How to Tackle Mental Fatigue: A Systematic Review of Potential Countermeasures and Their Underlying Mechanisms

Immediate and delayed effects of fantastical content on children's executive functions and mental transformation

Watching fantastical content has been shown to negatively affect young children's executive function (EF) skills. No study has investigated how long these negative effects persist and whether they extend to other cognitive skills. The current experimental study aimed to (1) detect how long fantastical content affects children's EF performance and (2) examine whether watching fantastical content negatively affects children's other (non-EF) cognitive task performance, namely mental transformation. A total of 120 5- and 6-year-old children (M = 66 months, SD = 5.52) were randomly assigned to one of the four following conditions: (a) immediate testing after watching an 8-min non-fantastical cartoon, (b) immediate testing after watching an 8-min fantastical cartoon, (c) 10-min delayed testing after watching a fantastical cartoon, and (d) immediate testing after an 8-min free play (control condition). After exposure to each condition, children were tested on EF and mental transformation measures. Results showed that children watching a fantastical cartoon performed worse on working memory and inhibitory control tasks than children watching a non-fantastical cartoon or playing. However, the 10-min delay between the watching and testing sessions eliminated the negative impact observed on inhibitory control. Groups did not differ on cognitive flexibility and mental transformation. As in previous studies, watching fantastical content negatively affected children's EFs, but this negative impact disappeared in a few minutes and seems unique to EFs. These results suggest that fantastical content may temporarily affect attentional and information processing systems related to EFs.

What's in a Message? Effects of Mental Fatigue and Message Framing on Motivation for Physical Activity

Many adults worldwide do not meet current physical activity (PA) guidelines. Mental fatigue decreases the likelihood of choosing to engage in PA. Message framing may enhance PA motivation when fatigued. We examined the effects of mental fatigue and message framing on PA motivation with additional focus on the messaging "congruency effect." Three hundred and twenty undergraduates completed measures of dispositional motivational orientation and were exposed to either gain-framed or loss-framed messages before completing an effort discounting questionnaire. Results showed lower motivation to engage in PA of higher intensities and longer durations. Direct effects of message framing on PA motivation were not significant. Interaction effects revealed that participants receiving messages congruent with their dominant motivational orientation showed increased motivation for light-intensity PA and decreased motivation for vigorous-intensity PA as mental fatigue increased. Findings suggest that providing messages congruent with one's dominant motivational orientation may increase motivation for engaging in light-intensity PA when fatigued.

Fatigue management: a systematic review of objective measurement techniques for cognitive fatigue

BACKGROUND

Cognitive fatigue is a complex psychobiological state whereby task performance cannot be maintained. Return-to-work protocols typically rely on self-report measures, therefore the current systematic review aimed to identify "real-time" measures of objective cognitive fatigue to inform return-to-work protocols.

METHODS

Studies were included if participants were at least 18 years old, assessed "real-time" objective cognitive fatigue that could be used outside of the lab (neuroimaging measures were, therefore, excluded), used an induction task that was separate to the measurement, were adequately powered, compared objective cognitive fatigue at baseline and post-induction, and included a cognitive fatigue induction task that was at least 30 minutes long.Nine electronic databases were searched until 31 December 2022 (MEDLINE; PsychArticle; PubMED, ProQuest; ProQuest for gray literature; Google Scholar; The Cochrane Library; The Health Technology Assessment Database; and Web of Science), with alerts set up on Google Scholar to notify of new relevant research since this date (reviewed until December 2023). The checklist for quasi-experimental studies (Joanna Briggs Institute, 2014) was used to assess the risk of bias. Whilst a meta-analysis was planned, the data were unsuitable so only a narrative synthesis was conducted.

RESULTS

Fifty-seven studies were included, which were conducted within a variety of settings including naturalistic work scenarios, driving, aviation, and artificial computer-based tasks.Whilst the review found a range of potential measurements, there were inconsistencies in findings across studies highlighting the need for more research into the reliable measurement of objective cognitive fatigue in natural settings.

DISCUSSION

The findings suggest that eye- and body-related measures may be sensitive measures of objective cognitive fatigue. However, comparisons across measurement types should be cautiously interpreted because eye-related and cognitive measures were far more common. The review highlighted the need for more consistent and transparent reporting across the field to advance our understanding of cognitive fatigue.

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.

The interplay of brain neurotransmission and mental fatigue: A research protocol

INTRODUCTION

Mental fatigue (MF) significantly affects both cognitive and physical performance. However, the precise mechanisms, particularly concerning neurotransmission, require further investigation. An implication of the role of dopamine (DA) and noradrenaline (NA) is stated, but empirical evidence for this theory still needs to be provided. To address this gap, we aim to investigate the role of brain neurotransmission in elucidating if, and how prolonged cognitive activity induces MF and its subsequent impact on cognitive performance.

