[Walking in the sun: heat stroke and heat exhaustion during the Four-Day March in Nijmegen, in 2006]. / Wandelen in de zon: hitteberoerte en hitte-uitputting tijdens de Nijmeegse Vierdaagse 2006.

The annual Four-Day March in Nijmegen, The Netherlands, in July 2006 was cancelled after the first day because two participants had died, men aged 65 and 57 years, and many had become unwell while walking in unusually high ambient temperatures. However, the cause of death of the two who died turned out to be cardiovascular and not heat-related. The case of two of the people that became unwell, men aged 58 and 59 years, respectively, shows that heat stroke and heat exhaustion were important causative conditions. Heat-related illnesses are relatively uncommon in the Netherlands due to its temperate climate. Heat stroke is the most severe of these and associated with a high mortality rate if not recognised and treated promptly. The primary cause is accumulation of heat due either to diminished loss or increased endogenous heat production, such as by physical exertion. Heat exhaustion is caused by salt or water depletion.