- Involuntary arm abduction that follows sustained isometric contraction of the deltoid and supraspinatus muscles (usually performed by pushing the upper extremity forcibly and against an immovable vertical surface while standing closely beside it). SYN: Kohnstamm phenomenon.
* * *af·ter·move·ment (af″tər-mvґmənt) spontaneous elevation of the upper limb by idiomuscular contraction after benumbing it by powerful pressure against a rigid object; called also Kohnstamm phenomenon.
Medical dictionary. 2011.