There are lots of sports medicine careers that offer generous pay and stable work. Sports is a huge business these days and often even high school sports teams will employ a professional training staff to look after the health of their athletes. When you think about all the college sports teams and then all the pro sports leagues you get a sense of how much work there is to go around.
But in order to get a good job you need a specialized sports medicine degree and many certifications. Competition for these jobs is stiff and the more you can do to set yourself apart as an exemplary trainer the better you will serve yourself.