I have read some references to this in books on proprioceptive neuromuscular facilitation and Voss and Knott are authors that first put this stuff into writing I think. The concept of irradiation is part of the theorectical framework for PNF. Check out Institute of Physical Art, continuing education courses and go to the required readings section and there are some free PDF articles on there that might help you, its been a little while since I have read this material but this might help you get some more answers. Hope this helps