There is nothing more appealing to active types than a health club, within walking distance, where the monthly fees are affordable and the exercise machines are all shiny and new. But exercisers past a certain age may do well to remember the cautionary adage about all that glitters.

My daughter, an adult herself, was with me when I signed up. Sitting in a glass-enclosed office, we still could hear the loud "music" from the exercise rooms. I hate loud music. The sales rep assured us that since not many people came during the day when most members were at work, turning down the volume would be no problem. My daughter, who'd often heard me yell - in order to be heard - "Turn that down!" as she grew up, sighed contentedly. Otherwise, she knew, it could not be borne.

Once I began exercising, they did occasionally lower the sound, but reluctantly. They looked at me as if I were such a twit that I soon gave up mentioning it. With speakers overhead, I found myself racing through the machines as fast as possible, goaded by music that sounded like British hooligans yelling in a down-market pub.

I stuck with it by using earplugs that kept falling out, by moving my mat practically out the door, by dropping some of the classes. Many a time, inside that roomful of treadmills with the sun shining through the windows, I wondered if I hadn't been better off breathing fresh air and feeling it on my arms and legs as I used to trot around an athletic field near my home.

In November a friendly trainer who did turn down the volume for me surprised me by suddenly jettisoning almost all of the exercises in favor of two intensive ones: lunges and overhead weights. Endlessly and torturously, we lunged until my knees hurt and my arms were barely operable days later.

During this three-week period my left knee hurt continuously and for the first time in a lifetime of tennis and running all over the world. When I told her she said she was teaching this system to other classes with some older people.

"How old?" I asked. "Fifty," she said as if she were describing Methuselahs.

"I have a daughter 50," I replied. She looked aghast.

I knew I must give it up. The teachers simply didn't know how much older muscles and ligaments could I should explain that while I have always been slender, I have been diagnosed with osteoporosis. I was not only enjoying using my active body, I also needed to use these weight machines for my bones. All the experts recommend it.

So I dashed through the various rooms, pushing and pulling, rowing and bicycling, climbing and treading, all to this anathematic bellowing. I was strengthening my bones while I was being deafened and reduced to a nervous dervish.

I also came to enjoy the walk up and down the pleasant tree-lined back roads to the gym, as well as some friends I made and with whom I would go on for lunch and laughs. I stuck with it for more than two years.

Although the club's exercisers were unsupervised, the glass-enclosed offices adjoining the treadmills and other equipment were beehives of activity. Salespeople worked the phones or interviewed potential customers, while those who were also trainers only helped those who had private lessons. At times I wished someone would come by so I could have one of the computerized machines explained, but I wasn't bothered until I was tossed off a treadmill and crashed onto the floor with only a nearby member to call, "All right?"

I decided to get out of the vast machine-filled rooms and into one where young women were exercising with small weights under the tutelage of a young teacher. The movements fascinated me despite the ear-splitting music over which the trainer shouted orders like a Marine sergeant.

"Mats! Push-ups! Five-pound weights! Drop them! Sit on your steps! Up, down, 10 times! Hold it! Pulse! Lie on your mat with your feet on the steps! Hold in your abs and gluteus, put your hands behind your head and raise your shoulders!"

I loved hopping around with the different weights and bars, bouncing up and down doing push-ups, sit-ups, squats and lunges. But the drumbeat from the six speakers throbbed in my ears, shattered my nerves. Hints that I hated the "music" - that more women my age might join if they'd lower or even dispense with it-caused the club staff to look at me in shocked bewilderment. They'd been trained to teach with loud music and with a microphone around their necks to shout over it. The price of health was bedlam.

 These gyms are for young people, I concluded. The teachers were all young women; they had no idea what someone older could take. Nor had I. But it's been five months, and my knee still hurts. I don't know if the .pain will cease or be permanent.

Meanwhile, I've returned to my old neighborhood track, and with only the chirping of birds to disturb the blissful silence, it's easier on my knee and nerves. To supplement the jogging, I bought some colorful dumbbells, and nowadays I jump out of bed, grab them and bounce around on my thick rug to the workouts on the morning tube.

I gave the health club my best shot. I followed the advice we hear so often: work out for stamina, for strong bones, for longevity. Even now I'm convinced that, if it doesn't cripple or deafen you, it can do a body a lot of good.

Things to Avoid When Exercising No-Longer-Young Joints

Since leaving the health club, I have discovered four half-hour morning classes on TV with lovely background music and women trainers who explain the exercises and give sensible preventive warnings. Cynthia Kereluk, a trainer from Canada, showed me how to do lunges and warned: "Be sure you never let your knee pass your toe or you'll strain your knee joint!"

Georgetown attorney Max Berry told me he hurt his knees and shoulders after working out with a personal trainer and was told by the sports medicine specialist in the orthopedic department of the Mayo Clinic, "No one over 40 should lift anything weighing more than two pounds above their shoulders. Never do military presses [push a barbell up over your head]. And once past 40 don't do any lunges, even modified. Chances are you'll do them wrong and hurt your knees."

Just the other day I read this advice in the University of California Berkeley Wellness Letter: "To protect your knees avoid the following: deep lunges; downhill running, cycling with the seat too low, taking large steps on a stairclimber and leg extensions with heavy weights. In addition, do not exercise in worn-out shoes; don't suddenly increase the intensity or length or your workouts; and don't run on very hard, very soft or hilly terrain."

Exercise professionals should know these things.