The oxford Concise Medical Dictionary defines fatigue as inability of an organism, an organ, or a tissue to give normal response to stimulus until a certain recovery period has elapsed. It also goes on to elaborate this concept further as mental or physical tiredness following prolonged intense activity. In context of the muscle power, this sensation happens due to accumulation of metabolic products within the muscles. Otherwise, in absence of other specific diseases, incorrect or inadequate food intake is projected as the most common cause of such feelings (Concise Medical Dictionary.
Oxford University Press, 2007). The Dictionary of Diet and Exercise characterizes fatigue as overwhelming need to reduce intensity of activity. When one becomes physiologically fatigued despite intense attempt, one is incapable of maintaining maximum power output of muscles. Therefore, it can be reasonably argued that fatigue is a safety device that conserves energy for vital activities and thus a means of preventing irreversible damage to body tissues. Fatigue may also be caused by biochemical mechanisms affecting the brain.
Some researchers suggest that concentrations of serotonin increase in the brain during exercise and cause fatigue. The increase may be associated with depletion of muscle glycogen and increases in fatty acids circulating in the blood. Serotonin levels in the brain may also increase when amino acids, called branched chain amino acids (BCAAs), are used as fuel, lowering the amount of BCAAs in the blood (Food and Fitness: A Dictionary of Diet and Exercise).
The other definitions that can be encountered in literature are multifarious. The common tune in researchers’ understanding of fatigue is a specific form of human inadequacy in which the individual experiences an aversion to exertion where he feels unable to carry on. Although such feelings may be generated by muscular effort, as might be contemplated exhaustion of the energy supply to the muscles may not be the invariable precursor in all the cases.
The sensation and state of fatigue may also stem from pain, anxiety, fear, or boredom without even a trace impairment of muscle function. Clinicians agree that there is existence of confusion in defining fatigue. In nursing practice, one can encounter presentations of fatigue when actually there is no cause associated with it; however, the reverse is also true. There are many clinical conditions where fatigue is the only complaint at presentation masking a serious pathological condition.
This battle between physiological and psychological aspects of fatigue becomes paramount while deciding the management strategy of a particular case of fatigue. Fatigue, indeed, may present in association with established medical or psychiatric condition, but it should be remembered that it can as well be idiopathic. Whatever may be the cause, fatigue has significant and lasting impact on daily functioning and quality of life, and treatment and management of fatigue is important in alleviating such effects in the long run (fatigue, (2007).
In Encyclop? dia Britannica). Since the physiological and psychological mechanisms underlying fatigue are understood poorly, it can be generally agreed upon the experiential fact that fatigue is the final common pathway for an array of causal factors. From this writer’s experience, most of the cases of fatigue happens in females, especially those with history of previous depression or fatigue are more prone to develop fatigue.
Many a cases reveal stress, may it be physical due to infection, psychological due to bereavement, or social due to work-related issues. In few occasions, factors like physical inactivity, emotional disorders, ongoing psychological or social stresses, or sleep abnormalities may precipitate clinically significant fatigue that must be attended to and managed. The literature has now recognized that the feeling of fatigue may also stem from pain, anxiety, fear, and boredom. The presence or absence of compromise of muscle function only makes the differences.
There was once held belief that work is the cause of fatigue, but industrial psychologists failed to show a close connection between the performances of an individual worker as direct measures of fatigue. The research thus attributed no significance to inner feelings at all, and the attention shifted from inner feelings of the subject to external phenomena not related to the subject at all. Obviously, it is clear that work output is a product of the subject, and that factor has not been pain adequate attention to (Sharpe, M. and Wilks, D. , 2002).