METHODS

This study (registration number: G095422N) will adopt a randomized cross-over design with sixteen healthy participants aged 18-35 years. The sessions include a familiarization, two experimental (DA: 20mg Methylphenidate; NA: 8mg Reboxetine) conditions, and one placebo (lactose tablet: 10mg) condition. A 60-minute individualized Stroop task will be used to investigate whether, and how the onset of MF changes under the influence of reuptake inhibitors. Attention and response inhibition will be assessed before and after the MF-inducing task using a Go/NoGo task. The integration of physiological (electroencephalography, heart rate), behavioral (attention, response inhibition), and subjective indicators (scales and questionnaires) will be used to detect the underlying mechanisms holistically. Data analysis will involve linear mixed models with significance at p<0.05.

DISCUSSION

The integration of diverse techniques and analyses offers a comprehensive perspective on the onset and impact of MF, introducing a novel approach. Future research plans involve extending this protocol to explore the connection between brain neurotransmission and physical fatigue. This protocol will further advance our understanding of the complex interplay between the brain and fatigue.

Brain Endurance Training Improves and Maintains Chest Press and Squat Jump Performance When Fatigued

ABSTRACT

Díaz-García, J, López-Gajardo, MÁ, Parraca, JA, Batalla, N, López-Rodríguez, R, and Ring, C. Brain endurance training improves and maintains chest press and squat jump performance when fatigued. J Strength Cond Res 38(9): 1568-1575, 2024-Mental fatigue can impair resistance exercise performance. Brain endurance training (BET)-the addition of demanding cognitive tasks to standard exercise training-improves endurance exercise performance more than standard training. Although BET has yet to be evaluated with resistance exercise, it is expected to improve performance, particularly when the performer feels mentally fatigued. The study employed a pretest (week 0), midtest (week 3), posttest (week 6), and follow-up (week 9) design, with subjects randomized to BET ( n = 46) or control (exercise training) ( n = 45) groups. In testing sessions, subjects performed chest press and squat jump exercises to failure before (feeling fresh) and after (feeling tired) a 30-minute cognitively demanding Stroop task. Training comprised 5 BET or control training sessions per week for 6 weeks. In each training session, subjects completed 4 sets of each exercise to failure, with each exercise set preceded by a 3-minute cognitive task (BET) or rest (control). Exercise performance (number of repetitions to failure) and mental fatigue markers were assessed. In pretesting, exercise performance did not differ between the groups. In midtesting and posttesting, BET performed more chest press and squat jump repetitions when fatigued by the 30-minute Stroop than control. The mental fatigue elicited by the Stroop task gradually declined with training in BET compared with control. In conclusion, BET enhanced resistance exercise performance compared with standard training when tested subsequent to a mentally fatiguing cognitive task. These benefits were maintained weeks after training ended. Brain endurance training is an effective method to mitigate the deleterious effects of mental fatigue on resistance exercise performance.

Does mental fatigue affect performance in racket sports? A systematic review

Mental fatigue impairs performance across several sports domains. However, a systematic review on its effects on racket sports performance has been lacking due to the previous scarcity of studies. This review aims to provide a comprehensive review the effects of mental fatigue on racket players' performance, with a discussion of the underlying mechanisms. A thorough search was conducted across five databases, including Web of Science, PubMed, SCOPUS, SPORTDiscus (via EBSCOhost), and the Psychological and Behavioral Science Collection (via EBSCOhost). The PICOS framework established the inclusion criteria: (1) healthy racket sports players; (2) induction of mental fatigue in both field and laboratory settings; (3) comparison of mental fatigue interventions with a control group (e.g., watching a movie or reading a magazine); (4) assessment of performance outcomes, including physical performance, skilled performance, and perceptual-cognitive performance; and (5) randomized controlled trials (RCTs), non-randomized controlled trials (non-RCTs), and non-randomized non-controlled trials. Mental fatigue manipulation, subjective evaluation, and (neuro)physiological markers were synthesized to support the successful induction of mental fatigue. Performance was categorized into tennis, table tennis, badminton, and padel based on the characteristics of specific racket sports domains. Secondary outcomes, such as the rate perception of effort (RPE) and motivation, were synthesized to explain the mechanisms based on the prominent theory of the Psychobiological model of endurance performance. Six studies revealed that mental fatigue impacts stroke performance in table tennis, affecting speed, accuracy, faults, and only second-serve accuracy in tennis. The response time of psychomotor performance increased in table tennis, padel, and badminton. Meanwhile, mental fatigue increased the RPE and remained unchanged in heart rate, blood glucose, and lactate, consistent with the Psychobiological model of endurance performance. Additionally, attention is suggested as a significant underlying psychobiological factor.

