ok, its a given that glutes are stronger than quads, hell they are the strongest muscle group period. so, if the glutes are the strongest, and they are, then the quads will give out before the glutes will. meaning, that even though the quads are spent out completely, the glutes are still going, giving you more reps. so, in a sense, your glutes are spotting your quads, allowing 10 reps where the quads gave out at 7-8. and whats the key word for growth? overload. and whats the best way to overload a muscle? forced reps. and what allows a forced rep to be performed? thats right, a spot. follow me? your glutes allow for maximum overload on the quads, by supplying a spot. if you pre exhaust, you simply limit the weight that can be used and in doing so, completely limit the potential for growth.

hams are not a major muscle group. they get trashed during a heavy squating session and dont require near the effort or volumn of quads, chest or back. i am all for localized blood flow. its why i train tri's and bi's together. i have 21 inch arms(lean, cut arms) and 31inch(lean and cut) upper legs. and i posted a pic.