Very briefly: No, you don't need a four-year degree to be a certified personal fitness trainer. You simply take a certification test. If you pass it, you're a certified personal fitness trainer! If you don't, you can take it as many times as needed to pass. (Of course, this costs hundreds of dollars each time you take the exam.)
Personally, I have experience - in both college and the "real world" - in
sports medicine and anatomy/physiology - and I believe that it's always good to absorb as much information as you possibly can (in school or otherwise). However, as stated previously, no, it's not required to go to college to become a certified trainer.
Whatever route you choose, good luck to you.
