You guys are being too complicated for this poor kid.
When you pull backwards on the stick, making you go up, all the blood in your body rushes to your feet, causing your vision to "black out".
When you push downwards on the stick, making you go down, all the blood in your body rushes to your head, causing your vision too "red out".
This is all connected to gravity, the force that makes you come down when you jump up.