Effect of the subjective intensity of fatigue and interoception on perceptual regulation and performance during sustained physical activity

Abstract

Background: The subjective experience of fatigue impairs an individual’s ability to sustain physical endurance performance. However, precise understanding of exactly how the perception of fatigue limits performance remains unclear. Methods: Here, we examined whether subjective intensity of perceived fatigue, pre-induced through prior upper body activity, differentially impacted performance and altered perceptual (effort) and affective responses during a sustained, isometric contraction in lower body. We also explored whether (cardiac) interoceptive awareness moderated the relationship between the perception of fatigue and effort. Using a repeated-measures study design, thirty male participants completed three experimental conditions, with the intensity of the pre-induced state of fatigue manipulated to evoke severe (SEV), moderate (MOD) and minimal (control; CON) perceptions prior to the performance of a sustained, sub-maximal contraction in the dominant knee extensors. Results: Participants’ capacity to sustain the isometric contraction was significantly impaired (vs. CON, MOD: -9.5 ± 19.1%, p=0.007; SEV: -13.7 ± 17.2%, p<0.001), with perception of effort higher (SEV, MOD vs. CON: b=-0.90, p<0.001), when perceptions of fatigue were elevated. However, the effect on performance (SEV vs. MOD: -2.5 ± 19.9%, p=0.455) and effort perception (SEV vs. MOD: b=-0.06, p=0.612) was not dependent upon the manipulated intensity of the pre-induced state of fatigue. Perceived fatigue was shown to predict the perception of effort during the endurance task. However, disassociation of perceptual constructs was evidenced with perceived effort, but not fatigue, associated with endurance time (CON: r=-0.57, p=0.004; MOD: r=-0.69, p<0.001; SEV: r=-0.59, p=0.003). Interoceptive awareness was shown to attenuate the relationship between perceived fatigue and effort, but only when fatigue was elevated within the experimental manipulations (b=-4.45, p=0.005). Conclusions: Perception of fatigue indirectly limits endurance performance by exerting influence over sensory processes making a physical task appear more effortful. Moreover, this effect is influenced by individual awareness of interoceptive representations of bodily states.

Perceived fatigue does not alter effort-based decision making but does undermine confidence in the ability to perform physical actions

“…Effort was quantified as the duration that a submaximal contraction (20% maximal voluntary contraction [MVC] force) of the dominant knee extensors (KE) was to be held for. Durations were individualised to each participant, representing percentiles of the maximum duration each participant could hold the contraction before task failure, with maximum performance derived from the best of three previous attempts (data reported previously; Greenhouse-Tucknott et al, 2021). This procedure enabled the normalisation of effort demands across both participants and sessions (Chong et al, 2015).…”