Sven sent me a link (NY Times) about how Dr Brooks, a scientist, has proven lactic acid to actually be a fuel for muscles, rather than a waste product of energy produced by muscles.
I find this extremely hard to believe since it means that lots of people are very very wrong. I did a quick googling and found a more thorough explanation, but still, I’d love to get a handle of Dr Brooks’ PhD thesis. If I do, and then if I do and actually read it, I’ll give my summary of how this proof is reality. Comment below if you would like this 
I just punched his name into PubMed, and this is his most recent article if you do feel like checking it out…
Am J Physiol Endocrinol Metab. 2006 Jun;290(6):E1237-44. Epub 2006 Jan 24.
Interesting stuff!
(Get access to PubMed through the library and you’ll be able to put that citation in and access the full text)