A metabolic conflict occurs between increased production of easily used substrates and inhibition of their metabolism in any injured animal. The terms ebb and flow describe the dwindling and rising tides of such activity. The ebb may last 24 to 72 hours; the flow is usually over within two weeks but may last up to eight weeks or longer in more severe cases. The ebb phase corresponds to the traumatic and initial post-traumatic period when there usually is adequate substrate (oxygen, glucose, fatty acid) to meet the diminished demand of the tissues. The flow phase is the period of convalescence. The object of the organism's initial defense following injury seems to stabilize the situation during the ebb phase (preservation of the internal milieu). The longer the ebb phase can be maintained and the more substrates that can be conserved, the more likely the animal will recover during the flow phase. The ebb phase is set in motion by an injury such as hemorrhage, burns, fractures, soft tissue damage by crushing sepsis, or diarrhea. After the ebb phase, a variable, integrated response of nervous, endocrine, and metabolic systems begins, which compromises normal function to achieve specific survival objectives (that is, protection, stabilization and adaptation). Systemic changes (such as tissue catabolism) devoted to caloric needs and local growth (that is, wound repair) are all directed at the ultimate objective of survival.