Older adults, drink up. You need plenty of water during exercise so your brain gets the full benefits of working out, researchers say.

"Middle-age and older adults often display a blunted thirst perception, which places them at risk for dehydration, and subsequently may reduce the cognitive [mental] health-related benefits of exercise," said Brandon Yates, of Spaulding Rehabilitation Hospital in Boston, and colleagues.

The researchers noted that previous studies have shown that dehydration reduces exercise performance and brain function in young people, but less is known about its impact on seniors.

The new study included recreational bicyclists, average age 55, who took part in a large cycling event on a warm day (78 to 86 degrees Fahrenheit). Before the event, the researchers tested the participants and divided them into two groups: dehydrated and normal hydration.

The cyclists took a timed thinking-skills test before and after the ride. Those in the normal hydration group completed the test much faster after the ride than before, while those in the dehydration group did not show much improvement.

"This suggests that older adults should adopt adequate drinking behaviors to reduce cognitive fatigue and potentially enhance the cognitive benefits of regular exercise participation," the researchers wrote in a news release from the American Physiological Society.

The study was presented Sunday at the American Physiological Society's annual meeting, in San Diego.