RT Journal Article SR Electronic T1 The problem with ultra-endurance athletes JF British Journal of Sports Medicine JO Br J Sports Med FD BMJ Publishing Group Ltd and British Association of Sport and Exercise Medicine SP 1085 OP 1085 DO 10.1136/bjsports-2011-090399 VO 45 IS 14 A1 Wortley, George A1 Islas, Arthur A YR 2011 UL http://bjsm.bmj.com/content/45/14/1085.abstract AB