The Central Governor Theory of Fatigue is an interesting model used to explain the causes of fatigue. We usually assume that our feelings of fatigue are caused from our muscles during exercise but this may not be the case. consider the examples below:
So you’re 2 hours in to your cycle and you are feeling tired, fatigued and not at all sure that you really want to keep going. Of course you do anyway, you’re training for something important to you so you summon a bit more energy and keep going. After a while, this new effort seems even more draining for you, but why? What is it that actually makes us tired?
Another example to think about: You are fit and strong, and usually a 15km run is a breeze but today there is none (a breeze) and the sun is beating down on you. You know that you aren’t really tired but for some reason you just can’t keep up with your normal pace. You are flagging and you can feel the energy draining out of you as you fight towards the end of your run. Again, why are you tired? You ate well, your muscles and liver are packed with glycogen from your high carbohydrate meals before the run so what is it? Maybe the dry hot air isn’t letting you breath properly?
In this article we will look at what we call the Central Governor Theory of Fatigue[i]. This is a response or even preemptive reaction to fatigue and it is central to why we feel tired, and essentially causes us to slow down and eventually stop. If we can train this response, we will increase our endurance capacity and therefore become better athletes, more able to survive in extreme conditions by increasing our endurance.
“Endurance – The ability to resist muscular, cardiovascular and neurological fatigue.”
What is the Central Governor Theory?
The Central Governor Theory of Fatigue suggests that instead of us failing to resist fatigue because we have run out of energy, in the form of blood glucose or muscle/liver glycogen as is typically thought. We actually stop ourselves from reaching the point where we would ever actually run out of energy at all. After all, if we actually completely run out of energy we will be six feet under, when a muscle is entirely depleted of its ability to metabolise (feed itself) it goes stiff, we call this “rigour” as in: rigour-mortis. Instead, the Central Governor Response comes from the brain and is a preemptive mechanism to prevent exhaustion, and not a response to the exhaustion itself. This is essentially what slows us down before we run ourselves in to the ground. It is, in a way a survival mechanism.
How does the Central Governor Theory work?
Of course it is possible to override the Central Governor but this can cause severe injuries or even death as we will see next.
So the Central Governor prevents us from killing ourselves by completely depleting our muscles of energy. But that is not it. There are other parts of the body that are much more vulnerable to the effects of high levels of exertion. As Noakes says: “The heart is the organ at greatest risk of developing an oxygen deficiency during stressful conditions – especially at extreme altitude”[ii]. The Central Governor comes in to effect in order to stop the heart from suffering damage. So how does this work?
Well, the heart is a muscle, not like any other. It is cardiac muscle as opposed to skeletal or smooth muscle. This is important as it doesn’t feel the same when it’s working hard, your legs burn when you run up a hill but your heart doesn’t feel the same pain. You don’t actually feel your heart getting tired. regardless of how long you have been working, do you? If the heart becomes oxygen starved, you will feel angina. This is bad news (as you would probably expect when your heart feels like it is being squeezed within your chest while you get referred stabbing pain in your chest and arms). What we must remember is that the heart requires oxygen too, it has its own oxygen supply and when this becomes compromised it is heart bypass time.
The Central Governor is in place to prevent the heart from ever becoming oxygen starved. It does this in a simple way. The brain usually sends messages to your muscles and recruits some muscle fibres (not the whole muscle at once) which contract, allowing you to walk/run/ski/climb). But when your brain notices changes, either in your homeostasis or even at altitude, when it reacts to the reduced oxygen level in the air breathed in; the brain stops recruiting more muscle fibres. The result is that you cannot work as hard any more. You can continue but at a slower pace. If this didn’t happen then the demands on the heart would increase up to the point where it would fail (ischemia or anaerobiosis). You are protecting a vital organ at the cost of your performance and so it is all rather sensible really.
The “So What?” of this is that we must have highly trained and very efficient muscle fibres in order for us to perform at any kind of respectable level when we are being told to take it easy by the Guvnor.
The most important thing to understand is that with this theory it means that we are in fact not going to fatigue to complete exhaustion. We will always be able to push on but at a slower pace or lower power output. Now this may not be enough to get you home unless you have trained to be strong enough to keep going at these low paces once tired. The feeling of fatigue is coming from your brain, not your muscles. It is effectively an in-built pacing mechanism.
Some would even say that fatigue is really an emotion. That is is an emotional expression of the subjective symptoms that develop. It is the evidence of a struggle going on between your conscious and sub-conscious wills.
If you are able to develop this Central Governor Response you may well develop your capacity to endure. If you train your body endure, even when it is being reigned back by this Governor, you may well do it for long enough to succeed.
Objective-X will be posting more articles on the Central Governor Theory, along with some ideas on the ways in which we can train it, so keep informed with the Resources section.
[i] Noakes (2001)
[ii] Noakes (2001