Sports stars turn out for Michelle Obama's 'Let's Move' event in Chicago

<div class="meta "><span class="caption-text ">Serena Williams on stage with first lady Michelle Obama at the &#34;Let&#39;s Move&#34; event at McCormick Place in Chicago, Thursday, February 28, 2013.</span></div>
February 28, 2013 10:49:23 AM PST