Bridging Exercise Science, Cognitive Psychology, and Medical Practice: Is “Cognitive Fatigue” a Remake of “The Emperor’s New Clothes”?

Abstract

Fatigue is such a multifaceted construct it has sprouted specific research fields and experts in domains as different as exercise physiology, cognitive psychology, human factors and engineering, and medical practice. It lacks a consensus definition: it is an experimental concept, a symptom, a risk, a cause (e.g., of performance decrement) and a consequence (e.g., of sleep deprivation). This fragmentation of knowledge leads to slower dissemination of novel insights, and thus to a poorer research. Indeed, what may seem as a novel result in one field, may very well be old news in another, hence leading to this “innovation” being a scientific equivalent to the emperor’s new clothes. The current paper aims to describe the common denominator in the different areas of expertise where fatigue is investigated. Indeed, rather than focusing on the differences in semantics and conceptualization, we hope that identifying common concepts may be inductive of easier multidisciplinary research. Considering the vastness of fatigue research in all areas identified as relevant-cognitive science, exercise physiology, and medical practice, this analysis has not the ambition to be an exhaustive review in all domains. We have reviewed the fatigue concepts and research in these areas and report the ones that are used to describe the proposed common model to be further investigated. The most promising common feature to cognitive science, exercise physiology and clinical practice is the notion of “perceived effort.” This allows to account for interindividual differences, as well as for the situational variations in fatigue. It is applicable to both mental and physical constructs. It integrates motivational and emotional dimensions. It overcomes current polemics in various research fields, and it does not draw on any semantic ambiguity. We thus suggest a new model of fatigue and performance, whether this performance is mental or physical; and whether it is in a clinical range or relates to optimal functioning.

The effect of ego depletion or mental fatigue on subsequent physical endurance performance: A meta-analysis

“…Two largely independent lines of research in psychology and exercise physiology have postulated theoretical frameworks that account for this phenomenon (e.g., Marcora et al, 2009;Muraven et al, 1998). As expected with two independent research fields, what appears to be the same phenomenon is studied with different experimental paradigms and explained using different explanations (Pattyn, Van Cutsem, Dessy, & Mairesse, 2018). In the present paper, we want to briefly introduce the two dominant theoretical models from both fields and highlight similarities in regard to the predictions they make regarding the effect of mental effort exertion on subsequent physical performance.…”

“…From the perspective of mental fatigue, this indicates that prior mental exertion leads to an accelerated increase in perception of effort which will then lead to a premature task termination (Marcora et al, 2009). (Pattyn et al, 2018)In this paradigm, the first task is often referred to as mental fatigue or cognitive fatigue task.…”

“…Possibly the main observable difference between research labelled as 'mental fatigue research' or 'ego depletion research' is the duration of the fatiguing (above or equal to 30 min; Van or depleting task (mostly less than 30 min). As Pattyn and colleagues recently stressed, the use of different terminology in the different scientific fields has led to independent streams of research, possibly inducing slower dissemination of ideas and rediscovery of 'old news' (Pattyn et al, 2018). Taking this point into account, the aim of the present paper is not to make a comparison of the relative explanatory merit between ego-depletion and mental fatigue research but to provide a datadriven discussion of the published literature in regard to key propositions made by both theories.…”

“…Third, both the ego depletion and the mental fatigue fields conceptualize the detrimental effect of mental exertion as some form of transient 'fatigue' (Pattyn et al, 2018). However, while longer exertion of mental effort can cause higher levels of perceived fatigue, this must not lead to impaired performance (Wolff, Sieber, et al, 2019).…”

Task duration and task order do not matter: no effect on self-control performance

“…Although cognitive fatigue and self-control should not be conflated, similarities on the conceptual and neuronal level have been highlighted recently 48 . It is therefore possible that the heterogenous findings on the ego depletion effect might at least partly stem from the inability to assess if the chosen measures capture depletion of resources on a phenomenological level.…”