Exercising the body and mind may be the best way to keep an older brain sharp, suggests a new study.

“The best medicine is physical activity,” lead researcher Ralph Martins told Reuters Health.

“At the end of the day, the two together – physical activity and cognitive training – gave us an additional benefit,” said Martins, who directs the Center of Excellence for Alzheimer’s Disease Research and Care at Edith Cowan University in Perth, Australia.

Martins and his colleagues studied 172 people from ages 60 to 85 years, assigning them randomly into four groups.

One group walked three days a week for an hour and did 40 minutes of resistance training twice a week for 16 weeks. Another group did hour-long computer brain-training exercises five days a week, also for 16 weeks. A third group did both the physical exercise and the computer activities. A fourth group maintained their regular routines.

The researchers write in Translational Psychiatry that only the group that engaged in both physical activity and computerized brain training showed significantly improved verbal memory, which helps people remember words and language.

The researchers note that the study failed to show benefits for executive functions that control focus, attention to details and goal setting. They also didn’t find benefits for visual memory, processing speed or attention.

Martins said physical exercise had the most profound and constant effect.

Dr. David Merrill also sees physical activity as the most useful aid to maintaining memory and cognitive ability as people age, but the combination of physical and mental exercise may offer “synergistic” benefits.

“What’s good for the muscular-skeletal system is good for the cardiovascular system, and it’s also good for the brain,” said Merrill, who is a geriatric psychiatrist at the David Geffen School of Medicine at the University of California, Los Angeles.

“Physical exercise sets the stage for the brain to be responsive to new information,” said Merrill, who was not involved with the new study. “You’re all ready to build new synapses, new connections.”

Both Martins and Merrill recommend that older people exercise regularly and stay intellectually involved. Both favor real-life challenges over computerized brain exercises.

Martins urges retirees to join service organizations, like the Rotary Club, and to dance for the physical exercise and mental acuity.

"Full retirement doesn’t make sense for graceful aging,” Merrill said. “People should try to keep working not only to maintain their self-identity but to challenge their brain.”

Merrill said the new research is the most recent of a handful of studies showing that a combination of interventions can help seniors remain mentally alert.

He advocates building up to more strenuous exercise than people did in the study.

“There’s lots of data that shows that being physically active is good for the brain,” he said. “It’s almost so intuitive that it defies logic that so few people are active physically.”

The U.S. Centers for Disease Control and Prevention recommends that older adults perform moderate and vigorous aerobic and muscle-strengthening activities at least twice a week.