Under this new “science of work,” fatigue was seen as the ultimate pathology of the working-class body, reducing workers’ capacity to perform continued physical or mental labor. As Steffan Blayney shows, the equation between health and efficiency did not go unchallenged. While biomedical and psychological experts sought to render the body measurable, governable, and intelligible, ordinary men and women found ways to resist the logics of productivity and efficiency imposed on them, and to articulate alternative perspectives on work, health, and the body.