This study aimed to examine the relationships between objectively measured daily physical activity (PA) and perceived neighborhood environment among Japanese preschool children. The relationships between PA and mental factors (e.g. unidentified complaints) were also examined. PA was assessed using a triaxial accelerometer (ActivTracer, GMS) for 6 consecutive days, including weekdays and weekends, in 361 four- to six-year-old Japanese children attending kindergartens or nursery schools. Neighborhood environment and mental factors were evaluated by a questionnaire. Data were collected between 2006 and 2008. Moderate-to-vigorous physical activity (MVPA) and physical activity level (PAL) were 99 (±30) min/day and 1.54 (±0.08), respectively. Relationships between MVPA and crime safety and nature in neighborhood were significant after adjustment for age, sex, body height and weight. Presence of hills was significantly associated with less time in PAR (physical activity ratio)≥4. On the other hand, relationships between the amount of time in 2>=PAR<3 and fatigue and between the amount of time in PAR<2 or 2>=PAR<3 and motion sickness were significant. The findings indicate that MVPA or PAR≥4 and sedentary or light activity in the preschool children are associated with some neighborhood environment attributes or unidentified complaints, respectively.
