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Understanding fatigue - towards a model of CFS

So, these are some of the factors that appear to be at work in the onset and maintenance of CFS. Let us now attempt to synthesize these into a model of the condition. This will in turn lead to a management strategy for improving condition. That fact that this management strategy has been shown to work lends indirect support to the model it is based on. Let us look at that first. Before proceeding though, again, a word of caution. You may recognise yourself in some of this. You may not. If it means nothing to you, go on to the self help section and try what is suggested there anyway. Let us first attempt to construct a typical CFS history and see how the factors above can help make sense of it.

The model

The black line represents the activity level of the person. The red line represents the activity limit of that person. like any other living thing, every individual will have a level of activity beyond which they cannot function for long. We all exceed this occasionally - running for a bus, going through the stress of studying for exams etc. Functioning beyond that limit for long will produce increasing fatigue, pain and propensity to illness.

Let us look at how this might work in practice. At the beginning of the graph, the individual is busy, but not too busy. The general flavour of that business could contain numerous factors - busy work, social life, exercise and sport, childcare commitments, being generally driven. As time goes on however, the individual is beginning to reach their limit. This can be for two reasons - either their activity level goes up, or their limit comes down. In fact the two will often go together. An increase in activity levels without time for rest will weaken the individual and lower the limit of coping. The longer one tries to function over or near one's limit, the more the limit will reduce. Sometime external circumstance - viral illness, life crises, will lead to an abrupt reduction of the person's limit.

An individual may carry on like this for some time, perhaps feeling increasingly tired or perhaps thriving on the pace. At point A in the graph comes the straw that breaks the camels back. Most clients that we see report some critical incident, usually a viral infection, sometimes an operation or other life event at which point they clearly feel themselves to be fatigued and ceasing to cope.

They may struggle on for some time. Between point A and B, they are trying to maintain their activity level whilst their ability to cope, their limit is reducing all the time. The further they get above that limit, the more they feel fatigued, ill and unable to cope, the lower that limit becomes. Two things can happen at point B. Either the individual will abruptly stop trying to cope and abruptly drop their activity levels (this is illustrated in Graph 1). Or they will gradually drop more and more from their life (see Graph 2).

Let us go through Graph 1 first. At point B the individual decides to stop work, drop responsibilities and rests. Again several things can happen at this point. The individual may not rest enough and attempt to resume their former activities too soon (point C), whilst they are still not recovered. This puts them in the red zone, leading to an abrupt return of fatigue and pain (point D). They may struggle on for a period, during which time their limit decreases further. At some point (E) they will return to rest again.

Most individual will eventually enter a period where they rest a lot, or do much less than they used to for a prolonged period. As pointed out above, prolonged rest is actually detrimental to the system, reducing the limit even further (between B and C; between E and F). This means that a lower and lower level activity will produce distressing symptoms. The person will naturally reduce their activity levels in response to this. In so doing, with the increase in rest and sleep that this usually entails, they will reduce their limit even further.

Eventually, at point F, most people reach a "stable state." They will have, through hard won experience, a knowledge of their current limit. On days when they are more symptom free than others they will push over it. This will then lead to symptom increase from which they will recover by resting for, perhaps, a day or two. Once the symptoms are less, they will push the limit again. These symptom lead patterns of activity and rest, the boom and bust cycle, characterize Chronic Fatigue Syndrome. You may recognize this end stage of having to live within a very narrow limit.

Let us look in a bit more detail at the physiology of boom and bust. When you do too much - that is when you exceed your current physical limits, given your current health and fitness, you cause the individual muscle fibres to behave abnormally. These are called eccentric contractions. Instead of a smooth co-ordinated contraction, the individual fibres pull against each other, causing microscopic areas of damage. Over the next 24-48 hours this damage repairs, but causes delayed pain. Hence the "boom" is not a good idea. Furthermore, because the excess activity leaves you exhausted, and in need of rest, during the following period exactly the opposite happens. The muscles get weaker, and even more vulnerable to the next period of activity. Back

Some people will reach that stable state without such dramatic ups and downs before hand. This is illustrated in Graph 2. . Here at point B rather than abruptly stopping everything, some individuals may gradually begin to drop more and more from their lives as keeping it all going is making them ill. Eventually, at point C, they will have reached a substantially lower level of activity than previously. Often people will, by this point, be only working and resting the remainder of the time. This reduction in activity and increase in rest will lead to a more gradual lowering of their activity tolerance than in Graph 1. Again they will reach a stage where they will be resting much more than before and expending energy in sustained bursts.

As I said you may not recognize yourself in any of these patterns or cycles, or you may recognize bits of it. The important point to grasp is that whatever started it off, the pattern of Chronic Fatigue often becomes self perpetuating, a vicious circle that one gradually enters and that it can be hard to break.

Author: Vincent Deary
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