Kohnstamm's phenomenon

First described by German neurologist Oskar Kohnstamm (1871-1917) in 1915, Kohnstamm's phenomenon is a sustained involuntary contraction of a muscle after a prolonged voluntary contraction. The simplest demonstration is to have a subject press against the wall by abducting the arm and then ask to step away from the wall. The arm will involuntarily rise.

Russian scientists Victor Gurfinkel, Mikhail Lebedev and Yuri Levick used Kohnstamm's phenomenon to activate tonogenic structures in humans and thereby demonstrate postural automatisms, such as neck reflexes.