Adaptive cognitive tasks for mental fatigue: An innovative paradigm for cognitive loading in human performance

OBJECTIVES

Mental fatigue (MF) can impair cognitive and physical performance in sport. We tested the hypothesis that a shorter adaptive Time Load Dual Back (TLDB) task induces MF faster than a longer Stroop; and subsequently impairs cognitive and intermittent running performance.

DESIGN

This study employed a randomized within-participant design.

METHODS

25 trained individuals performed a Yo-Yo test after one of four experimental conditions (30-min Stroop, 20-min and 10-min TLDB tasks, and active control). Cognitive performance was assessed using the Psychomotor Vigilance Task (PVT) before and after the experimental conditions. Measures of mood, workload, MF, RPE, heart rate (HR), heart rate variability (HRV) and blood lactate were collected. ANOVAs determined the effect of the 4 conditions.

RESULTS

Stroop and 20-min TLDB conditions impaired running performance similarly (p = .015), while no differences are reported for 10-min TLDB and Control. No significant differences in physiological parameters were reported during the Yo-Yo test although RPE was significantly higher in the Stroop and 20-min TLDB conditions (p = .014). Stroop and both TLDBs conditions impaired PVT's cognitive performance (p = .029), MF (p = .012), mental demand (p < .001), HR (p = .021) and HRV (p = .033); with 20-min TLDB task having the higher significant impact. Mood alterations were similar between Stroop and TLDB conditions.

CONCLUSIONS

Intermittent running (Yo-Yo) and cognitive (PVT) performances, and subjective ratings were impaired by 30-min Stroop and 20-min TLDB tasks; while 10-min TLDB did not to impair performance. Shorter adaptive modes seem to be more effective in inducing MF and could have relevant clinical applications to assess conditions such as traumatic brain injury and concussion.

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.

Physical Activity and Fatigue Symptoms: Neurotypical Adults and People with Chronic Multisymptom Illnesses

For neurotypical adults, a single bout of low-to-moderate intensity physical activity usually transiently improves feelings of energy. Similar bouts of exercise have the opposite effect of increased feelings of fatigue when performed by samples with chronic multisymptom illnesses (CMIs) such as Long-COVID, Gulf War Illness (GWI), or Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). The short-term adoption of regular moderate intensity physical activity (typical experiments are 1 to 6 months) among neurotypical adults results in small-to-moderate improvements in self-reported feelings of fatigue, energy, and vitality. Small improvements in these feelings, or no change at all, occur for CMIs, but limited data precludes strong conclusions. The mechanisms of exercise effects on fatigue, whether acute or chronic, are poorly understood but likely involve multiple neural circuits and associated transmitters. For CMIs, the mechanisms of acute worsening of fatigue with exercise may be driven by the yet unknown pathophysiological mechanisms of the disease (perhaps involving brain, immune and autonomic system dysfunction, and their interactions). Likewise, fatigue improvements may depend on whether chronic physical activity is a disease-modifying treatment.

Brain Endurance Training Improves Dynamic Calisthenic Exercise and Benefits Novel Exercise and Cognitive Performance: Evidence of Performance Enhancement and Near Transfer of Training

ABSTRACT

Dallaway, N, Mortimer, H, Gore, A, and Ring, C. Brain endurance training improves dynamic calisthenic exercise and benefits novel exercise and cognitive performance: Evidence of performance enhancement and near transfer of training. J Strength Cond Res XX(X): 000-000, 2024-The purpose of this dual study was to evaluate whether brain endurance training (BET)-a mental fatigue countermeasure involving physical and cognitive training-enhanced exercise compared with physical training alone. Two studies (N = 29) used a pretest/training/posttest design, with participants randomized to BET or control groups. During testing, participants performed calisthenic exercises (study 1: press-ups, wall sit, and plank; study 2: burpees, jump squats, leg raises, press-ups, and plank) to failure before and after completing 20-minute cognitive tasks (study 1: memory updating; study 2: memory updating, response inhibition, and nonexecutive functions). Training comprised 3 sessions per week for 4 weeks. In study 1 training sessions, participants completed 2 submaximal exercise sets; each exercise was followed by a 3-minute cognitive task with high (BET) or low (control) cognitive loads. In study 2 training sessions, participants completed 1 submaximal exercise set; after 12-minute cognitive tasks (BET) or rest (control), each exercise was preceded by a 3-minute cognitive task (BET) or rest (control). These cognitive tasks involved response inhibition and memory updating. Performance (exercise repetitions/duration), perceived exertion, and mental fatigue were assessed. In pretesting, exercise performance was matched between groups. In posttesting, BET groups performed more dynamic exercises than control groups but the same number of static exercises. Cognitive task performance was either greater for BET or not different between groups. Neither perceived exertion nor mental fatigue differed between groups and tests. Brain endurance training enhanced dynamic but not static calisthenic exercise performance compared with physical training alongside near transfer of training benefits for novel physical and cognitive task performance.

