Buchholz and Artinian (2009) defined physical activity and categorized it into three levels: low, moderate, and high. Triathlon as an activity that typically combines swimming, cycling and running in one event, belongs to high level and is considered as a hard discipline, requiring frequent, well-planned training. The three sports are performed consecutively with no breaks. As recreational athletes show a growing interest in long-distance events, and the participation in triathlon is increasing, the aim of this article is to try to understand the popularization of such a difficult sport as triathlon. The research question is what motivates people to participate in triathlon and why people feel this strong need to participate in such exhausting sports competition? It was decided to look for answers to the research questions in the available literature on the problem and in the review of research on participation in triathlon. It turns out that the basis of most of the considerations was the Self Determination Theory. Many authors have referred in their research to the Motivations of Marathoners Scale (MOMS).