One sneaker fits all.
Or according to government recommendations, you should do at least 2 1/2 hours of moderate aerobic activity per week and twice-weekly sessions of strength training to improve your health, no matter your age.
But don't physical fitness needs change as we grow older?
Not that much, it turns out.
Todd Miller, an associate professor in the Department of Exercise Science at George Washington University, says whether you're 20 years old or 60, you will need a combination of cardio and strength training to keep your heart and muscles in good shape and your weight under control.
The one difference may be that strength training becomes more crucial for everyday functional fitness as you get older.
"A big issue as you age is the risk of falling. And strength training that builds muscle power helps prevent falls," he says.
"People should do a combination of both cardio and strength" to meet those fitness goals, he says, but in general he sees an "overemphasis on cardio and underemphasis on strength."
The challenge, Miller says, is not deciding whether fitness needs are age-specific. It's getting people to do what they should do, at any age, to stay healthy and fit.
Only about 20 percent of Americans follow the government recommendations.
As you try to figure out a regime that keeps you healthy, here's some advice from three people — Miller, a trainer and tennis great Martina Navratilova — that may help you at any age.
The professional athlete
"As we age, we should exercise more often but for shorter periods of time," says Navratilova, 56, who writes a health and fitness column for AARP.
"And mix up your routine. Do strength, cardio, yoga. Do what feels good in the body, go easy on the joints," she says.
That's actually pretty much in line with government recommendations. "We know 150 minutes each week sounds like a lot of time, but you don't have to do it all at once. Not only is it best to spread your activity out during the week, but you can break it up into small chunks of time during the day. As long as you're doing your activity at a moderate or vigorous effort for at least 10 minutes at a time," says the Centers for Disease Control and Prevention, which recommends "a 10-minute brisk walk, 3 times a day, 5 days a week. This will give you a total of 150 minutes of moderate-intensity activity."
Navratilova says that when she was in her 20s, she worked out six hours a day and could do 70-pound triceps presses. No more. "Daily exercise? I don't do anything daily except eat and sleep," she says, joking.
"But I do think if you can do functional fitness — exercises designed to help someone better handle daily tasks — for an hour a day, that is great," she says. But for aging bodies, she adds, don't overdo it. "Be nice to yourself and listen to your body."
Navratilova says she recently began running again after a hiatus. "Nothing feels better than when you can run," she says. "But every day? Absolutely not. It's hard on your joints."
Now living in Miami, she mixes it up by adding bicycling and paddleboarding to her running and tennis cardio regimen.