Figure 5. Average changes in cardiac output (total blood flow) and leg blood flow during maximum cycling exercise in fit athletes with superimposed increases and decreases in inspiratory muscle work.

Limb vascular conductance and flow increased with reduced work of breathing and decreased with increased work of breathing. Stroke volume and cardiac output decreased with the reduced work of breathing and remained unchanged with increased work of breathing (also see bracketed note in the text on the quantification of respiratory muscle blood flow during exercise). Data adapted from Harms et al. (1997, 1998).