Prefrontal cortex oxygenation during a mentally fatiguing task in normoxia and hypoxia.

Mental fatigue (MF) and hypoxia impair cognitive performance through changes in brain hemodynamics. We want to elucidate the role of prefrontal cortex (PFC)-oxygenation in MF. Twelve participants (22.9 ± 3.5 years) completed four experimental trials, (1) MF in (normobaric) hypoxia (MF_HYP) (3.800 m; 13.5%O2), (2) MF in normoxia (MF_NOR) (98 m; 21.0%O2), (3) Control task in HYP (CON_HYP), (4) Control in NOR (CON_NOR). Participants performed a 2-back task, Digit Symbol Substitution test and Psychomotor Vigilance task before and after a 60-min Stroop task or an emotionally neutral documentary. Brain oxygenation was measured through functional Near Infrared Spectroscopy. Subjective feelings of MF and physiological measures (heart rate, oxygen saturation, blood glucose and hemoglobin) were recorded. The Stroop task resulted in increased subjective feelings of MF compared to watching the documentary. 2-back accuracy was lower post task compared to pre task in MF_NOR and CON_NOR, while no differences were found in the other cognitive tasks. The fraction of inspired oxygen did not impact feelings of MF. Although performing the Stroop resulted in higher subjective feelings of MF, hypoxia had no effect on the severity of self-reported MF. Additionally, this study could not provide evidence for a role of oxygenation of the PFC in the build-up of MF.

High Cognitive Effort Prior to Velocity-Based Training Sessions Reduces Rate of Force Development but Not Maximum Strength Gains in Untrained Male Adults.

This study aimed to analyze the chronic effect of high cognitive effort immediately before resistance exercise sessions on neuromuscular performance in untrained male adults. We used a mixed experimental design, with the group as between-participants factor and time as within-participants factor. Thirty-four participants were randomly assigned to two parallel groups: high cognitive effort (n = 17) and control (n = 17). Subjects in the control group were seated for 30 min before the resistance exercise sessions, while the high cognitive effort group completed incongruent trials of the Stroop task until subjective mental fatigue was present immediately before resistance exercise sessions. Participants attended 45 sessions over 15 weeks, consisting of three familiarizations, three baseline evaluations, 36 velocity-based training sessions, and three postexperiment evaluation sessions. Rate of force development (RFD) during the isometric mid-thigh pull, half back-squat 1-RM, and countermovement jump (CMJ) were measured before and after the 12-week intervention. A significant group × time interaction effect was found for the average RFD at 0-250 ms (p < 0.05), with greater improvements for the control group than for the high cognitive effort group. There was no group × time interaction for half back-squat 1-RM (p > 0.05). Also, there was no group × time interaction for CMJ (p > 0.05). In conclusion, repeated high cognitive effort immediately prior to resistance exercise sessions is a phenomenon that can induce greater early velocity loss and, consequently, impairs the improvements in RFD. However, this did not inhibit the increased performance for explosive strength and CMJ in male untrained adults. High cognitive effort before resistance exercise sessions should be avoided.

User Evaluation of a Shared Robot Control System Combining BCI and Eye Tracking in a Portable Augmented Reality User Interface.

This study evaluates an innovative control approach to assistive robotics by integrating brain-computer interface (BCI) technology and eye tracking into a shared control system for a mobile augmented reality user interface. Aimed at enhancing the autonomy of individuals with physical disabilities, particularly those with impaired motor function due to conditions such as stroke, the system utilizes BCI to interpret user intentions from electroencephalography signals and eye tracking to identify the object of focus, thus refining control commands. This integration seeks to create a more intuitive and responsive assistive robot control strategy. The real-world usability was evaluated, demonstrating significant potential to improve autonomy for individuals with severe motor impairments. The control system was compared with an eye-tracking-based alternative to identify areas needing improvement. Although BCI achieved an acceptable success rate of 0.83 in the final phase, eye tracking was more effective with a perfect success rate and consistently lower completion times (p<0.001). The user experience responses favored eye tracking in 11 out of 26 questions, with no significant differences in the remaining questions, and subjective fatigue was higher with BCI use (p=0.04). While BCI performance lagged behind eye tracking, the user evaluation supports the validity of our control strategy, showing that it could be deployed in real-world conditions and suggesting a pathway for further advancements.

The impact of an active and passive industrial back exoskeleton on functional performance.

