Workout needs for every age

Physical-activity needs shift with age and with longer days and (slightly) warmer weather, here's how to keep moving, from age 20 on up.

20s and 30s
Aim for at least five weekly 30-minute sessions of aerobic exercise. The sooner you start, the lower your lifetime risk of several common health problems, including coronary heart disease, hypertension, type 2 diabetes, obesity, and possibly certain cancers. Women should include weight-bearing exercises to help prevent osteoporosis later in life.

Ideally you should also work in two weekly strength-training sessions, although you can get by with one 20- to 30-minute session that involves all the major muscle groups. Stretch for 10 minutes at least every other day, preferably after workouts, when muscles are still pliable.

40s and 50s
Strive for a minimum of 30 minutes of aerobic exercise four days weekly, but squeeze in more if you can. Research shows that multiple bursts of activity are nearly as effective as one continuous session, so break it up if you need to. If you enjoy high-impact activities such as running or aggressive fitness classes, it's a good idea to alternate with a lower-impact dance class, swimming, or other activity that is easier on the joints.

Try to strength train three times per week, but two sessions will still provide substantial benefit. Aim for 8 to 12 repetitions per set (15 if you're out of shape) with enough resistance to make the last repetition difficult. Three sets are optimal; two work nearly as well. (Beginners can start with a single set.) Continue to stretch at least every other day.

60s and beyond
Aim for three to four 30 minute sessions of aerobic exercise each week, minimizing or eliminating high impact activities. Also, make time for strength, flexibility, and balance training, which become increasingly important as you age. Continue to stretch at least every other day.

If brisk walking or other weight-bearing exercises have become difficult, try water exercise. Two weekly strength-training sessions are enough, but wait at least a day, and possibly two, between sessions, as muscles need more time to recover. Use lighter weights and more repetitions—10 to 15 in each set. "It's critical that people in this age group exercise with proper form to avoid injury," says Cedric Bryant, Ph.D., chief science officer of the American Council on Exercise. It's worth paying for at least a couple of sessions with a certified personal trainer to develop a safe, effective routine you can continue on your own. Look for someone certified by fitness organizations such as the American College of Sports Medicine, the American Council on Exercise or the National Strength and Conditioning Association.

Never too late
If you've never been active, or have fallen off the wagon, you can still significantly increase your strength and fitness at any age. And good news is that exercise can slow or even reverse age-related physical declines. It's never too late to start!