Prevention now: avoid injuries later: how to keep your workouts on track and pain-free.

According to the Consumer Products Safety Commission, baby boomers aged 35 to 54 are racking up sports injuries at an unprecedented rate--33 percent more in 1998 than in 1991. The commission reports that totals for all sports-related injuries indicate that 365,000 injuries from 16 sports were treated in emergency rooms in 1998 alone. That number rises to 1 million when injuries treated medically in a setting other than an emergency room are included.

The Repetitive Motion Factor

While some of these physical injuries were caused by a macrotrauma (such as whacking an elbow with a tennis racket or turning an ankle while running) most injuries among people who have been working out for 20 years or longer, were microtraumas, or repetitive motion injuries, and resulting from chronic overuse or abuse. The importance of cross-training, or engaging in more than one type of physical activity to avoid the overuse of one set of muscles, cannot be overemphasized-no matter what form exercise takes.

"Our tissues become somewhat less compliant, and tendons tend to degenerate as we get older," says Dr. Robert A. Stanton, an orthopedic surgeon affiliated with Yale Medical School. After age 50, according to Stanton, we tend to lose muscle mass at the rate of about 10 percent each decade, though those who have been exercising for decades may slow that atrophy.

Avoiding Common Injuries

The most common athletic injury in sports, according to Tedd Mitchell, M.D., medical director for the Cooper Wellness Program in Dallas, is "runner's knee" (chondromalacia), the erosion of the cartilage covering the underside of the kneecap. Runners, especially those who have been at their sport for many years, need to vary their training intensity, get plenty of rest, and cross-train with activities such as swimming or cycling to give the feet a rest. The same is true for those who have engaged in high-impact aerobic workouts for a considerable time.

Michel Kolling, mature marketing director at the institute, most often sees posture-related injuries that are the result of incorrect alignment over time. Low back pain and frozen shoulders are common, as are injuries from lifting too much weight. Make sure you are using proper form during exercise. A good strength-training program can help improve posture, which often suffers when exercise is lacking.

Michael Wood, owner of Sports Performance Group in Boston, notes that among his clients the knee, rotator cuff, and back are most often injured. Wood, who works with many master athletes, finds that men's backs lose range of motion as muscles and ligaments tighten. Women remain more flexible, but tend to be weaker, especially in the abdominal area. Weak abdominals lead to back injuries because the back is trying to compensate. Wood suggests that if you are new to exercise, have a session or two with a qualified trainer to learn good technique so you won't harm yourself trying to stay in shape. Be sure to stretch before and after exercising.

Staying Healthy

To avoid athletic injury, Mitchell emphasizes cross-training, and strength training to strengthen muscles and tendons and to enable you to keep going longer. Strong muscles and tendons stand up better to the stress of exercise. Mitchell's runners swim, bike, or use an elliptical trainer once or twice a week in place of a running workout. "Once you get a person to engage in multiple sports, they like it better," he says. There is less boredom, and both calorie burning and biomechanical effort are greater. Mitchell also has his clients stretch because he believes this helps them avoid injury.

Factors That May Contribute to Injury

"We're reaching a point where people don't live 10 or 15 years after retirement, but another whole lifetime," says Ro DiBrezzo, codirector of the University of Arkansas Center for Aging Studies. Some people may have been physically active for 30 years. Around age 40 metabolism begins to slow and muscle mass starts to degenerate. "Cardiovascular capacity also lessens, and it is all part of natural aging," DiBrezzo reminds. "You need to reassess your lifestyle habits and consider modifying exercise routines to stay active for the long haul."

"Remember that it took many years to get like this," Wood tells those clients who are out of shape when they come to him. Follow an exercise program eight to 12 weeks, with two or three workouts per week, and by the second month you will feel stronger.

A recent joint study by the Mayo Clinic and the U.S. Navy found that people with low arches were at higher risk for stress fractures in the foot. Add to this the fact that as people get older, their feet become longer and wider. Padding on heels and balls of the feet thins, and the arch tends to fall a bit. These are natural changes, and you need to be aware of them. Even walking puts up to three times a person's body weight on one's feet, according to the American Academy of Orthopedic Surgeons (AAOS). Begin cross-training with another activity if you are presently doing all of your exercise on your feet. Swimming, biking, and rowing are good alternatives a day or two a week.

Normal walking and running transfers weight from heel to midfoot and arch, but if the arch and bones in the feet flatten and roll inward, this is over-pronation. This can lead to knee and back injuries, as well as Morton's Foot syndrome, where the big toe turns in toward the second toe. A doctor can diagnose overpronation and prescribe orthotic inserts to go in shoes, which can mean the difference between success and failure with exercise. DiBrezzo suggests a simple step that may make a big difference for some walkers and runners. "The best investment you can make is to buy two different kinds of walking or jogging shoes, then periodically alternate wearing them. Different shoes translate forces differently, and it can make a big impact on which muscles you work.

Coping With an Injury

Mitchell says it may take up to six months to recover fully from an injury, and knees may return to only about 90 percent of strength. An injured athlete who wants to maintain aerobic capacity must work out with an alternative activity while healing. Some injuries, such as tennis elbow and golfer's back, if caught early, may respond to rest, ice, and anti-inflammatory medications, but typically the injured person waits too long to seek treatment and will need therapy.

The problem of coping is exacerbated if the injury occurs in a lower extremity, like the knee, shin, or foot. Mitchell puts his injured runners on an exercise bike or elliptical trainer, or in the swimming pool if their knees won't tolerate the machines. He and Wood recommend that if you are new to exercise, or you are recovering from an injury, seek out the services of a certified personal trainer for a few sessions. "I can't overstress the importance of this," says Mitchell. "The trainer will show you how to use each strength-training machine, how to set the height of the bench, how many weight plates to use."

Summing Up

Make sure you get that initial checkup by a doctor before starting any exercise program. If you are on medications, especially beta-blockers, get your doctor's OK before beginning to exercise.

Sherry B. Hanson writes on health topics from Brunswick, Maine.