The Concepts of Functional Range Release

"Force is the language of cells.  Whether those forces are applied by external means by way of soft tissue therapy application, or internal means by way of active muscle contraction and movement, the cells ultimately don't know the difference.  They simply receive "communications (forces) from the environment, and then adapt to those message accordingly."

Dr. Andreo Spina

Here is a very cool article called From Athletes to Couch Potatoes.  It talks about how losing loading episodes (hunting etc..)  leads to less mobile and weaker bones in the legs.  Again, the force (language of cells) has been removed.  Less bone mass and strength and mobility.  You can read the article in about 5 minutes.  I highly recommend.