It's already the late stage of strength when you punch, so you should exhale, so that you can close your fist and inhale before the next punch. If you hold your breath with one punch, exhale after the punch. If your chest is attacked at this time, you will faint.

Holding your breath during exercise is often the last stage of a group of actions. This action is very laborious and takes a long time to complete. If you exhale, your strength will be dispersed.