This is an illustration of how actin generates force by volume expansion in amoeboid motility.  See my &lt;a href="<a rel="nofollow" class="external free" href="http://network.nature.com/blogs/user/rpg/2008/04/03/my-spaghetti-takes-up-more-room-than-yours">http://network.nature.com/blogs/user/rpg/2008/04/03/my-spaghetti-takes-up-more-room-than-yours</a>" rel="noreferrer nofollow"&gt;weblog&lt;/a&gt; at <em>Nature Network</em> and &lt;a href="<a rel="nofollow" class="external free" href="http://www.pnas.org/cgi/content/abstract/0708416105v1">http://www.pnas.org/cgi/content/abstract/0708416105v1</a>" rel="noreferrer nofollow"&gt;www.pnas.org/cgi/content/abstract/0708416105v1&lt;/a&gt; for details.
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