Abstract EN:

This history of the theories of fatigue ranges from the early years of the 18th century to the middle of the 20th century. In the 18th century, exhaustion came from the consumption of « animal spirits », from the wearing out of the «solid matters », or from the « tiredness » originating in « fluids » stagnation. Exhaustion is a consequence of violent activities, of sustained mental activity, or of the « sedentary » work ; but it also comes from sexual perversions. In the early 19th century, vigour therapies launched a debate over the origin of strength. Considering the energy of the body comes from the air we breathe in, does loss of breath play part in the growth of the fatigue ? When in the mid-19th century new knowledges came up concerning the physiological aspects of the muscle activity, tiredness was attribued to a lack of oxygen in the body and an excess of carbon dioxyde. Further explanations were proposed trougth the new physiology of the brain, in the ligth of advances in psychology. Then came the principales of training, later developped during the 20th century to justify the techniques founded on experience and aimed at making men toughs.