Ultrarunners Longitudinal TRAcking (ULTRA) Study For a research project, Prof. Martin Hoffman from the USA is looking for Ultralaufen, which has now completed at least one ultramarathon of more than 50 km. In his project, it’s about the question of whether the training for UltraNauf has a positive or negative impact on health.After completing the online questionnaire, the subjects will be questioned in periodic intervals for their health. The study can be found under https://clinicaltrials.gov/ct2/show/nct02014038