Fit seniors have a 'fitness age' of up to 25 years lower than their real age.

If you’re looking for a little motivation for your next marathon—or, hey, even your next trip to the gym—consider the age-defying athletes of the recent National Senior Games in Minneapolis-St. Paul, Minnesota.

The Games’ participants, who have to be at least 50 years old to qualify, have a "fitness age" of up to 25 years younger than their real age, according to research being done at the University of Maryland.

Pamela Peeke, an assistant professor of medicine at the university and a board member of the foundation that runs the National Senior Games, has surveyed 10,000 amateur athletes who qualified for the event.

The athletes compete in a wide range of sports, including triathlon, track and field, distance running, swimming, golf, and even that cruise ship staple, shuffleboard.

The fitness calculator
Peeke approached Ulrik Wisloff, who made news in 2014 as the Norwegian researcher and creator of an online fitness age calculator, as reported in the The New York Times. The calculator was designed to approximate a person’s cardiovascular fitness and relative fitness age based on age, sex, heart rate while resting and after exercise, waist size and current exercise regimen.

Peeke and Wisloff created a special site and asked the athletes to enter their data into the calculator and allow them to collect the results. The athletes’ average chronological age was 68 and their average fitness age was 43, according to The Times.

Because of the wide range of sporting events—athletes competing in triathlons and shuffleboard are likely at different fitness levels—Peeke and Wisloff will be analyzing the data further, to see if those who play more vigourous sports enjoy more age-defying benefits. They said they expect to have a paper ready to be published in a scientific journal soon.

For Peeke, 61, this research is also personal. As a runner herself, she sought out Wisloff after taking the test and learning that her fitness age is 36, according to The Times. Her devotion to the cause is also splashed on her Facebook page, where she urges readers to "assume the vertical" and get moving.

Read on for 7 keys on getting fit and how to slow the aging process.