personal trainer
From Longman Dictionary of Contemporary Englishpersonal trainerˌpersonal ˈtrainer noun [countable] someone whose job is to help people decide what type of exercise is best for them and show them how to do itExamples from the Corpuspersonal trainer• I've also hired a personal trainer.• No perfect-body personal trainer or low-fat chef for me.• On June 10,1996, I sought the service of a certified personal trainer, Rocco Mediate.• I'd been acting as Jennifer's personal trainer during filming and I'd been well paid.