Fatigue
Fatigue is the state of the muscle, and viscera or central nervous system of an organism, wherein it has prior physical activity and mental processing, but in the absence of enough rest, the outcomes would be insufficient capacity of the cells in the body to sustain the original level of activity by utilisation of the normal resources in the body (Hancock and Desmond, 2001). There are two types of fatigue the central and the peripheral:
Central Fatigue- Coccheto (2004) defined central fatigue as fatigue in the central nervous system which occurs in the large portion of the intercerebral control circuits that is due to the repression in the level of voluntary exciting that are subdued in numerous motor units to the level of voluntary neuromuscular junctions and the firing frequency. In addition, according to Gandevia (2001) the central part to fatigue is described as the decrease in the neural drive or nerve-based motor command in the working muscles wherein the outcome in the decline in the output of the force.
Peripheral Fatigue- according to Chaudhuri and Behan (2004) peripheral fatigue a disorder in the neuromuscular junction transmission and metabolic disease that is due to fatigability of the muscles wherein it is characterised by the failure to maintain the force during contraction of the muscles.
Physiological bases of Fatigue
Fatigue has a number of physiological bases, according to the Occupational Safety and Health Service the following bases are the physical exertion, sleep disruption, circadian disruption, domestic and social factors.
Physical Exertion- according to Grandjean (1988) it is a common source of fatigue wherein the level of fatigue depends on the frequency and length of application of the forces in the muscles, as well as the nature of work. In addition, Grandjean stated that physical exertion could be measured in many ways like electromyography, measuring the oxygen consumption, and counting heartbeats. The level of fitness of the worker plays an important role in the degree of fatigue that he or she experienced in the workplace. If a worker is not physically fit to perform in jobs that need a great amount of physical effort like manual labour, he or she will experience a tremendous amount of fatigue due to physical exertion. Furthermore, if a worker is not disciplined enough to take care of his or her health then fatigue could be easily felt by the worker.
Sleep Disruption- according to Caskadon and Roth (1991) in order to sustain the alertness of an individual in the work place, he or she needs a specific amount of sleep, however individuals have different needs in sleep and the factors that contribute to these differences are not yet well understood. Moreover, Caskadon and Dement (1981) discussed that if an individual have reduced his or her time of sleep by one hour it could cause increase in the level of sleepiness and can even lead to severe outcomes if it continues. Roth, Roehrs, Caskardon, and Dement (1994) stated that the quality of sleep and its continuity is a significant factor that could affect the consecutive alertness and performance of a worker. Sleep is very important to all individuals because lack of sleep will lead to stress and fatigue in the workplace. If an individual chooses to sleep late or not sleep at all, the result will be devastating because he or she will either be absent on the work or go to work but have a bad performance. According to Akerstedt (1991) there are three aspects in the work schedule of an individual that could disrupt sleep and these are:
- Longer hours in the workplace
- The hours of job is irregular
- And working in schedules that require people to work even though they should be asleep
Circadian Disruption- according to Dijk and Czeiler (1995) the circadian biological clock is the part of the body that efficiently programmes people to sleep during night time and be awake during the day. Moreover, it is the one that relates the daily cycle that lives in the functions of the physiology and behaviour of the body and synchronises with the cues of time in the environment. Dijk and Czeisler (1994) stated that the time and quality of sleep of an individual relies on his or her circadian clock. And an individual that is not able to adapt his or her circadian clock to shifting work schedules could degrade the efficiency and productivity of his or her performance which can lead to stress and fatigue in the workplace. Poor lifestyle choices could also contribute to the incomplete adaptation of the circadian clock, an example if the employee's schedule was changed from dayshift to night shift and does not gain enough sleep during day time to adjust his or her circadian clock, then most likely he or she will eventually get stress.