Due to differences in actuation and design, active and passive industrial back exoskeletons could influence functional performance, i.e., work performance, perceived task difficulty, and discomfort, differently. Therefore, this study investigated and compared the impact of the active CrayX (7 kg) and passive Paexo Back (4.5 kg) on functional performance. Eighteen participants performed twelve work-related tasks with both types of exoskeletons and without (NoExo). The CrayX hindered work performance up to 22% in multiple tasks, compared to the Paexo Back and NoExo, while work performance between NoExo and the Paexo Back condition was more comparable, except for stair climbing (13% hindrance). Perceived task difficulty and discomfort seldomly varied between both exoskeletons. Although the CrayX shows promise to benefit workers, limitations in hindrance and comfort should first be addressed. The Paexo Back has demonstrated an advantage in certain static tasks. However, increasing its potential across a broader range of tasks seems warranted.Practitioner Summary: Differences between industrial back exoskeletons with regard to functional performance, i.e. work performance, discomfort and perceived task difficulty, were investigated by evaluating the active CrayX and passive Paexo Back back exoskeletons. The CrayX significantly hindered functional performance, while the Paexo Back seldomly affected functional performance.Abbreviations: WMSD: Work-related musculoskeletal disorder; NoExo: No Exoskeleton; GD: General discomfort; PTD: Perceived task difficulty; BMI: Body Mass Index.

Reliability of a Submaximal Field Test in Wheelchair Rugby.

The aim was to investigate the test-retest reliability of performance and physiological variables of a submaximal wheelchair rugby field test. Eight trained wheelchair rugby athletes with a spinal cord injury (age: median 40, interquartile range 6.9 y; body mass: median 77.7, interquartile range 23.9 kg) performed a submaximal field test two times with a duration of 41 min, split up into four sets of eight min. Each set included eight laps with one eight-meter sprint (SP8) and one four-meter sprint (SP4). The absolute and relative reliability and the performance decrease (fatigue) across the sets were investigated. The examined variables were sprinting time, heart rate, and RPE. The measured parameters showed moderate (peak heart rate ICC3,1=0.663, peak rate of perceived exertion ICC3,1=0.718), good (SP4 ICC3,1=0.874), and excellent (mean heart rate ICC3,1=0.905, SP8 ICC3,1=0.985) test-retest reliability. Fatigue was observed for SP8 in test 2 between set 2/3 and set 2/4. For test 1 a significant decrease of performance for SP4 was found between set 2/3, set 2/4 and between set 3/4. In conclusion the submaximal field test showed moderate to excellent reliability for all measured parameters. The observed fatigue seems to be not clinically relevant. The test can be recommended to assess the effects of training or interventions.

Reproducibility of 20-min Time-trial Performance on a Virtual Cycling Platform.

This study aimed to analyse the reproducibility of mean power output during 20-min cycling time-trials, in a remote home-based setting, using the virtual-reality cycling software, Zwift. Forty-four cyclists (11 women, 33 men; 37±8 years old, 180±8 cm, 80.1±13.2 kg) performed 3×20-min time-trials on Zwift, using their own setup. Intra-class correlation coefficient (ICC), coefficient of variation (CV) and typical error (TE) were calculated for the overall sample, split into 4 performance groups based on mean relative power output (25% quartiles) and sex. Mean ICC, TE and CV of mean power output between time-trials were 0.97 [0.95-0.98], 9.4 W [8.0-11.3 W], and 3.7% [3.2-4.5], respectively. Women and men had similar outcomes (ICC: 0.96 [0.89-0.99] vs. 0.96 [0.92-0.98]; TE: 8.3 W [6.3-13.1] vs. 9.7 W [8.2-12.2]; CV: 3.8% [2.9-6.1] vs. 3.7% [3.1-4.7], respectively), although cyclists from the first quartile showed a lower CV in comparison to the overall sample (Q1: 2.6% [1.9-4.1] vs. overall: 3.7% [3.2-4.5]). Our results indicate that power output during 20-min cycling time-trials on Zwift are reproducible and provide sports scientists, coaches and athletes, benchmark values for future interventions in a virtual-reality environment.

Endurance exercise-induced and mental fatigue and the brain.

