Which muscle group is primarily stretched by elevating arms at the sides?

Elevating the arms at the sides primarily stretches the pectorals and shoulder internal rotators. This action creates tension along the front of the shoulders and chest, which are predominantly made up of the pectoralis major and minor muscles. When the arms are raised laterally, the position of the arms draws them away from the body, effectively elongating the pectoral muscles.

Additionally, the shoulder internal rotators—which include muscles such as the subscapularis and portions of the teres major—are also involved in this movement. As the arms lift to the sides, these internal rotators are subjected to a stretch as their natural position is expanded.

While the other choices list muscle groups that may experience some level of activity during shoulder movements, they do not primarily focus on the stretching effect created by elevating the arms at the sides. The trapezius, rhomboids, deltoids, biceps, latissimus dorsi, and obliques interact in different ways with shoulder movement and stabilization but do not receive the primary stretch associated with this specific arm position.