The data was collected for the TRIAL: TRansitions Into Active Living study funded by NWO (grant no.: NWA.1160.18.249). The original aim of the this study was to examine the influence of the life transitions ‘starting to work’ and ‘becoming a parent’ on physical activities and sports. In wave 1 (this codebook) we established a baseline of sports and daily physical activities of persons that could be ad risk to start their first real job at the labour market or become parent for the first time. In addition, we mapped the sports career of people from primary school until their first job and / or child if they already make the transition to work and / or parenthood. In wave 2 (October 2022) and wave 3 (October 2023) we hope to include transitions of respondents who started their first job and / or become parent for the first time. Be doing so we can actually see how this affect sports and daily physical activities, which could be explained by the other variables collected.