La performance sportive est influencée par de nombreux facteurs, lesquels s’influencent eux-mêmes réciproquement. La complexité de ces facteurs et de leurs relations ayant été négligée par les chercheurs, l’objet de la présente thèse était de rendre compte de cette complexité, à l’aide de méthodes empruntées à l’approche dynamique. Nous avons pu montrer que (a) les joueurs de football les plus experts construisent leur représentations du jeu en cours (les liens entre actions réalisées sur le terrain) avec des niveaux de complexité les plus élevés; (b) en aviron, une organisation motrice complexe, impliquant des interactions entre de nombreuses composantes, sous-tend la génération des mouvements de rame en cours; (c) le momentum psychologique en aviron se caractérise par des changements psychologiques et de performance qui s’inscrivent dans l’histoire de la performance; et (d) la performance excellente se développe à partir des interactions en cours entre les facteurs personnels et environnementaux couplés. Ces différents éclairages montrent l’intérêt d’une approche de la complexité pour comprendre les processus de performance. / The processes involved in human performance seem inherently complex and dynamic. For example, in order to “read the game”, a soccer player must integrate all the information from the ongoing movements and positions of team members, the opponents, the relative positions between them, where the ball is located, etc. Furthermore, an individual’s motor performance, which is particularly crucial in sports, depends on various simultaneous processes at different levels of the motor system: Cells, muscles, limbs, the brain, etc. In addition, individuals and teams do not perform in a void, but in achievement contexts, in which they strive for their goals, and their psychological states and performance may fluctuate as a function of many personal and environmental factors. For example, an athlete may enter a positive or negative spiral when perceiving that he or she is progressing or regressing in relation to the preferred goal or outcome (e.g., the victory). This perception of progress and regress, and the positive and negative psychological and behavioral (performance) changes accompanying this perception, are called positive and negative psychological momentum (PM; e.g., Gernigon, Briki, & Eykens, 2010). Positive and negative PM can emerge from one’s (or the opponent’s) mistakes, referee decisions, crowd behaviors, one’s psychological and physical state at a certain moment, and the interactions between these factors (Taylor & Demick, 1994). In addition, switching from performance on a relatively short time frame to a long-term process, individuals develop their abilities over multiple years, and hence over many practice or competition occasions. Ultimately, very few individuals develop world-class performance (e.g., winning Olympic medals), and their excellent abilities develop out of a combination of a variety of personal and environmental factors in interaction (e.g., motivation, coaching, family support, practice; Simonton, 1999). The current dissertation aims to capture complex dynamic performance-related processes, including the topics illustrated above. This means that we examine complexity at different levels (psychological, behavioral), time scales (from one training or competition session up to a career), as well as the interrelation between the processes across different levels and time scales.