There are basically two types of fatigue: physical (muscular) and general (mental). Physical fatigue is characterized by acute pain localized in the muscles, particularly those used for a long period in the exercise of a particular task. General fatigue is characterized by decreasing motivation and willingness to work, unusual sensitivity to situations and to other people, irrational stubbornness and disintegration of attention. Early researchers emphasized the importance of the accumulation of chemical products, such as lactic acid, in the production of fatigue. A more recent view is that fatigue is an outcome of frustration and conflict within the individual.
The Encyclopedia of World Problems and Human Potential is a collaboration between UIA and Mankind 2000, started in 1972. It is the result of an ambitious effort to collect and present information on the problems with which humanity is confronted, as well as the challenges such problems pose to concept formation, values and development strategies. Problems included are those identified in international periodicals but especially in the documents of some 60,000 international non-profit organizations, profiled in the Yearbook of International Organizations.
The Encyclopedia includes problems which such groups choose to perceive and act upon, whether or not their existence is denied by others claiming greater expertise. Indeed such claims and counter-claims figure in many of the problem descriptions in order to reflect the often paralyzing dynamics of international debate. In the light of the interdependence demonstrated among world problems in every sector, emphasis is placed on the need for approaches which are sufficiently complex to encompass the factions, conflicts and rival worldviews that undermine collective initiative towards a promising future.
Non-profit, apolitical, independent, and non-governmental in nature, the UIA has been a pioneer in the research, monitoring and provision of information on international organizations, international associations and their global challenges since 1907.