Backswing sway occurs when a golfer’s shifts his weight laterally so the upper body tilts towards the target. This causes too much lateral movement in the lower body, the golfer ends up having to make a downswing compensation so the flight path of the ball will likely slice or a hook.

The causes of backswing sway could be caused from physical limitations including:

Limited Core Stability
Weak Gluteus Maximus Muscles (buttocks)
Lack of Spinal Mobility
Tight Hamstrings
Tight Chest Muscles

To correct backswing sway, focus on Pilates balance exercises that stabilize core muscles and shift the body weight.