In this video, Golf Fitness Specialist Dick Bartling gives you an exercise on hip rotation.  There are many golfers that struggle with hip flexibility. One way to check this is to keep your upper body stable and then be able to turn your lower body by turning your hips and knees. You are creating separation and the ability to move the lower body without moving the upper body.  Cross your arms across your chest and move your hips and knees to help create flexibility.  To make this a little bit more golf specific, rotate your shoulders back into your back swing position and then starting with the lower body and following through with the upper body. Being able to rotate the lower body in a rotational operation without turning the upper body is very important towards proper golf swing mechanics.
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For a great tip on how to strengthen your glutes, click here.