(AP) -- The country's largest generation is running, walking, swimming and using exercise machines in hopes of changing the face of aging.
Baby boomers - the 78 million Americans born between 1946 and 1964 - are working to counteract the effects of getting older. They grew up watching Jane Fonda workout videos and were the first generation where large numbers exercised from their early years onward.
"Are the boomers playing more sports than 20 years ago? I think the answer to that is yes," said Tom Cove, president of Sports Goods Manufacturers Association. It annually surveys Americans about their exercise activities. "The boomers are dramatically more active and the numbers are much more skewed to fitness and outdoor activities."
They sign up for swimming classes and will pay to play basketball or hockey at odd hours in facilities used by youth during the day. People tend to do the same activities as in their youth, said Bill Beckner, research manager for the Virginia-based National Recreation and Parks Association. That could mean new sorts of senior activity centers.
"I keep waiting to see the first senior skate park," he said. "I won't be surprised when it shows up."
And while boomers like their exercise to be social, the number participating in organized team sports is growing slowly because scheduling the time can be difficult. Across all ages, the percentage of people participating in team sports grew by low single digits in the most recent survey in 2011, ending a two-year decline in sports such as tackle football, soccer, basketball and baseball. Participation had suffered due to the economic slowdown, Cove's survey states.
There is also the problem of availability: Many communities don't have enough fields for everyone who wants to play organized sports.
"Where ballparks are at a premium ... usually they have a priority for the kids," Beckner said.
Les Clemmons, 58, of Lubbock, played softball as a youngster and was happy eight years ago when he found an over-50 league. It grew so popular a few years ago - some games were starting at 10:30 p.m. - that players had to move beyond the one field the city gave the league one night a week. The league, now about 120-players strong plays at an older city park where it gets two fields one night a week.
The games provide more than just exercise, Clemmons said. Good friendships get built and are "the most important thing," he said. "It's more about camaraderie, teamwork."
His 57-year-old league colleague, banker Gary McCoy, agreed but said players also enjoy the competition.
"It gives us that competitive relief, sometimes comic," he said. "It's not the chronological age; it's how you feel."
Boomers also find themselves playing basketball and soccer early in the morning or late in the day. Where facilities are in higher demand, there is some squeezing out for space. That's where being older literally pays and businesses fill the void.
Take senior softball leagues, where participation is booming. Games are often played at privately owned and operated facilities.
"They're for-pay, first-class facilities," Cove said. "There is some evidence there is some crowding out (of youngsters). They're looking for who will pay and frankly the older ones are willing to pay."
Hockey facilities in some areas are tough to find for any age, he said.
"There aren't enough hockey rinks in the world," said Cove.
At health clubs, boomers are outpacing younger generations, said Dr. Vonda Wright, an orthopedic surgeon at the University of Pittsburgh Medical Center and a spokeswoman for the American Academy of Orthopaedic Surgeons. Those 55 and older are joining at a rate of 34 percent a year, while the rate for ages 35 to 55 is growing by only 18 percent a year, she said.
A million boomers joined health and fitness clubs between 2007 and 2010, according to a survey from the International Health, Racquet & Sportsclub Association.
Wright said research shows that 70 percent of how we age is lifestyle choices, while 30 percent is genetic.
Doctors say boomers who've been active most of their lives and are reaching their late 50s or early 60s can continue to do so but with modifications. For those who have been sedentary much of their lives, they say, it's never too late to start moving.
It is important for boomers to work to strengthen the muscle groups around joints, like knees and hips, to avoid injury.
Numbers crunched by the orthopedic surgeon's group show boomers are already feeling the ouch. Doctors' visits for symptoms and diseases of the musculoskeletal system and connective tissue in 2009 for boomers were markedly higher than five years earlier. Numbers of hip and knee replacements also are up.
Wright's suggestions for boomers are to work on flexibility, do aerobic exercise regularly, carry a load that uses muscles in three planes of motion, rather than using weight machines, and equilibrium and balance.
"I believe we are saving lives by saving mobility," Wright said.
Dr. Mimi Zumwalt, a 50-year-old orthopedic surgeon at Texas Tech University who has injured her both of her shoulders during fitness competitions, said active boomers need to think smarter about their bodies.
"You can't slow down the aging process but at least you can protect" your body better, she said. "You need to preserve whatever your body has left and respect it."
That's what Sandy Collins is doing. A Lubbock resident who works in the Texas Tech athletics department, she played on the Women's Tennis Association tour in the 1980s and 1990s, climbing to No. 17 in the world. Because of the wear and tear, she has had surgeries on her left shoulder and four on the same knee. She no longer plays competitively but hits with her teenage daughter.
"You learn your limitations quicker and you listen to them more," Collins said. "I understand my limitations and accept them because I don't plan on having any more surgeries."
Exercise doesn't stop with the boomer generation, though. Athletes near the century mark say it can be the proverbial fountain of youth. Houston's Harry Pepper played baseball, football and some tennis in his younger years.
At 101 he's still competing. Last year he was the sole entrant in the 100-year-olds' division at the senior games. He had to compete to win his division, so he bowled with the 95-year-olds, besting their bronze medal winner's score.
"If you want to live, you've got to move your body," Pepper said. "You lose it if you don't move it."
Explore further: Poll: Obesity hits more boomers than others in US