RESUMO
Physical fitness self-concept (PFSC) is an important predictor of motivation and physical activity in children. Recent studies revealed that not only PFSC but also its interplay with perceptions of one's ideal and ought physical fitness self are related to motivation and physical activity. As the meaning of ideal and ought selves in children is yet unclear, this study aimed to investigate how PFSC, ideal physical fitness self, and ought physical fitness self are related to children's motivation and physical activity. Six hundred forty-five children (Mage = 8.87 years) filled out questionnaires twice with an interval of approximately 8 months. Polynomial regression with response surface analyses and mediation analyses was conducted. Results showed that PFSC, rather than ideal and ought self-perceptions, is associated with autonomous motivation, self-efficacy, and physical activity. The relationship between PFSC and physical activity was mediated by self-efficacy. Findings indicate that physical activity promotion programs should include PFSC and self-efficacy enhancement in childhood.