It's great to see Cheryl Tiegs, the supermodel of the 1970s, back on a magazine cover again and looking as blond and perky as ever. But it's a little disconcerting that the former Sports Illustrated swimsuit model is now gracing the pages of Modern Maturity, the official organ of the American Association of Retired Persons.

Modern Maturity never struck me as a blond and perky publication. It seemed more like a gray and crotchety publication--a sort of Geezer Digest, a magazine that old folks peruse in doctors' offices while waiting for the doctor or death, whichever comes first.

But I was wrong about that. As it turns out, Modern Maturity is a magazine for a new breed of old folks--people who run marathons and climb mountains and do yoga, people who are not necessarily retired, or even old. I was wrong about AARP, too. Despite its name, the American Association of Retired Persons is not an organization of retired people. To be eligible for membership, you simply have to be 50, which is 15 years shy of the traditional age for retirement. This strikes me as odd, as if the American Medical Association had opened its ranks to high school freshmen.

Tiegs is 51 now, which makes her eligible for AARP membership. So are a lot of other people you wouldn't consider particularly decrepit. In every issue, Modern Maturity has a feature called "The Big Five-Oh," which pictures celebrities who've turned 50. Among the recent ones are Billy Joel, Shelley Long, Meryl Streep, Richard Gere and Pam Grier. There are also interviews with such typical senior citizens as Gregory Hines and Lesley Stahl. All of them are eligible to join AARP. All they have to do is pay $8 a year and they'll get many wonderful benefits, such as discounts at chain motels and a free subscription to Modern Maturity, which is sent to all 20 million AARP members six times a year.

Unfortunately, I'm not eligible to join AARP yet. I'm going to have to wait a looooong time. I won't turn 50 for dozens of, um, months. But after reading a few issues of Modern Maturity, I'm psyched. I'm eager to get aged as fast as possible.

That's because the geezers in Modern Maturity seem to be having one helluva time. They are "Living to the MAX," as the cover story in the current issue puts it. "Whether chasing gold medals or running around the neighborhood, 50-plus America is on the move," writes David Butwin. "More and more people are toning up, slimming down and attaining a fitness level belying their years."

The proof is in the pictures. There's a photo essay that shows fogies running races, lifting weights, pole-vaulting, long-jumping, throwing the discus. Apparently this modern variety of maturity is one big decathlon. There's even a picture of a woman who looks a bit like Granny on "The Beverly Hillbillies," except that she's engaged in the act of shot-putting.

In Modern Maturity, aging looks like a lot of fun and games--sort of like childhood, only better because you don't have to ask your mom if you can cross the street. I can't wait. I think I'll start eating right and staying fit so I can pole-vault and shot-put long enough to watch all these sullen, hipper-than-thou Gen-X'ers pawn their nose rings to pay for my Social Security.

The modern, mature people in Modern Maturity don't spend all their time engaged in the decathlon. They also travel a lot, frequently by bicycle. And sometimes, as chronicled in a recent issue, they'll fly their company seaplane from their palatial home in Seattle to go fishing off the coast of British Columbia so they can bring a huge fresh salmon back for a dinner party, where they serve it with Shrimp Marinade and Dungeness Crab and a Chinese Cabbage Salad.

What a life! The golden years sure look great in the pages of Modern Maturity. Well, at least in some of the pages. In the articles, it looks wonderful. In the ads, however, old age seems kind of scary.

In fact, the ads in Modern Maturity seem to belong to a totally different magazine. Reading the articles, you expect to see ads for running shoes or mountain-climbing equipment. Instead, you find ads for cholesterol medicines and herbal remedies for prostate problems and a video screen that magnifies those little things that are getting harder to see--such as your face when you're trying to shave.

One ad shows a dapper-looking gray-haired guy cruising along in a sporty blue convertible. Unfortunately, the sporty blue convertible is towing a trailer that carries a portable toilet. The ad asks the question: "How do you cope with frequent urination?" Another ad shows a woman who looks frightened or maybe just confused. It asks the question: "Is it forgetfulness . . . or Alzheimer's disease?" There's also an ad for an "External Vacuum Therapy System" for treating impotence. A vacuum? For impotence? Yikes!

This bizarre chasm between the articles and the ads is glaringly evident in one spread in the current issue. On the left page, Tiegs sits in a bucolic garden looking fetching in a low-cut shirt and tight athletic pants. On the right page, a portly, gray-haired guy sits in one of those little motorized carts that old folks zip around in when their decathlon days are over. There are a lot of ads for those contraptions, which have names like Pride Jazzy and The Rascal and Pride Scooters. In none of the ads are people climbing mountains or putting the shot.

Not surprisingly, I'd like to be the kind of retiree you see in the articles in Modern Maturity, not the kind you see in the ads in Modern Maturity. But I'm not sure you get to choose.

Soon, a new editor will take over Modern Maturity. His name is Hugh Delehanty and he recently finished a stint as the editor of the Utne Reader, which is a sort of Reader's Digest for countercultural folks. It will be interesting to see what he does. Will he bring old age into the New Age?

That remains to be seen. But one thing seems certain: The baby boomers are getting old and it promises to be an endlessly amusing spectacle.