Three physiologists tell us why the prescription "drink when you are thirsty" is usually the best guideline for deciding when and how much to drink. We will talk to Heinz Valtin of Dartmouth Medical School (retired); Mark Knepper, the chief of the Laboratory of Kidney & Electrolyte Metabolism of the National Heart Lung and Blood Institute; and Samuel Cheuvront, of the Thermal and Mountain Medicine Division of the U.S. Army Research Institute of Environmental Medicine about water consumption. They will answer the question: "Must I drink 64 ounces of water each day?" (Begins at 3:47)

To read the review of the eight-by-eight rule by Heinz Valtin, click here:

In the Buzz in Physiology, we look at studies involving a prosthetic device known as the Cheetah Flex Foot and whether it gives a runner who is a bilateral amputee an unfair advantage over limb-intact runners. We also summarize a study in mice in which adult bone marrow stem cells were used as a non-invasive therapy to repair cardiac tissue. And finally, we'll look at a study that finds that electro-acupuncture successfully reduced sympathetic nerve activity, normalized menstrual cycles and reduced testosterone in women with polycystic ovarian syndrome. (Begins at 1:05)