Well, there are many places to buy dextrose and maltodextrin.
NOW Foods is a cost effective company that supplies both these dirt cheap:
Carbo-Gain: 7 lbs maltodextrin- $12.99
Dextrose: 2 lbs- $2.00
My personal favorite is from
Trueprotein.com. Their maltodextrin IMO is a lot better and finer than NOW and costs $2.29 per pound.
A lot of people like a dextrose/malto combo PREworkout. I personally don't because the I crash pretty hard halfway through my workout from the dextrose. You could easily do 50 grams of maltodextrin 30 minutes before working out. I like my preworkout formulas to have only maltodextrin and BCAA's.
What I have been doing for the past month with phenominal success is putting 50 grams of waxy maize starch, 3 grams cee, and 3 scoops EAA's in my shake that I drink about 20 minutes before the gym... Zooom
