If you have issues with your latisimus back muscles and your shoulders are tight (the supine lat test), then you will have a tendency to lose your posture during the backswing and make a poor turn with your shoulders. The club will be off plane, and the loss of posture will make it difficult to produce solid contact.
Simulate a backswing by planting a pole overhanded with your left arm and underhanded with your right. Hold this position for 15 seconds, pulling toward your torso with your left arm and pushing away with your right.
Anchor the tubing around your feet and extend the other end behind your head. Push over your head, holding for 15 seconds.
From a crouching position with your head resting on the fist of one hand, slide your other arm along the ground as far as you can and then lift it as you roll your palm toward the sky. Hold this position for 15 seconds, then switch arms.