80 | Chapter 1 3 spare time becomes more constrained as well, as couples must try to blend their individual schedules to find ways to sleep, interact and in general spend time together (Kraaykamp et al., 2009; Moen, 2003). This leads to additional time restrictions, despite the economy of scale, which makes it more difficult to find empty time slots to practise a sport, especially within a sport club. Social resources increase as well, as cohabitation and marriage lead to a stronger relationship and more contact not only with one’s partner, but also with his or her social network (e.g., family, friends and acquaintances). Because of this increase in social resources and obligations, social payoffs of sport participation are believed to become less important, and the likelihood of giving up sport activities in order to participate in (more or less mandatory) partner-related social activities increases. Because of the increase in time restrictions and in partner-related social resources, we expect that starting to cohabit or getting married increases a young adult’s risk to stop practising a sport and end a sport club membership. Lastly, we turn to childbirth. The birthof a child leads not only tomore household work for parents, but also to new tasks and responsibilities, such as caring for and raising the new-born. Hence, the amount of spare time decreases, reducing opportunities for sport participation (Blum et al., 2004). With respect to social resources, most new parents are committed to building a strong relationship with their child. This places them in contexts where they meet and spend time with others in a similar position, for example, at childbirth classes or day-care centres. These interactions offer new child-related activities that compete with sport activities, particularly when leisure time is scarce. In sum, reduced temporal resources and increased child-related social resources lead us to expect that the birth of one’s first child increases a young adult’s risk to stop practising a sport and end a sport club membership.