Which of the following can increase G tolerance?

Tensing of muscles is known to greatly enhance G tolerance for aviation crew members. When a person tenses their muscles, particularly in the abdomen and legs, this creates an internal pressure that helps to maintain blood circulation and prevent blood from pooling in the lower parts of the body during high-G maneuvers. This muscular engagement is critical in counteracting the effects of increased gravitational forces, which can otherwise lead to G-induced Loss Of Consciousness (GLOC).

In contrast, options like a clear mental state or relaxed body posture may provide psychological benefits or comfort, but do not physically affect the body's ability to handle increased G forces. Similarly, prolonged sitting does not contribute positively to G tolerance and can actually be detrimental by not encouraging circulation in the lower extremities, potentially increasing the risk of G LOC. Therefore, muscle tension is the most effective strategy to enhance G tolerance during high-stress flight conditions.