You will want to show a potential employer that you know what you're doing, and that you are not just some beefcake who wants an excuse to hang out in a gym all day long. There are a number of certifications available, such as the American College of Sports Medicine (ACSM) and the National Strength and Conditioning Association (NSCA). To obtain one, you will likely have to have at least a high school diploma, as well as cardiopulmonary resuscitation (CPR) and automated external defibrillator (AED) certification. You will also have to pass an exam testing your knowledge of exercise science. Yep, that's right. There's science involved.