The biggest obstacle runners have is the need for proper hydration throughout the race. Improper hydration levels can lead to three types of illness.
caused by an imbalance of the body's electrolytes. Usually the first sign of heat illness.
rise in body temperature, dizziness, nausea, vomiting and headache are the signs.
complete failure of the body's ability to thermoregulate. Weakness, lethargy, confusion, disorientation, loss of consciousness, inability for the body to sweat.
The opposite end of the spectrum is the risk of hyponatremia. This is water intoxication and is caused when the body has taken in too much water and the sodium levels are dangerously low.