When most people think about the engine of the golf swing they think about the hips and shoulders or some part of your torso. After testing all of these variables along with the hands and arms we came to discover that the true engine of the golf swing was the trail hand (the right hand for most golfers). The reason that the trail hand is so important is the role that it plays in controlling your trail arm, trail shoulder, and trail side of the club and how those variables influence what the body does.