If you top shots, most likely you are standing up as you strike the ball. Ideally, you want to keep the same angle your torso and legs formed at address position the same throughout your swing.

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Many high-handicappers stand up (straighten their legs or lift their torsos) as they strike the ball resulting in an array of bad shots including thin and topped shots, pulls and slices. If you take a look at professionals, you will see that they keep their spine angle throughout their swing and even many squat down as they strike the ball.