I have always heard and read that they were bad for kids from an injury standpoint. DD used them for conditioning at her old gym, just 1.5lbs per leg. Today DD worked on her floor routine and they had her use them to work on her leap and split jump. OMG what a difference it made. Still I've heard and read many times that they are bad for them. How do you feel about them and in what situations do they lead to injury?