Peggy Grall

Instead of sweating on a gym treadmill that leaves your knees sore the next day, make a splash.

At fitness centers such as the YMCA and Brainerd Recreation Complex, there are several area water aerobic classes designed for swimmers and nonswimmers.

"A great thing about water fitness classes is that you can increase your strength and your cardiovascular endurance without taxing your body," said Peggy Grall, aquatic coordinator for the city of Chattanooga's Parks and Recreation Department.

"It's great for an injury rehab or (after) a knee or hip replacement," she said.

Ms. Grall said the city offers levels of water-fitness classes, a class for beginners and a more advanced program for cardiovascular and strength-building.

"As you're working in the water, you got a resistance that works with you and against you, so you're working all of your muscles," Ms. Grall said.

There is also a class geared toward people with arthritis that focuses on range of motion, flexibility and rehab.

"As you're working in the water, you get a resistance that works with you and against you, so you're working all of your muscles," said Ms. Grall. "You need a lot of core strength because of the turbulence, and the current of the water will cause you to stand up straight and hold your body tight, so that helps build your core."

Waterwalk is a popular class for older adults at the downtown YMCA.

The class, which is taught at the shallow end of the pool so that those participating can easily stand, is for all levels of fitness and is very low-impact.

"We focus a lot on balancing and strengthening the legs and the hips and getting them to move," said Emily Krause, the YMCA's assistant aquatic director who occasionally teaches the class.

Connie Watkins, 66, said she enrolled after her doctor suggested she take up some kind of exercise.

Although she was initially scared of the water, Ms. Watkins now regularly attends the class.

She said the exercise also has allowed her to completely go off her blood pressure medicine.

"I can tell a difference, like if I skip a week, my knees hurt," she said. "But once I get in that water, I can move."