Mike Fantigrassi, a trainer at the National Academy of Sports Medicine in Chandler, Ariz., says he makes balance and flexibility exercises a regular part of sessions with clients, but it's different for younger and older people.
"If we have 60 minutes, we would do about five minutes of flexibility for someone in their 20s or 30s," he says. "For someone 65 or older, we might do up to 15 minutes of flexibility."
It's not that the 20- or 30-year old should go completely without stretching (particularly of the postural muscles — chest, core, neck and shoulders — that get tight from sitting at a desk all day) or working on balance, he says. But younger bodies, generally speaking, are naturally looser than older ones and have not been subjected to as much wear and tear.
So when a 20-year-old reaches down to pick something up off the floor, he probably won't notice anything, but a 60-year-old may feel a tight hamstring.
Fantigrassi, who is 40, adds that the ability to generate muscle power suffers as we age, but we can slow the process down with such exercises as jumps — from foot to foot, or up and down from a bench or box. Eventually you're going to lose your basketball jump shot, but you can keep it alive longer by training the leg muscles that generate power.
Miller, 45, says that while building stronger muscles is protective for older people, strength training is important for everyone.
People begin to lose muscle mass and strength in their 30s, which slows metabolism. WebMD.com says that "each extra pound of muscle you carry can burn up to 50 additional calories — per day — just to maintain itself. Others, however, suggest that the muscle effect is probably much smaller.
Lifting weights can counteract muscle loss. Of course, you still may not be able to lift as much weight in your 60s as you could in your 20s, but you can slow muscle loss, which otherwise can decline by 5 percent per decade after age 30.
"The only difference between 20 and 60 is that you might be lifting less weight at 60. But the exercises themselves shouldn't change unless you have an injury, but that isn't age related," says Miller.
Strength training will also improve bone density, says Miller, who advocates the type of strength exercises where the feet are planted on the floor and generate force into the spine. It could be a regular squat. It could be a squat with dumbbells in your hands, resting on your shoulders. It could be one of those squat machines with padding on top of the shoulders.
Given that most Americans gain roughly a pound per year starting in their 20s, it's important at all ages to have cardio workouts in your week.
"If running feels good, then run," Miller says. Just make sure it feels OK in your joints. Whatever you choose, he says, the point is to get regular exercise no matter what age you are.