The adaptability of the heart can be observed during exercise, when the metabolic activity of
skeletal muscles increases. The cardiovascular system, consisting of the heart and blood vessels,
responds to exercise with an increase in heart rate and strength of contraction with each beat,
resulting in a higher cardiac output (cardiac output = quantity of blood pumped through the heart
per unit of time) and blood pressure. Positive pressure is created by forceful contraction of the
left ventricle of the heart, measured as systole. It is maintained during relaxation of the ventricle
by closure of the aortic valve and recoil of arteries, measured as diastole
