"You can maintain a very high performance standard into the sixth or seventh decade of life," said lead researcher Dr. Peter Jokl.
The 16-year study of top runners in the New York City Marathon found that the average times of older age groups improved more than the average times for younger age groups.
The top women runners aged 50 to 59 showed the greatest improvement, running the marathon as a group more than 2 minutes faster each year from 1983 to 1999. The top male runners in that age group improved about 8 seconds each year.
The study reinforces the notion that many older people grow weaker not simply because of age, but because they do not use their muscles as much as they did in their youth, said Jokl, a professor of orthopedics at the Yale School of Medicine.
Researchers expect older runners will continue to improve over time, as they try new training techniques and as American culture increasingly encourages older people, especially women, to exercise.
You do not have to be a marathoner to see the benefits either, Jokl and other researchers said. Regular exercise of any kind helps lower cholesterol, blood sugar and blood pressure, keeps weight down and improves mental outlook.
June Norman, 58, of Milford, said she has seen many benefits from her exercise regimen.
She has been running for 25 years and tests herself in the New Haven Road Race each Labor Day. On Monday, she ran the 20-kilometer race 5 seconds faster than she did the year before, to finish second in her age group. Her times overall have stayed about the same since she hit her 50s.
"I'd be interested to know why. You would think you would get slower or drop off quickly," Norman said.
She said she trains conservatively to avoid injuries and runs competitively twice a year for fun.
"I certainly feel a lot healthier than some of my friends," Norman said. "There is life after menopause."
Norman grew up in an era that discouraged women from exercising. Sweating or being muscular was thought to be unladylike, noted Daniel Perry, executive director of the Alliance for Aging Research, a nonprofit advocacy group in Washington.
"That earlier generation suffered from disapproval. By and large, femininity was defined as not being active in the playing field," Perry said. "Since the 1970s and 80s, girls have been encouraged and well-thought-of for being active in sports and exercise."
Even so, while many people know about the benefits of exercise, few are doing it, Perry said. A survey of baby boomers by the Alliance for Aging Research found that only a third of people born between 1946 and 1964 exercise regularly.
"The baby boomers are still being a little lazy, particularly the younger ones," he said. "If they all fail to get healthy, the country will be in dire straits."
Dr. Kerry Stewart, who teaches clinical exercise physiology at Johns Hopkins School of Medicine, said the Yale study mirrors findings he and other researchers have done on the athletic performance of older people.
A study of exercise training in people 55 and older found they can see the same amount of improvement in muscle strength, oxygen consumption and other benefits as people in their 20s and 30s.
"It proves the point that if people remain active, they certainly can get the full benefits of training," Stewart said.
Jokl's study was published in the August issue of the British Journal of Sports Medicine.