NEW FINDINGS: What is the topic of this review? It provides an overview of the recent papers linking brain neurotransmission with exercise-induced and/or mental fatigue. What advances does it highlight? The noradrenergic neurotransmitter system hastens central fatigue during prolonged exercise, a finding that coincides with a faster rate of increase in the rating of perceived exertion. 2) Mental fatigue affects several neurotransmitter systems, with presumably an important role for dopamine and adenosine, in multiple brain regions such as the prefrontal cortex and the anterior cingulate cortex. ABSTRACT: In sports and exercise science, fatigue is an elusive concept that has important implications in performance during exercise. It has been described in many ways (tiredness, exhaustion, lethargy or weariness) and describes a physical and/or mental state of being tired and lack of energy. Exercise-induced fatigue can be defined as an acute impairment of exercise performance, and a distinction has been made between peripheral and central fatigue. Mental fatigue can be defined as a psychobiological state caused by prolonged exertion that has the potential to reduce cognitive performance and exercise performance. Recent studies have given clear indications that brain catecholamines are involved in the onset of fatigue during endurance exercise. Evidence is provided indicating that the noradrenergic neurotransmitter system hastens central fatigue, a finding that coincides with a faster rate of increase in the rating of perceived exertion. Brain neurotransmission is also suggested to play an important role in mental fatigue. Several neurotransmitter systems might be implicated (with the most important role for dopamine and adenosine) in multiple brain regions, such as the prefrontal cortex and the anterior cingulate cortex, and the summation of these alterations might explain the impairment in endurance performance in a mentally fatigued state. Obviously, we have to keep in mind that fatigue is a very complex construct and that, besides brain neurochemistry, several other factors play a role in its onset.

Impairment of exercise performance following cold water immersion is not attenuated after 7 days of cold acclimation.

PURPOSE: It is well-documented that severe cold stress impairs exercise performance. Repeated immersion in cold water induces an insulative type of cold acclimation, wherein enhanced vasoconstriction leads to greater body heat retention, which may attenuate cold-induced exercise impairments. The purpose of this study, therefore, was to investigate changes in exercise performance during a 7-day insulative type of cold acclimation. METHODS: Twelve healthy participants consisting of eight males and four females (mean ± SD age: 25.6 ± 5.2 years, height: 174.0 ± 8.9 cm, weight: 75.6 ± 13.1 kg) performed a 20 min self-paced cycling test in 23 °C, 40% humidity without prior cold exposure. Twenty-four hours later they began a 7-day cold acclimation protocol (daily 90 min immersion in 10 °C water). On days one, four, and seven of cold acclimation, participants completed the same cycling test. Measurements of work completed, core and skin temperatures, heart rate, skin blood flow, perceived exertion, and thermal sensation were measured during each cycling test. RESULTS: Successful insulative cold acclimation was observed. Work produced during the baseline cycling test (220 ± 70 kJ) was greater (p < 0.001) than all three tests that were performed following immersions (195 ± 58, 197 ± 60, and 194 ± 62 kJ) despite similar ratings of perceived exertion during each test, suggesting that cold exposure impaired cycling performance. This impairment, however, was not attenuated over the cold acclimation period. CONCLUSIONS: Results suggest that insulative cold acclimation does not attenuate impairments in exercise performance that were observed following acute cold water immersion.

Repeated-sprints exercise in daylight fasting: carbohydrate mouth rinsing does not affect sprint and reaction time performance.

To determine the effect of carbohydrate mouth rinsing (CHO-MR) on physical and cognitive performance during repeated-sprints (RS) after 3 days of intermittent fasting (abstaining from food and fluid 14 h per day). In a randomized and counter-balanced manner 15 active healthy males in a fasted state performed a RS-protocol [RSP; 2 sets (SET1 and SET2) of 5×5 s maximal sprints, with each sprint interspersed with 25 s rest and 3 min of recovery between SET1 and SET2] on an instrumented non-motorized treadmill with embedded force sensors under three conditions: i) Control (CON; no-MR), ii) Placebo-MR (PLA-MR; 0% maltodextrin) and iii) CHO-MR (10% maltodextrin). Participants rinsed their mouth with either 10 mL of PLA-MR or CHO-MR solution for 5 s before each sprint. Sprint kinetics were measured for each sprint and reaction time (RTI) tasks (simple and complex) were assessed pre-, during- and post-RSP. There was no statistical main effect of CHO-MR on mean power, mean speed, and vertical stiffness during the sprints between the PLA-MR and CON condition. Additionally, no statistical main effect for CHO-MR on accuracy, movement time and reaction time during the RTI tasks was seen. CHO-MR did not affect physical (RSP) or cognitive (RTI) performance in participants who had observed 3 days of intermittent fasting (abstaining from food and fluid 14 h per day).

