We hate to sound like your mother, but there’s a reason why we always tell you to wrap your hands around the bar, including your thumb. And we’re not telling you that your feet should be pointing straight ahead for our own benefit. One obvious reason behind the droning advisories is safety, but there are plenty of other reasons why you should follow these fitness rules.

Pay attention to these mistakes you could be making in the gym, and the reasons why you should avoid them.