The fatigue illusion: the physical effects of mindlessness

The study challenges the conventional view of fatigue as solely a somatic response to physical limitations. It introduces the concept of "premature cognitive commitments," where blindly adopted attitudes restrict our perception of reality. Building on Langer's mind/body unity theory, the researchers hypothesize that fatigue perception is not solely determined by physiological factors but is also influenced by psychological factors and can be controlled. Existing research often focuses on the duality of mind and body, considering perceptions and physiological exertion separately. However, this research suggests that individuals can exert control over their physical ability through active mental control. The concept of "fatigue illusion" refers to assumptions, consciously or unconsciously adopted, limiting individual potential. The studies investigate whether perceived fatigue consistently emerges at certain milestones (fatigue set-in and peak) during tasks, suggesting it's an illusion rather than a direct reflection of energy depletion. Langerian mindfulness, defined as continually challenging our forecasts and creating novelty, is posited as a method to potentially postpone or even eliminate fatigue. Previous studies have shown the efficacy of mindfulness in addressing other limitations in human experiences such as aging, disease, and mental health. The five studies use diverse methods and participant groups to test the hypothesis that mindful techniques can affect fatigue milestones and the experience of fatigue itself. The studies collectively aim to provide generalizable findings, address potential confounders, and help establish the proportionality of subjective fatigue perceptions as supporting evidence for the fatigue illusion. Measuring the duration of fatigue, an often-neglected aspect, is also considered relevant to the research.

The paper reviews existing literature on fatigue, highlighting the prevailing view of fatigue as a conscious feeling linked to physiological changes caused by increased physical activity. The concept of tele-oanticipation, forecasting estimations of reserves and tolerance based on past experiences, is introduced. The authors discuss research on how differences in states during activity are mapped against a "proto-Self," with deviations from it resulting in increased conscious fatigue. The limited research on manipulating these assumptions of fatigue is noted. The paper contrasts the dualistic mind/body approach, separating perceptions from physiological exertion, with the monistic mind/body approach, emphasizing the interaction between them. Langer's socio-cognitive definition of mindfulness is presented as a tool to explore how fatigue is learned and adopted. Studies on fatigue milestones are discussed, emphasizing that perceived fatigue can occur at certain points even without reflecting actual energy reserves. The existing research is seen as viewing this as a fixed physiological barrier, while the authors propose that Langerian mindfulness can challenge these fixed assumptions, leading to potential changes in fatigue experience. Previous research demonstrating the malleability of perceptions is cited to support the idea that mindful interventions could influence perceptions of fatigue.

The research employed a multi-study design with varying methodologies and participant groups. **Study 1:** This study used self-reports of long-distance travel experiences (over 3 hours) from 28 college students to examine if perceived fatigue set-in (FS) and peak (FP) occurred at proportional milestones regardless of travel time. Participants indicated FS and FP on a 0–100% scale representing the total travel duration, along with their fatigue level on a 1–10 scale. **Study 2:** This study used a cognitive task (counting multiples of 3) with three difficulty levels (200, 400, and 600 integers) administered to 294 college students. EEG data (Neurosky Mindwave headsets) were collected, along with self-reports of FS, FP, perceived mistakes, and the desire to stop. The EEG data aimed to measure Alpha-wave amplitude and entropy as objective measures of fatigue. **Study 3:** This study involved 12 professional ballet dancers performing a developpé à la seconde for varying durations. This study investigated the fatigue illusion in a physically demanding situation and included self-reports of FS and FP, levels of fatigue, and the Positive and Negative Affect Scale-Short Form (PANAS-SF). Objective observers independently assessed fatigue from video recordings. **Study 4:** This study used a handgrip task with four conditions: a no-goal group and three timed groups (120s, 180s, 240s). 91 male college students participated. This study aimed to investigate the influence of task difficulty and individual characteristics (mindfulness, stress, free will, and affect) on the fatigue illusion using various psychological measures including the Langer Mindfulness Scale (LMS21), Perceived Stress Scale (PSS), Freewill and Determinism scale-Plus (FAD-Plus), and PANAS-SF. **Study 5:** This study employed a mindfulness manipulation in an arm-raising task. 55 participants were randomly assigned to three conditions: discontinuous (5 + 5 min arm raise), mindless/continuous (10 min arm raise), and mindful/continuous (10 min arm raise with a mindful sub-task). The study measured FS, FP, state mindfulness (reaction-time test), and trait mindfulness (LMS14). Objective observers independently assessed fatigue from Zoom recordings. A post-study question assessed willingness to repeat the study for compensation.

