[@Black Alice]

[quote=@Black Alice]
You are using your muscles to create a propulsion force, in order to throw a punch with those same muscles in the opposite direction.

Can you see the problem with this?
[/quote]

Not really.   First, the muscles used to throw your fist forwards aren't the same ones used to pull your arm back.  second,  you aren't using both groups at the same time.  You're using the ones to pull your arm back first and then you're using the ones that cause your fist to go forwards.