My apologies in advance that this posting has nothing to do with attack badgers, or doing strange things in the woods while naked. I came across this report in the context of a Conference I will be going to in Atlanta in April. If you are looking for a great source that explains things like Lactate Threshold, decription of energy systems etc., and the physiological response to exercise - either for one's own interest, being able to explain things to juniors etc. then check it out. Very clear and well written, esp. considering the complexity of some of this stuff.
www.cdc.gov/nccdphp/sgr/sgr.htm.
In particular check out Chapter 3: Physiologic Responses and Long-Term Adaptations to Exercise; also the Glossary of terms in Ch. 2.