The theme of the latest edition of the Hoogtelijn (mountaineering magazine of the Royal Dutch Climbing and Mountaineering Association) is Ultra – an adjective increasingly used in the world of endurance sports. You will read about a 12-hour climbing event, a mountain bike rally of 648 kilometers including 27,000 altimeters and about the Ultra Trail du Mont Blanc – a running race of 171 kilometers with no less than 10,000 altimeters. Marijn Sinkeldam, himself an enthusiastic trail runner as well as our colleague instructor of Wilderness First Aid (WFA) and WFA Mountain, writes in this same edition of the Hoogtelijn about the physiological effects and risks of these extreme sports performances (Dutch only).