The history of drinking during endurance exercise is an interesting one. It serves as a wonderful lesson for two reasons. First, it demonstrates a concept I’ve discussed at length before called the Hype cycle where a particular concept or method goes through a cycle of first overemphasis, then under emphasis, before eventually settling into its rightful place. This cycle can be seen almost anywhere, but in terms of training you’ve seen it with such things as “core” training, mileage, and interval training.
Though long I really like the blog post linked to above. I don’t really care about the information about hydration but really the hype cycle. The author shows how hydration has gone through the hype cycle. It is explained better in the link above but the basic idea is that new evidence is almost always overemphasized before a more realistic middle ground is adopted.
I have a feeling the barefoot running trend/craze is in the overemphasis phase of a hype cycle.