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.
Wiki Tag: thermogenic potential
Thermogenic potential and thermogenic fatigue
In 1930, Giaja published a paper entitled “Muscle fatigue and thermogenic potential”, in which he found that the maximal thermogenic potential decreases with intense muscle fatigue. This was his first foray into the research of adaptation, which he considered to be essential; in fact, he wrote that physiology could be defined as the science of functional adaptation of living beings. In the same paper, he showed that laboratory rats living at a variable room temperature could survive in temperatures close to 0°C without weight loss or hypothermia, while animals kept at the temperature of their thermal neutrality (32°C) die or experience hypothermia at the same low external temperature. Thus, Giaja concluded that the prolonged maintenance of animals at thermal neutrality significantly decreased their thermogenic potential by lowering the peak metabolism by 30%. In other work, he demonstrated that the growth of animals kept at thermal neutrality is slowed in comparison to that of animals exposed to lower temperatures. In the series of papers that followed, Giaja conducted a comparative study on different homeothermic organisms and demonstrated that the limit of resistance to cold depends on the previous thermal adaptation of the subject. Giaja termed this decrease in resistance to cold during combating low temperatures “thermogenic fatigue”.