Forcing Left and Right at Full Speed

The offense should be able to move back and forth and left and right.  The distance between the offense and the defense is three yards. The drill lasts for 30 seconds with the offense switching to defense at the end of 30 seconds.  Now, have the offense line up head to head with the defense.  The offense moves side to side only.  The defense attempts to stay on front of the offense.  Repeat this drill for 30 seconds and then switch from offense to defense.