Humans in Work System Environment - Fundamentals and Assessment Tools for Occupational Ergonomics - page 93

equations based on the investigations were accomplished with such work forms. The fictitious endurance
level of 100 W corresponds to the continuous endurance level of a young, healthy, male employee. It is
realistic, because only suitable employees are involved in heat work because of personal selection and
adaptation processes. The values for the work duration were applied in five geometrical stages: 15,
30 min, 1, 2, and 4 h. These values appear meaningful regarding their delimitations, since a continuous
work duration under 15 min represents a special case in operational practice, and a work duration over
4 h may not be accepted due to the laws of working time regulation.

5.5.3.4 Experimental Examination of the Model Results
Four test subjects were selected. These subjects differed broadly in terms of size, weight, and physical
efficiency and covered, therefore, a wide range of observable continuum. Three of these persons were
heat-adapted, that is, the test subjects had to generate a performance (on an ergometer) between 50
and 100 W for 2 h daily in a climatic chamber at an effective temperature of 33 8 C.

5.5.3.5 Conclusion
Both model results and experimental results were recorded in diagrams. The diagrams indicate that the
recovery time increases exponentially starting from a certain energetic load value and from a certain
effective temperature. The influence of the effective temperature begins with a certain temperature
level. Until this level the thermal regularization system of the human body is able to regulate the body
core temperature independent from the work duration due to a reconciliation of heat production and
heat dissipation.
It is evident in all test results that the four factors “effective temperature, muscular load, work dur-
ation, and individual characteristics of the working person” determine the characteristic curves. The
influence of the effective temperature begins, thereby, from a threshold value. This value is again sup-
posed to be dependent on the energetic-effective load, that is, an endurance level for the superposition
of these two types of loads. Beyond this point, the slope of the course of the curve is determined by the
energetic-effective load. The recovery time increases to the power of the energetic load value and the
effective temperature.
If the model results are compared with the experimental results, then it shows up that the tendency of
the courses of the curves exhibits large agreements (Figure 5.16).

5.5.4 Coordination of Movements as an Example of Work System
Design at Level S2
The combination of power-, speed-, and acceleration development of muscles and skeletal elements in a
purposeful process with spatial and temporal coaction is denominated coordination of movements.
Working persons coordinate the movement of their extremities and their body to act on the work
object indirectly and (with the help of work and operational funds) directly. Thus, they fulfill their
work tasks. Powers, which are raised by individual muscles are inter-connected regarding amount and
direction. Thereby, the movements of the extremities and the body are spatially and temporally
controlled.
The movement of the human body and its extremities in its entirety is a complicated mechanical
process. The principles of this process can quantitatively and causally are conceived by the use of biome-
chanical analysis. Apart from the proposition concerning movement coordination based on a predomi-
nately energetic-effective view, however, informational-mental principles are also important for the work
system design. Furthermore, movements are also temporal-operative processes, that is, the adjustment
quality to an optimal course concerning spatial approximation and movement economy, as well as con-
cerning speed-oriented, temporal aspects is achieved by continuous iteration of movements. This process
is denominated as an exercise, especially with short-cyclic-repetitive sensorimotor activities.
Selected realizations concerning biomechanic analyses, valuate-informatical processes, and exercise
processes are presented in the following (Luczak, 1983).