1. Once there is a problem, you need to take responsibility. If you don't take responsibility, you must provide evidence of not taking responsibility.

2. Generally, gyms are places for adults to exercise. You can post the relevant regulations of the gym in an important and eye-catching place, such as it is strictly forbidden to bring minors in, and you will be at your own risk if something happens.

3. If both parties feel aggrieved, they can call the police to collect evidence and make judgment through the people's police.

4. It is also possible that the gym has failed to fulfill the relevant duty of care and has certain responsibilities. Specific matters need specific treatment.