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The vagus nerve

Course video 115 of 164

When an athlete is underperforming, and you don’t know why, suspect chronic fatigue due to overtraining as the prime contributing factor. Unfortunately, because we don’t fully understand chronic fatigue our knowledge about overtraining remains scant. Hans Selye’s General Adaptation framework suggests it is likely due to too much training and insufficient recovery that leads to a prolonged maladaptation of physiological systems and structures. In this module you are provided insight into chronic fatigue and its relationship to overtraining.

In this course you will learn how to design the type of training that takes advantage of the plastic nature of the athlete’s body so you mold the right phenotype for a sport. We explore ways the muscular system can be designed to generate higher force and power and the type of training needed to mold the athlete's physical capacity so it meets the energy and biochemical demands of the sport. We also examine the cost of plasticity when it is carried beyond the ability of the body to adjust itself to meet the imposed training stresses. The cost of overextending plasticity comes in the form injuries and chronic fatigue. In essence, a coach can push the athlete’s body too far and it can fail. Upon completion of this course you will be able to assemble a scientifically sound annual training plan.

Impartido por:

Dr. Chris Brooks
Instructor

Transcripción

So let's now return for a few minutes to the vagus nerve.

If your athletes have an unexplained deterioration in their performance,

in conjunction with unexplained fatigue, and

they also show lack of motivation, the vagus nerve is likely involved.

Now, Professor Steven Porges, has proposed one of the most interesting

insights into how the vagus nerve works and he called it Polyvagal Theory.

And it explains an awful lot about these symptoms of chronic fatigue,

due to overtraining.

The theory is elegant and provides really valuable insights for coaches.

This slide here is showing a cross section of the brain stem with the vagus nerve and

the organs that the vagus nerve innovates, the lungs and the heart and

the stomach, etc., as it works its way through the body.

The brain stem is located just above and is connected to the spinal cord.

The cross section through the brain stem is at the dotted line here,

where the vagus nerve actually exits from the brain stem.

And here you see the brain stem when the other parts

of the brain are stripped away.

The vagus nerve is highlighted in green.

Now the brain stem is the oldest part of the brain.

It controls basic survival functions including heart rate,

digestion, blood pressure, and arousal, that is, being awake and

alert, and being ready for action.

So let's go back to the cross section view and

here's where Polyvagal Theory comes in.

One portion of the vagus nerve begins in the dorsal

motor nucleus X, or DMNX as it's shortened to.

The nerve fibers extend from this nucleus to a number of organs,

including the heart.

The second nucleus of the vagus nerve is called the nucleus ambiguus and

the fibers from this nucleus also link into the vagus nerve.

The dorsal motor nucleus X is a very ancient nucleus and

the nucleus ambiguus evolved much later.

The nerve fibers coming from the nucleus ambiguus are fairly fast and

therefore, they dominate the solo fibers that come from the DMNX.

Both nuclei send branches to the heart and

the significance of this will become apparent shortly.

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