Physical Activity Among Children Attending Preschools

METHODS

RESULTS

Means and SEs for time spent in sedentary activity, light physical activity, MVPA, and VPA are shown in Table 3. Boys exhibited significantly greater participation in MVPA and VPA than did girls. No significant gender differences were observed for time spent in sedentary and light activity. Compared with 3-year-olds, 4- and 5-year-olds exhibited significantly more sedentary intervals and significantly fewer light activity intervals. No age-related differences were observed for MVPA or VPA. Black children tended to be more physically active than white children; however, only the difference for VPA reached statistical significance. No differences in activity levels were observed among parent education groups.

The results of the regression analyses are shown in Table 4. For MVPA, model 1, including gender, age, race/ethnicity, BMI, and parent education, accounted for 4.3% of the variance in physical activity. The addition of the preschool in model 2 dramatically improved the prediction of MVPA, accounting for an additional 43.3% of the variance. In model 1, only gender and parent education emerged as significant predictors of MVPA. In model 2, gender, race/ethnicity, and preschool were significant predictors of MVPA.

For VPA, model 1, including gender, age, race/ethnicity, BMI, and parent education, accounted for 7.4% of the variance. The addition of the preschool in model 2 markedly improved the prediction of VPA, accounting for an additional 30.9% of the variance. In model 1, gender, BMI, and parent education emerged as significant predictors of VPA. In model 2, gender, race/ethnicity, BMI, and preschool were significant predictors.

DISCUSSION

A key finding of this study was that the preschool attended accounted for a substantial fraction of variance in child physical activity. This was true for both MVPA and VPA. Demographic factors such as gender and race were significantly associated with child physical activity, but the fractions of variance accounted for by these variables were small, compared with the fraction accounted for by the preschool. Mean minutes of MVPA, as measured objectively with accelerometry, varied from 4.4 to 10.2 minutes/hour among the 9 preschools included in this study. These findings indicate that physical activity levels of children attending preschools vary greatly among schools and, importantly, the characteristics of the school have a much greater influence on a child's activity level while in the school than do the child's personal demographic characteristics. These findings, which are consistent with those of Finn et al,¹⁹ are important because they suggest that school policies and practices directed toward providing preschool-aged children with physical activity have the potential to influence greatly the overall physical activity levels of young children in the United States, 56% of whom attend formal preschools.¹³

Recently released guidelines suggested that preschool-aged children should accumulate at least 120 minutes of physical activity per day, one-half of that time in structured physical activity and the remainder in unstructured, free-play settings.¹² The results of this study suggest that many preschool-aged children do not meet that standard. On average, the children in this study engaged in 7.7 minutes of MVPA per hour of preschool attendance (∼13% of observed time). Therefore, a child who attends a preschool for 8 hours would engage in ∼1 hour of MVPA. It seems unlikely that such a child would ordinarily engage in another 1 hour of physical activity outside the preschool setting. A factor that probably exerts a strong influence on physical activity in preschools is the time that children are allowed to play freely in settings that are conducive to physical activity, such as outdoor playgrounds or gymnasia. Previous studies with direct observational systems found that children engage in MVPA for ∼40% of the time they spend in outdoor recess,²⁰ a much larger proportion of time than the 13% observed for the entire school day in this study. Clearly, one potentially effective strategy for providing children with adequate physical activity is to provide them with appropriate amounts of time in recess and other free-play settings.

During the course of the preschool day, boys participated in significantly greater amounts of MVPA and VPA than did girls, similar to findings of other studies.^19,21–23 Currently, there is no definitive explanation regarding why girls participate in less physical activity than boys. The results of extensive meta-analyses suggest that sociocultural factors and not biological differences are primarily responsible for the gender gap in activity.^24,25 It is possible that gender differences in playing styles may account for girls' lesser participation in physical activity. Observational studies of preschool-aged children have consistently demonstrated that boys play in larger groups and in more open settings, engage in more risk-taking behavior, and play rougher games involving greater amounts of body contact than do girls.^26–28 Alternatively, girls may receive less encouragement from teachers and peers to engage in MVPA and VPA during the preschool day. However, previous studies examining physical activity behavior among preschool-aged children found no significant gender differences in prompts to be active.^20,22 Whatever the underlying explanation for the observed gender difference, our observation that 3- to 5-year-old girls participated in significantly less physical activity than did boys while attending preschool strongly supports the recommendation that efforts to promote physical activity among girls should begin early in life.^12,29 Additional studies are needed to identify the psychosocial and environmental factors that contribute to the gender difference in physical activity in the preschool setting.

