pre workout shakes

[moosecles]

i know post workout, 50g dextrose, with 50g whey is a great mix. However pre workout ive read alot about taking in protein/carb's, alot of ppl have it in a drink/shake. Now my question is if you should still use whey as the source of protein or?, and if so how much dextrose and whey would be used, and how much time before training should the shake be consumed.

thank you