If you're over 50, you need exercise to stay fit--no disputing that. But what are you doing to keep your brain lean and mean?

The concept of brain fitness has caught fire lately, with much of the attention focused on a new breed of software programs and games that claim to help older people maintain mental acuity and blunt the cognitive decline associated with aging.

Nancy Merz Nordstrom is a bit of a skeptic. An expert on lifelong learning, she agrees that a challenged, stimulated brain is key to vibrancy in later life. She just prefers a real-world approach to the virtual.

"You can use mind software on your own--I don't have any problem with it," Merz Nordstrom says. "It's just that you also need to get out of the house and stay active."

Merz Nordstrom would be the first to admit that she's biased on this topic; she's the director of the Elderhostel Institute Network, an association whose members include many of the Lifelong Learning Institutes around the country that run adult education programs.

She's also the author of a well-regarded book on the benefits of adult learning, Learning Later, Living Greater: The Secret for Making the Most of Your After-50 Years. The book is a great resource guide to the range of adult learning options and a catalyst for getting started.

"It's as simple as 'use it or lose it,'" Nordstrom says. "If we want to do everything possible to keep our whole being alert, vibrant and connected as we age, we have to continue to challenge ourselves."

A growing body of brain research backs her up on this point. Some of the findings--detailed in Merz Nordstrom's book--suggest that the brain's physical anatomy responds to learning by regenerating brain cells. The benefits include enhanced mental alertness, thought processes, response times and reflexes.

“When you look at the benefits gained from keeping your mind sharp, it's incredible," Merz Nordstrom says. "Lifelong learning is like a health club for your brain."

Americans appear to be getting the message. An AARP study forecast that more than 95 percent of Americans over age 50 will participate in learning activities of one type or another during their lifetimes. And another report, by a research arm of the U.S. Department of Education, showed that the number of older adults returning to the classroom more than doubled during the 1990s.

What are all those people studying?

Some are pursuing degrees or doing work-related study. But Merz Nordstrom focuses on the large numbers that are there for personal enrichment--the sheer joy of learning.

"What we find is that people want to study the things they never had time for before," Merz Nordstrom says. "If their college years were focused on a career, now they want to study liberal arts, or an artistic endeavor. The humanities are very big, especially history."

And not all that learning is going on in classrooms. Merz Nordstrom devotes substantial sections of her book to educational travel (after all, she works for Elderhostel) and learning-oriented community service opportunities.

"For most people, it will just be a question of how involved, how focused?" she says. "How big a part of your life do you want to make this?"

If you'd like to learn more, check out a local Lifelong Learning Institute Most--but not all--are run under the auspices of a college or university. Merz-Nordstrom recommends calling your local college or university to see if continuing education programs are offered for older adults.

Other good places to start:

• http://www.elderhostel.org/EIN/intro.asp web site offers database that can be searched by zip code.
• Institutes for Learning in Retirement. These programs are usually are run by participants, who develop the curriculum, and teach the classes. More information is available at the Elderhostel site.
• Your public library. Many have established resource centers for researching learning opportunities of all types.