Chatting with boys who like fitness can focus on fitness, which is a common hobby. Here are some suggestions:

1. Ask him about his fitness experience and suggestions: You can ask him how he started fitness, and do you have any suggestions or guidance.

2. Share your own fitness experience: If you have fitness experience, you can share your own experiences, challenges and ways to overcome them.

3. Discuss the benefits of fitness: You can discuss the physical and psychological benefits of fitness, such as enhancing physical fitness and self-confidence.

4. Explore fitness skills and methods: You can ask each other some fitness skills and methods, such as how to train effectively and how to eat.

5. Share photos and videos of fitness: If you have photos or videos of fitness, you can share them with each other or ask each other if they have similar works.

In short, the chat should focus on the common hobby of fitness and have a relaxed and happy exchange. At the same time, we should also respect each other's personal preferences and experiences and avoid topics that are too professional or inappropriate.