Regular exercise is supposed to be as necessary for the brain as for the body, and <b>in both cases it is not so much what we do as the doing of it from which we derive benefit. </b><br/><br/><i>-excerpt of "The Canterbury Puzzles" page 4 (</i><a href="http://www.mymathforum.com/books/thecanterburypuzzles/1/4.htm"><a href='http://www.mymathforum.com/books/thecanterburypuzzles/1/4.htm' target='_blank' rel='nofollow'>http://www.mymathforum.com/books/thecanterburypuzzles/1/4.htm</a> </a>)<br/><br/>What does the text in bold mean?