Skeletal muscle becomes fatigued with exercise due to a limited capacity for aerobic metabolism, causing a ventilatory response increase and breathlessness. These events result in ergoreflex activation, which in turn causes an activation of the sympathetic nervous system, an increase in vascular resistance and afterload, and a further reduction in cardiac function and blood flow to the periphery.
Redrawn from: Clark AL, Poole-Wilson PA, Coats AJS, J Am Coll Cardiol 1996; 28:1092.