my niece rocks herself when she is upset and doesn't get her way. She never causes bodily injury and if she somehow rocks a bit too hard she slows the pace or blocks with her hands. along with rocking she seams to enjoy the thud at the end of each rock. as if the best part of rocking is the sudden stop at each end front and back. when a rocking chair is available she jumps on the seat and rocks even though she's not upset. perhaps this is normal but I felt it couldn't hurt to submit my concerns.