"In my experience, I need to target the trapezius (the muscle that extends from your neck to the middle of your spine between your shoulder blades) to make sure my posture is good and that my shoulders and arms extend beautifully from my body," says Jennifer Anniston's yoga instructor Mandy Ingber. How do you target that tricky trapezius? Check out her secrets below.WORKOUT Lay on your stomach on an incline bench. Hold moderate weight in both hands, arms hanging at your sides. Keeping your shoulders relaxed and down, lift your arms up slowly until they are just above your body and return. Do three sets of eight reps two times per week for the best results.