Dr. V.K.Maheshwari, M.A. (Socio, Phil) B.Sc. M. Ed, Ph.D. Former Principal, K.L.D.A.V.(P.G) College, Roorkee, India
Mrs Sudha Rani Maheshwari, M.Sc (Zoology), B.Ed. Former Principal. A.K.P.I.College, Roorkee, India
Fatigue is a word by which we denote the diminished efficiency of the organism that seems to result from intense and sustained activity and which during a period of rest and more especially of sleep, gives place to full efficiency. A Fatigue can be described as the lack of energy and motivation (both physical and mental).
Physical fatigue – the person’s muscles cannot do things as easily as they used to. Physical fatigue is also known as muscle weakness, weakness, or lack of strength.
Psychological (mental) fatigue – concentrating on things has become harder. People may feel sleepy; have a decreased level of consciousness, and in some cases show signs similar to that of an intoxicated state.
Causes of fatigue
The possible causes of fatigue are virtually endless. Below are some (by no means all) possible causes of fatigue:
- Mental health (psychiatric) – when stress levels become excessive, they can easily cause fatigue. Stress and worry are two emotions that commonly cause tiredness
Clinical depression can cause tiredness for several reasons. Fatigue may be caused by the depression itself, or one of the problems associated with depression,.
- Metabolic – Cushing’s disease, kidney disease, electrolyte problems, diabetes, hypothyroidism, anemia, kidney disease, and liver disease.
- Drugs/Medications – some antidepressants, antihypertensive, steroids, antihistamines, medication withdrawal, sedatives, and anti-anxiety drugs.
- Heart and lung conditions - pneumonia, arrhythmias, asthma, , heart disease, coronary heart disease, and congestive heart failure.
- Sleep problems – working till late at night, jet lag, sleep apnea, narcolepsy, insomnia, and reflux esophagitis.
- Chronic pain – patients with chronic pain typically wake up tired, even after having slept for a long time. For many, pain disrupts their sleep, which also leaves them tired.
- Overweight and underweight – overweight/obesity is a rapidly growing problem in much of the world today.
The fatigued condition is revealed by symptoms or signs of two kinds, the objective and the subjective. The objective signs are drooping bodily attitudes, sluggish motions, and diminished efficiency. The subjective signs again are of two kinds, namely, localized bodily sensations of fatigue and a general sense of inefficiency, of difficulty in energizing, of lack of energy.
Factors responsible for fatigue
That which one call fatigue is no entity, and can not be accounted for in terms of any one kind of physiological change. Definitely the using up of reserve stores of energy is one factor. This factor may with advantage be called’ exhaustion’ we then recognize exhaustion as one of the factors of the syndrome we call fatigue. In some instances of fatigue it is of predominant, in others of relatively slight, importance.
A second great factor is the presence in the blood and tissues of products of metabolism which, acting both on the brain and on other tissues, and locally as well as in more diffuse manner, somehow retard metabolism.
A third principal factor is fatigue-sensation. This is a special quality of sensory impression excited in the afferent nerve-endings of muscles (and perhaps in other allied tissues, such as tendons and ligaments) in consequence of intense or prolonged activity. The nature of the stimulus, is not known, it may be chemical in part or whole. But, whatever the stimulus, the afferent currents excited in this way seem to have an inhibitory effect. If one hold out his right arm horizontally for half an hour, he begin, after a few seconds, to experience sensory effects, localized in the deltoid and other shoulder muscles; these sensations grow gradually more intense, and at the same time one find it necessary to put forth more and more effort to sustain the limb.
These two effects increase together during the first five minutes or so, and then seem to attain a maximum. If in spite of them I persist with his task, these local effects seem to diminish rather that to increase; but he become aware of a more central, less definable form of fatigue, an increasing difficulty in sustaining his effort. And at the end of half an hour I give up, feeling exhausted and aware that only some new and stronger motive could enable him to persist in his effort for a still longer time. Yet he has not expended any great amount of energy. If he had walked briskly for the same length of time, or swung a pair of clubs, he should have done much more muscular work.
The fatigue induced has, then, been essentially local. But though local it is not wholly a matter of the changes occurring in the muscles and other peripheral tissues. The local conditions are in the central nervous system also and there they are of two fold nature. There is a general inhibitory effect which I experience as something to be overcome by increased effort. It is probable that this may be rightly conceived as an obscure instinctive impulse to relaxation, to seek repose. But there is in all probability an actual blocking of the efferent nerve channels through which may effort innervates the deltoid muscle. This is indicated in two ways: first, the impulse to relax in general, it is not only an impulse to relax this effort but an impulse to general relaxation and repose; yet, if I relax my right arm, I can raise and sustain my left arm in spite of this impulse, with very much less effort, less will-power, than is required to persist in sustaining the right arm. Secondly, as I sustain my right arm, it begins to show tremors and coarse irregular slight movements which I cannot altogether prevent, and my innervation spreads more and more widely, overflowing into muscles that have no direct part in sustaining the arm.
There is good reason to believe that this local central fatigue has its main locus in the synapses upon the efferent path, perhaps chiefly in those at the spinal level. The synapses are the weak points, and the points of varying resistance, in the neural channels (the neurons themselves are extraordinarily resistant to fatigue), The synapses are susceptible to the influence of various drugs. I have shown reason to believe that they are subject to a rapidly oncoming fatigue (probable of the nature of self-poisoning) when kept in continued action; an effect which is rapidly removed as the blood washes away the products of metabolism.
During long-continued activity of brain and body the poisonous products of metabolism become diffused through all the tissues and body fluids. Then these products act upon all the synapses of the brain, raising their resistances to the passage of the nervous current; thus rendering all bodily and mental tasks more difficult, and tending to reduce me to passivity and sleep by way of this relative isolation of each neuron from its fellows; this is partial dissociation of all my nervous system.
After long-sustained activity of a varied kind, I am reduced to a condition is which I can only with the utmost difficulty resist the onset of sleep. I feel utterly tired; and, as soon as I sit down to rest, my eyes tend irresistibly to close and I fall asleep. No task that can be set the will is more severe, more trying, than that of resisting sleep in such conditions. Many a tired soldier has fallen asleep at his post, thought he knew that his yielding meant death and disgrace. In this condition the two factors of exhaustion and general diffuse poisoning of the brain by products of metabolism are probably of chief importance.
“Our fatigue is often caused not by work, but by worry, frustration and resentment”