Oxygen uptake, heart rate, and a-v O2 content difference at rest and during increasing levels of exercise

With exercise and an increase in work load, there is an increase in oxygen (O2) uptake (upper panel), heart rate (HR) (middle panel), and a-v O2 difference (lower panel). Exercise training produced an increase in the maximal oxygen uptake (VO2 max) that can be achieved (upper panel) and a decrease in maximal HR occurring at any given work load (dashed blue line, middle panel).