This study uniquely describes, using a large sport participation cohort, the participation patterns of young children in three sports and their withdrawal or transition from modified sports programs into club sport competitions. It is clear that most children do not transition from the modified sport program into club sport competitions in the same sport. However, there are a number of differences across age and sex.
This study showed that a high proportion of modified sport participants were young, especially males (4–6 years). Most did not transition to the affiliated club sport competition within a 4-year period; indeed, two-thirds of those who withdrew from modified sports programs did so immediately after the base year of the study, from which it is conjectured that many had only a single year/season of participation.
It is reported that young children tend to ‘sample’ sports during the ‘sampling years’ when they are given a range of different sports activities to ‘try out’ and through which they can develop fundamental motor skills . As children age they tend to specialise (‘specialising years’) and focus on just one or two sports after which they either move to the ‘investment’ or ‘recreational’ years . In light of sampling behaviour, high withdrawal rates from modified sports programs are perhaps to be expected, and as such these results may not necessarily indicate a problem. From a public health perspective, if early registration in a modified sport program fosters prolonged participation in any form of physical activity, it does not matter what ultimate form that takes. Of course, sports organisations may have a narrower self-interested focus. Sampling (also known as early diversification) has been linked to long-term sport involvement, and it is recommended that sport programs encourage early involvement in different sports and contexts . Further, it is posited that children who sample a variety of sports are exposed to unique socialisation experiences that shape personal development and social capital outcomes including intrapersonal skills, pro-social behaviour, healthy identity and diverse peer groups .
Regardless of whether it be through sampling or continuing in the one sport, there are considerable benefits if children can play sport continuously, instead of dropping out altogether. Recent literature suggests that children (aged 6–9) who participated continuously (over 3 years) in a club environment had better coordination levels than those who were discontinuous or did not participate at all . Furthermore, the basic level of motor coordination and the amount of club sport participation significantly predicted sport participation two years later . These outcomes have implications for elite pathways (investment years), as well as health-related benefits of sport participation (recreational years) in childhood and throughout the lifespan .
Whilst this study represents only three (albeit popular) sports, for these sports, very young males (ages 4–6) represented a much higher proportion of all male participants (72.5 %) than was the case for females (30.2 %). This may be linked to consistent reports of lower sport participation rates among females [19–21]. For instance, there is evidence that parents provide sons with more opportunities for sport participation than daughters . Verbal encouragement, support, and active participation from family members has been reported to help girls be physically active, along with strategies that focus on peers, the school and community to shape positive perceptions and attitudes towards girls’ participation in physical activities . It is important that girls are provided with opportunities to develop their motor coordination early, as the critical developmental period for motor development is before the age of five or six .
The present study also found that as a result of males being engaged in modified sport at earlier ages, the peak age of transition from a modified sport program to club sport competition was lower among males (7 years of age in the base year) than females (10 years of age). This may be because males perceive that they have become competent in the modified sport and are ready for competition, or perhaps they become ‘bored’ with the modified sport program and seek new challenges. Whilst transition to club sport competition does not necessarily mean that these children are ‘specialising’ in the sport, it is likely to involve/require higher levels of challenge and engagement than a modified sports program. Many club sport competitions involve training as well as competition, additional costs associated with memberships and uniforms, and additional costs and time associated with travel to games. As a result of these increased demands, it is likely that these children may be starting to move from sampling to specialising at early ages. It has been suggested that specialisation should not occur before the age of 13 in sports where peak performance is reached in adulthood , particularly as sampling provides opportunities to develop physical competencies and perceptions of competence which lead to motivation for continued participation . Interestingly, the peak rate of sport participation for both males and females in Australia has been reported to occur at around 11 to 13 years of age. Eime et al.  reported peak sport participation in five popular Australian sports at 10 and 11 years for boys and girls respectively. Other researchers have reported slightly higher sport participation peaks at ages 12–13 years in a national sample, and a decline of 50 % by age 16 .
This study extends the findings of others who have reported that boys are more active than girls , and highlights the fact that, at least in the three sports examined, boys tend to participate in organised sport much earlier than girls, and as result seek new challenges much earlier. However, it is possible that the available challenges may not be providing an environment that promotes lifelong involvement in sport for both boys and girls  as this study found that most participants of both sexes tend to withdraw from a particular modified sport program rather than transitioning into club competition in the same sport.
Modified sport programs are designed for children aged 4–12, however this current study has identified that many children participating in these programs are in the lowest part of the age-range (4–5 years). Given the developmental capacity required to play competitive club sport, perhaps very young children are getting bored after 1–2 years, but may not be old enough to play club competition, so they either drop-out of sport altogether or sample to another sport. Therefore for continued participation in a given sport, an intermediate program in the sport participation pathway may be required. An example is Tennis Hot Shots Leagues which is aligned to the modified program and provides children with a chance to practice their skills in a modified competition structure, with modified balls and scoring .
The drive for children to focus on higher levels of engagement in sport at earlier ages may also influence their perceptions of competence. Children’s perceptions of competence in late childhood (ages 8–12) is largely the result of comparison with their peers . Comparisons of motor skill proficiency and physical activity performance are commonly reported as factors influencing non-sport participation, and are often influenced by peer teasing [23, 29, 30]. One study reported that adolescent girls perceived sports clubs as being exclusively for skilled participants, which regulated their non-participation in this setting (Casey M, Mooney A, Smith J et al. Power, regulation and physically active identities: The experiences of rural and regional living adolescent girls. Gender and Education 2014, Under Review). Others have also reported that the dominance of particular sports activities, particularly in regional and rural communities, can significantly limit the meanings constructed about being physically active, whereby some sporting activities are considered the privilege of the skilled, attractive and popular social elite . If children are transitioning to club competition at early ages (7 for males and 10 for females) they may be participating with children who are older and who have greater physical competency, and consequently impacting their perceptions of competence and subsequent motivation for continued participation. Further, the modified sports programs investigated in this study are often delivered unisex, and therefore do not take into account differences between sexes. This study showed that boys and girls tend to start and withdraw or transition from the modified sports programs at different ages, whilst other studies have reported sex differences in the acquisition of motor skills for children . Therefore, the same program may not be suitable for both boys and girls of similar ages, as their level of competence and mastery of fundamental motor skills are likely to differ.
This study had a number of limitations. The findings of this study were limited to only three Australian sports, albeit popular ones, and cannot necessarily be generalised to sports in general. Two of the three sports were dominated by males and one by females, although this imbalance did not limit our ability to identify sex differences in the patterns of participation. Data limitations and anonymity provisions precluded us from identifying or quantifying the proportions of participants in multiple sports in the base year or those who transferred into a different sport in later years. According to a recent national survey , 28.6 % of Australian children aged 5–14 years (34.8 % of boys and 22.2 % of girls) reported playing more than one sport in the 12 months prior to interview; however this included all sports, compared with only three sports in the present study, and much of it would be attributable to participation in different sports at different times of the year. Further, we assumed that non-registration in a later year implied withdrawal from the particular sport, whereas a proportion of assumed withdrawals may have migrated interstate but maintained their participation in the sport; however, considering that outward migration in 2010–11 amounted to 1.1 % of the Victorian population [33, 34], the effect on our conclusions is minimal. A strength of the study was its inclusion of the total population of participants in three representative modified sports in a large sub-national region. Future research should examine a range of modified sports programs and club sport competitions to better understand participation and withdrawal trends and to understand the socio-ecological factors influencing children’s participation, transition and withdrawal from modified sports programs.