Vascular Shunt Mechanism

Vascular Shunt Mechanism

Vascular Shunt Mechanism

In this post, we will discuss the Vascular Shunt Mechanism:

  • What is the Vascular Shunt Mechanism?
  • How does the Vascular Shunt Mechanism work?
  • What is Vasodilation?
  • What is Vasoconstriction?
  • Why is this useful in sport?

What is the Vascular Shunt Mechanism?

The Vascular Shunt Mechanism is the redistribution of the blood due to the demands of exercise. 

The vascular shunt mechanism increases or decreases (redistribute) the blood flow to certain areas of the body.

Vascular Shunt Mechanism

How does the Vascular Shunt Mechanism work?

At resting levels, the majority of the blood in the body is directed towards organs. Research suggests that only 20% of blood being pumped from the heart (Cardiac Output) is distributed to the muscles. However during exercise, the body can redistribute up to 80% of blood in the body to the muscles.

This redistribution of blood has several benefits to athletes which will be discussed later on in this post.

The vascular shunt mechanism begins at the Vasomotor Control Centre (VCC). The VCC controls blood pressure and is located in the Medulla Oblongata. 

The VCC stimulates the Sympathetic Nervous System to redistribute the blood carried along the vessels to all parts of the body. But how? 

As an athlete starts exercising, oxygen levels within the muscles begins to decrease. The decrease is because the oxygen is being used up by the muscles (You can read our article on the energy systems here).

The VCC will then begin to reduce the blood flow from the organs. Allowing more blood to flow to the muscles instead. This is achieved by Vasodilation and Vasoconstriction.

Once an athlete finishes exercising, the oxygen levels within the muscles will begin to increase gradually. This is because the body will no longer be using up as much oxygen (Read more on the energy systems here). The VCC will then redistribute the blood back to the main organs as the muscles will no longer need higher oxygen levels.

What is Vasodilation?

Vasodilation is when the smooth muscle of the arteries, arterioles and pre-capillary sphincters leading the certain parts of the body relaxes. This process means that more blood can pass through these vessels due to the greater diameter. 

What is Vasoconstriction?

Vasoconstriction is the opposite of vasodilation. Vasoconstriction is when the smooth muscle of the arteries, arterioles and pre-capillary sphincters contract. As smooth muscle contracts, the diameter of these vessels become smaller and reduces the blood flow.

The easiest way to remember the difference between the two methods is that constriction makes the vessels smaller, and dilation means the vessels become bigger.

Why is this useful in sport?

The ability to redistribute blood to different parts of the body aids performance during exercise. During rest, only 20% of blood is distributed to the muscles; the rest of the blood is going to most of the organs. The body uses blood for vital processes such as digestion.

However, during exercise, the body can redistribute up to 80% of the bodies blood to the muscles. This additional blood will enable more oxygen to be delivered to the muscles. 

Our article on the different energy systems explains how oxygen is used to provide the body with energy. During exercise, the vital organs will still receive a supply of blood to maintain functions but not at optimum levels (Hence why some people get a stitch during exercise. This is because the stomach is not receiving enough blood to breakdown the food).

The additional oxygen delivered to the muscles will enable to body to perform at a higher intensity for longer. This will mean athletes will be able to run, sprint, jump or throw for longer.

Without the Vascular Shunt Mechanism, the body would fatigue quicker and athletes would not perform at the same intensity.

What can sports coaches and athletes do to make the most of the Vascular Shunt Mechanism?

The first step sports coaches and athletes can take to encourage the vascular shunt mechanism is to complete a thorough warm up before exercise. One unknown consequence of a warm up is that vessels leading to the muscles will already be vasodilated. This is due to the initial involvement of exercise.

This will that mean when the athlete starts the event such as a football match, they will be unlikely to tire quicker than to somebody who does not complete a warm up. This is because the body will already be pumping around the additional blood flow due to the vascular shunt mechanism.

The second step coaches and athletes can take is to complete a thorough cool down after exercise. This is because the body will begin to redistribute blood back to the organs quicker than if a cool down is completed. Maintaining additional blood flow will reduce Excess Post Oxygen Consumption and improve the recovery of the athlete.

Summary 

To conclude, the vascular shunt mechanism is the redistribution of blood during or after exercise. Coaches and athletes need to be aware of the benefits and how a warm up and cool down can improve performance and recovery.

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