Blacking Out with Heavy Lifting

Question:

I’m a weightlifter (Olympic-style) and have had some troubles with blacking out or getting light headed when I come up with heavy (90 to 100 percent) efforts in the Clean. I have been told that this is due to a blood pressure change during the lift and that increasing my fitness level should help with the problem. I don’t feel any less cardio fit than when I was not having this problem. Are you able to shed some light on this?

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