What effect do high G forces have on the body?

High G forces exert a significant impact on the body, particularly in relation to cardiovascular function. When subjected to high G forces, the body's ability to maintain normal blood circulation can be compromised. This occurs because increased gravitational forces cause blood to pool in the lower extremities, reducing venous return to the heart and subsequently decreasing cardiac output. As a result, the heart may struggle to pump enough blood effectively to meet the body's metabolic demands. This altered hemodynamics can lead to symptoms such as dizziness or loss of consciousness, commonly referred to as G-induced Loss of Consciousness (GLOC).

In contrast to the other options, which suggest improvements in oxygenation, circulation, or cognitive function, the physiological impact of high G forces primarily revolves around the challenges presented to cardiac efficiency and systemic circulation, making the reduction in cardiac output a critical concern.