Though she's not an experienced backpacker, Virginia Boyack -- at age 53 -- strapped on a pack this summer and, with her husband, climbed to the summit of California's Mt. Whitney, the highest mountain in the continental United States.

And, taking a shortcut on the way down, she plopped on her rear, lifted her boots and plummeted on the seat of her pants hundreds of yards down a steep snow chute.

It was, she admits, a bit dangerous, but, "I felt like a kid. It was glorious."

All of which goes to show that older people can have the spunk and vitality of juniors half their age. Which, as it turns out, is a point Boyack wants to make.

Boyack heads the private sector subcommittee of the 1981 White House Conference on the Aging, whose responsibility is to explore the impact on both employers and employees as the nation's workforce grows older.

We are facing, she says, "a gerontological boom." In the next few decades, the post-World War II babies who first crowded our schools and now overflow the junior ranks in the job market will become the older workers.

They will have then, as they have always had in their progress through life, the clout of their numbers.

It is, Boyack says, the responsibility of private business to work with labor, government and the individual "to redesign the work environment" to meet the different needs of this changing workforce.

Formerly the director of pre-retirement planning programs at the Andrus Gerontology Center at the University of Southern California, Boyack now is vice president for life and retirement planning porgrams at California Federal Savings and Loan Association in Los Angleles.

Employers are finding, she says, that workers from the baby boom generation differ from their predecessors in that they "are making more of the decisions about their personal growth. They're more willing to explore options. And it's a mobile workforce."

In her field, the older worker is generally defined as someone "over 40." But that, she believes, is a long way from being over-the-hill.

"The older worker," she asserts quite firmly, "is a vital, experienced, knowledgeable person who industry must tap more intelligently. Many people feel that older persons are our nations greatest natural resource," which too often "is being allowed to waste away."

She deplores "the myth" that the older worker has a higher absentee rate and is less productive.

"It's not so. The older worker has lower absenteeism. There's a desire to work, to do the job. The older worker seems to have something invested in the job."

Additionally, "We have very definite data that the older worker is highly productive, that he or she is able to take responsibility and fulfill it."

The older worker also "is concerned about loyalty and trust." One conference member, she says, raised the issue that employers aren't interested in training the older worker because "they're short term."

But an employer challenged him. "We've been training younger people," he said, "and they stay two or four years and then leave us."

One California department store chain, she says, "is trying to attract older women, because the turnover of younger women is a tremendous problem."

A growing number of firms already have begun looking into more flexible working arrangements for older employees. Among the options:

Sabbaticals : "In academia, you can take off nine months to work on an intense project that interests you," Boyack says. "Why not in the private sector of mid-life?"

Flexitime : Employees choose their own starting and stopping times within a limit.

Job-sharing : Two people share a job. They can each work a half-day or a half-year, depending on the arrangement.

Phasing : An older worker, she says, phases in a younger employee while preparing eventually to retire.

Reassignment : If it's a move down, or even sideways, older workers may see this as a "demotion," she says, "since we've all been raised with the concept we must rise on the ladder. But it can be changed into a positive concept if older workers are allowed to pursue their own objectives."

With the workforce getting older, she says, age is going to be less of a factor when employers are hiring.

What will be "more relevant" are "vitality, knowledge, skill and experience." Which are exactly what the older worker has to offer.