While the pathophysiology affecting patients after Fontan palliation versus those with orthostatic intolerance is quite different, a common therapeutic approach exists. Exercise training, specifically augmenting the lower extremity skeletal muscle pump, improves the suboptimal haemodynamics of "preload failure" and thus clinical outcomes for each patient group. In this review, we will describe the problematic physiology affecting these patients, examine the anatomy and haemodynamics of the skeletal muscle pump, and finally review how exercise benefits both groups of patients through augmentation of musculovenous force.