The golf swing is governed by physics and Newton's laws of motion. Without getting into the mathematics and a multitude of equations I will endeavor to simplify what is going on. Take a machine nut and tie it to a string about a foot in length. Be sure to tie it securely so the nut doesn't come flying off. Take the string in your hand with the nut hanging. Start twirling the nut in a circle. Keep twirling it and try to make the nut twirl faster. What you will notice is that you have to pull on the string to make the nut go faster. That pulling force is called centripetal force. The faster you pull the faster the nut will go. The speed of that pulling force at the hub of the radius i.e. the string held in your fingers is what Miura termed Parametric Acceleration. The faster you pull the faster the nut travels. In a golf swing the string is the player's lead arm (left for right handed player) and the club shaft. The center point for the swing is the left shoulder. The faster the left shoulder pulls the faster the club head goes. Brute force has nothing to do with it. The pulling action accelerates the club head.