That is exactly what I am suggesting. Well parts of the muscle are in a rotating fashion. The MUs that are activated rotate around to save energy. It is what allows us to maintain posture and limb control automatically. I have primarily read about it via Exercise physiology text books from ACSM and Human Kinetics, but it is also used in medical dictionaries and I have witnessed it first hand in lab settings.
A quick google brings this up (link below) which just touches on it for a sentence:
http://users.rcn.com/jkimball.ma.ult...M/Muscles.html
It may be easier to look up residual muscle tension if you are looking for scholarly articles.