Coming out of your swing also referred to as early extension is generally caused by more of a physical reason rather than a mechanical reason. Meaning something in your body is too tight and you can’t hold your posture. In my case my upper back and shoulders are very tight. The best thing to try and avoid this is shorten your back swing, work on getting your hands wider instead of higher on your back swing. Deep overhead squats and goblet squats are good exercises as well.
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What’s a good drill to avoid “coming out” of your swing, or standing up during impact? Especially when swinging hard.
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