Effects of a structured recess intervention on physical activity levels, cardiorespiratory fitness, and anthropometric characteristics in primary school children.

Non-curricular time spent in school context might provide a potential opportunity to promote physical activity (PA) and enhance children’s health. This study examined the effects of a structured recess intervention over 12 weeks on cardiorespiratory fitness (CRF), PA daily levels and anthropometric characteristics, in 2nd and 3rd grade school children. This non-randomized controlled study included 100 children (age, 7.5 ± 0.5 yr, body mass 29.6 ± 6.0 kg, height, 1.25 ± 0.06 m) recruited from two primary schools, which served as intervention (INT) or control (CON). The INT school underwent a 15 min structured and physically active recess 4 times per week for 12 weeks, while the CON school maintained its usual unstructured recess routine. Steps count and PA at different intensities (Light, LPA; moderate, MPA; vigorous, VPA; moderate-to-vigorous, MVPA) during week days (WD) and weekends (WE) were assessed by accelerometry pre- and post-intervention. CRF and anthropometric parameters were also assessed in both conditions. Overall, there was a main effect of time for cardiorespiratory fitness (+ 4%, P = 0.004, pη2 =0.042 ), time spent in LPA (+14.3%, P = 0.015, pη2 = 0.032) and MPA (+28%, P = 0.049 , pη2 = 0.021) during WD, although, we observed no time x group interaction: P = 0.864, pη2 = 0.001, P = 0.363, pη2 = 0.005, P = 0.085, pη2 = 0.016, respectively. We observed no main effect of time for any of the anthropometric measures (P > 0.05 in all cases), steps count, VPA and MVPA during WD and PA measures during WE. Over the 12 weeks of intervention in this study, we observed higher levels of LPA and MPA during WD, and improved cardiorespiratory fitness, however, this was not different between the INT and CON schools. This may suggest that children engage in sufficient amount of PA during recess on their own, suggesting that adults’ effort to increase PA levels can be focused on other parts of the children’s free time spent in school. However, future in-school research may also benefit from evaluating a more precise volume, intensity and type of PA during recess to induce beneficial effects on children’s fitness and anthropometrics.