Cells
An individual can drink too much water. Excess hydration can lead to electrolyte disruption by diluting fluids in the body to the point that concentrations of electrolytes are too low for normal function. Depletion of electrolytes can disrupt function of muscles and nerves, leading to a variety of symptoms up to and including death. Harm from consumption of water are very rare, as a healthy person would have to drink an extreme amount of water in a very short period of time to experience significant harmful effects. Excess hydration is usually only experienced due to drug abuse or when forced.
When an athlete does not get enough oxygen to meet the demands of his or her system, cells cannot maintain a cycle of aerobic respiration and begin producing energy through anaerobic respiration. Aeorobic respiration is 18 times more efficient than anaerobic respiration at producing the adenosine triphosphate used to transport energy within cells from the pyruvate left over from glycolysis. Anaerobic respiration also has the side-effect of producing potentially harmful chemicals. The primary byproduct is lactic acid, but butyric acid and acetone also occur. The theoretical final result of oxygen deprivation is death, due to the buildup of byproducts from anaerobic respiration and the severe reduction in energy production. In athletics, death from oxygen deprivation is rare, as it usually causes unconsiousness first, which immidiately ceases the strenuous activity that significantly contributes to inadaquate availability of oxygen.
Athletes engage in carbohydrate loading before endurance events to increase the amount of glucose stored in the body in the form of glycogen. Carbohydrate loading consists of decreased activity combined with a high intake of carbohydrates. Carbohydrate loading gives an endurance athlete a larger supply of easily-metabolized glycogen for use during an event. Having a larger source of fuel that is easy to metabolize gives an athlete an endurance advantage over the competition. Foods high in starch such as breads, cereals and pasta are most likely to work well for carbohydrate loading. Simple carbohydrates such as sugars are usually metabolized too quickly to be useful.
