Final answer:
The trapezius and serratus anterior muscles act as a force couple on the scapula during shoulder elevation.
Step-by-step explanation:
The muscles that act as a force couple on the scapula during shoulder elevation are the trapezius and the serratus anterior. These muscles work together to stabilize and move the scapula, allowing for the elevation of the shoulder. When the trapezius contracts, it lifts and supports the scapula, while the serratus anterior contracts to rotate the scapula and pull it against the thoracic wall, facilitating the upward movement of the arm.