A New Framework to Understand and Study Exercise-Induced Perceived Fatigue as a Metacognitive Inference of Dyshomeostasis.

Novel theories have emerged in the past decade pertaining to how the brain processes internal body sensations and how such processes underpin not only perception but also how we act in the world. These neuroscientific advances offer new perspectives for research and practice allied to medicine, sport and exercise science. The construct of perceived fatigue has been understudied until recent recognition of its prevalence and influence on perceptions and behaviours in health, diseases and performance. The aim of the present perspective piece is to propose a theoretical and conceptual framework for understanding perceived fatigue and its emergence during exercise. We encourage the use of the definition proposed by Micklewright et al. (2017), that is "a feeling of diminishing capacity to cope with physical or mental stressors, either imagined or real", from a critique of contemporary taxonomies and a distinction made with other key percepts in the field of medicine, sport and exercise. We also offer some methodological considerations for its measure. We then succinctly describe a neurobiologically plausible mechanistic underpinning of exercise-induced perceived fatigue based on the theory of predictive processing applied to homeostatic regulation through allostatic control and metacognition. Finally, we position the model of perceived fatigue through Metacognitive Inference of Dyshomeostasis (MID) within the wider corpus of knowledge. We first contrast the MID model with the most dominant biology-grounded models of perceived fatigue proposed in the literature to then provide preliminary evidence in support of the MID model and suggest some testable predictions for future research.