This paper considers girls' participation in running and other outdoor physical activities in their local areas in London, UK. The paper is concerned with the operation of risk discourses in and around this participation and looks at the way that such discourses impacted on girls' opportunities to take part in physical activities that required outdoor space. Drawing on data from longitudinal research into girls' participation in sport and physical activity, the findings suggested that girls, in particular, were subject to risk discourses around their participation in physical activities which constructed the girls as "weak", and "vulnerable". I look at the ways in which girls understood these messages and how they came to define certain spaces and activities as either "safe" or "unsafe". I look in particular at how girls were able to resist certain constructions of their embodied physical capacities and also at the ways in which this was constrained by specific incidences of sexual harassment.