The most suitable reason is that you feel better than ordinary people after fitness.

But you ignore two common sense (which is also lacking in domestic films):

First, the equipment in the gym can't improve people's combat effectiveness, and even weaken people's combat effectiveness.

Second: Fitness, or building muscles, is a process of destruction and regeneration. Destroy muscles during exercise, and you will grow bigger and stronger muscles after rest. In other words, being strong and healthy is a period of weakness.

Finally, if you fight, there are three basic hard requirements that you can't get from equipment and fitness.

First: combat capability.

Second: flexibility

Third: reaction

Conclusion: If your purpose is to show your fighting capacity, then take part in fighting or martial arts training. Gyms are used for beauty.