I majored in microbiology with an emphasis in physiology when I was at UCSB and racing on the cycling-team. Also worked part-time at Open Air Bikes and Bike'alog during that time. Everything kinda all worked together pretty well. I do a lot of my research on these sites:

Harvard School of Public Health
Journal of Applied Physiology
American Journal of Clinical Nutrition


Here's some cycling-specific sites I've found that translates the concepts into real-world user-friendly form:

CPtips - physiology index
CPtips - carbohydrates, note the info on recovery drinks near the bottom.