Yao Ming's basketball can't last a lifetime, and neither can Liu Xiang's. Loew, the coach of Germany's World Cup champion, is not young either. He doesn't need to play with the players when he trains them, does he?
Different ages have different development directions, and different ages have different courses and classes that suit them. If you have been a coach in this industry for 10 years, you can only say that you have failed. Trainers, senior lecturers and nutritionist club managers set up their own studios. All are possible development directions (567GO).
Fitness instructor is not a youth meal, but a job that can make you young.