A Proposal for a Unifying Set of Definitions of Fatigue

Abstract

In this paper, we propose a set of unifying definitions that are useful in all areas of fatigue research while remaining neutral to the various theories about fatigue. We first set up two criteria and four desiderata that a definition for interdisciplinary use needs to fulfill: (i) non-circularity, (ii) finiteness, (iii) broadness, (iv) precision, (v) neutrality, and (vi) phenomenon-focus. We argue that other existing attempts to unify definitions within fatigue research do not fulfill all of these criteria and desiderata. Instead, we argue for a set of stipulative definitions, centered around performance measures and subjective estimations, is required in order to maximize clarity. In total, a set of 13 distinct definitions of fatigue and fatigue-related phenomena is presented. These definitions will help facilitate communication between different researchers, link phenomena from divergent research fields together, facilitate application and knowledge production, and increase the specificity for hypothesis testing.

The Link Between Energy-Related Sensations and Metabolism: Implications for Treating Fatigue

“…An improved assessment of fatigue that includes the sexual domain might provide useful in addressing this problem. Another distinction that can be made is between state fatigue (referring to the momentary sensation of fatigue), trait fatigue (the overall disposition of sensation of fatigue), prolonged state fatigue (general tendency of sensation of fatigue within a defined time period), and pathological fatigue (when the general tendency of sensation of fatigue is perceived to interfere with everyday life; for a full description see Skau et al, 2021). Penner and Paul (2017) also suggest that differentiating between primary, secondary, and comorbid fatigue is of clinical importance: symptoms of primary fatigue can be considered part of the underlying disease and emerge independently from other comorbidities, as it is the case in multiple sclerosis (MS).…”

“…Energy-related sensations such as fatigue are phenomena that, despite being researched in various fields, such as medicine, cognitive psychology, or exercise physiology, still lack consensus definitions and taxonomy ( Pattyn et al, 2018 ; Skau et al, 2021 ). As Pattyn et al (2018) and Skau et al (2021) point out, this fragmentation of knowledge hinders innovation, interdisciplinary collaboration, communication, and can lead to confusion or to a situation where advances in one field do not reach other fields, causing the phenomenon of “reinventing the wheel.” Skau et al (2021) have proposed two criteria that an interdisciplinary definition needs to fulfil: the first is non-circularity, meaning that no part of the term defined (in this case fatigue) should be defined by itself or have already been used in the definitions of a prior definition.…”

“…Energy-related sensations such as fatigue are phenomena that, despite being researched in various fields, such as medicine, cognitive psychology, or exercise physiology, still lack consensus definitions and taxonomy ( Pattyn et al, 2018 ; Skau et al, 2021 ). As Pattyn et al (2018) and Skau et al (2021) point out, this fragmentation of knowledge hinders innovation, interdisciplinary collaboration, communication, and can lead to confusion or to a situation where advances in one field do not reach other fields, causing the phenomenon of “reinventing the wheel.” Skau et al (2021) have proposed two criteria that an interdisciplinary definition needs to fulfil: the first is non-circularity, meaning that no part of the term defined (in this case fatigue) should be defined by itself or have already been used in the definitions of a prior definition. An example of circularity would be defining fatigue as “feeling of exhaustion or lack of energy,” when exhaustion itself was defined as “feeling of fatigue or lack of energy.” The second criterion is finiteness, according to which at the end of the definition chain there should be some primitives or undefined terms that get their meaning from meta-linguistic practices, such as ostensive procedures, i.e., pointing out examples, such as pointing to a blue object to define the colour blue ( Skau et al, 2021 ).…”

“…As Pattyn et al (2018) and Skau et al (2021) point out, this fragmentation of knowledge hinders innovation, interdisciplinary collaboration, communication, and can lead to confusion or to a situation where advances in one field do not reach other fields, causing the phenomenon of “reinventing the wheel.” Skau et al (2021) have proposed two criteria that an interdisciplinary definition needs to fulfil: the first is non-circularity, meaning that no part of the term defined (in this case fatigue) should be defined by itself or have already been used in the definitions of a prior definition. An example of circularity would be defining fatigue as “feeling of exhaustion or lack of energy,” when exhaustion itself was defined as “feeling of fatigue or lack of energy.” The second criterion is finiteness, according to which at the end of the definition chain there should be some primitives or undefined terms that get their meaning from meta-linguistic practices, such as ostensive procedures, i.e., pointing out examples, such as pointing to a blue object to define the colour blue ( Skau et al, 2021 ). In addition to these two criteria, Skau et al (2021) propose four desiderata: broadness (the definition is broad enough so that it can be used in different fields), precision (the definition is precise enough to avoid multiple interpretations), neutrality (the definition should not depend on a certain theory), and phenomenon focus (the definition should not involve explanations or should do so to a minimal extent).…”

“…An example of circularity would be defining fatigue as “feeling of exhaustion or lack of energy,” when exhaustion itself was defined as “feeling of fatigue or lack of energy.” The second criterion is finiteness, according to which at the end of the definition chain there should be some primitives or undefined terms that get their meaning from meta-linguistic practices, such as ostensive procedures, i.e., pointing out examples, such as pointing to a blue object to define the colour blue ( Skau et al, 2021 ). In addition to these two criteria, Skau et al (2021) propose four desiderata: broadness (the definition is broad enough so that it can be used in different fields), precision (the definition is precise enough to avoid multiple interpretations), neutrality (the definition should not depend on a certain theory), and phenomenon focus (the definition should not involve explanations or should do so to a minimal extent).…”