The Smith machine shrug is a great way to target the trapezius muscle. Despite popular belief, the trapezius is not part of the shoulders. It is a back muscle that allows the shoulders to move in different directions (e.g. elevating and lowering the shoulders).
Adjust the Smith machine bar to a low setting (just above the knee or mid-thigh is ideal). Begin with your feet shoulder width apart. Grab the bar using an overhand grip. Your hands should be shoulder width apart as well. Keep your arms straight, then slowly elevate your shoulders as high as you can. Return to the starting position and repeat the exercise as needed. Never let the shoulders drop on the way down. Be sure to resist gravity as the bar descends. Throughout this exercise, be sure to maintain a straight back. Your stomach should be sucked in.
Grab bar with shoulder width grip. Allow shoulders to drop slightly.
Elevate the shoulders as high as possible. Maintain straight posture.
Slowly return to starting position. Control the momentum.