The objective of this paper is to analyze the actors’ interactions around this tourism diversification process based on outdoor sports, and in particular trail running, in the Pays of Allevard. To understand the tourism diversification process, it is necessary to analyze the way the local actors use the sport, take ownership of it, and transform it according to their interests, in particular to make it a tourism resource. The results show that the actors supporting the diversification project all practice the sport in question, and therefore have an interest in its development. Thus, trail running was considered as a godsend by certain economic actors, enabling them to offer new services. Sport therefore becomes an economic resource, but also a communication and territorial marketing tool when the objective is to rejuvenate the image of the territory. However, certain local elected officials question the relevance of this diversification project, whose economic impacts remain difficult to quantify. Moreover, this opposition to the development of a new sports activity within the destination illustrates the resonance of traditionalism with respect to the management of a territory. And disagreements concerning the positioning to be adopted make it difficult to construct a tourist identity for the destination.