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Heart rate

During aerobic exercise, peripheral veins, particularly those within muscle, dilate to accommodate the increased blood flow through exercising muscle. The skeletal-muscle pump assists in returning blood to the heart and maintaining cardiac output. A sudden cessation of strenuous exercise may cause blood to pool in peripheral dilated veins and the heart must beat faster and harder to adequately oxygenate the body and maintain blood pressure.[citation needed] A cool-down period allows a more gradual return to venous tone, and allows a gradual decline in heart rate that reduces stress on the organ. Resting Heart rate after a cool down period of 6 minutes is notably lower than after 6 minutes of total rest following equal exertion.