“Approximately 3,200 kcal could meet the daily energy requirements for physical exercise for a 70 kg person whereas 2,600 calories was sufficient for simple office work.
The metabolism of a farm worker during harvesting would require 4,300 kcal. The peak values of the daily calorie consumption for lumberjacks would amount to approximately 6,000 kcal for a 70 kg person. Long-distance racing cyclists, however, could reach a peak daily metabolic rate of 11,000 kcal.
Rubner [see Roux, 1895] believed that the limiting factor for the uptake of calories in the human body was the intestinal system. A repeat of such great exertion over several days would inevitably lead to loss of body weight.” (Tipton, 2014, p.62).
Roux, W. (1895) Collected Texts about the Development of Organism. Volume 1: Functional Adaptation [in German]. Leipzig: Engelmann.
Tipton, C.M. (Ed) (2014) History of Exercise Physiology. Leeds: Human Kinetics.