Your running shoes/tennis racquet/softball glove/high-school sports trophy collection are tucked into the back of some closet, quietly gathering dust. Nowadays your main form of exercise is walking between the couch and the fridge. You're handier with the remote than you are with a racquet.

And yet … you'd like to be in better shape. Maybe even train in a particular sport. Maybe even compete in the Senior Games. Crazy, right — at your age?

Nope. You're never too old for physical activity, said Mary Frances Visser, a professor of human performance at Mankato State University who researches the effects of exercise on older adults.

"Physiologically there are no real limits," said Visser, an associate editor for the Journal of Aging and Physical Activity. "You're limited by your own physiology in certain ways, but in terms of saying 'Nobody over the age of 60 should ever do X' — that's nuts."

Aging itself can bring upon a desire for better health, said Gary Westlund, founder and president of Charities Challenge, a nonprofit that sponsors races focusing on health issues.

"It's a very common experience that people, when they get into their 60s and even 70s, one of their motivations is, 'I want to be a better man this year than I was last year,' That includes, of course, 'I want to be healthier, fitter, I want to run faster, row faster,'" said Westlund, who is certified as a health and fitness specialist by the American College of Sports Medicine (ACSM).

Exercise is especially important as you get older because physically fit people are better able to cope with, and heal from, health challenges that accompany aging.

Even if you're already experiencing some of those challenges — even if you basically haven't risen from the couch since George Bush Sr. was president — it is possible to get back what you have lost.

Visser knows a woman who "was a total couch potato all of her life" until, at 55, she decided to compete in the Senior Games in the 50-yard dash. She spent a year training and eventually "wound up medaling in the 100-yard dash in the National Senior Games."

Westlund met an 85-year-old runner at his organization's Challenge Aging 5K race last fall.

"It was his first road race I believe, or one of his first road races. He had taken up running at 83. He had the fastest 5K time in Minnesota last year — at any 5K — for a man 85 or older."

This year's Minnesota Senior Games are May 28 to 31 — probably too tight a deadline if you're just now lacing up a new pair of sneakers. But you could start training for next year, Visser said. (And next year's state games are qualifiers for the nationals.)

If you have a medical condition — high blood pressure, diabetes, heart history problems, joint disease — check with your doctor, Westlund said. Otherwise, women up to age 55 and men up to 45 can probably start doing light to moderate exercise without the doctor's green light. Information about aging and physical activity is available at the ACSM's website (www.acsm.org), the National Institutes of Health's Senior Health site (www.nihseniorhealth.gov/exerciseforolderadult) and the National Institute on Aging's site (www.nia.nih.gov/health/publication/exercise-physical-activity/introduction).

When you first start, don't expect to whip yourself into shape in a week. "The human body at 20 and the human body at 50 are very different," Visser said. "You can really, really hurt yourself if you do too much too soon."

Visser recommends starting with five minutes of activity and working up to eight, then 10 and on up to at least 30. Add weightlifting, stretching and so on to regain muscle mass, flexibility and balance. □