This chapter discusses how the overlapping practices of sport and theatre contributed to early modern boy actors' performances, arguing that sport and exercise formed a crucial part of boy actors' training for the professional stage. The first half of the chapter takes as its focus the educational writings and theatrical activity of the educational theorist and practitioner Richard Mulcaster, tracing the influence of his physically minded pedagogical ideals on the robustly physical Elizabethan and Jacobean boy company repertories. The second half of the chapter provides an in-depth discussion of the staging of sport in John Marston's What You Will and John Day's The Isle of Gulls, drawing on practical experiments with staging these scenes in the present-day Sam Wanamaker Playhouse to consider the processes by which a boy actor may have come to perform precise and physically challenging aspects of dramaturgy. It demonstrates that a practical approach to critically neglected plays offers new perspectives on the dramatic possibilities afforded to the first and youngest interpreters of early modern drama which keep the skilled performing body as the rightful centre of attention.