The barbell shrug is a weight training exercise that targets the muscles of the upper back and shoulders, specifically the trapezius. It is typically performed using a barbell, which is a long bar with weight plates attached to either end.

To perform the exercise, you will need to stand with your feet hip-width apart and grip the barbell with an overhand grip, palms facing down. From there, you will need to lift your shoulders upward toward your ears, keeping your arms straight and your elbows close to your body. Be sure to keep your chest up and avoid rounding your shoulders or hunching your back during the exercise. 

It's also important to use a weight that is challenging but manageable and to avoid swinging the barbell or using momentum to lift the weight.