Imagine a spin class where people jump over bikes as if they were pommel horses, or hang off the back of the seat while pedaling their feet. At aqua spin classes, stationary bikes are submerged in a pool where the water is 3½ to 6 feet deep, enabling participants to perform gravity-defying moves that would never fly on dry land. The 50-minute classes offered by Montgomery County Recreation combine movements from stationary cycling and water aerobics for a full-body, high-intensity, yet low-impact workout. Water provides resistance, but also cushions and protects joints. Like traditional spin classes, an instructor leads participants through various exercises set to fun, upbeat music. Classes are held once a week during sessions that last approximately three months and cost $111 for county residents, $126 for nonresidents at Martin Luther King Jr. Swim Center; $119 for residents and $134 for nonresidents at Kennedy Shriver Aquatic Center.

Martin Luther King Jr. Swim Center, 1201 Jackson Road, Silver Spring, 240-777-8060; Kennedy Shriver Aquatic Center, 5900 Executive Blvd., North Bethesda, 240-777-8070; grams/aquatics/waterfitness.html