Time trend changes in the amount and type of physical activities over a 20-year period in urban elementary school sixth-graders

Abstract

The purpose of this study was to examine time trend changes in the amount and type of physical activities obtained by an accelerometer and an activity record over a 20-year period in urban elementary schoolchildren. A total of 388 sixth-grade children (11–12 years old) in an elementary school in Kyoto participated in the study (n = 125 in 1999, 108 in 2009, and 155 in 2017/2018). The size and shape of the school district did not change. The school schedule was nearly the same in 1999, 2009, and 2017/2018. The children were instructed to wear an accelerometer for 5 consecutive weekdays and to keep minute-by-minute activity records with the assistance of their parents. The percentage of overweight/obese children increased with time, but the increases were not significant. The step count per day, activity energy expenditure, and physical activity level were significantly lower than they were 20 years ago, and they were significantly higher than they were 10 years ago. The time spent playing outdoors was significantly shorter than it was 20 years ago, and while it was significantly longer than it was 10 years ago. Independently from year, the time spent playing outdoors was strongly correlated with accelerometer-derived physical activity. The time spent walking to school, sleeping, studying in girls was correlated with accelerometer-derived physical activity. The factor of activity pattern related to secular changes of accelerometer-derived physical activity over the 20-year period is the time spent walking to school, sleeping in boys and the time spent club activity in girls.