Tyrese Cooper lowered his own U.S No. 1 400m to 45.38 at the Great Southwest Classic. <br /><br />Cooper is chasing after Obea Moore's national high school sophomore class record of 45.14.<br /><br />Website: http://milesplit.com <br />Subscribe: http://bit.ly/2oJSZDS<br /><br />Follow MileSplit<br />Facebook: https://www.facebook.com/MileSplit <br />Twitter: https://twitter.com/milesplit <br />Instagram: https://www.instagram.com/milesplit/
