Hi Robert. I think that you’ve received some solid advice here from the other posters. Like other ancillary health professions (including physical therapy assistant) personal training requires your being officially recognized as a personal trainer (by getting your certification) will be an important first step towards becoming an advanced trainer. Taking and passing your certification test should not be a major problem with your background, however be aware that since your practice has been primarily in a rehabilitation setting, you will probably need to bone-up on working with healthy populations in order to better prepare for the certification test. Your work with the football team will help immensely!
Good luck, and welcome to the profession.