markatger asked: It seems like it might be off because you are not actually walking across ground. How do they calibrate it?

_fauxtragedy asked: I’ve been on the treadmills thrice and would like to continue to work out. The problem is my mother believes they’re bad because someone told her that I still need to grow (I’m 14) and my muscles will grow stiff resulting in an operation. Is this true? What other ways can I work [...]