Athletes with meditation experience counteract the detrimental effect of mental fatigue on endurance performance and neurocognitive functions

The current study examined whether meditation experience is associated with changes in endurance performance and inhibitory control-relevant neurocognitive functions caused by mental fatigue. Twenty-four athletes with meditation experience (AME) and twenty-five athletes without meditation experience (AWME) underwent a 30-min incongruent Stroop test in mental fatigue condition (MF) and a 30-min congruent Stroop test in control condition (CON) in a randomised-counterbalanced order. Inhibitory control-relevant neurocognitive functions were assessed using Flanker task and event-related potentials, followed by an endurance task using the Bruce treadmill protocol. Visual analogue scale was used to evaluate perceived mental fatigue (VAS-MF) before (T1), after Stroop test (T2) and after Flanker task (T3), and VAS for motivation (VAS-M) was used to evaluate motivation in Flanker task and endurance task. Results indicated that, compared to the CON, AWME in the MF exhibited overall lower accuracy, smaller incongruent N2 amplitude of the Flanker task (ps < .05), and shorter time to exhaustion (TTE) of the endurance task (p < .001), whereas AME did not exhibited difference in these outcomes between the conditions. Along with athletes in the MF reported lower VAS-M in endurance task. These findings suggest the benefits of meditation experience in mitigating the negative effects of mental fatigue.

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.

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.

The counteractive effects of interventions addressing mental fatigue on sport-specific performance among athletes: A systematic review with a meta-analysis

The deleterious consequences of mental fatigue (MF) on athletes in diverse sporting domains have been subject to extensive inquiry. However, the efficacy of interventions to counteract the effects of MF remains largely elusive. This review aims to evaluate the effects of counteractive interventions on the sport-specific performance of mentally fatigued athletes. Moreover, synthesizes the current evidence on which sports effectively counter the detrimental effects of MF with interventions, highlighting potential avenues for upcoming research. A systematic search was executed via Web of Science, Scopus, PubMed, and EBSCOhost, in addition to Google Scholar and references for grey literature. A meta-analysis was executed to compute effect sizes for different interventions with 13 qualified papers. Interventions include transcranial direct current stimulation, person-fit, mindfulness, glucose supplementation, caffeine mouth rinsing, and nature exposure showed potential to mitigate the detrimental effects on sport-specific performance, particularly in shooting accuracy (ES = 0.591; p = 0.001), decision-making accuracy (ES = 0.553; p = 0.006), and reaction time (ES = -0.871; p < 0.001), however, not in completion time (ES = -0.302; p = 0.182). This review underscores the unique roles of self-regulatory resources and directed attention. Nonetheless, a cautious interpretation of the findings is warranted given the paucity of investigations involving potential interventions in numerous other sports, such as volleyball, Australian football, cricket, and boxing.

Counteracting mental fatigue for athletes: a systematic review of the interventions

The deleterious effects of mental fatigue (MF) on athletes have been carefully studied in various sports, such as soccer, badminton, and swimming. Even though many researchers have sought ways to ameliorate the negative impact of MF, there is still a lack of studies that review the interventions used to counteract MF among athletes. This review aims to report the current evidence exploring the effects of interventions on MF and sport-specific performance, including sport-specific motor performance and perceptual-cognitive skills. Web of Science, Scopus, PubMed, and SPORTDicus (EBSCOhost) were combed through to find relevant publications. Additionally, the references and Google Scholar were searched for any grey literature. For the current review, we included only randomized controlled trials that involved athletes, a primary task to induce MF, interventions to counter MF with comparable protocols, and the outcomes of sport-specific motor performance and perceptual-cognitive skill. The selection criteria resulted in the inclusion of 10 articles. The manipulations of autonomous self-control exertion, person-fit, nature exposure, mindfulness, and transactional direct current stimulation showed that positive interventions counteract MF and improve sport-specific performance in different domains, including strength, speed, skill, stamina, and perceptual-cognitive skills. The selected interventions could significantly counteract MF and improve subsequent sport-specific performance. Moreover, self-regulation and attention resources showed the importance of the potential mechanisms behind the relevant interventions.

Mental fatigue impairs repeated sprint and jump performance in team sport athletes

OBJECTIVES

We tested whether mental fatigue (MF), induced by a cognitively-demanding task, would impair repeated sprint ability (RSA) and repeated jump ability (RJA) performance, and whether physical fatigue and MF would impair psychomotor vigilance.

