Fatigue: Definition, Physiological Explanation, Types & Causes

Fatigue: Definition, Physiological Explanation, Types & Causes



Fatigue is a human thing that will be felt by every human being. This is because even from birth until near death, humans have the urge to move and carry out various activities. All movements and activities carried out are of course meaningful or at least have meaning and function for humans.



But the more movements and activities that are carried out, the less our desire and ability to do them. This is referred to as fatigue, as a result of the limit of human ability to have the desire and strength to carry out a movement and activity.


Definition of Fatigue

Fatigue is a loss of self-energy resulting from excessive energy use due to completing various work tasks that exceed individual capacities or strengths (Warsah & Daheri, 2021, p. 153). Fatigue can be interpreted as a different condition for each individual, but all of these individuals experience a loss of efficiency, decreased work capacity and endurance.


Fatigue is a state or condition, whether physical or psychological, not a certain urge. Certain urges that make us not want to do something may be laziness from feelings. However, it is also possible that the laziness we experience can occur as a result of feeling tired or fed up with something. This is the reason why fatigue is included in mixed mental symptoms which can consist of loss of attention (cognition), which can cause negative affect, and lead to loss of motivation (conation).



Causes of Fatigue

Fatigue is caused by the ongoing activity or work, both physical and spiritual activities that are carried out continuously for a long time. Therefore, fatigue can also be categorized as a kind of stress. An example is how a profession can cause work fatigue which is known as bournout which is a type of stress experienced by many people in companies with a high hustle culture. Some other factors that cause fatigue are as follows.


Intrinsic Factor

Fatigue can be caused from within a person or also known as an intrinsic factor. Some of the causes of fatigue from the intrinsic side are as follows.



Age is related to performance because increasing age will be followed by the process of degeneration of the organs so that in this case the ability of the organs will decrease. With a decrease in the ability of organs, this will cause the workforce to experience fatigue more easily.


In the female workforce there will be a biological cycle every month in the body’s mechanisms so that it will affect their physical and psychological conditions and this will cause the level of female fatigue to be greater than the fatigue level of men.

Nutritional status

Nutritional status is one of the factors of work capacity, where a state of malnutrition with a heavy workload will interfere with work and reduce efficiency and result in fatigue.

Health Status

There are several diseases that can affect fatigue, for example someone who experiences heart pain if there is a lack of blood, mostly attacks the left ventricle of the heart so that the lungs will experience congestion and the patient will experience shortness of breath so that they will experience fatigue.

Psychic State

Psychic state, namely a response that is interpreted in the wrong way, so that it is primarily an activity of an organ, resulting in tensions that can increase a person’s level of fatigue.

Extrinsic Factors

Apart from coming from within, fatigue can also be caused by external factors or extrinsic factors. Some of the extrinsic factors that can cause fatigue include the following.



Workload and Working Time

Workload is the volume of work that is imposed on the workforce both physically and mentally and is their responsibility. Each job is a burden for the perpetrator and each workforce has its own ability to handle its workload as this direct workload. Workload determines how long a person can work without causing fatigue or distraction. On work that is too heavy and excessive will also accelerate the fatigue of an individual.

Physical Work Environment

The physical work environment that affects fatigue includes lighting, noise and work climate such as whether or not lighting is good, the working climate of the workplace (temperature or temperature, air humidity, wind speed, etc.).


Sound that is too loud and lasts a long time can cause stimulation of the area near the hearing reception area to ringing. This situation will cause fatigue is a functional reaction from the center of consciousness, namely the cerebral cortex which is influenced by antagonistic systems, namely the inhibiting system (inhibition) and the system (activation).

Ergonomic Factors

Ergonomics can reduce workload and work fatigue. Ergonomics also plays a role in maximizing comfort, safety and work efficiency.

Fatigue Physiology

Physiologically, according to Suma’mur (2014) the state and feeling of tiredness or exhaustion is a functional reaction of the center of consciousness, namely the brain (cortex celebri), which is influenced by two antagonistic systems, namely the inhibiting system (inhibition) and the driving system (activation).



Inhibition or blocking systems work on the thalamus (thalamus) which can reduce the human’s ability to react and cause a tendency to sleep.