Across all five studies, participants consistently perceived fatigue at proportional milestones, supporting the fatigue illusion hypothesis. Study 1 (travel) found no significant difference in FS and FP percentages across different travel durations. Study 2 (counting task) also found similar FS and FP proportions across varying task difficulty levels, with EEG data suggesting brain activity patterns corresponding to fatigue perception. Study 3 (ballet dancers) showed an earlier FS than other studies possibly due to the highly technical nature of the task, yet still maintaining a distinct FP. While inter-rater reliability was lower for FS than FP, the results still indicate a consistent pattern. No significant correlation was observed between affect and fatigue perception in this study. Study 4 (handgrip task) showed that those in the No-goal group reported significantly earlier FS and FP than timed groups, demonstrating the influence of goal setting on fatigue perception. Mindfulness measures showed correlations with reduced fatigue at FS. Study 5 (arm raise) showed no significant difference in FS and FP across interventions (discontinuous, mindless continuous, mindful continuous), indicating the robustness of the fatigue illusion. However, objective observations showed that the mindful continuous group was subjectively less fatigued despite higher objective fatigue ratings, suggesting a possible disconnection between subjective experience and objective measurements. Linear regressions indicated no significant association between mindfulness and FS but showed that participants with higher novelty-producing scores reported earlier FP. The discontinuous intervention showed potential for manipulating the fatigue illusion, but it needs further investigation to determine if it postpones or advances fatigue. The mindful group, however, displayed a later FS compared to the average FS across all conditions, suggesting mindfulness might be influential in this manner.

The findings strongly support the existence of a fatigue illusion, where perceived fatigue is not solely determined by physiological factors but is significantly influenced by psychological factors. The consistency of perceived fatigue milestones across diverse tasks and participant groups highlights the robustness of this illusion. The study's investigation into the role of individual characteristics, such as mindfulness, stress, and affect, revealed complex interactions. While individual traits did not directly influence the overall pattern of the fatigue illusion, some aspects of mindfulness, particularly novelty production, showed correlations with levels of reported fatigue, suggesting that a mindful approach could potentially modulate the experience of fatigue. The manipulation of task duration (discontinuity) also showed potential for influencing fatigue perception, though further research is needed to clarify the mechanism. The difference between subjective and objective measures of fatigue in Study 5 warrants further exploration, suggesting the limitations of relying on either one alone.

This research provides substantial evidence for a fatigue illusion characterized by predictable milestones of perceived fatigue. While largely resistant to direct individual influence, the illusion is potentially malleable through specific interventions, such as goal setting and mindfulness strategies, especially in terms of affecting the perceived FP. Future research should focus on clarifying the mechanisms behind these interventions and on exploring the interaction between subjective and objective measures of fatigue. Further investigation into the influence of intra-individual characteristics on the fatigue illusion is crucial to understand the cognitive and affective processes involved.

Several limitations should be acknowledged. The sample sizes in some studies were relatively small, particularly Study 3, limiting the generalizability of those findings. The reliance on self-report measures for fatigue perception introduces potential biases. Furthermore, the study primarily focused on college students and professional dancers, limiting its generalizability to other populations. While the study explored various factors influencing fatigue perception, further investigation into specific types of mindfulness practices may provide greater insight into their effectiveness in managing fatigue.