Repeated Sprints in Fasted State Impair Reaction Time Performance.

OBJECTIVE: The aim of this study was to assess the effects of 3-day Islamic intermittent fasting (3d-IF) on cognitive performance and serum levels of neurotrophic factors (brain-derived neurotrophic factor [BDNF] and vascular endothelial growth factor [VEGF]) before and after repeated sprints. METHODS: Twenty-one physically active male Muslims (29.8 ± 5.9 years, exercising 4 ± 1.5 times/week) were randomly assigned to one of 2 experimental sessions: the control or nonfasting session (CS) or the fasting session (FS). These 2 sessions occurred 7 days apart in a counterbalanced crossover design. In both conditions, the test was performed at the same time of day, approximately 1 hour before sunset. In the FS, the test occurred on the third day of the 3d-IF and involved the participants' performance of the following: (a) two series of 5 maximal 5-second sprints and (b) 2 cognitive tasks: One Touch Stockings (OTS) and reaction time (simple and complex RTI). RESULTS: In both conditions, the participants' reaction times during the RTI test were similar at the pre- and mid-exercise points, but postexercise, simple and complex reaction times were higher in FS compared to CS (p = 0.045, effect size [ES] = 0.21 and p = 0.006, ES = 0.41, respectively). However, OTS performance and serum levels of neurotrophic factors were not influenced by the 3d-IF. CONCLUSION: Simple and complex reaction times during the RTI test were negatively affected by the 3d-IF after 2 bouts of intensive repeated sprints.

The influence of a mild thermal challenge and severe hypoxia on exercise performance and serum BDNF.

AIM: To examine the isolated and combined effects of severe hypoxia and a mild thermal challenge on performance, physiological measures, cognition, and serum brain-derived neurotrophic factor (BDNF). METHODS: Nine trained male athletes (age: 23 ± 3 years; W max: 333 ± 45 W) completed four experimental trials (CON: 15 °C/0 m, ALT: 15 °C/3800 m, TEMP: 25 °C/0 m, ALT + TEMP: 25 °C/3800 m) in a double blind, randomized, cross-over design. Subjects cycled for 30 min in a self-paced test starting at 75% W max, their goal was to 'perform as much work as possible in 30 min.' Power output, heart rate, blood lactate, pulse oximetry, core and skin temperature, thermal sensation, ratings of perceived exertion, reaction time (RT), and BDNF were assessed. RESULTS: The amount of work produced in 30 min was reduced by temperature (F(1,8) = 7.1; p = 0.029; 360 ± 19 kJ in 15 °C; 344 ± 18 kJ in 25 °C) and altitude (F(1,8) = 94.2; p < 0.001; 427 ± 24 kJ at sea level; 277 ± 15 kJ at altitude), yet there was no interaction effect. Altitude increased mean RT (F(1,8) = 8.0; p = 0.022; 281.9 ± 9.4 ms at sea level; 289.3 ± 10.0 ms at altitude) and RT variability (F(1,8) = 8.5; p = 0.020; 44 ± 3 ms at sea level: 50 ± 4 ms at altitude). Exercise increased BDNF (F(1,8) = 15.2; p = 0.005; PRE: 21.8 ± 1.3 ng/mL; POST: 26.5 ± 2.1 ng/mL). CONCLUSION: Exercise capacity was significantly reduced due to an increase in altitude (3800 m; -34.3%) or a 10 °C increase in ambient temperature (-3.2%). The combination of both stressors showed to be additive (-38.0 %). Altitude induced an increase in RT and RT variability presenting a deterioration in cognitive functioning during acute hypoxia. Exercise significantly increased BDNF, but no effect of altitude on the BDNF concentration was observed.

Mental Fatigue in Sport-From Impaired Performance to Increased Injury Risk.

