PURPOSE: To use Ecological Momentary Assessment with mobile phones to describe where and with whom children's leisure-time physical activity occurs. DESIGN: Repeated assessments across 4 days (Friday–Monday) during nonschool time (20 total). SETTING: Chino, California, and surrounding communities. SUBJECTS: Primarily low to middle income children (N = 121; aged 9–13 years; x¯ = 11.0 years, SD = 1.2 years; 52% male, 38% Hispanic/Latino). MEASURES: Electronic surveys measured current activity (e.g., active play/sports/exercise, watching TV/movies), social company (e.g., family, friends, alone), physical location (e.g., home, outdoors, school), and other perceived contextual features (e.g., safety, traffic, vegetation, distance from home). ANALYSIS: Multilevel linear and multinomial logistic regression. RESULTS: Most of children's physical activity occurred outdoors (away from home) (42%), followed by at home (indoors) (30%), front/backyard (at home) (8%), someone else's house (8%), at a gym/recreation center (3%), and other locations (9%). Children's physical activity took place most often with multiple categories of people together (e.g., friends and family) (39%), followed by family members only (32%), alone (15%), and with friends only (13%). Age, weight status, income, and racial/ethnic differences in physical activity contexts were observed. CONCLUSIONS: The most frequently reported contexts for children's leisure time physical activity were outdoors and with family members and friends together.
