Instead, make sure you're well-conditioned and "listen to your body," Haas said. Switching to less rigorous activities is sometimes the answer. "If your knee is killing you every day after you run, you're probably not doing the right sport."
Haralee Weintraub, 58, changed her exercise routine after injuring her back during a "boot-camp" class at her gym two years ago. The first time it happened, the Portland, Ore., online business owner was doing "full-out toe men's push-ups." A few months later the same thing happened during leg squats — pain that started in her lower back and shot down her leg. Because it was hard to stand, she went both times to the doctor, who diagnosed sciatica, common nerve pain likely caused by an aging disc in her lower back, and by overuse.
A physical therapist had her do exercises to strengthen muscles in her abdomen and near the sciatic nerve in her back, and leg exercises to stretch the buttocks' gluteal muscles.
Weintraub has switched to gentler "girls" knee push-ups and stopped doing lunges. But she still likes to snowshoe, bicycle, hike and walk, and is determined to stay fit.
"Hopefully I'll have another 25 years of activity and not be compromised with physical mobility issues," she said.
Unlike Weintraub, Gene Wilberg tried to tough out his injury, which probably prolonged his recovery. The tip-off that he should have gotten treatment sooner was persistent pain that interfered with his usual activities.
The 62-year-old Naperville, Ill., business consultant was helping his daughter move into an apartment two years ago when he felt a sudden pain in his upper right arm while lifting a box. The pain persisted and made it difficult to twist open jars and pursue hobbies including cycling 15-plus miles a week and skiing. He eventually just stopped using that arm.
After a few months Wilberg went to the doctor, who found a partial bicep tendon tear in his upper arm. Surgery was a possibility, but Wilberg wanted to try physical therapy instead. It took about four months to get his arm back in shape, lifting light dumbbells and using resistance bands. Wilberg says he was told not using his arm had allowed the muscles to atrophy.
"If you wait too long, sometimes you actually just end up delaying your overall recovery" and adding to the cost of medical treatment, said Nathan Sels, Weintraub's physical therapist.
Rob Landel, a physical therapist and professor at the University of Southern California, says many of his baby boomer patients try to cram all their exercise and activity into a weekend but do nothing during the week to prepare. That puts extra stress on bodies and raises chances for injuries.
So, for example, for those who like to go on long weekend runs, he recommends treadmill sessions or short jogs during the week, or other leg-strengthening exercises.
There's growing evidence that stretching right before an activity can hurt your performance, Landel said. After a run or tennis match is a better time to stretch, when muscles are warmed up. And routinely doing stretching and strengthening exercises during the week helps keep muscles strong and limber.
Landel knows that from personal experience. He's 53 and has painful tendinitis in both knees from playing volleyball for more than 30 years. That sometimes makes it difficult to get up and down on floor mats while helping patients with treatment.
"It's kind of embarrassing working with patients and you have to kind of crawl up the furniture to stand up. If I just exercise my legs, then I don't have those problems," Landel said.
Leg presses and other exercise that build up strength reduce his pain, and help his volleyball game, too, he said.
"The stronger you are, the better your joints tolerate stress," he said.
NIH information on sports injuries: http://1.usa.gov/qldiJW
Aging America is a joint AP-APME project examining the aging of the baby boomers and the impact that this silver tsunami will have on the communities in which they live.