Humans in Work System Environment - Fundamentals and Assessment Tools for Occupational Ergonomics - page 75

The characteristics of a person who has the ability to perform is influenced by four categories. These are
the constitution-, disposition-, qualification-, and adaptation characteristics (Figure 5.6). Constitution
characteristics are unchangeable ratios in the life cycle of humans. Among these characteristics are
gender, somatotype, and ethnical origin. Disposition characteristics are variable, however, the working
person has no direct influence on this. Disposition characteristics cover the age, body weight, the state
of health, and the intelligence of a working person. Beyond that, the biorhythm belongs to the disposition
characteristics. This means that the human efficiency in the course of a day is subject to fluctuations. The
entirety of all knowledge, skills, and experiences of a working person are understood as qualification
characteristics, which a working person must have for carrying out activities at the workplace. Charac-
teristics, which affect the human ability and are changeable at short notice are called adaptation charac-
teristics. Adaptation characteristics refer to the fatigue and recovery, as well as the strain of a working
person. With the beginning of an activity numerous physical and psychological conversion procedures
start, whereby humans adapt increasingly to the workload caused by the activity. Manual labor, for
example, leads to a rise of the heart rate and the muscle blood circulation, in order to be able to meet
the demanded achievement. The realization became generally accepted that an optimal achievement of
working humans is only ensured in the long term, if the fatigue caused by the work stays within limits.
Most of the determinants mentioned for the ability are mutually dependent on each other, for
example, somatotype and body weight, age and experience, skills and strain. Differences between
people or changes within a person, however, do not have to lead inevitably to differences in the achieve-
ment. Measurable effects on the achievement cannot be determined due to the existence of mutual com-
pensation mechanisms.
Constitution characteristics are solely influenced by the selection of personnel. Disposition character-
istics can also be affected by other measures. Specifications of some characteristics can be changed within
a limited range also through measures of work system design. For example, realizations of the influence
of biorhythm on the human ability effect the shift work models. Qualification characteristics can be
FIGURE 5.6 Individual determinants of human performance (From Luczak, H., 1989, Wesen Menschlicher
Leistung. In: Institut f¨r angewandte. Arbeitswissenschaft (ed.): Arbeitsgestaltung in Produktion und Verwaltung.
Cologne: Bachem, pp. 39-60, With Permission).