In total, 745 football players aged 14–21 years from elite teams within all clubs participating in the NPL, participated in this study. The data of 27 players were removed due to incomplete responses of all variables, leaving 718 players (Mage = 16.2, SD = 1.8) available for further analyses (see Table 1 for sample overview). The statistical analyses were divided into three main sections (see chapter on Statistical analyses). For the first section all players in the sample were included. For the two other sections, the players were categorized into two groups based on their current contract status (professional or non-professional)