Life without sex might be safer but it would be unbearably dull. It is the sex instinct which makes women seem beautiful, which they are once in a blue moon, and men seem wise and brave, which they never are at all. Throttle it, denaturalize it, take it away, and human existence would be reduced to the prosaic, laborious, boresome, imbecile level of life in an anthill. - H.L. Mencken

It is one of life's little ironies that the idea of our parents having sex makes us cringe, given that most of us owe our existence to their having done so.

And the thought of grandparents getting it on?

Even creepier.

Get over yourselves, says Betsy Crane.

Luckily, the opprobrium of children has not resulted in mass abstinence among people over 50, says Crane, a professor of human sexuality at Widener University. An archaic social stigma prevails nonetheless and it is not healthy for anyone, she says. This is one of the issues Crane will raise Wednesday during a workshop on the importance of continuing to enjoy sex as we age.

Research shows that a great many of the progenitors in question, as well as their cohorts who have never reproduced, continue to boff for decades after they have gone gray and jiggly.

When Maroon 5's lead singer Adam Levine moves like Jagger, for instance, he's emulating a 70-year-old soon-to-be-great-grandfather who surely has not forsaken the pleasures of the flesh.

A 2008 study in the New England Journal of Medicine found that more than half of those over age 50 and a quarter of those 75 to 85 were still sexually active.

That's not enough, says Crane, who believes that for their own good, older adults should be using their fun parts a lot more often.

"Sex is good for your health," she says. "It lowers blood pressure, elevates mood, boosts immunity, burns calories, and helps you sleep better." She also cites studies showing that men who have sex more often have a lower incidence of heart attacks.

Last year, at a health conference on aging sponsored by the Raymond and Miriam Klein JCC and the Einstein Healthcare Network, Crane ran a half-hour workshop about remaining sexually alive.

"People were standing in the aisles to hear it," said Ellen Warren, project manager of the event.

This year, like last, the Forever Young 2013 conference will cover a wide range of topics. Experts will speak about managing stress, retaining memory, improving nutrition, treating chronic diseases, and avoiding injuries during exercise.

About 150 to 200 participants are expected to attend the event, which will be held Wednesday night at the Hilton hotel on City Avenue. Because Crane drew such a large crowd last time, Warren said, the organizers invited her back, giving her a full hour and a larger room.

At Widener, Crane's office, which is decorated with posters and sculptures of blooming female genitalia, reflects her candor. Not surprisingly, the shelves are filled with CDs and texts about sex, including the book she cowrote with her husband, Sexual Lives: A Reader on the Theories and Realities of Human Sexualities.

Speaking with the same unabashed humor as Dr. Ruth (but with a subtler accent as she is from upstate New York), Crane broaches subjects that she says have been hush-hush for too long.

The common myths about sex after 50 set expectations too high for men and too low for women, Crane says.

"Men think that other men are desiring sex all the time and keeping it hard because they're not talking to each other," she says. And older women, who also avoid talking with friends about sex, have been led to believe that diminished libido is destiny.

"We've been told that if you're not beautiful and young, sex is not for you. But the truth is that a lot of women are really enjoying sex throughout their whole lives."

Baby boomers, she says, are especially hungry for information. "We lived through the sexual revolution and we're not going to give up on sex as easily as the last generation, if we can get some help being more comfortable."

A product of a Catholic girls' education from kindergarten through college, Crane, now 64, says that like many of her peers, she was ignorant about her own body for years. "This is another period of our lives we are entering uneducated," she says.

She offers many of the usual tips for long-lived couples about how to rekindle physical intimacy. Make time for romance. Hold hands. Kiss. Set dates for sex.

But then she goes beyond the yadda yadda yadda.

It can be self-defeating, for example, to plan a night out with dinner and a few glasses of wine, then come home at 11 and expect to make sparks fly.

"The chances are, you're going to be too tired," Crane says. "So make a date for sex when you are more likely to have the energy. Sunday mornings, maybe. Or Saturday afternoons."

Since one partner usually has more interest than the other, she adds, it is important to make good on your promise when you schedule a rendezvous.

"Otherwise, one of you is going to be disappointed and eventually give up."

Venturing into even racier territory, Crane strongly advocates the use of sex toys.

For all their sexual adventurism in the 1960s and '70s, this is a realm that many boomers have yet to explore, she says.

"I think every woman should be given a vibrator for her 16th birthday," Crane says. And while the suggestion may shock many women over 50, she says the odds are that their daughters have owned and enjoyed them for years.

Even during her longer, hour-long workshop this year, she says she will only have time to skim the surface of her subject - the importance of lubricants, reading erotica, appreciating "outercourse," ceding and assuming control in bed, adapting creatively to physical disabilities, using pillows and new positions, and finding pleasure with oneself.

"For both men and women, hormone-driven sexual desire tapers off. Sex becomes more of a decision. It can seem odd," she says. "But once you make a decision, it can be fun. And there's a lot more fun to be had."

The Forever Young event will be held Wednesday from 5:30 p.m. to 9 p.m. at the Hilton Philadelphia City Avenue, 4200 City Ave. $80 admission includes dinner. 215 698-7300, Ext. 101