14 | Chapter 1 Wicker, 2009; Van Tuyckom & Scheerder, 2014) and beyond (e.g., in the U.S. and Canada, see: Humphreys & Ruseski, 2009, 2010). A limitation of most of these studies on determinants of sport participation, however, is that they lack theoretical rigour. As stated by Breuer & Wicker (2008), mostly, statistical trial and error procedures lead to significant determinants that have little theoretical basis and, consequently, do not explain why these factors influence sport participationmeaningfully. This often results in excessive or inadequately complex models, which are difficult to interpret and to use in practice, for example to develop sport policy and sport programmes or interventions. From age to life events. Sport participation over the life course Age is another important individual factor for sport participation, according to earlier research. In the Netherlands, as in other countries, overall sport participation rates are lower in older age groups than in younger age groups (European Commission, 2018; Pulles & Wendel-Vos, 2018). Practising sport at least 12 times a year and sport club membership are most common among children of 6 through 11 years old, with participation rate of 92% and 80%, respectively. In the age groups that follow, these rates decline (The Netherlands Institute for Social Research (SCP) & Statistics Netherlands, 2018b), as shown in Table 1.1. This Table also shows that 69.9% of Dutch youngsters aged 12 through 17 practise sport on a weekly basis, which is relatively more that the group of children aged 4 through 11. However, again, the rates drop in the following age groups (Statistics Netherlands & RIVM, 2020). Many cross-sectional studies still affirmthe traditional assumptionof decreasing sport activity with increasing age (e.g., Breuer & Wicker, 2009; European Commission, 2018; Hovemann & Wicker, 2009; Schoenborn & Barnes, 2002). A major drawback of these cross-sectional studies is that developments over the life course of individuals are not measured, and that it remains unclear if the identified differences in sport activity between age groups can really be ascribed to age effects (i.e., the effects of increasing age; getting older) (Breuer et al., 2010). Studies with a life-course perspective, employing more advanced data and using longitudinal or cohort sequence analysis, are much scarcer and reveal different and sometimes contradictory findings (Breuer et al., 2010; Curtis et al., 2000; Hovemann & Wicker, 2009; Jenkin et al., 2017). For example, Curtis et al. (2000) found positive correlations between age and sport activity in general, whereas Breuer & Wicker (2009) found positive correlations