The occurrence of a heat illness can and will ultimately lead to performance break-down, performance dropout and in extreme cases to lasting health damages.
Problems with the thermoregulation usually go along with a high sweat-related deficit due to lacking fluid, an electrolyte inbalance and also central fatigue.
In case of sunstroke or heatstroke, an intensive overexposure of the head to the sun can lead to restlessness, dizziness and nausea. This can also occur through extremely high metabolic heat production during average intense endurance performances (mountain running, short triathlon, …).
However, as a result of long-lasting performance the increased fluid loss (saline deficiency) causes heat exhaustion. Body temperature is above 41 °C with a hot, dry skin and impaired consciousness.
Heat cramps may also occur through painful muscle cramps (spasms) in the most severely stressed muscles hours after straining.
Heat exhaustion is accompanied by headaches, drowsiness, dizziness and nausea. The skin is usually cold and gray.
An analysis of medical incidents in the famous Hawaii Ironman race showed that over 80% of the affected people suffered from heat illness through loss of fluids and electrolytes.