The thoracic spine, which is basically your upper torso, is designed to be mobile and allow rotation. We need to twist and turn the upper torso over a stable platform of our low back, hips, and legs to create power in the backswing. If you lack mobility in your thoracic spine, you’ll be restricted on how far you can turn your torso, therefore limiting your backswing. Here is an exercise to help you increase the mobility in your thoracic spine so you can learn to make a better turn.

Stand in a modified golf stance with a club placed behind your shoulders.
Keeping your lower body stable, rock your shoulder back and forth for a few repetitions.
Then turn your torso completely as if you were doing a backswing.
Hold the position for 8 to 10 counts and return to the start position.
Repeat on opposite side