The regulation of prolonged physical activity is recognised as a cognitive process implemented by the brain, believed to prevent harmful perturbations to homeostatsis. However, despite extensive interest in this area and the development of various models exploring the nature of 'fatigue', our understanding of the fudamental mechanics of this central regulation remains limited. Drawing upon the field of neuroeconomics, the limits of exercise tolerance has more recently been conceptualised as a continuous decision-making process, derived through ongoing cost/benefit computations; the perception of fatigue reflecting a motivational input, signalling disturbances in the balance between the 'benefit' associated with current exercise behaviour and the accumulating physiological cost. This proposed framework may provide an opportunity to elucidate the neurobiological mechanisms of this elusive phenomenon. The source of this putative cost signal during acute exercise however, remains unclear, with the contribution of efferent and afferent processes in fatigue perception often debated. Interoception, or an awareness of internal bodily changes, principally mediated by small sensory afferent fibres of the periphery, has been implicated as a primary determinant in the development of fatigue and the termination of exercise performance. As such, the aim of the project is to explore the limits of exercise tolerance as a value-based decision-making process, identifying the potential role of interoception within this cognitive computation, in an attempt to delineate the constraints to physical work capacity in both health and disease.