DESIGN

Randomized within-participant design.

METHODS

After establishing baseline peak countermovement jump (CMJ), 18 male participants performed 12 maximal 20-m (10-m linear + 10-m directional) repeated sprints (RSA random test) followed by 12 maximal repeated CMJs (RJA test) subsequent to 30-min Stroop task (MF) or a documentary (Control). Peak and mean running time and height, percent decrement score (Sdec), blood lactate, heart rate and RPE were measured for CMJ, RSA, and RJA tests. MF (M-VAS) and psychomotor vigilance [psychomotor vigilance test (PVT)] were measured at baseline, after each condition, and after the RSA/RJA tests.

RESULTS

Compared to Control, the Stroop task elevated MF (p = .001), RPE ratings (all p < .031), and mean and Sdec performance in directional (but not linear) RSA (all p < .032) and RJA tests (all p < .034). PVT score worsened after Stroop task (p = .011) but not Control, declined after RSA/RJA tests in both conditions (all p < .023) and was lower in the MF condition (p = .029). No condition differences were noted for peak (CMJ, RSA and RJA tests) performance, blood lactate, and heart rate.

CONCLUSIONS

MF impairs directional RSA, and RJA performance. This impairment was linked with increased RPE and without physiological changes. The progressive impairment in PVT score suggests a cumulatively negative effect of mental and physical fatigue on psychomotor vigilance.

"A sprained ankle is the biggest sign of mental fatigue": A qualitative study of the perceptions and experiences of mental fatigue in professional ballet

Mental fatigue is known to influence endurance, skill, and tactical performance in sport. Research investigating the impact of mental fatigue on tasks that combine physical, cognitive, and aesthetic performance such as professional ballet does not exist.

OBJECTIVE

To understand the perceptions and experiences of mental fatigue in professional ballet.

DESIGN

Qualitative, focus groups and semi-structured interviews.

SETTING

The Australian Ballet.

PARTICIPANTS

Thirty-nine professional ballet dancers (53% of the company) and six dance staff members aged 18 years or above (53% female).

MAIN OUTCOME MEASURES

N/a.

RESULTS

The average focus group and interview length was 48 ± 7 min and 41 ± 8 min. Key categories were; (1) Dancers and dance staff perceive that new learning contributes to mental fatigue, (2) Dancers perceive changes to their mood and perception of effort when they are mentally fatigued, and (3) Dancers and dance staff perceive that mental fatigue negatively affects their physical and cognitive performance and, increases their risk of injury.

CONCLUSION

This is the first study where participants associated mental fatigue with injury risk and provides a springboard to measure the impact of mental fatigue on learning, injury, and performance in professional ballet.

Global practitioner assessment and management of mental fatigue and mental recovery in high-performance sport: A need for evidence-based best-practice guidelines

BACKGROUND

Mental fatigue and mental recovery have gained scientific attention in relation to sporting performance, yet best practice assessment and management methods are lacking. A greater understanding of current knowledge and practices in high-performance sport are necessary.

OBJECTIVE

To understand the contemporary knowledge, beliefs, monitoring processes, management strategies, perceived responsibility, sources of evidence, and challenges, when assessing the mental fatigue and mental recovery of athletes in high-performance sport.

METHODS

A mixed-methods survey approach obtained information from 156 multi-disciplinary high-performance sport practitioners. Descriptive outputs were reported and potential differences between key concepts were detected using Wilcoxon-signed rank analysis. Thematic analysis interpreted open-text responses.

RESULTS

Only 11.5% and 5.1% of respondents indicated they were "very" knowledgeable about mental fatigue and mental recovery, respectively. Knowledge (p < 0.001) and confidence in application (p = 0.001) were significantly greater for mental fatigue than mental recovery. Nearly all respondents perceived mental fatigue and mental recovery impacted training and competition performance, with a greater negative impact during competition (p < 0.001). A limited number of respondents reported deliberate assessment (31.1%) or management (51.2%) of mental fatigue and mental recovery. A combination of sources of evidence were used to inform practice, with common challenges to implementation including staff knowledge, athlete-buy in, time-availability, and a lack of evidence. Practitioners reported that assessing and managing mental fatigue and mental recovery was multi-disciplinary in nature.

CONCLUSION

Practitioners reported that mental fatigue and mental recovery did impact performance, yet this was not reflected in the implementation of evidence-based assessment and management practices in high-performance sport.

