Measurement and Reduction of Fatigue

PSYCH-105 Industrial Psychology

Chapter 12: Fatigue and Boredom

Unit 1

Unit 2

Unit 3

Unit 4


Measurement of Fatigue


Angelo Masso (1915), an Italian scientist, was the first to develop an instrument known as that ‘Ergograph’ which made it possible to investigate the relation between fatigue and work in a relatively isolated part of the body. The use of the ‘Ergograph’ has established a number of important relationships, each of which has a definite application to the industry and is discussed fellows:

  1. If the contractions with a given load are placed one every two seconds, there is a gradual decrees in the amplitude of the contractions until finally no further contractions can be made. 
  2. If the contractions with the given load are spaced within 10 seconds, there is no apparent evidence of fatigue.
  3. If the load is lifted in a fast rhythm it produce more fatigue for the lift then the same load lifted at a slower rhythm
  4. The time for complete recovery increases rapidly as the period of work is increased
  5. The activity of other sets of muscles reduces the ability of the figure to do work\
  6. The ability of the muscle to do work is decreased by lose of sleep, mental activity, hunger and failure of the muscle
  7. The ability of the muscle to do work is increased by massaging the muscle, injecting sugar in the blood stream and by good health and nourished body
  8. The rate of fatigue differs greatly in different people.
Fig.: Simple Ergograph
A. Strap for fixing forearm; B. Strap through staples for fixing fingers not in use; C. Ring for finger to be tested; D. Brass runner graduated in sixteenths of an inch; E. Maximum recorder; F. Pen carrier; G. Writing pen; H. Pulley; K. Weight; L. Cord. The part shaded in the diagram is cut out of the table.

Work Curve

Work curve represents a graph between the level of performance and time spent at work. As the practices or techniques to minimize fatigue depend to a great extent on the nature of the work curve, its discovery and use are important. 

Depending upon the nature of work, three kinds of work curves may be obtained, viz., simple muscular, Complex muscular, and mental work curve.

1. Simple Muscular Work Curve

Simple muscular activity curve is derived by recording the units and output of a group of muscles against the force of some weight or spring. It can be seen from figure ‘1’ that the curve for simple task shows a short warm-up period followed by a high level of performance. Subsequently, a sudden drop occurs to a point of complete exhaustion. One can generally conclude from study of such curves that the more complex and rapid the task, the faster the fatigue sets in. Moderate task permits a great total amount of work before complete exhaustions occurs than doing heavier task.

Fig.: A Simple Muscular Work Curve

2. Complex Muscular Work Curve

This curve depicts the amount of work done per unit of time in analytical industrial situations as a complex muscular task. This job is assumed to be motor in nature and monotones. Under normal conditions, when a person begins to work, it is easy and even pleasant, and the rate of output shows an increase. This stage may be called warm-up period. After about two hours or so conditions become uniform and the output levels off for half an hour or so. After this there is a decline in the interest and pleasure at work and there is some decline in the rate of output until lunch break. The productivity immediately after the lunch break may be lower as compared to the productivity at the time of going to the lunch. But the productivity again increases to the peek and after some time, it starts declining until the shift ends. There are sudden fluctuations in the rate of productivity because of certain factors which are outside the control of the worker.

Fig.: A Complex Muscular Work Curve

3. Mental Work Curve

As shown in figure 3 mental work decrement occurs in quantity, speed and accuracy of output as in muscular work. However, the individual differences and the nature of work tend to determine the timing of extent of such declines. The work decrement in mental task requiring continuous attention has been attributed to interferences to known as ‘blocks’. Prolonged mental work result in incapacity to evaluate what is being read. Common characteristics of prolonged mental work are increased errors and an increase in the amount of time necessary to assimilate written material or to solve perplexing problems towards the end of the period. In addition to this, the physical state of the body is not indication of its mentally satisfying state, although there is a state of tension which expresses itself in both muscular and neural form during the mental work. Consequences of mental overwork in children are disturbance of vision, headache, bleeding from nose, loss of aptitude and indigestion, cerebral disorder and nervousness. 

Fig.: Mental Work Curve

Reduction of Fatigue

  1. Work study (method and motion study): Efficient use of motion, overtime limitations
  2. Proper working hours (reduced hours)
  3. Sufficient rest period 
  4. Industrial training
  5. Industrial atmosphere (Suitable light, temperature, air, noise, cleanliness, and humidity) 
  6. Work place lay out (reduce unnecessary movements)
  7. Ergonomics (designing of tool, equipment and machines)
  8. Sufficient sleep
  9. To remove personal problems
  10. Sufficient refreshment 
  11. High morale 
  12. Medical facilities (examination after every 6 month or 1 year to keep them fit)
  13. Employee counselling (to overcome personal problems)
  14. Music (reduce monotony and increase production)
  15. Hiring suitable employees

Author – Dr. Niyati Garg

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