It's 12:50 p.m., a few minutes before break time at Ethicon Corp. in Somerville, N.J. Eight hundred production workers sit at their assembly line posts, making surgical implements and supplies of every description.

The work is tedious and demanding, tiring the muscles of the hands and lower back.

At one station, where about 30 women are polishing and inspecting surgical needles, an exercise instructor in gym shorts arrives with her boom box. "Come on, ladies," she says, turning up the volume. "It's time."

And for the next six minutes, their routine of polish-and-inspect is replaced by a regimen of move-and-stretch.

About half of the production workers at Ethicon, both men and women, participate in six-minute "ergonomic exercise" sessions twice during their shifts. The rest of the employes will be phased into the program next year.

"I can see the difference in my arms and fingers," says Fran Brezinski, 50, a needle inspector. "And exercise isn't something I've done before."

Brezinski is one of the country's 31 million so-called blue-collar workers, a broad category comprising auto workers and seamstresses, plumbers and truck drivers, orderlies and janitors.

While their counterparts behind desks have been quick to join expensive fitness clubs and sign up for time-consuming aerobics classes, the general health of the working class has lagged. They smoke more. They're more overweight. According to a study in the Journal of the American Medical Association, they're more than 70 percent likelier than office workers to die of heart disease.

Now, an increasing number of companies with a variety of motives are taking steps to bolster the health of their workers. Firms that were quick to realize how costly it is to replace a personnel director who dies of a heart attack now also realize the increased costs associated with an out-of-shape assembly line worker.

But how much can a company do? When does well-intentioned paternalism become Big Brother interference? Might some firms, in the name of cutting costs, be reluctant to hire the unfit? Financial Incentive

The driving force between the upsurge in worker fitness programs is a combination of health and money. In some studies, half of all deaths have been linked to controllable factors like weight and smoking.

The National Center for Health Statistics found, for example, in 1983 that about 40 percent of blue-collar workers smoke cigarettes, compared with less than 30 percent of white-collar workers. While the number of all smokers in the United States continues to decline, said Robert Hutchings of the Centers for Disease Control, the disparity between blue-collar and white-collar smoking is expected to continue.

People who smoke a pack a day have medical claims that are 18 percent higher than people who don't smoke, according to a recent study jointly conducted by Milliman & Robertson, an actuarial firm, and Control Data Corp.

So even a relatively simple and inexpensive stop-smoking class, perhaps the most basic of at-work "wellness programs," might well save firms hundreds of thousands of dollars in medical costs.

In the face of statistics like those -- plus the fact that medical costs are now a whopping 10.9 percent of GNP and that employer medical costs increased 7.7 percent in 1986 over the previous year -- the number of wellness plans is skyrocketing. According to Business Insurance Magazine, 5 percent of U.S. corporations had programs in 1982, and seven times as many -- 36 percent -- had them last year.

Individuals, too -- who are increasingly paying part of the health insurance premium or are forced to cough up co-payments -- have financial incentives of their own to join fitness programs.

According to Robert Friedland, a research associate with the Employee Benefit Research Institute, most insurance plans were redesigned in the late 1970s and early '80s to increase employe contributions. This is often a hardship for blue-collar workers, especially because, according to Friedland, only 4 percent of all employes have copayments or deductibles that are income-related. "For everyone else," says Friedland, "your costs are the same whether you're the CEO or the janitor."

This is the climate that has led to the emergence of an entirely new industry: the at-work health promotion managers. Three companies in the fore of this new field are: Control Data's Staying Well, which has marketed consulting programs to about 500 companies nationwide, including Chrysler, Motorola and Honeywell; Johnson & Johnson's Health Management Inc., whose 25 customers include IBM; and, The Travelers' Taking Care program, which provides health promotion planning to such firms as Black & Decker and the Maryland National Bank.

Most of the programs work through distributors, often hospitals, who use health care staff members to market programs that range from health screening and a wide variety of fitness and counseling programs to just one course, such as smoking cessation or stress management.

A fitness program usually begins with a series of management-level meetings between the health-management firm and the company that wants to shape up. There they decide how much help they want -- from just a few booklets to a fully staffed center of gym teachers and counselors.

Most plans start with a health screening of first a few employes, then the rest of the personnel.

Health screening usually requires employes to fill out questionnaires about their health and life-style habits and sometimes to take medical tests such as blood pressure and cholesterol levels. That information is confidential -- between the counselor and the worker -- though employers do receive general trend data.

In the more comprehensive programs, medical officers go over the results of the questionnaires with employes and try to help them make changes, such as losing weight or getting more exercise if that is what's indicated.

"Are companies in this for the long haul," asks William Hoffman, a benefits specialist for the United Auto Workers. "Do they realize the long-term commitment they have to make to life-style changes?"

Hoffman is concerned that if health-care savings don't come in right away, corporations will pull out of health-management programs. "This has high visibility now," he says, "but it could go away."

No conclusive data are available yet on medical cost savings attributable to wellness programs. Stephen Brink, a consulting actuary with Milliman & Robertson who wrote the company's study, says that "it's difficult to measure heart attacks that didn't happen, but given that people with more serious medical problems have greater utilization patterns, doing away with those problems can reduce costs."

According to Control Data's David Anderson, costs per employe for company health promotion programs range from $10 to $50. So far at Control Data's internal program at least, "we're saving more than we're spending," he says.

Getting People to Work Out

Sending coaches into the factories is only part of the plan. The real goal of wellness programs is to lure people out of the workplace and into the gym, and to get them to change their habits.

In the experience of some firms, this has been easier among office workers than among factory workers.

