life." This means less touch football, Pate says, and more walking, cycling, swimming and jogging.

But even the best physical education programs don't always allow enough time for activity. Since a portion of class time is often spent on instruction, kids may not get the recommended 20 to 30 minutes of vigorous exercise every day, notes the American College of Sports Medicine.

One of the best ways to help kids improve their fitness, experts agree, is to set an example. Active parents tend to have children who are active and fit, several studies indicate.

"Invite children to walk or bike with you" instead of taking the car, recommends the Melpomene Institute for Women's Health Research in St. Paul, Minn. "Help them set goals that are reasonable and achievable for their age, maturity, psychological make-up and ability. Stress enjoyment and personal improvement over winning." Children also can take classes or join clubs devoted to various activities.

"We must make fitness a family affair," Schwarzenegger says. "When I was growing up, every morning we had squats and sit-ups 15 minutes before breakfast."

In an age when parents are looking for new ways to communicate with their youngsters, exercise is one way to do it, he says. "A walk after dinner, a half hour of playing catch, a bike ride together, kicking the soccer ball. The great thing is that it will be fun."

Bodyworks appears on alternate Tuesdays.

Resources for Parents

"Physical Education: A Performance Checklist," President's Council on Physical Fitness and Sports, Dept. 153, 450 Fifth St. NW, Washington, D.C. 20001.

"Fit to Achieve," American Alliance for Health, Physical Education, Recreation and Dance, 1900 Association Dr., Reston, Va. 22091.

"Exercise Is Kid's Stuff." Send a self-addressed, business-size envelope with 50 cents' postage: American Running and Fitness Association, 9310 Old Georgetown Rd., Bethesda, Md. 20814.

"Fit Kids," Melpomene Institute, 1010 University Ave., St. Paul, Minn. 55413.

"Fitnessgram," Institute for Aerobics Research, 12330 Preston Rd., Dallas, Tex. 75230.