The McKenzies, who are in their 80s, participate in spinning classes and aerobics at Wood Valley Racquet Club and Fitness Center in Topeka, Kan.
"I think it really helps," Jean McKenzie said.
There are between 50 and 60 participants in the club's low-impact fitness class for seniors that meets three times a week.
Teacher Julia Johnson said she gets as much enjoyment from the class as the seniors she leads.
"They are actually the ones who are very inspiring," she said. "They keep moving. They keep their activity level up."
Participants take part in about 40 minutes of aerobic activity and work on balance and strength training, Johnson said.
But it isn't all about fitness.
Seniors also attend for social reasons. Each month, the classes celebrate birthdays with a luncheon.
Alba Blocker, who teaches a fitness class for people with arthritis, described her students as an "intimate group."
"It's a very social atmosphere," Blocker said. "A place where people make friends."
The arthritis classes are taught by Arthritis Foundation-certified instructors.
Students participate in standing work, joint mobility warm-ups and stretching exercises, and work on toning, endurance, balance and coordination.
"It gets the kinks out," said participant Mary Jane Barnett of Topeka.
"It keeps you awake and keeps you going," said Ed Schwerdt of Topeka, who also takes the class.
The classes are free to seniors who belong to Senior Spirit, a program offered through St. Francis Health Center.
Senior Spirit is a free program for people 65 and older who want to keep informed about health, said Linda Ruiz, communications specialist for St. Francis and Senior Spirit manager.
The program offers the free exercise classes, free quarterly educational programs designed for older adults, free blood pressure checks and other discounts.
"The population is aging, and we're getting more seniors every day," Ruiz said.
"We feel the more we can keep them healthy, the more it increases their quality of life and helps them with so many different things."