I can remember at one especially tough rugby practice trying to better grasp why, even though I was in fairly good condition, I was still puffing and panting, my muscles were on fire and my brain was trying to force me to quit.
As I progressed through my university years of studying I developed a better appreciation and understanding of the mechanisms of fatigue - better known as the theory of Peripheral fatigue.
Peripheral fatigue states that as the body works harder, certain physiological changes take place leading to distress and fatigue and ultimately a decrease in the level of performance. The accepted reason for this fatigue was said to be an increasing concentration of Hydrogen ions, causing an increase in the bodies acidity levels.
This led to muscles "shutting down" or not functioning as they should - commonly experienced as a sensation of heavy, tight and tingling muscles throughout the body - mostly in the arms and the legs.
This paradigm has been accepted for decades, but now there is a another school of thought. It is called the theory of Central fatigue.
In simple terms, the theory suggests that fatigue during athletic activities is actually regulated by a center in the brain, which is where the information from both the external and the internal environment is .
The external environment includes factors such as temperature, humidity, altitude, while the internal environment includes factors such as: level of hydration, fatigue state, glycogen store levels and more.
A continuous stream of information is gathered by the bodies many receptors and then sent to the brain, where it is integrated, evaluated and assessed.
The result: the amount of output (watts, beats per minute, minutes per mile etc) being produced by the body is closely monitored and controlled to avoid a "catastrophic" event taking place for example: death, in the most extreme situations, or not completing a race.
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The central "governor" aims to ensure the bodies survival under the many challenging situations we are faced with every day.
Something which has intrigues me to this day is the bodies ability to moderate and adjust levels of output through the course of an activity.
At the start of a race, an analysis of data acquired via our bodies various receptors, provides information necessary for this "governor" to make subconscious calculations as to what it will allow you to do.
It will, for example, allow you to run an 8:30 / mile, for 13 miles, because your level of training is sufficient, you are hydrated and your energy stores are optimal. The temperature is not to high or low and the humidity just right.
As you move through the course, continuous feedback reveals you are not under any dire physiological, psychological or anatomical distress, and with 5 miles to run, you feel capable of increasing the pace to 7:30 / mile.
1 mile to go and pick up the pace to 6:30 / per mile.
The mind feels comfortable that for 1 mile you will not sustain any catastrophic damage running at 6:30 / per mile. Would you be able to run at 6:30 / mile for 13 miles? All things considered likely not - and the mind is 100% cognitive of this.
This is how we are able to "kick" at the end of race and elevate our performance to beyond the output we were doing at the outset of the race.
As we study the body in more depth over the coming years I am positive new theories and facts will certainly surface giving us an even better understanding of the relationship between fatigue and human performance.