Fatigue and Human Performance

Performing a physical or cognitive task over extended periods of time is important in human life and is required during prolonged daily, physical, educational, vocational, and sports activities. The execution of sustained physical or cognitive activities inevitably leads to (state) fatigue, which can be defined as a psychophysiological symptom that is characterized by an impaired physical and/or cognitive function as well as altered perceptual responses and/or emotional states as a result of interactions between performance fatigability and perceived fatigability (Figure 1A) (Enoka und Duchateau 2016; Noakes 2012; Kluger et al. 2013; Gruet 2018; Behrens et al. 2018; Behrens et al. 2021). The degree of fatigability, irrespective if induced by motor or cognitive tasks, has detrimental effects on the capacity of the motor and cognitive systems of humans with negative consequences, e.g., for productivity, exercise behaviour, physical activity, and daily activities. In the worst case, as with old people and clinical populations, this results in a reduced quality of life (or even accidents/death) because the high fatigability conflicts with the adequate execution of daily activities (Figure 1B) (Enoka und Duchateau 2016; Noakes 2012; Kluger et al. 2013; Gruet 2018; Behrens et al. 2021). In the long run, this leads to a reduced motor and cognitive capacity, mobility, independence and social participation in these populations. Therefore, identifying the age-, sex-, and task-specific neural and physiological mechanisms of motor and cognitive task-induced state fatigue is the first step for the targeted application of tailored interventions. For example, there are acute and chronic interventions that can improve neural and/or muscle function with positive effects on performance and exercise tolerance in different populations (Grgic et al. 2020; Husmann et al 2019; Casaburi et al. 1997).