Here's a few pieces of info on G-LOC.
G-LOC is indeed a form of cerebral hypoxia. Under Gs, the blood, which carries the oxygen, is forced out of the brain. The first symptom will be the loss of color vision. Everything becomes grey. If you keep pushing it, so to speak, you will experience tunnel vision, where you lose your peripherals. If you push it further, you will black out. At that point, you are still concious, but cannot see a thing. The last thing that will happen to you is a loss of conciousness. In that case, you have no control over anything.
There are a few factors that influence your G Tolerance. First, and the most important one in my mind, is your natural vertical distance between your heart and your head. The shorter that distance is, the less pressure is required to carry the blood to the brain. Shorter people will tolerate more Gs, in general. One way aircraft designer capitalized on that is by reclining the ejection seat, minimizing the vertical distance between the heart and the brain. The F-16 has a 30 degrees recline on the seat, diminishing that distance by 20%.
The second factor is your blood pressure. The higher it is, the more Gs it will take for your blood to be forced out of your brain. There are ways to increase your blood pressure as you are pulling Gs. The first one is with a G-Suit. By compressing the lower legs, the thighs and the abdomen, you increase your overall blood pressure. The second one is by doing a G-Straining manoever. By compressing every muscle you can, you will increase your blood pressure. Holding your breath and "pushign it" against your chest will help as well. So, being in a good shape can help. Having a greater muscle mass will help you increase you blood pressure as you are straining your muscles. However, a long distance runner with a resting heart beat of 42 and an extremely low blood pressure will not tolerate Gs better than a smoker, fat food eating individual with a blood pressure up the roof.
The last factor I can think of is your VO2 max. The more oxygen your body can process and utilize, the better. Now, remember when I said that a marathon runner with a very low blood pressure will not do good? Well, it's probably true, however his VO2 max is probably very good. In the end, you want to achieve a balance.
Now, onto the CF training. It is only given to pilots that are selected to fly jets. Once you are finished Phase IIA in Moose Jaw and are selected to go jets, you'll be sent on a 3-day paid vacation trip to Toronto to complete the training. The half of the first day is ground school. You learn all the theory and practice the G-Straining on a chair. In the PM, you do your Centrifuge run. There are 4 profiles, the first one being a "warm up". It's a gradual onset (no g-pants) with no straining until you start feeling the symptoms. The second run is a rapid onset (no g-pants) to 5Gs for 20 seconds. The third run (and probably the most failed one) is a rapid onset to 6Gs (no G-Pants) for 15 seconds. The last one is a rapid onset to 7.5Gs for 10 seconds and down to 5G for 30 seconds (with G-Pants).
The Gs in the centrifuge are very different than what you feel in the jet. I don't know why, but that's the way it is. I personally thought that 6Gs in the centrifuge was much, much more agressive than 6Gs in a Hornet.
The second day is for anyone that failed to redo the runs.
As far as the individual in Jetstream that didn't pass the centrifuge training, he still flies the Hornet. He eventually passed the centrifuge training.
Hope this helps,
