What is the effect of positive G's after experiencing negative G's called?

The phenomenon described, where positive G-forces follow negative G-forces, is often referred to as the push-pull effect. This effect occurs because the body experiences a rapid change in orientation and forces acting upon it, which can lead to a range of physiological responses. When transitioning from negative G's to positive G's, blood can rush towards the head, causing transient symptoms such as visual disturbances or "tunnel vision," as well as feelings of heaviness. Understanding this effect is crucial for pilots and others who experience rapid changes in G-forces, as it can impact situational awareness and overall performance.

The other choices represent different concepts. G tolerance reduction refers to the body's diminished ability to withstand G-forces due to factors like fatigue, dehydration, or inadequate training. Acceleration retention relates to the ability of the body to continue feeling the effects of acceleration after the forces have been removed, which is a different physiological response. Vertical speed compromise refers to potential issues in managing vertical movements, particularly in aviation, which also doesn't directly relate to the transition between G-forces.