Population surveys and descriptive epidemiologic studies have consistently observed children and adolescents from ethnic minorities to be less active than their white counterparts.^30,31 Few studies, however, have investigated the influence of race/ethnicity on physical activity behavior among preschool-aged children. In the study by McKenzie et al,²² Mexican American children were significantly less active and expended less energy than did their white counterparts in both settings (free play at home and during outdoor recess). Importantly, when home and recess activity levels were reexamined 2 years later in elementary school, Mexican American children continued to be less active than white children, which prompted the authors to suggest that racial/ethnic differences in physical activity might have their origins in early childhood.²⁰ In contrast to those findings, Baranowski et al²³ observed no significant differences in physical activity among white, black, and Mexican American children. In the present study, we compared the physical activity levels of white and black children during the preschool day. After controlling for the influence of preschool setting and other demographic variables, black children were found to be significantly more active than white children during the preschool day. This finding not only is in conflict with the results of previous preschool studies^22,23 but also is inconsistent with the results of previous investigations in which black elementary school children were found to be less active than their white counterparts.^32–34 Although the public health importance of our findings hinges on successful replication with larger, more representative samples of preschool-aged children, our observation of a significant racial/ethnic difference in physical activity during the preschool day raises several important questions for future research, including the following. Do racial/ethnic differences in physical activity levels during the preschool day generalize to other behavioral settings (eg, home)? What are the psychosocial and environmental factors that explain racial/ethnic differences in physical activity levels during the preschool day? What is the influence of race/ethnicity on the trajectory of physical activity behavior during the transition from preschool to elementary school?

The findings of this study suggest that physicians and other health care providers can help address the obesity epidemic by influencing the physical activity policies and practices of the preschools in their communities. Also, physicians who serve on licensing boards for preschools and those who serve as advisors to preschools in their communities can raise the issue of physical activity as a child health issue that preschools should address. In addition, health care providers can advise parents to consider physical activity services when they select a preschool for their child.

This study had limitations that should be noted. First, data were collected only during the preschool day; therefore, conclusions cannot be drawn regarding the impact of activity in the preschool on the overall physical activity of children. Second, the generalizability of the findings might be limited by the fact that all of the participating preschools were located in 1 metropolitan area. Also, data collection times were not uniform among demographic groups and types of schools. Black children were monitored for more days than were white children, and children attending Head Start preschools were monitored for fewer hours per day than were children attending other preschools. Although this factor might have influenced the findings, post hoc analyses indicated that the major conclusions of the study were not confounded by asymmetry in observation times among demographic and school groups. The asymmetry in observation times was associated with the inclusion of Head Start preschools, which in South Carolina enroll a disproportionately high percentage of black children and which operate for only ∼6 hours per day. We replicated our core analyses after deleting data collected in Head Start preschools, and the findings were essentially the same as those with such schools included. That is, black children (54% of the reduced sample, n = 166) had higher MVPA and VPA levels than did white children, and the preschools accounted for the largest proportion of the variance.

CONCLUSIONS

Accelerometry was used to measure the physical activity levels of children attending preschools. It was found that, on average, children participated in ∼7 minutes of MVPA per hour of attendance at the preschool. Physical activity levels were significantly higher for boys than for girls, and black children were more active than white children. Activity levels of children were highly variable among schools, with averages ranging from 4.4 to 10.2 minutes of MVPA per hour among the 9 schools in which children were observed. The preschool that each child attended accounted for a sizeable fraction of the variance in child physical activity, which suggests that policies and practices of preschools have an important influence on the overall activity levels of the children the schools serve. Future research should examine the impact of specific school policies and practices on physical activity levels of preschool students, and subsequent policy intervention studies should test the effectiveness of specific preschool policies on physical activity and weight status among young children.