Water aerobics instructor Jennifer Bonnett works up a sweat as she jogs in place on the side of the pool. As she calls out instructions and demonstrates exercises, 35 heads bob up and down in the pool, imitating her motions. Water aerobics is one of the most popular workout classes offered at the YMCA of Concord. 8:30 a.m. classes on Mondays, Wednesdays and Fridays frequently fill the pool to its 50-person capacity. Participants scatter across the pool, each absorbed in their own rhythm.
