Westcott adds that older adults, who are hitting the gym in increasing numbers, might want to avoid explosive, high velocity activities.

Barbara Bushman of the American College of Sports Medicine says regular physical activity, rather than a sedentary lifestyle, has the potential to minimize the physiological changes that occur with age and inactivity, in addition to limiting the progression of chronic diseases.

"Older adults can benefit from exercise. Although absolute improvements may be less than for younger adults, relative increases can be similar," Bushman says, adding that older adults may take longer to make improvements.

At 54,Florida-based fitness trainer and wellness coach Shirley Archer noticed that if she did no weight training she lost lean body muscle at a faster rate. She also found it harder to get it back.

Happily for Archer, who has enjoyed running, cycling and hiking, her endurance activities remain unaffected by her aging.

"I feel that I have not lost any endurance," says Archer, author of the book Fitness 9 to 5: Easy Exercises for the Working Week.

As people age, she explains, they lose muscle fibers that produce quick powerful bursts before fibers that are engaged in endurance activities, such as running or cycling.

She says that is why older athletes, who cannot physically compete against younger athletes when it comes to strength and power, can remain competitive in endurance sports.

The aging exerciser also faces longer warm-up and recovery times, as the body is stiffer and slower to heal, Archer says.

And the burning of fewer calories means paying even more attention to diet.

Reuters