Longitudinal study tracks activity load in a single player progressing from grassroots to professional football in Norway.

While former studies into talent development in football have considered elite clubs and retrospective studies, this single-case study provides detailed data on the training activities of a 13-year-old male football player in a grassroots club who later became a professional at the highest level in Norway. An intrinsic longitudinal single-case study design was adopted to develop an in-depth, contextually grounded understanding of the load and forms of physical activity within and beyond organized football as performed and experienced by one specific player over the course of a full year in a grassroots football environment. The empirical material includes daily logging and categorization of all activities in a training dairy, with notes provided by the player - and supplemented with in-depth semi-structured interview with the player. The dataset comprises 733 h of activity over one year, the majority of which consisted of organized football-specific activity (team training: 196 h; matches including warm-up: 84; private football academy training: 110). In addition, the player engaged in 157 h of unorganized football (alone: 79; with friends: 78), sport-related school activities (physical education: 59; unorganized football play in the schoolyard: 28), and 99 h of individual non–football-specific training such as strength training, injury-prevention exercise, and recreational activities including cross-country skiing and family leisure. This case from grassroots football demonstrates substantial variation between deliberate practice and deliberate play. Two categories that are conceptually distinct yet appear equally important in the developmental pathway. At the same time, some training forms represent a blend of play and practice. For instance, unorganized football with friends in this study displays several characteristics typically associated with deliberate practice, whereas team training with a coach also contains elements of play.