I am trying to better understand aerobic energy and what is breaking down in the case of CFS. Unfortunately, I don't have the science background on aerobic respiration, and I am getting lost in biochemical equations. I need a higher level picture. This article describes three types or "stages" of aerobic energy named glycolysis, krebs cycle, and electron transport: http://www.buzzle.com/articles/aerobic-and-anaerobic-respiration.html This article confuses me because they list the first step as glycolysis, and then they say glycolysis does not need oxygen. Well, that would be anaerobic glycolysis, not aerobic glycolysis? What am I not understanding there? Based on their description, it sounds like there is no glycolysis that requires oxygen? Why would they describe an anaerobic process that requires glucose in an aerobic metabolism section of the article? What about krebs cycle and electron transport? Are those used side by side at the same time in the same tissues? Where can I get a good overview of what these are and how they are used that does not immediately become a textbook on biochemistry? Just seeing something at a high level would be really helpful before I dig into details later. Now here is where I get even more confused: at what point does fat start being used instead of glucose, and is that fat being used in krebs cycle, electron transport, or yet another process that is aerobic? And, finally, what are the current best theories about which of these processes are breaking down for a CFS patient? I gather that much of the problem is about NADH (which is the output of many of these processes) not being able to convert back to NAD+. Is that sufficient to explain all of the post exercise malaise symptoms?