Cooling down

Cooling down, also called warming down, is an easy exercise that will allow the body to gradually transition from an exertional state to a resting or near-resting state. Depending on the intensity of the exercise, cooling down can involve a slow jog or walk, or with lower intensities, stretching can be used. Cooling down allows the heart rate to return to its resting rate. Contrary to popular belief, cool down does not reduce delayed-onset muscle soreness and muscle soreness is not caused by lactate production during intense exercise. There is no strong evidence that cooling down is necessary, although anecdotally cooling down may reduce dizziness for professional or serious athletes after strenuous workouts.

Procedure
Cool downs should involve a gradual yet continuous decrease in exercise intensity (i.e. from a hard run to an easy jog to a brisk walk), stretching, and rehydration. Durations can vary for different people, but 3-7 minutes is considered adequate.

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. 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.