Histories of teachers' experiences in the United States between the 1880s and the 1930s argue that teaching restrained and often debilitated teachers' bodies. The emerging theory of constraint is limited, however, because the historiography of American teachers focuses for the most part only on the months when school was in session. This examination of publications in which education leaders discussed how teachers should spend their summers and teachers' memoirs, diaries, and letters, reveals a full quarter of the year during which the focus was on the rejuvenation of teachers' bodies. As administrative efforts to control teachers' bodies extended into the summer months, leaders expressed their concern by prescribing rest. The meaning of "rest", however, soon evolved into reinvigoration through breathing fresh air and physical activity. Full of vitality, teachers' own accounts reveal how their summer activities released them from the restraints of teaching. Rural teachers engaged in agricultural work and other outdoor activities, and urban teachers communed with nature and exercised in the open air. These activities had important gender ramifications: they allowed women to challenge boundaries by demonstrating the robustness of a "new woman" and men to reinforce boundaries by demonstrating rugged masculinity. In both cases, teachers used the summer months to revitalise bodies worn down by the physical restrictions of teaching, as administrators directed.