2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
568
PERCEIVED QUALITY OF FATIGUE DURING SOME
OCCUPATIONAL TASKS
Rakesh D. Raut, H .V. Bhasin
NITIE, Viharlake, Mumbai-87, India.
Contact person: rakeshkumar@nitie.edu
INTRODUCTION
A fundamental but difficult question concerns the meaning of fatigue and how it best can be
defined. The problem with the concept of fatigue is that people may be referring to distinctly
different states, although they are using the same terms, and thereby misunderstandings may
arise (Åhsberg, 1998). Many psychological effects are caused by a decrease in the physical
work capacity of the individual. Objective measurements of physical stress, such as measured
by the physical laboratory tests, do not present the whole picture of what is really going on
internally and that person's perception of the physical stress (Deeb, 1999). Since people
generally react to the world, as they perceive it and not as pure reality, it becomes extremely
important to study and establish some kind of relationship between subjective (as reported by
the person) and objective (as measured physically) measurements of physical stress (Borg,
1970).
Psychophysics is commonly defined as the quantitative branch of the study of perception. It
investigates the correspondence between the magnitudes of stimulus properties as assessed by
the instruments of physics, and as assessed by the perceptual systems of people (Baird and
Noma, 1978). Over the years, many types of scales were developed to be used in
psychophysical studies. Three of the most commonly used types are: (1) category scaling
techniques with two types: the interval scales and the rating scales; (2) ratio scaling
techniques; and (3) rating scale techniques which are the most commonly used in psychology
and represent one kind of category scale. The most commonly used scale for the assessment
of subjective qualities during dynamic physical work is the rated perceived exertion (RPE)
15-point scale (6-20) developed by Borg (1970). This RPE scale (Table 1) is commonly used
when direct estimation of the subjective intensity is needed. The advantage of rating scales is
that they allow for direct inter-individual or intra-individual comparisons because the person
reacts to the stimuli in an absolute manner (Borg, 1982). Using the CR-10 scale, it should be
possible to answer the following questions: how strong/weak is a particular intensity, and how
much stronger/ weaker it is when compared with another? In either question, the level of
intensity is determined by its position on the scale. For example, number 10 on the scale is
defined as an extremely strong perception of effort and exertion.
Table 1: Borg's category-ratio scale (CR-10)
0 Nothing at all
0.5 Extremely weak (just noticeable)
1 Very weak
2 Weak (light)
3 Moderate
4
5 Strong (heavy)
6
7 Very strong
8
9 Very weak
10 Extremely strong (almost max.)
(*) Maximal