The personal trainer certification course is just a single class. It covers everything from the business end of the position to body mechanics and the basics theory of muscle building as well as weight loss. You can use this certification to work in a gym or for yourself. The only other course, not required by the AFPA but usually necessary to obtain the appropriate insurance is CPR certification. In order to take the course you must speak English, be 18 years old and have a functional knowledge of arithmetic. The total course takes up to six months, but you can run it as quickly as you like.
Two other courses are available to expand on your knowledge of personal training. These build on each other through advanced personal training to master personal training. Think of it as climbing the ladder through the levels of algebra--you use the skills from the first class and learn new techniques in each subsequent course. You also further delve into body mechanics and internal systems so you can be a more effective personal trainer.
The other base class that might be required for some specialty assignments is nutrition and wellness consultant certification. This will walk you through the specifics of how food works with the body to build muscle and store fat. This course will help teach you the nutritional ramifications so you can work that into your training to give your clients better results. Diet changes also tend to be an easier, long-lasting way to maintain healthy body weight even when clients are not able to exercise as much.
With the basic personal training certification and the nutrition and wellness certification you can go on to any number of specialties. Specialties include things such as post-rehab exercise, stability ball trainer, strength trainer and pre- or post-natal exercise specialist. Many of the class instructors such as yoga or cyclist instructor do not require a personal trainer certificate, but gyms find it helpful if you can do both types of instructing.