1. Sport is for professionals. This idea applies only in the case of performance sports. The native qualities required for professional sportsmen (speed, skills, specific height, etc.) can only be developed, they can't be formed by training. As long as the aim of a regular person is not performance, almost all sports can be practiced for keeping the body in a good shape. It's all about dosing the training you chose, so that the benefits are bigger than wear and tear...