TO understand your middle-aged body and its capacity for abuse, picture a rubber band that has been sitting around in a drawer. It is not as supple as a new one, may even be brittle in places, and it is certainly more prone to snap. But before you curl up in a drawer yourself, utterly deflated, remember, there are ways you can stay strong and limber. Just as steady, gentle use can prolong the life of a rubber band, regular exercise and taking time to warm up can help you avoid injury and stay active. It is folly to go on a ski trip or sign up for the club tennis tournament without some preparation, experts advise. Be realistic and pace yourself, they say.

Understanding Your Body

As professional athletes know, aging affects performance. Diminishing muscle mass, at a rate of about 1 percent a year after age 40, is one of the changes. The loss of muscle tissue adds up — reaching 10 percent over a decade — without regular weight training to negate it.

”A subtle weakness at 40 or 50 becomes frailty at 60 or 70,” said Dr. Nicholas A. DiNubile, an orthopedic consultant to the Philadelphia 76ers and a spokesman for the American Academy of Orthopedic Surgeons. Muscle mass not only affects strength but weight because muscle tissue is an important calorie burner.

The gradual loss of water, collagen and blood flow throughout the body also takes a toll. Tendons become less elastic, more vulnerable to tearing, causing tennis elbows, golfer’s wrists and aching shoulders.
The discs in the back, designed to cushion the spine’s notches like tiny shock absorbers, also start to shrivel. ”What was a grape becomes a raisin,” Dr. DiNubile said.

Similarly, loss of cartilage can affect the joints, including hips, knees and ankles. The normal progression of change may not bother everyone. ”Joints do remarkably well,” Dr. DiNubile said. ”Most go a lifetime without wearing.” But damage from an old injury can become inflamed as one ages, and healing takes longer because cells do not divide and repair themselves as readily.

Preparing Your Body

The better shape you are in, the less likely you will be injured and the more quickly you will recover if you are hurt. But even fit people should avoid jumping into a new sport or an eleveated level of activity without some preparation.

”Whatever you entertain to do, make sure you first do something for strength and flexibility,” said Dr. Barton Nisonson, a former team doctor for the New York Rangers and the New York Jets and now chief of sports medicine at Lenox Hill Hospital in Manhattan. ”Remember, you are not 18.”

Before exercising or competing, warm up by running in place or doing jumping jacks — anything to get the blood flowing and the sweat dripping. Body heat relaxes the muscles, making them suppler. Direct heat from a moist towel or shower can also help.
Recent studies are mixed on whether stretching prevents injuries as much as has been believed, according to Dr. John L. Turner, director of sports medicine education at the Indiana University Center for Sports Medicine. ”But it certainly doesn’t hurt and my recommendation is to still do that,” he said.

Ease yourself into a new sport, or one you have not practiced in years, he added. Even if you used to run five miles a day, start with a half mile three times a week. See how you feel. Gradually increase your distance and frequency. Try to alternate your forms of exercise to allow your body to recover, like running one day to work the legs and rowing the next for the upper body.

”The greatest population of folks I see are 35- to 55-year-old men trying to get back into activities they did before they started kid-raising and the career thing,” Dr. Turner said. ”And there are three main reasons those folks end up in my office. They get into trouble when they do things too much, too fast or too long.”

Condition for ski trips, marathons and tournaments by starting to train four to six weeks ahead with appropriate exercises. Jogging uphill and downhill makes sense before downhill skiing, said Dr. P. Dean Cummings, a Phoenix orthopedist and the medical director for the National Academy of Sports Medicine in Calabasas, Calif.

Dr. Cummings and Mike Clark, the academy’s president and chief executive, also recommend a thorough, functional evaluation of the body’s strengths and weaknesses, followed by a custom exercise program.

Even then, they and others emphasized, you need to warm up and go slow.

Listening to Your Body

Left-shoulder and left-arm pain, with no apparent sports injury, can signal a heart attack and warrant immediate medical attention, Dr. Nisonson said.

After you exercise, pain that is generalized or on both sides of the body tends to come from muscle overuse and should clear up with a few days’ rest, said Mr. Clark, a physical therapist and former running back at the University of Wisconsin.
But pain on only one side of the body, or in one spot, suggests an injury and should be evaluated. Similarly, pain that wakes you at night or does not go away in a week deserves professional attention, Dr. Turner and others said.

Swelling joints, joints that cannot fully bend or straighten and any deformity are also symptoms of injury.

”With experience you learn the difference between a little bit of muscle soreness versus an injury,” Dr. DiNubile said. ”Muscle soreness tends to be symmetrical and in the center of the muscle, as opposed to in the joint. It’s usually not as severe and goes away in a day or two.”

Worried about crunching and cracking sounds in your body? If there is no pain or swelling, they are benign, Dr. Turner said. But noises that also hurt can mean a problem.

Try not to ignore ankle sprains, Dr. Turner added. Repeated sprains leave a joint unstable, leading to more sprains and often requiring surgery. ”If you get the same ankle sprain two or three times, definitely see a physician,” Dr. Turner said.

Healing Your Body

The rule of thumb remains ice for injury, heat for recovery.

Apply ice to reduce swelling and pain for 48 hours, then switch to heat to soothe stiff muscles, Dr. Turner said.

Alternating hot and cold baths can also speed recovery by accelerating blood flow, Mr. Clark said. Think of Scandinavians plunging into the snow after a stint in the sauna. If your pain is in an isolated part of your body, he said, ice it quickly. Finally, experts say, do not forget to rest.