Playing long, hard and high may invoke the Valsalva Maneuver whereby one may effect the fall in blood pressure resulting in dizziness and even fainting. As the pressure inside the chest rises, blood is forced out of pulmonary circulation into the left atrium causing a mild rise in blood pressure. The pressure in the chest impedes the return of blood back into the heart. Subsequently, the output of the heart is reduced and blood pressure falls. When the chest pressure is released, this allows the pulmonary vessels and aorta to re-expand causing a further initial slight fall in blood pressure due to decreased left ventricular return and increased aortic volume, respectively. Blood return to the heart is enhanced by the effect of entry of blood which had been dammed back, causing a rapid increase in cardiac output and of blood pressure. The pressure usually rises above normal before returning to a normal level. Deviation from this response pattern signifies either abnormal heart function or abnormal automatic nervous control of the heart.