Trainers.net is a great brandable keyword domain name for your business.
".net" domains can be associated with networks/communities. For example: a network of personal trainers.
In the european markets, trainers usually refers to athletic shoes. In most other markets the word trainers can be associated with the term "personal trainer".
Activities, sports and health are a growing market across the world and many people look for good trainers in the various physical activities they want to try or excel at.
Exercise, sport specific, health and recovery training are all related areas where a trainer might be searched for.