I would say that there isn't a time when you CAN"T take them. its always fine to take your BCAAs but they aren't something that I always have.
Ya, I too had the impression that BCAA's were always good to have...but it is worthwhile to invest in a free-form supplement? You get them (iso-leucine, leucine, valine) in whey supplements in varying proportions, no?
Maybe someone can post some scientific literature about the purported benefits of BCAA supplementation.
