I came across an excellent review, including comments by the sport scientists who reviewed the article, at the sportSci.org Web Site today on Sodium Bicarbonate (Baking Soda) as an ergogenic aid. This is commonly called "soda-loading" and involves ingesting a fairly significant quantity of baking soda in water an hour or so before an event. The alkaline bicarbonate ion is believed to buffer the acid produced by anaerobic exercise. The authors note that, "There are sufficient data to suggest that buffering agents can improve performances in such events as the 400-m sprint, 1-km cycling time trial, and Olympic rowing." Admittedly, the article is almost ten years old, but it does provide interesting reading. If anyone has experience with this, or knows of more recent work in the area please add your comments!
The article details many studies and some impressive improvements in performance in events lasting as long as an hour. In fact, in international events the benefits may be equivalent to a good taper, and could gives enough of a benefit to put an athlete into the medals. It should be noted though that it also potentially comes at a price - serious gastrointestinal problems for some, not to mention the ethical question of using a substance in abnormal quantities just to enhance performance.
Reading Matthew Pinsent's excellent book, A Lifetime in a Race, I was a somewhat surprised to see him write that two of his teammates in the GB four in Atlanta (not certain but I know it was an Olympic final) were soda-loading before the race. The fact that they did it is testimony to the belief amongst elite rowers that it works. The fact that they didn't all do it though also is a comment on the possible problems I would suggest.
I did try this for one erg test as a university student years ago, out of curiosity. I came away feeling that it had given me a false sense of security and that I had gone out far too hard as a result. I didn't ever try it again, but more testing might have helped me find a way to make it more useful.