In a situated-cognition framework, this article takes an ergonomic approach to describing and interpreting a user’s activity on a computer-assisted interactive learning environment. The environment was designed to improve sports instructors’ knowledge and understanding of some of the major issues in sports training. By focusing on the dynamics of the user-computer interaction, this exploratory study was aimed at validating the system prototype and proposing effective, user-friendly enhancements. The meaning the user grants to his/her actions and the organization of those actions are studied in reference to course-of-action theory. Observation data for a user was collected on-line and supplemented a posteriori by self-appraisal verbalization data. The results present a description and an explanation of the local and global organization of the user’s course of action. They demonstrate the complexity of his exploration and learning activity, how he activates and constructs knowledge during action, and his emotional states that alternate between feelings of apprehension, enjoyment, and effort. The implications of these results for the design of computer-assisted learning environments are discussed.