Carbohydrate Nutrition and Skill Performance in Soccer

In soccer, players must perform a variety of sport-specific skills usually during or immediately after running, often at sprint speed. The quality of the skill performed is likely influenced by the volume of work done in attacking and defending over the duration of the match. Even the most highly skilful players succumb to the impact of fatigue both physical and mental, which may result in underperforming skills at key moments in a match. Fitness is the platform on which skill is performed during team sport. With the onset of fatigue, tired players find it ever more difficult to successfully perform basic skills. Therefore, it is not surprising that teams spend a large proportion of their training time on fitness. While acknowledging the central role of fitness in team sport, the importance of team tactics, underpinned by spatial awareness, must not be neglected. It is well established that a high-carbohydrate diet before a match and, as a supplement during match play, helps delay the onset of fatigue. There is some evidence that players ingesting carbohydrate can maintain sport-relevant skills for the duration of exercise more successfully compared with when ingesting placebo or water. However, most of the assessments of sport-specific skills have been performed in a controlled, non-contested environment. Although these methods may be judged as not ecologically valid, they do rule out the confounding influences of competition on skill performance. The aim of this brief review is to explore whether carbohydrate ingestion, while delaying fatigue during match play, may also help retain sport soccer-specific skill performance.

Thinking About Elite Performance: The Experience and Impact of Mental Fatigue in Elite Sport Coaching

PURPOSE

Mental fatigue causes decreases in aspects of athletes' performance. Elite coaches commonly undertake cognitively demanding tasks and are seemingly at similar risk of subsequent performance impairment. However, elite sport coaches' experiences of mental fatigue, alongside other markers of psychobiological stress, have yet to be quantified.

METHODS

Three elite coaching and performance staff (2 women and 1 man) provided 100-mm visual analog scale ratings of mental fatigue, physical fatigue, readiness to perform, and salivary samples for later cortisol (sCort) and alpha-amylase (sAA) analysis. Data were obtained on the same morning each week across a 16-week preseason. Data were subset by individual coach for descriptive and repeated-measures correlational analyses.

RESULTS

Fluctuating mental fatigue was observed over the 16 weeks (min-max; coach 1 = 25-86 AU; coach 2 = 0-51 AU; and coach 3 = 15 - 76 AU). Elevated levels of mental fatigue were reported at multiple time points, with individual variability observed. sCort (in nanomoles per liter), sAA (in micromoles per liter), and sAA:sCort indicated that coaches experienced psychophysiological stress (min-max; coach 1 sCort = 8.42-17.31, sAA = 52.40-113.06, sAA:sCort = 3.20-12.80; coach 2 sCort = 4.20-9.70, sAA = 158.80-307.20, sAA:sCort = 21.10-61.70; and coach 3 sCort = 6.81-19.66, sAA = 86.55-495.85, sAA:sCort = 4.90-35.50). A significant inverse relationship between mental fatigue and readiness to perform (r = -.44 [-.64 to -.17], P = .002) was identified.

CONCLUSIONS

Elite sport coaches report elevated instances of mental fatigue during a preseason training period. Those involved in elite sports should act to understand the presence and potential subsequent impacts of staff mental fatigue and consider management or mitigation strategies. Optimization of the cognitive performance of coaches and performance staff presents as a potential source of competitive advantage.

Brain endurance training improves shot speed and accuracy in grassroots padel players

OBJECTIVES

Evidence that mental fatigue impairs sport performance has created a demand for countermeasures. We examined the effects of brain endurance training, a form of fatigue-inoculation, on shot performance in grassroots padel players.

DESIGN

A pre-, mid- and post-test design, with participants randomized to brain endurance training (n = 30) or control (n = 31) groups.

METHODS

During testing, participants completed a Padel Stroke Performance Test, before and after a demanding 30-min cognitive task (Stroop). Training comprised 3 sessions/week for 6 weeks. In each training session, participants completed 10-min warm-up, 15-min technical drills, 15-min tactical drills, and 20-min simulated games. These physical activities were intermixed with short 4-min periods of Stroop (brain endurance training group) or rest (control group) totaling 20-min. Performance was measured by shot speed and accuracy of padel strokes. Mental fatigue indices were measured before and after the Stroop task using a visual analog scale rating, a psychomotor vigilance task, and a go/no-go task.

RESULTS

During testing, the 30-min Stroop task elicited a state of mental fatigue, confirmed by higher subjective ratings, slower responses during the psychomotor vigilance task, and slower saccade latencies during the go/no go task. Compared to pre-testing, in mid- and post-testing, the brain endurance training group hit progressively faster and more accurate padel shots after the Stroop task compared to controls.

CONCLUSIONS

Brain endurance training enhanced skill-based psychomotor performance when fatigued compared to standard padel training. Brain endurance training is a countermeasure that promotes mental fatigue durability.

