The familiar "use it or lose it" axiom is the key to maintaining good quality of life well into the Golden Years.

That's the opinion of family physician Larry Bernstein, chief medical officer of Jewish Geriatric Services in Longmeadow, Mass.

Bernstein points out that staying active means staying mentally and socially active as well as physically active.

Research indicates that the more that aging adults continue to use their mental abilities, the sharper their thinking remains in later life. That makes them better able to deal with physical challenges and medical problems that may occur as time goes on, Bernstein notes.

He advises seniors to continue growing and learning by participating in classes at senior centers, universities, libraries and museums, or through independent study. An estimated 90 percent of adult Americans enjoy and benefit from some type of self-directed growth during their later years, Bernstein says.

Maintaining social contact is also important. Actress June Allyson, who was appointed by President Ronald Reagan to the President's Council on Aging in 1988, is an outspoken advocate on programs for seniors. Allyson, who starred in more than 60 movie musicals and features beginning in the 1940s, suggests that seniors try to encounter a variety of people and places on a regular basis.

If you can't get to the people, she says, ask the people to come to you.

For those who can get out, volunteering with local organizations or joining groups that share your interests, such as gardening clubs or book clubs, is a good way to maintain social contact. Those who can't get out can still reach out to others by telephoning family and friends on a regular basis.

Churches, senior centers and synagogues often sponsor visiting programs that will send someone out to visit seniors in their home to reduce isolation. Programs such as Meals On Wheels not only offer daily meal delivery but also provide a visit from a friendly volunteer.

Allyson says she is convinced a positive attitude is another of the keys to remaining active. She suggests seniors focus on what they can do rather than what they cannot do, and view each new situation as a challenge instead of a potential problem.

She also recommends remaining as independent as possible by relying on yourself first and others second. But, she says, it's also important to recognize when you need help and to then seek it.

Exercise also helps maintain good physical, mental and emotional health in the later years. A recent study conducted by American Sports Data, Inc. for the Sporting Goods Manufacturers of America trade association indicates that folks 55 and older are not just sitting around. They're up and exercising.

Recreational walking is by far the most popular form of physical activity for this age group. According to the survey, more than 12 million older Americans walk for recreation on a regular basis.

In addition to enabling people to keep heart, lungs, bones and other body components healthy, recreational walking can be an opportunity for social contact if you join a walking group. Many senior centers and organizations such as the YMCA offer recreational walking groups.

Or join a gym. Many gyms offer senior fitness programs that are geared to the abilities of older folks. Classes range from light standing aerobics to chair exercise, and some are offered free of charge to members of senior organizations.

Judi Sheppard Missett, founder and chief executive officer of Jazzercise Inc., is a major proponent of exercise for people in all stages of life. Missett, who is now in her 60s, has designed a light version of her dance-based Jazzercise exercise program that is tailored for seniors.

Gentle yoga classes, which are offered at many YMCAs, gyms, senior centers and yoga centers, are excellent for maintaining or increasing flexibility, strengthening bones and improving functions of vital organs, notes Jill Badonsky, a yoga instructor in San Diego.

Because yoga is a meditative form of exercise, it can also have a calming effect that aids in sleep and digestion, and it helps relieve anxiety, Badonsky says.

Other physical activities that seniors have embraced include fitness walking, treadmill exercise, golf, swimming, bowling, stationary cycling, day hiking, lifting free weights and using weight/resistance machines.

"Weight resistance exercise is particularly important in maintaining strong bones," says Karen Reasoner, founder of the Mastery of Movement exercise program. "Post-menopausal women are especially at risk for bone loss, osteoporosis and fractures, so weight-bearing exercise such as walking or lifting light weights can be quite beneficial."