Kenneth David’s eyes light up as he speaks about the effects that exercise has on the brain. And the body.

The 80-year-old retired psychologist was diagnosed with arthritis several years ago, which was especially difficult since he’s still active in research and writing. It affected his hands, thumbs, neck and his ability to walk.

“We use our thumbs for everything, minute by minute, but we don’t think about it,” he said.

David, a Honolulu resident, started participating in the Enhanced Fitness arthritis management exercise program at the Nuuanu YMCA and religiously attends three times a week. The classes, which have been recognized nationally by the Centers for Disease Control and Prevention, the federal Department of Health and Human Services and the Administration on Aging, are designed to help older adults become more active and empowered for independent living.

The program at local YMCAs, offered in four-week sessions, has served 120 people, ages 55 to 92, so far. Stretching, resistance exercises and balancing postures are done during class.

According to Erin Farmer of the YMCA, 70 percent of Enhanced Fitness members saw improvement in physical functioning, 62 percent an improvement in depression, 45 percent an improvement in social functioning, and there’s been an 80 percent retention rate in participants.

“It helps with joint pain, flexibility and balance,” David said. “As you get older, your balance isn’t as good. And with arthritis it’s even more important to have good balance.”

DAVID said he’s noticed that since he started the exercise program, he doesn’t have as much pain, and his focus has improved, allowing him to continue his research. He retired in 2010 after 10 years as a researcher and project developer with the state Department of Health. Prior to that he taught at the University of Maryland.

He has been able to expand his fitness routine so that he’s working out six days each week, including weightlifting using strength-training machines and piling up mileage on a treadmill. After the YMCA Enhanced Fitness class, he stays to participate in a class for those dealing with Parkinson’s disease, which provides additional exercises focused on flexibility, balance and strength training.

“In the first couple of months, I was slow to switch to the next movement. Now it’s a lot easier.”

The cost of the YMCA Enhanced Fitness program is $29 per four-month session for members, $169 for nonmembers.

Programs on diabetes prevention, blood pressure management and surviving cancer are also offered. For more information, email healthprograms@ymca.com.