Beneath your skin lies a massive network of blood vessels. The arteries, veins and capillaries that make up your blood stream are responsible not only for the circulation of blood, nutrients and hormones, but also for the regulation of temperature. A noticeable response to the regulation of body temperature by the vessels is seen during exercise in the form of changes in skin tone and color.
Vessel Walls
The walls of blood vessels are made of smooth muscle tissue. Smooth muscle is a type of involuntary tissue, meaning it doesn’t require a conscious effort for action. Other areas of the body where smooth muscle is found are in the heart and intestines.
Blood Flow Regulation
Vasodilation and vasoconstriction are the types of muscular contractions that occur within the vessel. With vasodilation, the smooth muscle causes the vessel to open wide, allowing for a greater flow of blood through the vessel. Vasoconstriction is the exact opposite. The smooth muscle contracts and clamps down, restricting the rate of flow.
Heat Dissipation
During exercise body temperature quickly rises. This causes the capillaries under the skin to vasodilate. The vessels do this in an attempt to promote a decrease in temperature by releasing heat from the blood stream. Since the capillaries are so close to the surface of your skin, it creates a flushed appearance. The number of capillaries in your face is high, which is why your face may appear to be redder than the rest of your body.
Blood Pooling
Conversely, if you were to jump off the treadmill without a cool-down period, you might experience blood pooling. Blood pooling is when a large volume of blood remains in your extremities and doesn't return to the heart and brain as quickly as needed. Your skin would become very pale and you might experience dizziness. The pale color of the skin is caused by network wide vasoconstriction. The blood vessels are clamping down in order to push the blood from the surface and extremities back to your core organs.
