As an ultra runner in his 40s, Mike Morton -- an Army Green Beret -- shows a resolve and toughness that is unique even among the die-hard ultra-running community

From the very first time he ran an ultra marathon, Mike Morton showed a relentless resolve to keep churning and to keep pushing himself to his limits. Now in his 40s after having to take several years off from distance running because of multiple deployments to Iraq and Afghanistan as one of the Army's Green Berets, Morton has been a dominant force in races of 100 miles and longer. My story for ESPN.com's Endurance Sports section: http://espn.go.com/sports/endurance/story/_/id/10072374/endurance-sports-combat-lessons-transfer-ultra-running-green-beret-mike-morton