Factors affecting the consumption of working time and the strain on the worker in some
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Date
1975
Authors
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Journal ISSN
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Publisher
Sokoine University of Agriculture
Abstract
The purpose of the study was to formulate an ergonomic model for forest
work to serve as frame of reference for theoretical and empirical analysis, to
examine the correlations of independent variables in play in forest work such
as human, conditions and working method variables with consumption of working
time and the physical strain on the worker. The investigation was confined in
the empirical material to the cutting of roll-seedlings and the lifting of seedlings in
the nursery-, and to the cutting of pulpwood by two working methods, i.e. mediumheavy
and heavy work. The final aim was to formulate and test hypotheses of
forest work science, postulate new hypotheses and outline an overall theory on
the basis of systems analysis. An additional special object was to study the
application of the principle of comparative time study in an empirical material
and to apply the same principle in pulse rate investigations. This is termed the
principle of comparative work study.
The work performance was illustrated by a system scheme (Fig. 1). The
scheme comprised the following main groups of elements: worker’s inclination for
work, working capacity, reflexes and instincts, decision process, environmental
factors, working methods and habits, work performance, output, earnings, and
effects on the worker. The model was made up parallclly from abstract and
concrete concepts, the aim being to make it suitable for the set of concepts of the
theory of work study and the level of theory formulation. The model included
the feedback from the effects on the worker-sample element group to the
worker’s qualities.
The literature on forest work studies in which some correlations introduced in
the model were investigated is reviewed in Chapter 23. Owing to the great
number of output studies they were treated as an example. The greatest part of
the research activity has been analysis of the relations between environmental
factors — and of them primarily the work difficulty factors — and the work
output.
The previously outlined system formula is examined in Chapter 24 as a
cybernetic, probabilistic system in which the elements as such were conceived
to embrace complex linkages and to be of the black-box type. The information transfer of these sample elements was illustrated by only one channel and
information was consequently analysed merely as a symbolical expression of space
and event. The decision process and the effects of reflexes and instincts were
examined as the self-regulatory mechanism of the model. Feedbacks were
established both within the worker and between the worker and environment.
Principles influencing the formulation of the theory' of work science were
postulated on the basis of the general properties of the system, such as threshold
values, correlations, the principles of isomorphism and homomorphism:
— If a correlation proves to be significant it is relevant at least in the
population represented by the material and possibly also in other populations.
— On the other hand, if no significant correlation is established between
some independent variables there may nevertheless be a significant correlation in
some other population or after some threshold values.
— Il is useful for development of the theory' to explain the trend of the
correlations and the internal conformities to law and mechanism of the elements.
— It is assumed hypothetically that the constancy of the relative per-worker
working time and strain value is influenced by the difference between the
worker’s capabilities that the working methods and working conditions require
and by his attitude to the working methods under comparison and his experience.
— model taken from nature through simplifications is the more servicable
the more deterministic it is.
— Empirical work study generally' observes coded messages by indirect means
and it is therefore seldom possible to demonstrate direct physiological causal
relationships; what results is explanations of the ”either-or” or ”both-and” type.
The system description of the work was developed in Chapter 25 by
hypothetical insertion in the model of elements formed by the set of concepts
of work study principles (Fig. 2). The concepts are: speed of work, physical
strain, ratio between physical strain and maximal performance, total strain during
the working day, psychic strain, relative consumption of time, average consumption
of time, deviation of consumption of time, average strain, deviation of strain,
relative strain, and attitudes to work.
The quantitative and abstract levels of the concepts of the model were
studied using the M-67-meta theory. Fig. 3 shows the concept hierarchies and
the measuring features of the concepts. In processing the measuring features for
formulation of the theory in the empirical part, concepts of the same quantitativencss
arc used which are sub-concepts of the high real theoretical concepts:
the worker’s capacity' and inclination for work, effects on the worker, performance,
output and environmental factors. Fig. 4 shows the processes as a being model:
performance — output and performance — effects on the worker, the worker’s
resources (capacity for work) and feelings (inclination for work) and working
conditions (environment) which influence the interrelations of these processes. The Jiving organism
state of equilibrium. It
logical theories that if a
was found to be a system which seeks to preserve a
was assumed from reference to physiological and psychofactor
causes a greater deviation in the equilibrium of
the organism than the conditions of other factors, that factor dominates the
behaviour of the organism. This theory was applied in the empirical part to
explain the phenomena established. In the empirical part the effect was examined of different factors on the
consumption of working time, the physical strain on the worker, and the application
of certain work study principles in the nursery to the cutting of roJlseedlings,
the lifting of pine seedlings and the logging of pulpwood in grapple
piles alongside the strip road (working method 2) and a 4-m wide zone for which
the bunch size required was reduced (working method 1). The material and the
measurements made are described in Chapter 32.
The most important results were as follows. Owing to the paucity of degrees
of freedom which interfered with testing they were distributed into statistically
significant correlations and hypothetical correlations:
— Consumption of working time was explained significantly in regression
analysis by so-called work difficulty factors, working method, moving speed
which illustrates the speed of the work, the time of the working day, the
ordinal number of the working day and some independent variables that portray
the worker.
Description
PhD Thesis
Keywords
Ergonomic model, Forest, Forst management, Working time-forest