The literature describing the effects of mental fatigue (MF) has grown tremendously. This is accompanied by identification of a host of performance-determining parameters affected by MF. MF results from prolonged cognitive effort and predominantly affects physical, technical, tactical, and perceptual-cognitive dimensions of sport, while physiological parameters (eg, heart rate, lactate) and physical aspects of maximal and supramaximal efforts are predominantly unaffected. The aim of this paper was to provide an overview of the parameters described in the literature as influenced by MF. By identifying the different parameters, we not only see how they affect the performance of athletes but also raise concerns about the potentially increased injury risk due to MF. Preliminary evidence suggests that subsequent disturbances in balance, motor skills, and decision-making processes could potentially increase the vulnerability to injury. An abundance of lab-based studies looked into the effects of MF on performance; however, many questions remain about the mechanisms of origin and neurophysiological causes of MF, and only small steps have been taken to translate this knowledge into practice. Thus, there is a need for more research into the underlying mechanisms of MF and the role of the brain, as well as more applied research with a high ecological validity that also takes into account the potential increased risk of injury due to MF.

Prolonged theoretical classes impact students' perceptions: an observational study.

Mental fatigue (MF) arises during prolonged demanding cognitive activity and results in acute feelings of tiredness and a decreased physical and/or cognitive performance capacity. An often-overlooked population that is significantly at risk for the development of MF are university students. The current study investigated the impact of prolonged in-person theoretical classes on the perceptions of MF, boredom, and sleepiness among 27 Slovenian university students (first-year physiotherapy). Their subjective experiences at various time points during a 4-h class interspersed with a 20 min break were assessed with a repeated measures ANOVA and consequent Bonferroni post-hoc tests (significance set at <0.05). Subjective MF and sleepiness significantly increased during the first and the second part of the class (p < 0.05), while they significantly decreased during the break (p < 0.05). Boredom levels only increased significantly during the second part of the class (p < 0.05). Additionally, students who had inadequate sleep the night before the class reported higher levels of MF at the beginning of the class. This study highlighted a significant impact of a theoretical class on subjective feelings of mental fatigue and showed that a break in the middle of the class temporarily alleviated this negative impact. These results emphasize the importance of adequate sleep, effective breaks, and strategies to manage cognitive workload in optimizing students' cognitive well-being and academic performance. Further research is needed to better understand the underlying factors and develop targeted interventions to support students' cognitive functioning and well-being during prolonged academic sessions.

Prolonged cognitive effort impairs inhibitory control and causes significant mental fatigue after an endurance session with an auditive distractor in professional soccer players.

BACKGROUND: Throughout official soccer matches, the presence of cheer by the crowd could be considered a critical auditive distraction that could further impair the cognitive interference control system, multiple object tracking (MOT) skill, heart rate variability (HRV), and increase mental fatigue. As the resource is not immediately replenished, the impairment of the cognitive interference control system may be delayed following a soccer game. Then, evaluating the recovery time course of the cognitive interference control system, MOT skill, HRV, and mental fatigue after prolonged tasks combining physical, endurance, and cognitive effort are essential. PURPOSE: We aimed to analyze the acute effect of cognitive effort and auditive distractor with 24-h follow-up throughout a prolonged endurance session on inhibitory control, subjective mental fatigue, MOT skill, and HRV in professional soccer players. METHODS: Twenty professional male soccer players were recruited (23.56 ± 3.8 years, 78.1 ± 6.9 kg, 1.77 ± 0.06 m, and 12.5 ± 5.3% body fat). The sessions were performed in a randomized and counterbalanced crossover design, divided into four experimental conditions: endurance, endurance + MOT, endurance + MOT + AD, and endurance + AD. The soccer players completed the incongruent Stroop task utilizing an eye-tracker to assess cognitive effort. MOT task, subjective mental fatigue, and HRV were evaluated before the endurance training (60%Δ of maximal aerobic velocity during 40-min) and after 30-min and 24-h of recovery. These sessions were designed to investigate the acute effect of prolonged cognitive effort (repeated MOT throughout the endurance task) and AD (constant crowd noise and coach's voice each 15-40 s, totalizing = 80 voices) on inhibitory control, MOT skills, HRV, and subjective mental fatigue after a fixed endurance training session. RESULTS: There was no condition × time interaction for accuracy of inhibitory control (p > 0.05, ηp2 = 0.001). There was a significant condition × time interaction for inhibitory control response time (p < 0.05, ηp2 = 0.16). A higher response time of inhibitory control was found for the endurance + MOT + AD and endurance + MOT experimental sessions (p < 0.05). There was a significant condition × time interaction for subjective mental fatigue (p < 0.05, ηp2 = 0.46). A higher subjective mental fatigue was found for the endurance + MOT + AD and endurance + MOT experimental sessions (p < 0.05). There was no condition × time interaction for HRV (p > 0.05, ηp2 = 0.02). CONCLUSION: We concluded that cognitive effort throughout a prolonged endurance session impaired inhibitory control and increased mental fatigue without promoting greater MOT skill and HRV changes in professional soccer players.

