Joints stiffen with age, and muscles lose strength and elasticity. Musculoskeletal ailments are now the top reason for seeking medical care in the U.S. Sports-related injuries are sending boomers to the emergency room in record numbers.

Face it: You are not 25 anymore.

"Boomers need to know that there's a new fitness paradigm," says Marjorie J. Albohm, a certified athletic trainer affiliated with the Indiana OrthopedicHospital in Indianapolis. "It's not about how many miles you run or how much you can bench-press. It is about balance, strength and mobility, which will protect you against falls and injuries as you age."

Equipment isn't costly. Many trainers and physical therapists are devising programs using exercise balls($20), resistance bands ($4) and light weights ($2 and up). Yoga and Pilates classes are increasingly popular for those over 45. Stretching before and after exercise is critical - and doesn't cost anything. More gyms are adding fitness classes that emphasize range of motionand balance.

Cost: An evaluation and program devised by a physical therapist starts at about $150 to $200; weekly training with a certified athletic trainer runs from $1,500 to $3,500 a year.

Downside: You can't brag about how far you ran or how much you lifted. Start early enough and you won't get to experience the latest advances in arthroscopy and hip replacement. But that's a small price to pay.For more: Good advice for boomer fitness can be found at acefitness.org/getfit