Secular changes in total steps and moderate-to-vigorous physical activity among fourth-grade students in Japan in 2003/2004 and 2016/2017

No study has investigated secular changes in both total steps and moderate-to-vigorous physical activity (MVPA) among Japanese children. This study examined the secular changes of total steps and MVPA among fourth-grade students in Japan in 2003/2004 and 2016/2017. It was performed at a school in Okayama Prefecture in Japan. A total of 452 participants (226 boys and 226 girls; mean age, 9.6 ± 0.5 years) participated in the study. We measured total steps and MVPA of the participants by using the same methods in 2003/2004 and 2016/2017. An uniaxial accelerometer was used to measure total steps and MVPA. On weekdays and weekends, the total steps and MVPA were lowered by approximately 1,000–3,000 steps/day and 10 min/day, respectively, in boys and by 1,000 steps/day and 5 min/day, respectively, in girls in 2016/2017 in comparison to 2003/2004. In both boys and girls, the percentage of children meeting 60 minutes/day of MVPA decreased in 2016/2017(weekdays: boys 21.8%, girls 6.0%; weekends: boys 3.8%, girls 4.1%) compared with 2003/2004 (weekdays: boys 48.2%, girls 11.6%; weekends: boys 7.8%, girls 7.6%). In conclusion, the results demonstrated that total steps and MVPA of fourth-grade students in Japan were lower in 2016/2017 than in 2003/2004.