Research suggests that a considerable amount of children and adolescents drop out from sports when they grow older [1, 2]. Consequently, by the end of elementary school a considerable amount of children does not meet the health-related recommendations of sixty minutes or more moderate to vigorous physical activity (MVPA) per day . Sports are considered one specific form of PA that contributes to children’s and adolescents’ overall engagement in MVPA . When compared to other forms of physical activities, sports participation typically involves physical exertion and skill development, and the competition of individuals or teams against one another . In order for more children to meet the health-recommendations regarding PA, the need arises to develop and implement promotion strategies for an active lifestyle, with the promotion of sports participation among children and adolescents as one possible strategy.
Schools are considered to be ideal settings for implementing such promotion strategies since children of all socioeconomic backgrounds spend considerable amounts of time at school. Furthermore, while required educational training degrees differ between countries, in most countries teachers are required to have a teacher education degree and most school are equipped with the necessary facilities to provide PA opportunities [6–8]. Although Physical Education (PE) is acknowledged to be an important intra-curricular medium within the school context for the promotion of sports participation among youth [9, 10], PE hours in most school curricula are limited, and in many countries not mandatory . Furthermore, within the limited curricular time, physical education’s diverse learning objectives are not exclusively related to promoting PA and sports participation. Within the school-community context possible additional sources for PA opportunities, including sports participation, thus need to be explored .
Due to considerable differences between different educational systems, various terms are used interchangeably within the literature to describe possibilities for school-based sports activities outside the PE curriculum (extracurricular school-based sports). Most authors apply the term extracurricular school-based sports when referring to the provision of activities at school outside the formal PE curriculum, most often during after-school hours and lunch breaks [13–15]. In the current paper, extracurricular school-based sports are defined in a similar way: ‘all sports activities not included in the curriculum but organized by the school either during lunch break, during after-school hours or on Wednesday-afternoon (typically a free afternoon in Flemish elementary schools) in which pupils can voluntarily participate’.
Extracurricular school-based sports are considered to be easily accessible in terms of location and costs. They usually involve participation together with class- or schoolmates and are generally less competitive when compared to organized community sports which makes participation not limited to sports-talented children . Hence, in such a context, extracurricular school-based sports programs are typically put forward as programs that reach those children who are not participating in community sports . This is different to the situation in the US, where extracurricular school-based sports can sometimes be selective and highly competitive in nature . Despite these positive inclusive features of extracurricular school-based sports, little research has been conducted to explore which children participate in extracurricular school-based sports programs, and whether such programs indeed reach children who are not active in community-based sports. Hence, the first aim of the present study was to investigate how many children not engaging in community sports do participate in extracurricular school-based sports programs.
There is already some evidence suggesting that the provision of PA organized at school is effective to increase children’s activity levels, with children being more physically active if there is an extensive PA-offer at school [19, 20]. According to Powers et al. , pupils’ PA-levels at school could be improved by increasing the participation, duration, and frequency of existing programs and by implementing programs before school and at lunchtime. The potential of such programs for the promotion of PA among adolescents is also acknowledged by other authors [15, 21, 22]. However, in most of these studies, it is not clear whether certain groups of pupils, characterized by common demographic (sex, age, SES), psychosocial (e.g., motivation, social support) or behavioral (e.g., participation in community sports) characteristics are more or less represented in extracurricular school-based sports, and whether pupils participating in extracurricular school-based sports are overall more or less active than their non-participating counterparts. Pupils who participate in extracurricular school-based sports are physically active during the time spent in extracurricular school-based sports but it is not clear whether they are more or less physically active outside these extracurricular school-based sports. Consequently, a second purpose of the present study was to investigate whether the group of pupils participating in extracurricular school-based sports differs from other groups (not participating in any organized sports or participating in community sports) in terms of overall activity levels.
Besides differing in PA-levels, children participating in extracurricular school-based sports might also differ from those not participating in extracurricular school-based sports in their motivation towards sports. Specifically, some pupils might be optimally motivated toward sports, but not get the chances (e.g. no parental support) to participate in sports outside the school context . For this group of pupils, participation in extracurricular school-based sports might provide the only extracurricular opportunity to be active. Hence, a third aim of the present study was to investigate differences in motivation towards sports between children participating in extracurricular school-based sports and children not engaging in any form of organized sports.
In the present study, the concept of motivation was approached from the perspective of the Self-Determination Theory (SDT) . This macro-theory of motivation provides an understanding of why people initiate and persist in behaviors  and distinguishes between autonomous motivation, controlled motivation and amotivation for sports. Autonomous motivation involves the regulation of behavior with the experiences of volition, psychological freedom, and reflective self-endorsement and is considered the most optimal form of motivation . The second type of motivation is controlled motivation, which refers to the pressured engagement in an activity. Autonomous motivation and controlled motivation are contrasted with amotivation, which exists when people lack intentionality or engage in behaviors for unknown reasons . For example, an amotivated pupil claims to have no idea why he should bother participating in extracurricular school-based sports. Hagger et al.  examined the relation between motivation for PE and motivation for sports in leisure time, outside the school. However, the relationship between extracurricular school-based sports participation and motivation towards sports has, to our knowledge, not yet been investigated. If we find that extracurricular school-based sports programs mainly attract those children who are already autonomously motivated towards sports, and furthermore there remains a large group of children that is not optimally motivated and is also not reached, the question arises how the promoting role of extracurricular school-based sports can be optimized so that groups with less optimal motivational profiles are reached.
In summary, the primary aim of this study was to investigate how many pupils not engaging in community sports do participate in extracurricular school-based sports. The second aim was to assess if extracurricular school-based sports participants were more physically active in daily life than children who do not participate in extracurricular school-based sports, while controlling for their participation in community sports. The last aim was to evaluate whether children who participate in extracurricular school-based sports, compared to those who do not, are better (i.e., more autonomously) or relatively worse (i.e., more controlled) motivated or amotivated to participate in sports in general. As the transition from childhood to adolescence is known to be a risk-period for decreased PA and sports participation [28, 29], the target group of the current study consisted of children of the last two grades of elementary school.