Final answer:
The shoulder girdle muscles play a crucial role in providing stability and facilitating movement when carrying a load.
Step-by-step explanation:
The pectoral girdle consists of the clavicle, scapula, and proximal end of the humerus, along with the muscles that stabilize and position these bones. When carrying a heavy load on your shoulder or in your hand, the shoulder girdle undergoes rotation and movement to provide support and stability. This allows you to bear the weight and move the load more efficiently.
For example, when you pick up a heavy book bag and carry it on only one shoulder, the shoulder lifts as the scapula superiorly rotates to increase weight-bearing support.
Therefore, when carrying a load, the shoulder girdle muscles play a crucial role in providing stability and facilitating movement to minimize strain and potential injuries.