There are numerous references throughout the film to fear of heights and falling. See also
Acclimatization
Fear of falling
Head for heights
List of phobias

Citations
General and cited sources
Sartorius, N.; Henderson, A.S.; Strotzka, H.; Lipowski, Z.; Yu-cun, S.; You-xin, X.; Strömgren, E.; Glatzel, J.;  et al. "The ICD-10 Classification of Mental and Behavioural Disorders Clinical descriptions and diagnostic guidelines" (PDF). World Health Organization. p. 114. Retrieved 23 June 2021. External links
"The scariest path in the world? ", a direct test, video shot on El Camino del Rey, approaching Makinodromo
"Fear of Heights"—A comprehensive guide with useful resources on Acrophobia known as Fear of Heights.
In non-human animals
In some regions (e.g. much of the northeastern and northwestern US and adjacent Canada, and the southeastern US), selenium deficiency in some animal species is common unless supplementation is carried out. Selenium deficiency is responsible (either alone or together with vitamin E deficiency) for many of the cases of WMD ("white muscle disease"), evidenced at slaughter or during necropsy by whitish appearance of striated muscle tissue due to bleaching by peroxides and hydroperoxides. Although this degenerative disease can occur in foals, pigs and other animal species, ruminants are particularly susceptible. In general, absorption of dietary selenium is lower in ruminants than in non-ruminants, and is lower from forages than from grain. Sheep are more susceptible than cattle to WMD, and goats are more susceptible than sheep. Because of seleniums role in certain peroxidases (converting hydroperoxides to alcohols) and because of the antioxidant role of vitamin E (preventing hydroperoxide formation), a low level of Se can be somewhat (but not wholly) compensated by a high level of vitamin E.  (In the animal, localization of peroxidases and vitamin E differs, partly because of the fat-solubility of vitamin E.)   Some studies have indicated that about 0.12 or 0.23 mg Se per kg of dry matter intake may be sufficient for avoiding Se deficiency in sheep in some circumstances. However, somewhat higher Se intake may be required for avoidance of  WMD where certain legumes are consumed.