Meanwhile the activation or propulsion system is contained in the reticularis formation which can stimulate the vegetative center for ergotropic conversion of organs in the body towards work, fighting, escaping, and so on.

So based on this concept the condition of a person at a time is very dependent on the results of the work between the two antagonistic systems in question. If the inhibiting system is in a stronger position than the driving system, a person is in a state of exhaustion. Conversely, if the propulsion system is stronger than the inhibiting system, then a person is in a fresh state or not tired.


The Krebs cycle produces carbon dioxide and energy in the form of adenosine triphosphate (ATP). ATP is the body’s main source of energy used to carry out daily activities or work. Fatigue is the result of accumulation of lactic acid in the muscles and in the bloodstream. Accumulation of lactic acid can cause a decrease in muscle work and the possibility of peripheral and central nervous factors influencing the process of fatigue. When the muscles contract, glycogen is converted into lactic acid and this acid is a product that can inhibit the continuity of muscle work resulting in fatigue.


In the recovery stage, a process occurs that converts some of the lactic acid back into glycogen, allowing the muscles to function normally again. The provision of oxygen affects the speed of recovery of muscle function. If the workload of the muscles is not too great then the muscles can maintain balance, excess lactic acid does not accumulate so that the work capacity of the muscles returns to normal, does not decrease.


According to Simpson (in Setyawati, 2011 in Warsah & Daheri, 2021, p. 155) muscle fatigue occurs due to a lack of oxygen and the accumulation of muscle metabolites (in the form of lactic acid and CO2) which do not enter the bloodstream (Hastuti, 2015) .


Types of Fatigue

As previously stated, defeat can be caused by physical or mental factors. Based on this, we can divide the types or types of fatigue into physical and spiritual fatigue which will be explained as follows.


physical exhaustion,

namely fatigue caused by reduced physical or body strength, so that one cannot do something properly. Factors such as physical fatigue can be caused by the use of great physical strength to the limit, or factors of health and disability.

spiritual exhaustion,

Spiritual fatigue is fatigue caused by loss of desire or reduced thinking power so that one cannot do jobs that require mental or psychic strength properly.

Physical and spiritual exhaustion,

Actually, physical fatigue cannot be separated from spiritual fatigue, and vice versa. In short, it can be said that physical fatigue and spiritual fatigue have a reciprocal relationship and influence each other (Ahmadi, 2003 in Warsah & Daheri, 2018, p. 156). For example, fatigue and stress due to conditions related to work pose a risk of interfering with the effectiveness and productivity of workers because this kind of work takes a lot of physical and spiritual energy.

Fatigue Theory

Fatigue is one of the mixed symptoms or human mental processes because it has a lot to do with the productivity and efficiency of human work which can be caused by work fatigue. Therefore, many experts have researched it and produced various conceptualizations and theories that can cause and overcome fatigue or fatigue. Here are some theories of fatigue according to experts.


Intoxication Theory

Intoxication consists of the word “into” or “intra” which means “in”, and “toxicum” which means “poison”. Thus, intoxication is the presence of poison or an excess of a residual substance in our body which, in the context of fatigue, means it can cause fatigue. In the body, there is an exchange of substances, blood circulation and combustion. Due to the exchange of substances, circulation of blood and combustion, various waste materials or residues arise. Then these waste substances enter the blood circulation and finally enter the nervous system. This is where they cause some sort of venomous or poison stuff to form. According to the theory of intoxication, this process causes fatigue, both physically and spiritually, both locally and throughout the body.


Biological Theory

The biological theory of fatigue was put forward by Edward Thorndike, a psychologist in the 19th century who produced many psychological theories in the field of education. This theory includes a new theory that seeks the causes of sluggishness of the laws of human life. Thorndike showed that two events that occur in humans, if he works long, will occur:


Reduction of energy in us, causing symptoms of fatigue.

Feelings of boredom, working for longer periods of time leads to feelings of boredom. Boredom reduces feelings of satisfaction at work. This is also felt as lethargy/fatigue (Mardianto, 2014 in Warsah & Daheri, 2021, p. 156).

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