Fundamentally speaking, it is to increase the density of muscles, that is, the strength of muscles.

To give an inappropriate example: in a snowball fight in winter, the snowball gets tighter and harder, and the more painful it is to hit people, the less fragile it is.

Specifically, it is necessary to strengthen some routine exercises of arms and legs. We can do push-ups and dumbbells on our arms. If you want to practice calf strength, you can practice heel lifting or sandbag running in situ. You can do squats on your thighs. Of course, we should pay attention to science and step by step.

There are few muscles in the neck, so you can only do some head movements to enhance flexibility, and the abdomen is mainly abdominal muscle movements.