Piezoelectric Effect Basics
A piezoelectric substance is one that produces an electric charge when a mechanical stress is applied (the substance is squeezed or stretched). Conversely, a mechanical deformation (the substance shrinks or expands) is produced when an electric field is applied.'
From: http://www.aurelienr.com/electronique/piezo/piezo.pdf
An area that has Qi flowing into it, by one trained in internal Iron Shirt; can have the area strengthened by this force running through it. This is a piezoelectric effect.
A similar analogy, is trying to bend a fire hose while water is running through it; you cannot.
‘We must look at what modern Western science has discovered about bioelectromagnetic energy. Many bioelectricity-related reports have been published, and frequently the results are closely related to what is experienced in Chinese Qigong training and medical science. For example, during the electrophysiological research of the 1960's, several investigators discovered that bones are piezoelectric; that is, when they are stressed, mechanical energy is converted to electrical energy in the form of electric current. This might explain one of the practices of Marrow Washing Qigong in which the stress on the bones and muscles is increased in certain ways to increase the Qi circulation.
It is understood now that the human body is constructed of many different electrically conductive materials, and that it forms a living electromagnetic field and circuit. Electromagnetic energy is continuously being generated in the human body through the biochemical reaction in food and air assimilation, and circulated by the electromotive forces (EMF) generated within the body.’
A Modern Definition of Chi, by Dr. Yang Jwing-Ming, August 2nd, 2011