Interindividual Variability in Mental Fatigue-Related Impairments in Endurance Performance: A Systematic Review and Multiple Meta-regression

BACKGROUND

The negative effect of mental fatigue (MF) on physical performance has recently been questioned. One reason behind this could lie in the interindividual differences in MF-susceptibility and the individual features influencing them. However, the range of individual differences in mental fatigue-susceptibility is not known, and there is no clear consensus on which individual features could be responsible for these differences.

OBJECTIVE

To give an overview of interindividual differences in the effects of MF on whole-body endurance performance, and individual features influencing this effect.

METHODS

The review was registered on the PROSPERO database (CRD42022293242). PubMed, Web of Science, SPORTDiscus and PsycINFO were searched until the 16th of June 2022 for studies detailing the effect of MF on dynamic maximal whole-body endurance performance. Studies needed to include healthy participants, describe at least one individual feature in participant characteristics, and apply at least one manipulation check. The Cochrane crossover risk of bias tool was used to assess risk of bias. The meta-analysis and regression were conducted in R.

RESULTS

Twenty-eight studies were included, with 23 added to the meta-analysis. Overall risk of bias of the included studies was high, with only three presenting an unclear or low rating. The meta-analysis shows the effect of MF on endurance performance was on average slightly negative (g = - 0.32, [95% CI - 0.46; - 0.18], p < 0.001). The multiple meta-regression showed no significant influences of the included features (i.e. age, sex, body mass index and physical fitness level) on MF-susceptibility.

CONCLUSIONS

The present review confirmed the negative impact of MF on endurance performance. However, no individual features influencing MF-susceptibility were identified. This can partially be explained by the multiple methodological limitations such as underreporting of participant characteristics, lack of standardization across studies, and the restricted inclusion of potentially relevant variables. Future research should include a rigorous description of multiple different individual features (e.g., performance level, diet, etc.) to further elucidate MF mechanisms.

Mental fatigue changes from regular season to play-offs in semiprofessional soccer: A comparison by training days

The main purpose was to compare by each training the mental load and fatigue reported by semiprofessional soccer players comparing between regular season phase and the play-offs. Fifty-three players (M_age  = 24.59 years) for two teams participated during the 2020/21 season. Mental load was measured with a Likert questionnaire. Mental fatigue was quantified with a Visual Analogue Scale. Four trainings were recorded each week (Monday = MD+1, Wednesday = MD-4, Thursday = MD-3 and Saturday = MD-1), with a competitive match on Sunday across 10 weeks (five dates of regular season - five dates of play-offs). A Linear Mixed Model was performed with R-studio, using the training days and the competitive phase as independent variables. The influence of time played as co-variable was also checked. Results showed MD+1 as the more mentally fatiguing day in both phases, although MD-4 were the training with higher mental load reported (p = 0.001). Comparing phases, mental fatigue was significantly higher during the play-offs (p = 0.037). With regard time played, players that did not usually play showed a decrease in mental load during the play-offs. Then, we recommend coaches to use recovery strategies for mental fatigue, avoid mentally fatiguing tasks close to competition and considerer the time played as a factor which may contribute to individual differences in player mental fatigue.

Mental Fatigue: The Cost of Cognitive Loading on Weight Lifting, Resistance Training, and Cycling Performance

PURPOSE

Mental fatigue (MF) can impair physical performance in sport. We tested the hypothesis that cognitive load alone, and intermixed with standard resistance training, would induce MF, increase rating of perceived exertion (RPE), alter perception of weight lifting and training, and impair cycling time-trial performance.

METHODS

This 2-part study employed a within-participant design. In part 1, after establishing leg-extension 1-repetition maximum (1RM), 16 participants lifted and briefly held weights at 20%, 40%, 60%, and 80% of 1RM. RPE and electromyography (EMG) were measured for each lift. During the testing sessions, participants completed cognitive tasks (MF condition) or watched neutral videos (control condition) for 90 minutes before lifting the weights. In part 2, they completed submaximal resistance training comprising 6 weight training exercises followed by a 20-minute cycling time trial. In the MF condition, they completed cognitive tasks before and between weight training exercises. In the control condition, they watched neutral videos. Mood (Brunel Mood Scale), workload (National Aeronautics and Space Administration Task Load Index), MF-visual analogue scale (MF-VAS), RPE, psychomotor vigilance, distance cycled, power output, heart rate, and blood lactate were measured.

RESULTS

In part 1, the cognitive task increased lift-induced RPE (P = .011), increased MF-VAS (P = .002), and altered mood (P < .001) compared with control. EMG did not differ between conditions. In part 2, the cognitive tasks increased RPE (P < .001), MF-VAS (P < .001), and mental workload (P < .001), but reduced cycling time-trial power (P = .032) and distance (P = .023) compared with control. Heart rate and blood lactate did not differ between conditions.

