Saudino (2012) US

1-year longitudinal study examining sources of continuity & change in activity level

314 same-sex pairs of twins at age 2 (144 MZ & 168 DZ), 304 pairs at age 3 (141 MZ & 163 DZ)

Accelerometer: 48.22 h (continuous 48 h) Questionnaire by parents: 10 questions regarding children’s behavior in specific situations Questionnaire by observers: 30 items evaluating infant behavior

Age, and environment (home and lab)

Males were significantly more active than females on all measures of activity level (AL). With the exception of observer-rated AL, there were significant age effects for AL. The pattern of change across age, however, differed according to AL measure or situation. (For the actigraph measures, AL in the home significantly increased, whereas AL in the laboratory and parental rating decreased from ages 2 to 3.)

Shen et al. (2013) US

4-month longitudinal study examining seasonal variation from fall to winter in PA among preschoolers

46 3 - 4 yr children at baseline (43% boys, mean age = 4.15 yr, mean BMI = 17.41)

Accelerometer: 10.7 hr/d for 4.1 days (at least 3 days including at least 1 weekend day) In-school time: 6.8 hr/d After-school time: 3.9 hr/d

Season (fall and winter)

During school attendance, there was no difference in LPA, MPA, and VPA between fall and winter for either girls or boys. In after-school time, significantly more LPA occurred in fall relative to winter for both boys and girls. In addition, girls spent more time in MPA and LVPA in fall than that in winter. In contrast, no differences in MPA and VPA were observed in boys. The seasonality on weekdays was not evident, but during weekends, both girls and boys spent more time in LPA, MPA, and LVPA in fall than that in winter.

Taylor et al. (2009, 2013) NZ

4-year longitudinal study determining how overall activity & time in different intensities of activity change in children followed from 3 to 7 years

227 3 yr children at baseline (56% boys)

Accelerometer: at least 3 hours per day for 5 days

Questionnaire by parents: “the amount of time spent each week in various activities”, “child’s level of activity relative to their peers” & “the number of hours per week that children attend childcare”

Age, sex, weight status, time awake, parental PA, week days/weekend, and season

Day of the week, season, hours of childcare, or birth order did not affect daily PA at any age.

At 5 years, PA had declined substantially to around half that observed at 3 years. Activity levels were similar at 6-7 years as they were just prior to s tarting school.

Boys were more physically active than girls. Children showed higher counts per minute but a lower LMV: S ratio on weekend compared with weekdays. Rain and cold weather significantly decreased on activity.

Parental activity correlated weakly with the child’s activity at 3 and 4 yr, but only the father’s activity remained a significant predictor of the child’s activity after adjustment for confounders.