I think I agree with the child development person quoted:
Laura Berk, a child-development professor at Illinois State University and author of the book "Child Development," says while there is no evidence that gym classes help babies acquire physical skills more quickly, they can be a positive influence. "Kids encounter enough diversity in a typical home environment to help build motor skills," she says. "But these classes ingrain the idea of physical activity into kids from a young age, which is important." When conducted in a safe setting, they pose no harm and can be a fun thing for parents to do with little ones, she adds.