The most important variables in marathon performance are based on a combination of physiological, anthropometric, nutritional, motivational and training factors. This key information for assessing performance in a long-distance running race, which involves considerable psycho-physical effort, is acquired partly in sports medicine centres and exercise physiology laboratories, and partly directly in the field. Domenico Carlomagno, sports and fitness trainer at the Mapei Sport Research Centre, tells us about this in this first of three videos in the Cubetti di Sapere series dedicated to marathons.