At Ethicon, for example, the Johnson & Johnson-owned manufacturer in New Jersey, the modern fitness center includes a gym, basketball court and showers -- and 12 instructors who teach courses in exercise, stress management and weight control.

Since it opened three years ago, the center has been filled with white-collar yuppies.

"Those are the ones who come to us," says Patricia Goias, manager of the "Live for Life" program at Ethicon. "We're making a special effort to make the other workers at the company feel welcome, too."

Many people can't afford the time before or after work, if that's when classes are held, because of travel time or family responsibility.

Another area of resistance for some union members is the view that fitness programs are a way firms can appear to care about the health of workers instead of dealing with more pressing hazards of the workplace.

Dr. Laura Welch, director of the occupational medicine program at George Washington University School of Medicine, says that employers could have a more profound effect on their workers' health by paying attention to the nature of jobs themselves -- how much and how often employes are required to lift things, for example. "Jobs have to be designed to fit the physical ability of workers," says Welch.

At Tristar Sports in Middletown, Conn., maker of Olin skis, the company found that repetitive motion during manufacturing was causing hand injuries and that lifting heavy ski molds was causing back injuries. Robert Lehet, Tristar's parts and molds supervisor, says that by redesigning manufacturing tools and issuing guidelines on how to life ski molds, the company was able to reduce workers' injuries.

Ethicon's ergonomic exercises have proven to be a way of breaking down some barriers, company officials contend. All of the instructors who conduct the exercise classes are also on duty at the company's fitness center and encourage production workers to join classes and clinics.

Fran Brzezinski and Phyllis Calabrese, 63, a needle polisher at Ethicon, have started going to exercise classes after work since joining the ergonomic workout routines during their shifts.

"Getting to know the instructors makes me feel a little more comfortable once I get to the fitness center," says Calabrese.

Pepsico has also taken its health promotion program to the shop floor. The company's medical officers found that some workers, especially those who lift and load, were having problems with their wrists. Exercises were developed especially for those workers, and they now do them each morning for a few minutes before work starts, according to Charles Rogers, Pepsico's vice president for compensation and benefits.

Another approach is to bring programs to the communities where people live instead of to the companies where they work.

The Stanford Five-City project is a major effort aimed at changing the life-style habits of entire communities. The program is being funded in part by the National Heart, Lung and Blood Institute and, according to Dr. John Farquar, director of the Stanford Center for Research in Disease Prevention, the project's three objectives are to: lower individual's risk factors for chronic heart disease, reduce the numbers of premature deaths by reducing controllable risk factors such as obersity, and encourage communities to adopt programs that will educate people about how to reduce their risk of heart disease.

According to Farquar, the researchers have already been able to detect changes in blood pressure, smoking, diet and cholesterol. One of the key concerns of the project was to be able to have the community take over after the funding ended, "a kind of technology transfer," says Farquar. "What you need to do is to train teachers and community workers so that the community itself can be in charge of its own health program."

Such a community program was started in New Mexico last year, spearheaded by Sen. Jeff Bingaman (D-N.M.). A longtime health promotion advocate, Bingaman took New Mexico officials to Stanford to meet with Farquar and his colleagues to set up a community-wide program. Called HealthNet New Mexico, the project is designed to last 10 years.

"So far," says Bingaman, "we've gotten a tremendous response, and 30 communities and 200 employers have gotten involved. Programs include media campaigns on the topics, materials given out at schools, offices and even supermarkets where people on the 10-week weight loss program could pay their fee and then be weighed in."

Probably the best feature of HealthNet New Mexico is that it's not a one-shot deal. Each 10-week series is repeated every year, making diet, exercise, smoking cessation and weight control a continuous goal and giving everyone a chance to participate -- next time, if not this time. Participation in the program costs $5 per person, often paid by employers, and includes information packets and awards such as T-shirts.

Still other wellness plans are run by labor unions. The International Ladies Garment Workers Union, for example, has created a Saturday morning exercise class for mostly Spanish-speaking women workers in Yonkers, N.Y., that has been very well attended. Many union officials prefer work-site intervention because they think it has the advantage of continuity.

"Work-site programs seem to work better than community-based progams," says Meredith Miller, assistant director of research for employe benefits at the Service Employee International Union, which has 850,000 members. Programs at work "seem have a better track record in terms of continuing care, which is important in health promotion."

The Next Step

Whether they are at-work or community-based programs, they all seem to point in the direction of using the fitness sessions as a basis for setting health insurance rates -- just as smokers now pay more for life insurance. Those who participate save; those who don't pay the full rate.

So far, the insurance industry has been slow to put theory into practice and reduce health premiums for companies or individuals that participate in fitness programs. Prudential Insurance, however, does have a program called Health Sketch, which links the premiums of smaller companies to employe answers to 50 life-style questions instead of the average of claims across the companies in the pool.

Yet many health leaders are concerned about the trend toward linking health insurance rates to employe wellness.

"You can legally set rates based on merit," says George J. Annas, professor of health law at Boston University School of Medicine and School of Public Health, "just as you do with car insurance. The question is how would you monitor it, how could you find out if someone is smoking at home?"

For the moment, few insurance companies seem to be marketing such a program, though David Levinson, insurance commissioner of Delaware, has called for insurance companies in that state to give discounts to companies that have health promotion programs. Hearings on this proposal are to begin next month.

How quickly these programs continue to catch on remains to be seen. Controlling people's health is an inexact science; even the health-management firms acknowledge that the best they can do is improve the overall health of a work force while making no promises for an individual.

Which is why people like the UAW's Hoffman still have nagging doubts. "You have to question concern for employes' life styles," says Hoffman, "if there are still environmental hazards in their workplace."Fran Lunzer is an associate editor at High Technology Business magazine in Boston.