It's time to get smarter about exercise

Doctors at the knee-replacement area of Pennsylvania Hospital in Philadelphia say they are seeing a much higher volume of people in their 30s and 40s with osteoarthritis in their knees.

It's symbolic of a situation that is getting worse all across the country, particularly with baby boomers. They want to stay healthy and vibrant, but some aren't being smart about how they go about it. They still feel like they're 20, but their bodies are older.

Turning 40 can be a pain in the neck, and in the ankles, back, groin, shoulders, and hamstrings. Baby boomers are suffering more than a million sports injuries every year. The highest numbers are from bicycling, basketball, baseball, and running, according to the U.S. Consumer Product Safety Commission.

The idea of exercise is to stay in good physical condition. Biking on mountain trails or trying to relive your glory days playing basketball or football in a weekend-warrior style is not the way to do it.

Aging can't be avoided, but injuries can. Exercise appropriately and watch for signs like muscle soreness and joint pain. Then change your routine.