Abstract

The Kohnstamm phenomenon occurs when continued use of a muscle causes involuntary movement of that muscle after relaxation, leading to a feeling of lightness in the limb. The phenomenon can be observed in the arms when one pushes the outside of the hand against a surface for a prolonged period of time and then relaxes, and the arm then involuntarily raises and the arm begins to feel incredibly light. This project measures muscular effort using force plates and records muscle activity via EMG to reveal more information behind the Kohnstamm phenomenon, as well as address the mechanisms in the human body contribute to the phenomenon. To quantify the effect, subjects were instructed to push against a door frame with force sensors attached, giving maximal effort for 30 seconds. Subjects repeated the experiment at two different frame widths (1.00m and 1.25m), which were presented in random order. While research is ongoing, our preliminary results found that the majority of subjects experienced the phenomenon, but about 15% of subjects did not. Most who experienced the phenomenon self-reported that the effect was greater at the narrower frame width. This observation, coupled with EMG analysis, suggests that the phenomenon occurs from re-engagement of shoulder muscles, especially the supraspinatus, following the end of the sustained contraction.

How to Cite