There are two kinds of boxing force: external force and internal force. The external force is manifested as the shaking of sandbags. The greater the shaking amplitude of the sandbag, the greater your external force. The internal force is represented by the depression of sandbags. When a punch is punched on the sandbag, the sandbag vibrates little or even does not vibrate, but the sandbag sinks in. These two forces have different effects on human body. When an external force hits the human body, it will expand wherever it hits, and people will be beaten down; When the internal force hits people, there is no obvious external reaction, and the internal tissue is traumatized. People may not be able to move, but organs such as internal organs are broken. In fact, the so-called inner strength is the inner strength of the family boxing.