The way that machines can hurt you is that they use a “piston style” of training (you go forward and backwards over and over hitting almost the exact same muscle tissue and not allowing your body to use very much range of motion) so they (machines) don’t allow very much other tissue to be used. So that repetitive use of the same area over and over is what can cause injury. So using dumbbells, for instance, is a better choice because the weights are more free to move and doesn’t use a “piston style” of pressure! Thanks for your input! I appreciate it!