Comparison of activity level in daily life with heart rate: Application to elderly persons of different ambulatory abilities

Decline in objective physical activity over a 10-year period in a Japanese elementary school

Background

The purpose of this study was to examine the change in accelerometer-derived daily physical activity (PA) and activity record-derived daily activities over a 10-year period in urban elementary schoolchildren in Japan.

Methods

A total of 233 sixth-grade children (11–12 years old) in a same elementary school in Kyoto participated in the study (n = 125 and 108 in 1999 and 2009, respectively). The participant rate is 91.9 and 98.2 % in 1999 and 2009, respectively. The size and shape of the school district was not changed. The children were instructed to wear an accelerometer for 5 consecutive days of weekday and to keep minute-by-minute 24-h activity records with the assistance of their parents. The school-day scheduling was similar between 1999 and 2009 (29 and 27 sessions of 45-min class per week, respectively).

Results

From 1999 to 2009, step counts considerably decreased (20,832 vs. 12,237 steps per day in boys and 16,087 vs. 10,748 steps per day in girls; P < 0.001) with concomitant significant decreases in total energy expenditure (P = 0.011), activity energy expenditure (P < 0.001), and physical activity level (P < 0.001). Time spent playing outdoors and walking to school were also significantly less in 2009 than 1999 (P < 0.001). Accelerometer-measured PA was significantly associated with the amount of time spent playing outdoors and walking to school.

Conclusions

These results indicate that elementary schoolchildren in 2009 spend less time playing outdoors and walking to school, perform less PA, and take fewer steps than children of a decade ago.

Physical activity, energy intake, and obesity prevalence among urban and rural schoolchildren aged 11–12 years in Japan

The prevalence of childhood overweight and obesity has been shown to differ among regions, including rural–urban regional differences within nations. This study obtained simultaneous accelerometry-derived physical activity, 24 h activity, and food records to clarify the potential contributing factors to rural–urban differences in childhood overweight and obesity in Japan. Sixth-grade children (n = 227, 11–12 years old) from two urban elementary schools in Kyoto and four rural elementary schools in Tohoku participated in the study. The children were instructed to wear a pedometer that included a uniaxial accelerometer and, assisted by their parents, keep minute-by-minute 24 h activity and food records. For 12 children, the total energy expenditure was measured by the doubly labeled water method that was used to correct the Lifecorder-predicted activity energy expenditure and physical activity level. The overweight and obesity prevalence was significantly higher in rural than in urban children. The number of steps per day, activity energy expenditure, physical activity level, and duration of walking to school were significantly lower in rural than in urban children. In contrast, the reported energy intake did not differ significantly between the regions. The physical activity and duration of the walk to school were significantly correlated with body mass index. Rural children had a higher prevalence of overweight and obesity, and this may be at least partly caused by lower physical activity, especially less time spent walking to school, than urban children.