In 1979, Pol Pot and the Khmer Rouge were forced from power by the invading Vietnamese. Pol Pot officially resigned the leadership in 1985 but appears to have retained considerable influence.
Muscle fatigue. Muscle fatigue is the decline in ability of a muscle to generate force. It can be a result of vigorous exercise but abnormal fatigue may be caused by barriers to or interference with the different stages of muscle contraction.
Physical fatigue can be caused by a lack of energy in the muscle, by a decrease of the efficiency of the neuromuscular junction or by a reduction of the drive originating from the central nervous system. The central component of fatigue is triggered by an increase of the level of serotonin in the central nervous system.