The cardio-respiratory system (heart and lungs) is efficient in maintaining oxygen and carbon dioxide levels in the blood most of the time. However, during very strenuous exercise, the cardio-respiratory system may become less efficient in maintaining equilibrium of these gases. Known as exercise-induced arterial hypoxemia (EIAH), this condition is characterized by a reduction in oxygen levels in the arterial blood, starving muscles of oxygen and impairing exercise capacity. In men, EIAH has been found to be prevalent mainly in highly-trained endurance athletes at near maximal exercise intensities. However, research has demonstrated that women who are not highly trained may experience EIAH, and at lower exercise intensities. This may be due to anatomical differences: women have smaller lungs, airways, and surface areas for gas exchange relative to men. One potential explanation for the EIAH phenomenon is through intrapulmonary arteriovenous shunting, where instead of taking its normal route through the lungs to gain oxygen, deoxygenated blood from the veins is diverted directly back into the heart. This results in lower oxygen levels in the arterial blood and less oxygen available for the working muscles. Research suggests that intrapulmonary arteriovenous shunting exists in healthy, exercising humans. Jill Kennedy is conducting the first systematic study of whether intrapulmonary arteriovenous shunting accounts for EIAH observed in women during exercise. She will also explore whether this relationship is influenced by fitness. Kennedy’s research will shed new light on female physiological responses to dynamic exercise with respect to the pulmonary system. Ultimately, this knowledge could lead to the establishment of scientifically-based, gender-specific exercise prescription guidelines for women throughout their life span.