What physical capability does the high crawl primarily test?

The high crawl primarily tests upper body strength and coordination. This exercise requires the Marine to support their body weight using their arms while simultaneously coordinating limb movement to advance forward. It emphasizes the muscles in the shoulders, chest, and arms, which are essential for maintaining the necessary strength to perform the crawl effectively. Additionally, the coordination aspect is crucial, as the Marine must move their arms and legs in a fluid manner to navigate through the exercise without losing balance or efficiency.

While each of the other options highlights important physical capabilities, the high crawl specifically challenges the upper body in a way that simulates real combat scenarios, making the correct answer focused on upper body strength and coordination.