<i>Bodies are like machines, if you use them a lot they will wear out because of over-use.</i><p>This is a poor analogy. Bodies can heal (i.e. regenerate tissue). Machines cannot. If this analogy was true, ultra-marathoners would be wearing out their joints rapidly. That&#x27;s not what is being observed though.<p>What is true is that you can injure joints by increasing the workload too fast. Joints can strengthen and adapt to increased loads but it happens slowly. So don&#x27;t go from running 5 miles per outing to running 10 miles. Limit yourself to a gradual increase.<p><a href="http:&#x2F;&#x2F;journals.plos.org&#x2F;plosone&#x2F;article?id=10.1371&#x2F;journal.pone.0083867" rel="nofollow">http:&#x2F;&#x2F;journals.plos.org&#x2F;plosone&#x2F;article?id=10.1371&#x2F;journal....</a><p><a href="http:&#x2F;&#x2F;content.time.com&#x2F;time&#x2F;health&#x2F;article&#x2F;0,8599,1948208,00.html" rel="nofollow">http:&#x2F;&#x2F;content.time.com&#x2F;time&#x2F;health&#x2F;article&#x2F;0,8599,1948208,0...</a>