Resumen:
The analyses of ultraendurance athletes have provided new insights into the limits of human performance capacity and into medical complications when going beyond the physical limits. Ultradistance running poses a unique stress on the athlete. In their Viewpoint, Millet et al. (3) argued that determinants of performance in ultraendurance are subjected to a compromise between two main parameters: energy cost and lower limb tissue injury. The latter results from a complex combination of extrinsic factors (training errors including lack of specific strength, inappropriate footwear, inappropriate running surface, and terrain) and intrinsic factors (poor flexibility, biomechanical lower extremity malalignment, anthropometry, previous injury, running experience). Concerning the former, environmental conditions, training, and perhaps most importantly fluid and fuel intake all contribute to energy balance state and so race performance. In fact, nutrient intake during ultradistance races has been found to be below the estimated energy cost (1). Despite a low relative intensity the energy cost of running (expressed in mlO2) is increased during ultradistance trail running races (2) compared with level runnin...