Digestion & Kidney Blood Flow During Exercise

Using energy is the only way that your muscles can contract to produce movements. Long-term, sustainable energy production needs oxygen. The vessels inside your body innervate every muscle, both smooth and skeletal. However, during exercise the demand for oxygen is so great that blood flow must redirected toward those working cells. Without adequate oxygen from blood flow, your body would never be able to participate in physical activity. This means sacrificing blood flow to the digestive and kidney organs.

Blood Flow During Exercise

During rest, about 15 to 20 percent of blood supplies the skeletal muscle. However, during exercise, this must increase to 80 percent or more. To facilitate this change, your body systematically redirects blood away from the parts of the body that are not as active during exercise. The digestive organs as well as the kidneys receive less blood during exercise.

Mechanism

The way blood flow is directed is quite simple. Your veins and arteries are dynamic, meaning they have the ability to move, changing their size. To reduce blood flow to the digestive organs and kidneys during exercise, the blood vessels that innervate these organs constrict. A small vessel means less blood flow can penetrate, so more blood is available for the cells that need it most.

Central Nervous System

The command center of the body is the brain, which regulates the changes that occur in your blood flow. The brain has two branches of the nervous system that take over at different times. During exercise, the sympathetic nervous system takes over. This system induces changes in blood flow by increasing heart rate, blood pressure, cardiac output and vasodilation or constriction of blood vessels. The other branch is the parasympathetic nervous system, also known as the "rest and digest" system because it innervates your body during rest. This is the system that will increase blood flow for digestion and kidneys.

Norepinephrine

The sympathetic nervous system is able to influence blood flow by releasing a neurotransmitter known as epinephrine. When epinephrine innervates the body, it both vasoconstricts the arteries and veins leading to digestive, reproductive and urinary organs. At the same time, it vasodilates the vessels leading to the skeletal muscles and liver, which is necessary for providing nutrients to the skeletal muscles.