First, you can walk up to her and say, Beauty, do you come every day? You are in such good shape to exercise! Remember that women can't stand praise, believe me. The more you praise her, the more interested she is, and slowly you start talking to her.
Secondly, if you are good at fitness, there are many ways. You can observe what she did wrong behind her back, walk slowly to her and tell her what you should do to get the best results there. This method is the best. Just once, he will remember you. Come a few more times and get to know you. You can chat on WeChat, often make an appointment to go to the gym together, and slowly you will have a chance to start.