The construct of psychological fatigue : a psychometric and experimental analysis
Fatigue is a familiar and commonplace occurrence, but attempts to investigate the
nature of fatigue have been inconclusive. Following more than a hundred years of
extensive research, the construct is still ill-defined. This has resulted in a series of
different strands of research, producing results concomitant with each researcher's own
idea of what constitutes fatigue.
Two central questions remain unresolved: (1) what sort of a construct is fatigue? and
(2) should fatigue be conceptualised as a single, one dimensional state, generated by a
range of different conditions, or a multidimensional state, incorporating a number of
distinct but related states? There is an implicit assumption within the literature (and
every-day language) that there is more than one 'type' of fatigue. However, there is
currently no theoretical model which outlines the types of fatigue which should be
incorporated in a theoretical framework and which explains the relationships between
these fatigue types.
The work presented in this thesis represents an attempt to address these issues using
both psychometric and experimental approaches. Preliminary work investigated the
psychometric basis for a unitary or multidimensional construct. This separately
addressed the constructs of state and trait fatigue and, on the basis of the findings, state
and trait multiple fatigue questionnaires were developed.
A series of four experiments were then carried out which manipulated different types of
work to facilitate an investigation of the dynamic development of fatigue. The first three
experiments focused on the separate effects of mental and physical fatigue, and the final
experiment considered the nature of their interaction.Both experimental and psychometric analyses supported the proposition of a
multidimensional construct. The evidence in support of a multidimensional construct of
trait fatigue was particularly strong. However, while the evidence in support of a
multidimensional construct of state fatigue was less convincing, the experimental
manipulations of different types of workload did produce states of fatigue that were
subjectively different and also different patterns of fatigue after-effects.