Research has consistently revealed gender differences in physical self-concept and engagement in physical activity, with results typically favouring boys. Despite strong evidence to suggest that socialisation results in physical activity taking on different meanings and experiences for girls and boys, these different meanings have rarely been considered in interventions targeting youth physical inactivity. Studies of self-objectification have shown that - women, particularly adolescent girls, experience the negative impact of self-objectification (e.g., disordered eating, depression and decreased body satisfaction) more than males, although males are increasingly being subject to sexual objectification in society. Developmental differences in measures of physical self-concept have been less clear than gendered differences but have major implications for when interventions targeting physical inactivity and body image should be initiated.