The position of the left foot during set up and the swing can have a significant impact on how a left handed golfer strikes the ball.
On a normal full swing when trying to hit a straight shot, the left foot should be set back and opposite the right. This will ensure the alignment remains parallel to the ball to target line and the back swing has a stable base to turn against.
Because of the dynamic nature of the golf swing, the left foot does need to become more active during the through swing.
Motion of the Left Foot
For the left handed golfer, the left foot stays rooted and braced against the ground until the beginning of the down swing. The golf swing works in a kinetic sequence which sees the back swing move in the follow order; hands, arms, shoulders, torso, hips, knees and finally, if necessary to increase turn, the right foot.
The down swing works in the opposite - the sequence beginning with the left foot, knees, hips, torso, shoulders, arms and finally hands. During the down swing, the left foot will push from the ground, rolling up on to the toe at the finish of the follow through. This push and roll on to the toe will add a significant amount of power to the shot.
Alterations of Left Foot Position
Although for a standard straight shot the feet need to be aligned, the left foot can be moved into alternative positions to alter the type of shot being played.
The alignment of the feet and shoulders effect swing path which in conjunction with the club face position at impact determines the flight of the ball. If a left handed golfer withdraws the left foot more (draws it back) the swing path will be more from in-to-out, encouraging more of a draw shot. Moving the foot further forward will encourage an out-to-in swing path. This will favor a fade shot.
The left foot should also be withdrawn and the stance opened on a number of other shots such as the high floating bunker shot and the lob shot.
The foot needs to support the turn of the back swing and push forward during the down swing to encourage more power. But it can also be moved into different positions to alter the shape of shots. The left handed golfer needs to be aware of how the back foot can be used to not only add power but shape shots.