One of the basics of Tohei Sensei's teaching is to lead the mind rather than force the body. He often expressed it as "if mind moves, body moves." This is true of receiving a Ki test and in performing an Aikido technique. I have been musing on this more recently, especially since we were practicing "painless" nikkyo techniques at the National Ki Conference. Scientists are also doing research that is creating a lot of good questions about how the mind works. There is a great article about this in yesterday's New York Times.
Here is a link to the article. The best research always ends up with more questions than answers. This is certainly true of the research mentioned in the article.