I would also have to agree on just the pre/post due to cost here is a cool articel showing why BCAA arent really effective during workout though.
The American Journal of Physiology, August 2001 v281 i2 pE365
BCAA intake affects protein metabolism in muscle after but not during exercise
in humans. EVA BLOMSTRAND; BENGT SALTIN.
Author's Abstract: COPYRIGHT 2001 American Physiological Society
Branched-chain amino acids (BCAA) or a placebo was given to seven subjects
during 1 h of ergometer cycle exercise and a 2-h recovery period. Intake of
BCAA did not influence the rate of exchange of the aromatic amino acids,
tyrosine and phenylalanine, in the legs during exercise or the increase in
their concentration in muscle. The increase was ~30% in both conditions. On
the other hand, in the recovery period after exercise, a faster decrease in
the muscle concentration of aromatic amino acids was found in the BCAA
experiment (46% compared with 25% in the placebo condition). There was also a
tendency to a smaller release (an average of 32%) of these amino acids from
the legs during the 2-h recovery. The results suggest that BCAA have a protein-
sparing effect during the recovery after exercise, either that protein
synthesis has been stimulated and/or protein degradation has decreased, but
the data during exercise are too variable to make any conclusions about the
effects during exercise. The effect in the recovery period does not seem to be
mediated by insulin.