Giaja published a paper on the minimal energy consumption for life support with B. Maleš in 1921, showing that, as in poikilotherms, the energy consumption in homeotherms also depends on external temperature*. This paper is considered his first venture into studying hypothermia. In line with this study, in another paper in 1922 with B. Maleš, Giaja defines the oxygen consumption at normal and lethally high (40°C) external temperatures. He then introduced a parameter termed “peak metabolism” and defined its relationship to the classical basal metabolism and the dependence of both on various environmental factors. Thus, he defined peak metabolism as a counterpoint to basal metabolism – the limiting point of thermoregulation during fasting or in the cold. Giaja also introduced the “metabolic quotient”, or the ratio of peak to basal metabolism that defines caloric consumption. In 1925, he reported on the relationship between the loss of heat and basal metabolism as well as the role of some endocrine factors (insulin and adrenergics) in heat production.