Deficits in neurocognitive performance in patients with chronic ankle instability during a neurocognitive balance task - A retrospective case-control study.

OBJECTIVES: To assess the neurocognitive performance while maintaining balance of patients experiencing CAI compared to healthy controls. In patients with CAI, the affected limb was also compared to the contralateral limb. DESIGN: A retrospective case-control study. SETTING: Laboratory study. PARTICIPANTS: We included 27 patients with CAI and 21 healthy controls. METHODS: The study consisted of two sessions, namely familiarisation and experimentation, which were scheduled with a gap of at least one week between them. During the experimental trial, both groups performed the Y-Balance Test and Reactive Balance Test once on each limb. MAIN OUTCOME MEASURES: The main outcome measures are accuracy and visuomotor response time (VMRT) calculated via video-analysis and with the Fitlight™-hardware and software respectively during the Reactive Balance Test (RBT). RESULTS: No data was excluded from the final analysis. Patients with CAI exhibited significantly lower accuracy than healthy controls, with a mean difference of 8.7% (±3.0)%. There were no differences for VMRT between groups. Additionally, no significant differences were observed between the affected and contralateral limb of the patient group for both accuracy and VMRT. CONCLUSIONS: Patients with CAI showed lower accuracy, but similar VMRT compared to healthy controls during a neurocognitive balance task, indicating impaired neurocognitive function. Patients exhibit comparable speed to healthy individuals when completing neurocognitive balance tasks, yet they display a higher frequency of accuracy errors in accurately perceiving their environment and making decisions under time constraints. Future research should gain more insights in which other cognitive domains are affected in patients with CAI for a better grasp of this condition's underlying mechanism.

Test-retest, intra- and inter-rater reliability of the reactive balance test in patients with chronic ankle instability.

Introduction: The Reactive Balance Test (RBT) could be a valuable addition to research on chronic ankle instability (CAI) and clinical practice, but before it can be used in clinical practice it needs to be reliable. It has already been proven reliable in healthy recreational athletes, but not yet in patients with CAI who have shown persistent deficits in dynamic balance. The study aimed to determine the test-retest, intra-, and inter-rater reliability of the RBT in patients with CAI, and the test-retest and inter-rater reliability of the newly developed RBT score sheet. Methods: We used a repeated-measures, single-group design to administer the RBT to CAI patients on three occasions, scored by multiple raters. We included 27 participants with CAI. The study used multiple reliability measures, including Pearson r, intra-class correlations (ICC), standard error of measurement (SEM), standard error of prediction (SEP), minimal detectable change (MDC), and Bland-Altman plots, to evaluate the reliability of the RBT's outcome measures (visuomotor response time and accuracy). It also assessed the test-retest and inter-rater reliability of the RBT score sheet using the same measures. Results: The ICC measures for test-retest reliability were similar for accuracy (0.609) and VMRT (0.594). Intra-rater reliability had high correlations and ICCs for accuracy (r = 0.816, ICC = 0.815) and VMRT (r = 0.802, ICC = 0.800). Inter-rater reliability had a higher ICC for VMRT (0.868) than for accuracy (0.690). Conclusion: Test-retest reliability was moderate, intra-rater reliability was good, and inter-rater reliability showed moderate reliability for accuracy and good reliability for VMRT. Additionally, the RBT shows robust SEM and mean difference measures. The score sheet method also demonstrated moderate test-retest reliability, while inter-rater reliability was good to excellent. This suggests that the RBT can be a valuable tool in assessing and monitoring balance in patients with CAI.

The Impact of Mental Fatigue on a Strength Endurance Task: Is There a Role for the Movement-Related Cortical Potential?

