the "y" triangle

The "Y" Triangle is the position at address.   The grip is formed and body gets positioned for the shot.   The club is positioned at the point of origin for the shot.   

The force of the "Y Triangle is a vertical force pushing the club toward the ground.

The elbows are locked, and muscles extended.

Many times you will see the forearm muscles exposed in tour pros in this position.

The torso initiates the movement of the "Y" Triangle.   The "Y" Triangle is maintained until the natural hinging of the rear elbow allows the extension of the swing passed the range of motion of the player.

On the downswing, there is a natural unhinging of the rear elbow, as the torso drives the arms back toward the ball.