g-force is the force to which a vehicle or its crew is subjected due to the vehicle's acceleration or deceleration, measured in multiples of normal earth gravity.

 

Negative g is the acceleration that a subject experiences as acting from below (feet-to-head direction). Also known as eyeballs up.

 

Acceleration stress

Acceleration stress is the physiological effect of high acceleration or deceleration on the human body. Acceleration stress increases with the magnitude and duration of the acceleration. Longitudinal accelerations cannot be tolerated as well as transverse ones as the former have a much stronger influence on the cardiovascular system.

 

Acceleration tolerance

Acceleration tolerance is the maximum acceleration or deceleration that a pilot or astronaut can withstand before losing consciousness.