When it comes to gym etiquette, we already know to avoid cellphone conversations, re-rack our weights, and curl anywhere outside the squat rack. But there are plenty of lesser-known blunders you could be making at the gym that may upset or disrupt others. Worse, some of these mistakes could negatively affect your health.

Take extra precaution and learn the 13 things you should never do in a gym. Believe us, you’ll make a lot less enemies.