No matter what your age, you can improve your fitness. If it's been a long time since you've exercised and you're feeling less than fit, you might think that it's too late to make a change. But you're wrong. You can improve your fitness at any age.

Best way to get into shape After easing into fitness, this is what those over 40 should aspire to do regularly: moderate aerobic activity for 30 minutes daily (100 steps per minute) muscle strengthening with all major muscle groups three days a week. balance exercises two days a week at minimum.

The takeaway: Start or continue to do 30 minutes of aerobic exercise, such as brisk walking, running, biking, or dancing. Then build up weekly workouts to the levels of study participants. Their routines included: One high-intensity aerobic session.

“You can regain approximately one-half of your fitness in 10 to 14 days with moderately hard workouts,” Dr. Coyle said. After this initial period of retraining, the amount of time it takes to get the rest of your fitness back to prebreak levels can vary depending on how much catching up you have to do.