This study described the duration of SB and PAs classified as ambulatory and non-ambulatory activity measured using triaxial accelerometry during school cleaning time, and morning and lunch recesses in Japanese primary school children. Gender differences were also identified. For boys, the proportions of MPA, VPA, and MVPA in morning and lunch recesses and SB in morning recess time were significantly higher than those during school cleaning time and the LPA during morning and lunch recesses was lower than those during school cleaning time. For girls, similar results were obtained and SB during lunch time was higher than those during school cleaning time. Moreover, the percentage of total MVPA during school cleaning time and morning and lunch recesses in total MVPA on school days was 19.4 ± 6.8% per day on school days (15 ± 5 min/day) for boys and 16.9 ± 5.8% (10 ± 4 min/day) for girls. MVPA time during each of school cleaning time and morning and lunch recesses was not long but the total amount cannot be ignored.
Many studies have examined PA levels of young people during school recess times [7, 8]. However, to our knowledge, this is the first study in which the PA and SB during school cleaning time were examined. In a previous study of primary school children, using the respiratory measurements to examine METs for primary school children participating in the main activities in school cleaning time at Japanese schools (e.g., sweeping up, clearing away items and washing the floor), studies have found that the average MET values for these three activities were 3.15 ± 0.73, 3.01 ± 0.58 and 4.41 ± 0.69 MET, respectively . Recently, Butte et al. developed “A Youth Compendium of Physical Activities” to estimate the energy costs of PAs using data on youth only . They showed many types of housekeeping were more than 3METs in primary school aged children (e.g. dusting, dusting and sweeping, hanging out washing, sweeping). Although school cleaning time can be an opportunity for MVPA, our research found no evidence concerning substantial PA during school cleaning time for primary school children under free-living conditions. The average percentage of total MVPA during school cleaning time in the present study was 19.3 ± 8.2% for boys and 15.9 ± 8.4% for girls (Table 2), which corresponds to about 2 to 3 min/day. Thus, these findings suggest that the contribution to MVPA was not high for either gender. If school cleaning time is 20 min per day and all the time is regarded as MVPA, total MVPA time may be overestimated by almost 15 min per day. During school cleaning time, the percentages of non-ambulatory MVPA were significantly higher than those in morning recess for girls, whereas total MVPA, ambulatory MVPA, and SB during school cleaning time were significantly lower than those in morning recess for both boys and girls and SB in lunch recess for girls. Thus, the contents of PA and SB differed between the school cleaning time and morning and lunch recesses. Surprisingly, for girls in the present study, the partial correlations of MVPA between school cleaning time and morning or lunch recesses were weak or moderate. On the other hand, there was little correlation for boys (Table 3). This result suggests that boys might distinguish their activities in terms of educational vs play.
In the present study, the percentage of time spent in MVPA during morning recess (20 to 30%) was similar to previous studies of 8–11 year-olds from Canada , 5–10 year-olds in the UK , 9–12 year-olds in Hungary , and third-sixth grade children in the United States . However, another study reported MVPA of 63–78% based on evaluations of pedometer engagement in third-fifth grade children in the United States . On the other hand, in the present study SB during morning recess (17% in boys and 23% in girls) was lower than that seen in the above-mentioned studies (from 35 to 64%) [15,16,17]. The percentage of time spent in SB during morning and lunch recess in the present study was similar to previous studies of 9–11 year-olds from the US (22%) during the recess/lunch time period . Differences in methods used to assess PA may account, in part, for differences in our results relative to previous studies. In addition, except for four schools, all schools in the present study had the policy: “On days with good weather, as a rule, students play in the school playground during morning and lunch recesses” This policy might explain why the SB during morning recess was lower than that of previous studies.
A previous systematic review found that during school recess periods (recess and lunchtime), boys were consistently more active than girls . The present study is consistent with these earlier results in that PAs for boys during lunch recess were higher than that for girls. However, there were no gender differences in non-ambulatory MPA among morning and lunch recesses and non-ambulatory MVPA among lunch recess times. The non-ambulatory LPAs and total LPA times for girls were higher than those for boys. Evidence from our study supports the assertion that both ambulatory activity and non-ambulatory activity are important factors in evaluating PA lifestyles in primary school children. These data may be particularly important for providing insight into gender as a determinant of PA in primary school children. Moreover, SB times for girls in the present study were longer than those for boys during morning and lunch recesses. Other previous studies reported that boys view recess as an opportunity to play competitive games that often dominate the available space . In comparison, girls may view recess as an opportunity to socialize with friends . The similarity in MVPA among boys and girls during morning recess, but lower amounts of SB for girls during lunch recess, indicates the need for future research to compare in greater detail the specific activities and behaviors of boys and girls during recesses. Identifying activities that differ by gender could be critical for the development of activity promotion strategies, and may help to inform evidence-based practices and policies designed to increase PA and decrease SB in primary school children.
The contribution of school cleaning time and morning and lunch recesses to daily MVPA for boys and girls was 19.4% (15 min/day) and 16.9% (10 min/day), respectively. These data suggest that cleaning time and morning and lunch recesses do not contribute significantly to overall daily PA levels on school days for primary school children. One reason for the low PA during morning or lunch recess was that the recess periods are only 15–20 min/day. A previous review reported that lunch time lengths in previous studies was 30–86 min/day (some studies that were considered included the time taken to eat lunch in the overall lunch period length), although the length of the morning recess in the present study (15–20 min/day) is similar to previous studies concerning schoolchildren in the UK, Belgium, Cyprus and the United States . Parrish et al.  reported that the proportion of active children at each school and the actual number of minutes the children spent in the playground during the observational data collection period showed a positive correlation of r = .318 (P = .289). Moreover, the Tokyo Metropolitan Board of Education examined daily step counts for boys and girls who lived in Tokyo and found that step counts after school were higher than those during school . Wood and Hall compared PA during morning playtime (15 min) and lunch playtime (60 min), and physical education classes, and found that time in MVPA was significantly longer during physical education than playtime (P < 0.01) . Thus, future research should examine PA and SB of Japanese primary school children during the time after school and physical education classes.
There are several methodological points and limitations to be considered in the interpretation of these results. First, although the accelerometer Active style Pro is a widely used to measure PA and SB in Japan, it cannot provide information about the types of activities being performed or the context. Therefore, direct observational approaches for contextual PA and BS information are necessary. Second, our sample was not a representative for Japanese children. The strengths of our study include: an objective measure of SB and PA to classify ambulatory and non-ambulatory activity, and the use of a sample of Japanese primary school children from 14 schools. Notably, the present data were recorded in 10-s epochs, which may be sufficiently sensitive to detect short bursts of vigorous activity [26, 27]. Short time periods for data recording could be better reflect movement patterns of children.