The upper portion of the trapezius can be developed by elevating the shoulders. Common exercises for this movement are shoulder shrugs and upright rows. Middle fibers are developed by pulling shoulder blades together. Best exercises for this movement are rowing exercises and deadlifts. The lower part can be developed by drawing the shoulder blades downward while keeping the arms almost straight and stiff. This can be done in a pull-down station for example.
A person can feel the muscles of the superior trapezius become active by holding a weight in front of them in one hand, and with the other, touching the area between the shoulder and the neck. It is common for non-experienced gym users to focus mostly to the upper portion of the muscle, and thus forgetting the important middle part and creating muscle imbalances, which can heavily affect posture and compromise shoulder health.