I just realized this poster said the soldier who died was drinking ENERGY drinks, which is not to be confused with SPORTS drinks. ENERGY drinks are high in caffeine which is a diuretic. It is aso a cardiac stimulant, so combining heat with exercise and caffeine with no water is clearly a lethal thing to do. The heart rate will elevate because of the exercise, the heat and the dehydration. After a while it won't be able to keep up. Prolonged rapid heart rates can be fatal because the heart is a muscle, and just like other muscles, when it runs out of the free glycogen (sugar) from the blood it will draw stored glycogen from the muscle tissue, and it will produce lactic acid in the process. The lactic acid causes classic chest pain, which is the body's way of saying "Dude! Give me a break!" If you exercise through chest pain (which a young person might do) eventually the heart will arrest because there's nothing left to fuel it's activity.

MNS