The current study was the first to examine associations between participation in organized sports and objectively measured PA and ST outside preschool time, during preschool time and throughout the day in preschool-aged children. Our findings showed that approximately 50% of children participated in organized sports for 1 or more hours/week. Participation in organized sports was positively associated with children’s MVPA and steps outside preschool time and throughout the whole day. There was no association between participation in organized sports and PA during preschool time. Thus, findings from the current study do not support a PA compensation in preschool children participating in organized sports.
Studies in school aged children and adolescents have shown a positive association between participation in organized sports and children’s accelerometer measured PA throughout the day (33–35). Previous studies have also shown a significant interaction between organized sports participation and sex on children’s PA (34–36). Results from the current study showing that organized sports participation was associated with 6.0 minutes (10%) more MVPA throughout the day, and potentially a greater association in boys compared with girls, are in line with those presented in above-mentioned studies. The activity-stat hypothesis is supported by several exercise intervention studies in older children (school aged), showing a compensation in PA (17). In contrast, results from the current study show that preschoolers who participate in organized sports are equally active as those who do not participate in organized sports during preschool time and more active both outside preschool time and throughout the whole day.
Given the low and decreasing levels of PA among young children (5, 37), it is important to find effective strategies to increase young children’s PA. Meta-analyses data of trials examining the effectiveness of interventions to increase PA in children show minor treatment effects; adding up to approximately 4 minutes of additional walking or running per day (38). Although the results from this cross-sectional study cannot be compared to results from that of interventions, the 6.0 minutes (10%) more MVPA associated with participation in organized sports is a practically significant difference which may warrant further intervention studies of organized sports in preschool children. This finding, in combination with the positive effect participation in organized sports may have on the tracking of PA from childhood to adulthood (4), supports early life participation in organized sports as a strategy to achieve higher levels of PA throughout childhood, adolescence and adulthood. The higher PA level, potentially resulted from participation in organized sports, can further benefit a wide range of health indicator in preschool children comprising bone strength, motor development, fitness and psychosocial health (1). However, the observational and cross-sectional nature of the current study can only provide evidence of a positive association between organized sports participation and PA throughout the day in preschoolers. A randomized controlled trial in preschool aged children is warranted to examine if the associations observed in the current study hold.
A strength of this study was the accelerometer measured PA which limit several biases associated with self-reported measures, e.g. social desirability and recall difficulties. Second, the time-stamped accelerometer PA data and detailed daily data on time at and outside preschool enabled us to assess the association between organized sport participation and PA levels during preschool time, outside preschool time and throughout the day. Third, in the aspect of obtaining organized sports participation information and objectively measured PA data, the current study included a fairly large number of children in a previous unstudied age group.
Limitations of our study include that information on organized sports participation relied on parental self-reporting, which has several inherent biases and we did not take type of sport performed into account. Second, the observational and cross-sectional nature of the study preclude any inference about causality, and we cannot rule out that our results may be explained by unmeasured confounders or reverse causality, i.e. children who are more active chose to participate in organized sports and not vice versa. Third, although accelerometry is considered as a desirable measurement of PA among preschool aged children in free-living conditions, hip-worn accelerometers are unable to detect some types of PA, e.g. cycling, swimming or PA involving upper body movements (39). Forth, by using the normal filter to process accelerometer data we may have underestimated children’s number of steps taken per day. Fifth, the sample of preschool children was selected based on acceptance of the invitation from the invited children and parents which could potentially influence the generalizability of the study. Finally, the study population was homogenous in terms of socio-economic aspects and urbanity. This is of importance as participation in organized sports may be associated with household finances due to high costs for many of these activities. Consequently, our results have limited generalizability to rural and lower socioeconomic areas.