Hiking is a popular outdoor activity that if practiced regularly, can bring significant health benefits. Moreover, considering that hikers range from expert mountaineers to older adults with limited physical capabilities, it touches a large target audience, and is strategically included in several tourism packages across the globe. Thus, a precise characterization of the tracks, especially regarding their points of difficulty, is crucial to effectively cope with the challenge of identifying the best-suited hiking trails for heterogeneous users. This paper introduces a semantic model for representing and integrating the main characteristics of a track, including their different types of difficulties, using Semantic Web ontologies. The construction of knowledge graphs that use such a model may constitute a first step towards a system for personalized recommendations of trails based on difficulty-classification criteria.