What is Fatigue?

Fatigue has a few definitions. It is the awareness of reduced capacity to do a physical or mental activity OR the subjective sense of reduced or lack of energy (i.e. lassitude). Either way, fatigue is considered a subjective experience. As such, the experience of fatigue arises from our body’s central nervous system- the brain to be precise. It is universal – we all experience fatigue at one point in time or another – and it is conceptually related to the energetic demands of the body to complete work, mental or physical work.

Fatigue is not equal to being tired. Rather, sleep is a factor that will impact the level and possibly the development of fatigue because the purpose of sleep is to restore the functioning of physiological systems. Thus, if sleep is too short, or otherwise disrupted over prolonged periods, we will notice that our body will lose the energy levels required to perform work consistently, which results in physical and mental deterioration.

When a person’s physiological system cannot restore energy levels, fatigue can become pathological. Thus, fatigue can occur secondary to disease or injury (pathological fatigue), or as a result of overexerting oneself (normal fatigue). Therefore, we distinguish between normal versus pathological fatigue.

Normal fatigue, the fatigue we all experience when we overexert ourselves, is easily mended with sleep, rest, or changing activities. It is a factor that is built into our system to make us aware of when it is ‘enough’. Although the biological processes leading up to fatigue are not fully understood, one impacting factor is our perception of the level of fatigue. In order to actually notice fatigue, a person needs to become conscious of it.

However, when we are busy with other things, we may not notice because as humans we can only pay conscious attention to one thing or experience at a time- all other processing happens in the background -so to speak- outside of our conscious awareness. If you observe yourself, you likely will notice that sometimes the same activity under the same conditions can make you feel more fatigued when you do them alone as opposed to doing the activity with a friend. When you talk to your friend, your conscious attention is paid to the conversation, and you would only realize ‘out of the ordinary exertion’ that tips the balance towards noticing the degree of energy spent on the physical activity. This short example shows how external and internal processes work together to change what we consciously notice. At the same time, our perception can tell us incorrect information- we need to interpret what we perceive. Thus, sometimes, the experience of feeling tired or fatigued can be deceiving, and when we actually change activities and get more active, the perception of fatigue dissipates.

Going on a walk and talking to a friend, which allows for doing a more strenuous walk more easily, and then having a rest and re-fuel (e.g. sleep and/ or eat), can be considered helpful (barring some circumstances). But when the activity is more continuous like work or completing studies (e.g. years and decades), fatigue that is not attended to with sufficient breaks, changes in activities, ergonomic furniture, stress-reduction, self-care activities, and other impacting factors can change the balance in the physiological system over time. And granted, some people have more energy than others, which I see as individual differences. But as mentioned above, we distinguish between normal fatigue and the fatigue that is considered pathological.

Pathological fatigue refers to the type of fatigue that can result from injury or disease. It is characterized by its:

  • chronicity (it’s long-lasting),
  • resistance to rest (rest does not alleviate it sufficiently),
  • the inordinate effort a person has to exert for tasks, and
  • the limited endurance or rapid mental or physical exhaustion a person feels when doing to a task

Another question concerning pathological fatigue is what comes first- the pathological fatigue that therefore results in emotional distress and depression as can happen following brain injury or the mental health issue such as depression that then creates fatigue. In mental health conditions such as clinical depression, fatigue is considered a symptom, suggesting that clinical depression is the main culprit – different physiological processes go awry and result in depression-, which then also leads to fatigue among other symptoms.

If you experience fatigue that interferes with or takes over your life, it may be helpful for you to seek help. If clinical depression is the driver of fatigue, depression treatment may be beneficial to you. If fatigue following injury is the driver of your emotional distress, however, other treatment avenues are likely indicated in addition to therapeutic emotional support.

Heike @ Mind your Brain supports people whose challenges include brain injury and cognitive aging. Areas that she provides help with include cognition, brain health, cognitive rehabilitation, stress management, anxiety, and, of course, fatigue management.

You can read more on fatigue management and the emotional impact it can have @ Emotional Distress and Symptom Management following Injury and Disease, while more information on the idea of fatigue treatment can be found here

If you have additional questions for Heike, you can find her contact information here.

What is Fatigue?
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What is Fatigue?
This article explains the differences between normal and pathological fatigue
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Mind your Brain
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