Which factor is crucial for synchronization in performing AGSM?

Synchronization during the Anti-G overload Straining Maneuver (AGSM) is primarily dependent on the coordination of breathing and body posture. This coordination is vital because the AGSM requires a specific sequence of muscle contractions combined with controlled breathing to effectively manage the effects of increased G-force on the body.

When performing AGSM, it is necessary to maintain a firm body position while managing airflow and pressure within the chest cavity. Properly coordinating breathing with body posture helps maximize the effectiveness of the maneuver, ensuring that blood flow to the brain is maintained and that the individual does not experience G-induced loss of consciousness (GLOC). The diaphragm's movement during effective breathing must be in harmony with the body’s muscular responses to maintain blood circulation and support overall physiological stability.

While other factors, such as heart rate and pressure, are also important in the context of high G-force environments, they are not as directly involved in the synchronization that is essential for the AGSM to be effective. Thus, the coordination of breathing and body posture is indeed the crucial factor for successful performance of AGSM.