Final answer:
During forced inspiration, the primary neck muscles utilized to elevate the sternum and rib cage are the scalene muscles, which are essential for increasing lung volume.
Step-by-step explanation:
During forced inspiration after heavy exercise or in cases of respiratory distress, several neck muscles are utilized to elevate the sternum and the rib cage, thereby increasing lung volume. The primary muscles involved in this process are the scalene muscles.
The scalenes are accessory muscles of inspiration that, when contracted, lift the thoracic wall, thus facilitating deeper inspiration. This action is particularly necessary during situations requiring increased oxygen intake or when normal breathing is compromised due to respiratory conditions.