Definition of fatigue

Fatigue is still a medical mystery. Broadly speaking, this is what they have discovered so far: there are two types of fatigue:

- peripheral fatigue
- central fatigue

Peripheral fatigue is basically muscular tiredness, whereas central fatigue is related to the central nervous system. Central fatigue is the one we're all interested in because this is the one that affects most people with various illnesses and, if you have persistent (or chronic) fatigue, this is where you will be having difficulties.

If you have chronic fatigue symptoms, then you will go on a medical diagnosis journey where the doctors attempt to find an underlying disease process. There are three outcomes:

- they may find an underlying cause for the fatigue and, if you are lucky, they may be able to treat you and the fatigue will go away.
- they may find the cause of the fatigue but there is no treatment to alleviate the fatigue.
- they may find no cause of the fatigue and there is nothing they can do.

Ultimately, you may be left with central fatigue that you have to manage yourself.

Having lived with fatigue for many years, I can tell you that there are different types of fatigue mechanisms at play and it seems like one broad definition (central fatigue) is not enough - the fatigue has a different feel to it depending on what goes on. Here are some examples:

- there is the 'sick to the core' fatigue - this is the worst kind and it feels like you're on your way out
- there is the fatigue that 'never goes away' - you go to sleep and it's still there in the morning
- there is the normal tiredness - a busy day and you need a rest
- there is insomnia fatigue - you didn't get enough sleep and you feel worn out
- there is complete exhaustion - you feel like you are going to collapse, most unpleasant
- there is mood fatigue - this is when you feel depressed
- there is hangover fatigue - you've taken medicine or something that makes you weary next day
- there is post exertion malaise - you did something physical or mental and now you are tired out

All these things make you feel tired but they have different qualities to them, and you would expect different underlying causes, but let's not go there just yet.

Suffice to say, fatigue is a new landscape that you will need to explore and different types of fatigue need different approaches - you would not expect someone who is 'sick to the core' to start doing exercise therapy of some sort.