Background: Research on adolescent physical activity motives is largely divided into separate bodies of literature: one focusing on rational motives and another on automatic motives. However, it is likely that these two processes are interconnected, with rational process potentially mitigating the vulnerabilities to poor physical activity caused by automatic processes (i.e., affect, fatigue, or energy levels). Adolescence is a key period of development when self-regulation of affect, cognition, and behavior is not yet fully formed. As a result, adolescents may be particularly susceptible to the influence of automatic processes that negatively impact physical activity.

Purpose: The current study seeks to explore variables central to self-determination theory as moderators of the relationship between automatic motives and physical activity in adolescents.

Methods: A 20-day ecological momentary assessment (EMA) study, in which 100 adolescents aged 13-18 years old were asked to indicate baseline social support, motivation, and competence for physical activity. Subsequently, participants wore an Actigraph accelerometer 24 hours per day and answered EMA surveys assessing automatic motives 4 times per day using time-based signaling.

Results: There was a significant interaction between within-person positive affect and amotivation as a predictor of MVPA (b = -0.02, p < .05) with 95% CI [-0.04, -0.01] and sedentary time (b = 0.10, p < .01) with 95% CI [0.04, 0.16]. There was also a significant interaction between within-person negative affect and amotivation as a predictor of sedentary time (b = -0.08, p < .05) with 95% CI [-0.14, -0.01]. Within-person fatigue interacted with friend social support (b = 0.05, p < .01) with 95% CI [0.02, 0.08], amotivation (b = 0.03, p < .05) with 95% CI [0.003, 0.06], and controlled motivation (b = -0.03, p < .01) with 95% CI [-0.05, 0.01] in relation to MVPA.

Conclusions: Overall, findings from this study reveal that rational and automatic motives are intertwined, highlighting the need to explore them together as targets for physical activity and sedentary time intervention efforts. This novel perspective opens a new avenue for understanding how these motives interact, suggesting that future research should also consider past experiences, affective responses, and affect processing as key factors.