The phenomenon of after-contraction, though of considerable neurologic interest, has received comparatively little attention. It is regarded as the result of an after-discharge from the nervous system and may be elicited when any set of muscles, for instance, those involved in raising the extended arm or leg, is voluntarily kept in action against resistance for a period of time. The phenomenon consists of an involuntary repetition of the originally intended movement and a feeling of lightness or floating upward of the part following relaxation of the contracting muscles and removal of the resistance. Thus, if one stands against a wall and forcefully pushes the hand of the stiffly extended arm against it, then relaxes the contracting muscle group and steps away, the arm slowly rises toward a horizontal position. The subject who is performing this experiment for the first time, in complete ignorance of the expected result, is usually surprised
SAPIRSTEIN MR, HERMAN RC, WECHSLER IS. MECHANISM OF AFTER-CONTRACTION: FURTHER STUDIES. Arch NeurPsych. 1938;40(2):300–312. doi:10.1001/archneurpsyc.1938.02270080084004
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