ABSTRACT
This chapter discusses dehydration and hyperthermia as a cause of fatigue during exercise. The concepts of dehydration and hyperthermia are often linked as though one cannot exist without the other. This is not the case. The chapter highlights the classical mechanisms of dehydration-induced fatigue, along with other less well known potential mechanisms of dehydration-induced fatigue. Sweating is the main way that the body dissipates heat produced from the increase in energy metabolism during exercise. The chapter discusses the evolution of knowledge regarding dehydration and exercise fatigue. It also highlights the potential role of hyperthermia in impaired exercise performance, discusses the critical core temperature hypothesis, and highlights more recent work that challenges this hypothesis. Hyperthermia can impact on exercise performance in several ways, both peripheral and central. The chapter discusses these mechanisms. There is a potential link between alterations in brain neurotransmitters and the development of central fatigue during exercise in the heat.
