Which of the following muscle pairs are not Agonist/Antagonist?

The correct answer highlights that the levator scapula and superior trapezius do not function as an agonist-antagonist pair because they actually work in harmony rather than opposition. The levator scapula primarily elevates and rotates the scapula, while the superior trapezius also aids in elevating the scapula and is involved in other movements such as adduction. Since both muscles contribute to similar actions of scapular elevation, they do not demonstrate the agonist-antagonist relationship characterized by one muscle causing a movement (agonist) while another opposes that movement (antagonist).

In contrast, the other options involve muscle pairs that typically engage in opposing actions. For instance, the anterior deltoid and posterior deltoid serve as agonist-antagonist pairs because the anterior deltoid is primarily responsible for shoulder flexion, while the posterior deltoid facilitates shoulder extension. Similarly, the pectorals and latissimus dorsi engage in opposing movements at the shoulder joint, with the pectorals flexing and the latissimus dorsi extending. Additionally, the abdominals and spinal erectors also represent agonist-antagonist dynamics, as the abdominals flex the spine whereas the spinal ere