Athletic trainers are well versed in the sciences including biology, chemistry and physics. Please review the information on http://www.nata.org/career-education as in order to be a licensed trainer you want to receive your education from an accredited provider. I would encourage you to look into athletic training classes through your local community college as some privately run programs (offered through your local gym) may be both expensive and not accredited. You may also want to look into schools that offer exercise physiology or performance studies. Most importantly, as a trainer you need to be a model of good health.