Why do jet fighter pilots need to wear G-suits?

To answer this I'll tell you how the G suit works. The suit is only pair of Chaps that has a waist that wraps around your gut. It has a hose that plugs into the aircraft which forces compressed air into bladders built into the suit. When the aircraft makes tight turns, causing g loads on the pilot, it forces the air into the lower legs, thighs, and gut area to force blood back up into the torso and to prevent it from pooling into your legs. If you lose too much blood from your head under these loads you WILL lose consciousness and pass out. Once you pass out you will lose control and risk crashing. The G suit does not do all the work however, it only helps. The pilot or passenger in the aircraft still has to do an enourmous amount of work to retain consciousness. He must flex the muscles in his legs and abs as hard as he can and take short, forced breaths. If you have ever lifted weights at a gym with your legs for an extended period of time, you have a small idea of how much stress it is on your body.