“Shared physical custody” means a child has periods of residing with, and being under the supervision of, each parent consistent with the provisions of § 48-9-206 of this code: Provided, That physical custody shall be shared by the parents in such a way as to assure a child has frequent and continuing contact with both parents. Such frequent and continuing contact with both parents is rebuttably presumed to be in the best interests of the child unless the evidence shows otherwise.