Edmund Jacobsen, the renowned physiologist, demonstrated extensively that when people imagine body movements, the motor nerves in these areas actually fire and the muscle fibers contract. These movements, called micromovements, can be very subtle, but even if they are not visible to the eye, they can be picked up by electromyographic machines. This response is remarkable in itself, but even more interesting is the fact that the body builds nerve circuits, that is, it “learns”, based on imagery exercises that result in micromovements. This learning is the basis of the imagery exercises that athletes use to improve their performance.
When they picture successful completion of an activity, their performance actually improves. The micromovements improve the athletes’ performance as they increase the athletes’ confidence in their ability to perform. Imagery has also been shown to have immediate physiological effects on body systems other than the muscles. It directly affects the gastrointestinal tract…imagery affects virtually every organ in the body
(Samuels, Michael. Healing with the Mind’s Eye, 2003, pp. 73-74)