PURPOSE: Several mechanisms have been proposed to explain how mental fatigue degrades sport performance. In terms of endurance performance, a role for an increased perceived exertion has been demonstrated. Using electroencephalography and, more specifically, the movement-related cortical potential (MRCP), the present study explored the neural mechanisms that could underlie the mental fatigue-associated increase in perceived exertion. METHODS: Fourteen participants (age, 23 ± 2 yr; 5 women, 9 men) performed one familiarization and two experimental trials in a randomized, blinded, crossover study design. Participants had to complete a submaximal leg extension task after a mentally fatiguing task (EXP; individualized 60-min Stroop task) or control task (CON; documentary). The leg extension task consisted of performing 100 extensions at 35% of 1 repetition maximum, during which multiple physiological (heart rate, electroencephalography) and subjective measures (self-reported feeling of mental fatigue, cognitive load, behand motivation, ratings of perceived exertion) were assessed. RESULTS: Self-reported feeling of mental fatigue was higher in EXP (72 ± 18) compared with CON (37 ± 17; P < 0.001). A significant decrease in flanker accuracy was detected only in EXP (from 0.96 ± 0.03% to 0.03%; P < 0.05). No significant differences between conditions were found in MRCP characteristics and perceived exertion. Specifically in EXP, alpha wave power increased during the leg extension task ( P < 0.01). CONCLUSIONS: Mental fatigue did not impact the perceived exertion or MRCP characteristics during the leg extension task. This could be related to low perceived exertion and/or the absence of a performance outcome during the leg extension task. The increase in alpha power during the leg extension task in EXP suggests that participants may engage a focused internal attention mechanism to maintain performance and mitigate feelings of fatigue.

Electrophysiological impact of mental fatigue on brain activity during a bike task: A wavelet analysis approach.

This study explored how mental fatigue affects brain activity during a low-intensity bike task utilising a continuous wavelet transformation in electroencephalography (EEG) analysis. The aim was to examine changes in brain activity potentially linked to central motor commands and to investigate their relationship with ratings of perceived exertion (RPE). In this study, sixteen participants (age: 21 ± 6 y, 7 females, 9 males) underwent one familiarization and two experimental trials in a randomised, blinded, cross-over study design. Participants executed a low-intensity bike task (9 min; 45 rpm; intensity (W): 10 % below aerobic threshold) after performing a mentally fatiguing (individualized 60-min Stroop task) or a control (documentary) task. Physiological (heart rate, EEG) and subjective measures (self-reported feeling of mental fatigue, RPE, cognitive load, motivation) were assessed prior, during and after the bike task. Post-Stroop, self-reported feeling of mental fatigue was higher in the intervention group (EXP) (74 ± 16) than in the control group (CON) (37 ± 17; p < 0.001). No significant differences in RPE during the bike task were observed between conditions. EEG analysis revealed significant differences (p < 0.05) in beta frequency (13-30 Hz) during the bike task, with EXP exhibiting more desynchronization during the pedal push phase and synchronization during the pedal release phase. These results suggest that mental fatigue, confirmed by both subjective and neurophysiological markers, did not significantly impact RPE during the bike task, possibly due to the use of the CR100 scale or absence of a performance outcome. However, EEG data did reveal significant beta band alterations during the task, indicating increased neural effort under mental fatigue. These findings reveal, for the first time, how motor-related brain activity at the motor cortex is impacted during a low-intensity bike task when mentally fatigued.

Evaluating the real-world usability of BCI control systems with augmented reality: a user study protocol.

Brain-computer interfaces (BCI) enable users to control devices through their brain activity. Motor imagery (MI), the neural activity resulting from an individual imagining performing a movement, is a common control paradigm. This study introduces a user-centric evaluation protocol for assessing the performance and user experience of an MI-based BCI control system utilizing augmented reality. Augmented reality is employed to enhance user interaction by displaying environment-aware actions, and guiding users on the necessary imagined movements for specific device commands. One of the major gaps in existing research is the lack of comprehensive evaluation methodologies, particularly in real-world conditions. To address this gap, our protocol combines quantitative and qualitative assessments across three phases. In the initial phase, the BCI prototype's technical robustness is validated. Subsequently, the second phase involves a performance assessment of the control system. The third phase introduces a comparative analysis between the prototype and an alternative approach, incorporating detailed user experience evaluations through questionnaires and comparisons with non-BCI control methods. Participants engage in various tasks, such as object sorting, picking and placing, and playing a board game using the BCI control system. The evaluation procedure is designed for versatility, intending applicability beyond the specific use case presented. Its adaptability enables easy customization to meet the specific user requirements of the investigated BCI control application. This user-centric evaluation protocol offers a comprehensive framework for iterative improvements to the BCI prototype, ensuring technical validation, performance assessment, and user experience evaluation in a systematic and user-focused manner.