CONCLUSION

A state of MF induced by cognitive load, alone or intermixed with physical load, increased RPE during weight lifting and training and impaired subsequent cycling performance.

Nature exposure might be the intervention to improve the self-regulation and skilled performance in mentally fatigue athletes: A narrative review and conceptual framework

Background

Due to causing inability of self-regulation (ego depletion) and executive functions such as directed attention and visual searching for relevant information (e.g., the ball location and the position of teammates), mental fatigue impairs skilled performance in various sports. On the other hand, natural scenes could improve directed attention, which may considerably benefit visual searching ability and self-regulation. However, nature exposure as a potential intervention to improve skilled performance among mentally fatigued athletes has not been discussed thoroughly.

Purpose

To propose the potential intervention for the impairment of skilled performance among mentally fatigued athletes and generate a framework for future studies.

Methods

A narrative review was applied to search broadly across disciplines, retrieving literature from several databases (PubMed, Web of Science, Scopus, and EBSCOhost).

Results

Thirty-three works of literature including 39 experiments (mental fatigue 15; ego depletion 5; and nature exposure 19) were obtained. Finally, a conceptual framework was built regarding the effect of nature exposure intervention on skilled performance in athletes for future studies.

Conclusion

Three theories (the psychobiological model of exercise performance, the strength model of self-regulation, and attention restoration theory) could be potentially integrated to be a conceptual framework and explain the mechanism of preventing prior mental exertion (e.g., mental fatigue and ego depletion). Future studies could examine more on the duration of the intervention.

Do Cognitive, Physical, and Combined Tasks Induce Similar Levels of Mental Fatigue? Testing the Effects of Different Moderating Variables

Experts have highlighted the importance of coaches knowing the level of mental fatigue (MF) induced by different tasks. This study aimed to compare the mentally fatiguing nature of cognitive, physical, and combined tasks and, additionally, assess the effect of different moderating variables on MF. Twenty-three physically active (16 males: Mage = 24 years; seven females: Mage = 22.57 years) participants performed three experimental sessions: (a) physically fatiguing: 30 min of cycloergometer work (at 65%-75% of maximum heart rate), (b) mentally fatiguing: 30 min of an incongruent Stroop task, and (c) mixed fatiguing: 30 min of combining the physically and mentally fatiguing protocols. Subjective MF (visual analog scale), reaction time (psychomotor vigilance task), and cognitive performance (Stroop) were measured throughout the different protocols. Results showed significant increments in subjective MF after all tasks, with the mental and mixed protocols showing significantly higher increases. Only the mentally fatiguing protocol caused significant impairments in reaction time. No significant effects of sex, years of experience, or degree of mental toughness were observed. These results suggest that the use of all these tasks, and especially the mentally fatiguing exercises, should be avoided immediately prior to competitions due to the negative consequences of MF on performance. Moreover, this effect seems to be independent of the sex, years of experience, or mental toughness of athletes.

The Counteractive Effect of Self-Regulation-Based Interventions on Prior Mental Exertion: A Systematic Review of Randomised Controlled Trials

BACKGROUND

Many investigations have been performed on the effects of mental exertion that consumes self-regulatory resources and then affects physical and/or cognitive performance later on. However, the effect of manipulating self-regulation and interventions to attenuate this negative effect remains unclear. Moreover, there is continuous controversy regarding the resource model of self-regulation.

OBJECTIVE

We conducted a systematic review to assess the literature on manipulating self-regulation based on four ingredients (standard, monitoring, strength, and motivation) in order to counter mental exertion and improve physical and/or cognitive performance. The results provide more insight into the resource model.

METHOD

A thorough search was conducted to extract the relevant literature from several databases, as well as Google Scholar, and the sources from the references were included as grey literature. A self-regulation intervention compared to a control condition, a physical and/or cognitive task, and a randomised controlled trial were selected.

RESULT

A total of 39 publications were included. Regarding the four components of self-regulation, the interventions could mainly be divided into the following: (i) standard: implementation intervention; (ii) monitoring: biofeedback and time monitoring; (iii) strength: repeated exercise, mindfulness, nature exposure, and recovery strategies; (iv) motivation: autonomy-supportive and monetary incentives. The majority of the interventions led to significant improvement in subsequent self-regulatory performance. In addition, the resource model of self-regulation and attention-restoration theory were the most frequently used theories and supported relevant interventions.

CONCLUSION

In line with the resource model, manipulating the four components of self-regulation can effectively attenuate the negative influence of mental exertion. The conservation proposed in the strength model of self-regulation was supported in the current findings to explain the role of motivation in the self-regulation process. Future studies can focus on attention as the centre of the metaphorical resource in the model.