Fiona Gillison

Based on the tenets in self-determination theory, a dual-process model of motivational processes was tested to predict accelerometer-assessed estimates of adolescents’ light physical activity (LPA), moderate to vigorous physical activity (MVPA), and sedentary time. Here, we hypothesized that (a) perceptions of psychological need support for exercise would be positively associated with LPA and MVPA and negatively associated with sedentary time via exercise-related psychological need satisfaction and autonomous exercise motivation and (b) perceptions of psychological need thwarting for exercise would be negatively associated with LPA and MVPA and positively associated with sedentary time via exercise-related psychological need frustration and controlled exercise motivation. Adolescents ( N = 338; 234 female) age 11–15 years ( M = 12.75, SD = .90) wore an ActiGraph accelerometer for 8 days and completed questionnaires pertaining to the self-determination-theory variables. Results showed psychological need support to indirectly and positively predict LPA and MVPA via psychological need satisfaction and autonomous exercise motivation. Although directly predictive of need frustration and indirectly predictive of controlled motivation and amotivation, the hypothesized effects from psychological need thwarting to the behavioral outcomes were nonsignificant. The current findings highlight the important role that need-supportive environments play in facilitating autonomous exercise motivation and behavior by being conducive to exercise-related psychological need satisfaction.