General adaptation syndrome is a theory of stress proposed by the Hungarian physician and endochrinologist Hans Selye. The theory states that when encountering stressors, the organism undergoes a predictable three-stage process when reacting to the stressors. The stages are:

– Alarm phase, an acute phase in which the body mobilizes energy for a fast and intense response.

– Resistance phase, in which the body also mobilizes energy, but as a longer term response, of lower intensity.

– Exhaustion phase, where the body has been in the resistance phase so long, that it is drained of its energy resources, and is no longer able to maintain a response. In this stage, maladaptive diseases will occur.

Source:

Thomas, J. Q., Kotecki, J.E. (2011). Physical Activity & Health: An Interactive Approach, Third Edition. (pp. 216-217) Sudbury, MA: Jones and Bartlett