Portrait of Professor Samuele Marcora

Professor Samuele Marcora

Professor

About

Professor Samuele Marcora received his Bachelor in Physical Education from the State University of Milan (Italy). He then studied for an MSc in Human Performance at the University of Wisconsin-La Crosse (USA), and for a PhD in Clinical Exercise Physiology at the University of Wales-Bangor (UK). After a successful academic career at Bangor University, Professor Marcora began his post as Director of Research at the University of Kent at the end of 2010. His role is to stimulate, coordinate, monitor and assess all research activity within the School of Sport and Exercise Sciences.

In 2006, Professor Marcora changed his research direction and decided to integrate exercise physiology with motivation psychology and cognitive neuroscience. This psychobiological approach has generated several innovative studies including the effects of mental fatigue on endurance performance and brain training for endurance athletes (Brain Endurance Training). Professor Marcora had been research consultant for MAPEI Sport Service in Italy where he contributed to highly cited research on football and mountain biking physiology.

In his spare time, Professor Marcora enjoys riding his two motorbikes. In 2013, he completed a gruelling 3-month ride from London to Beijing through Central Asia and Tibet to investigate fatigue in motorbike riders. If you are interested in Professor Marcora's research on fatigue in motorbike riders, you can listen to his recent interview on Adventure Rider Radio here.

Research interests

My current research combines physiology and psychology in a truly interdisciplinary approach to investigate fatigue and endurance performance.

The ultimate goal of my research programme is to find new ways to improve performance of endurance athletes, and reduce physical and mental fatigue in a variety of populations. These populations include soldiers, motorbike riders, and patients affected by diseases such as cancer, rheumatoid arthritis, and chronic kidney disease.

My previous research includes research into the mechanisms, assessment and treatment of muscle wasting, and applied sports science research (eg, football training and mountain biking).

Publications

Showing 50 of 61 total publications in the Kent Academic Repository. View all publications.

Article

  • Angius, L., Marcora, S., Hopker, J. and Mauger, A. (2018). The Effect of Anodal Transcranial Direct Current Stimulation Over Left and Right Temporal Cortex on the Cardiovascular Response: A Comparative Study. Frontiers in Physiology [Online] 9. Available at: https://doi.org/10.3389/fphys.2018.01822.
    Background: Stimulation of the right and left anterior insular cortex, increases
    and decreases the cardiovascular response respectively, thus indicating the brain’s
    lateralization of the neural control of circulation. Previous experiments have
    demonstrated that transcranial direct current stimulation (tDCS) modulates the
    autonomic cardiovascular control when applied over the temporal cortex. Given the
    importance of neural control for a normal hemodynamic response, and the potential
    for the use of tDCS in the treatment of cardiovascular diseases, this study investigated
    whether tDCS was capable of modulating autonomic regulation.
    Methods: Cardiovascular response was monitored during a post-exercise muscle
    ischemia (PEMI) test, which is well-documented to increase sympathetic drive. A group
    of 12 healthy participants performed a PEMI test in a control (Control), sham (Sham)
    and two different experimental sessions where the anodal electrode was applied over
    the left temporal cortex and right temporal cortex with the cathodal electrode placed
    over the contralateral supraorbital area. Stimulation lasted 20 min at 2 mA. The
    hemodynamic profile was measured during a PEMI test. The cardiovascular parameters
    were continuously measured with a transthoracic bio-impedance device both during the
    PEMI test and during tDCS.
    Results: None of the subjects presented any side effects during or after tDCS
    stimulation. A consistent cardiovascular response during PEMI test was observed in all
    conditions. Statistical analysis did not find any significant interaction and any significant
    main effect of condition on cardiovascular parameters (all ps > 0.316) after tDCS.
    No statistical differences regarding the hemodynamic responses were found between
    conditions and time during tDCS stimulation (p > 0.05).
    Discussion: This is the first study comparing the cardiovascular response after tDCS
    stimulation of left and right TC both during exercise and at rest. The results of the current study suggest that anodal tDCS of the left and right TC does not affect functional
    cardiovascular response during exercise PEMI test and during tDCS. In light of the
    present and previous findings, the effect of tDCS on the cardiovascular response
    remains inconclusive.
  • Anstiss, P., Meijen, C., Madigan, D. and Marcora, S. (2018). Development and Initial Validation of the Endurance Sport Self-efficacy Scale (ESSES). Psychology of Sport and Exercise [Online] 38:176-183. Available at: https://doi.org/10.1016/j.psychsport.2018.06.015.
    Self-efficacy is likely to be an important psychological construct for endurance sport performance. Research into the role of self-efficacy, however, is limited as there is currently no validated measure of endurance sport self-efficacy. Consequently, the purpose of the present research was to develop and validate the Endurance Sport Self-Efficacy Scale (ESSES). In Study 1, an initial item pool was developed following a review of the literature. These items were then examined for content validity by an expert panel. In Study 2, the resultant 18 items were subjected to exploratory factor analyses. These analyses provided support for a unidimensional scale comprised of 11 items. Study 2 also provided evidence for the ESSES’s convergent validity. In Study 3, using confirmatory factor analyses, further support was found for the 11-item unidimensional structure. Study 3 also provided evidence for the ESSES’s convergent and concurrent validity. The present findings provide initial evidence that the ESSES is a valid and reliable measure of self-efficacy beliefs in endurance sports.
  • Van Cutsem, J., De Pauw, K., Marcora, S., Meeusen, R. and Roelands, B. (2018). A caffeine-maltodextrin mouth rinse counters mental fatigue. Psychopharmacology [Online] 235:947-958. Available at: https://doi.org/10.1007/s00213-017-4809-0.
    Introduction
    Mental fatigue is a psychobiological state caused by prolonged periods of demanding cognitive activity that has negative implications on many aspects in daily life. Caffeine and carbohydrate ingestion have been shown to be able to reduce these negative effects of mental fatigue. Intake of these substances might however be less desirable in some situations (e.g., restricted caloric intake, Ramadan). Rinsing caffeine or glucose within the mouth has already been shown to improve exercise performance. Therefore, we sought to evaluate the effect of frequent caffeine-maltodextrin (CAF-MALT) mouth rinsing on mental fatigue induced by a prolonged cognitive task.

    Methods
    Ten males (age 23?±?2 years, physical activity 7.3?±?4.3 h/week, low CAF users) performed two trials. Participants first completed a Flanker task (3 min), then performed a 90-min mentally fatiguing task (Stroop task), followed by another Flanker task. Before the start and after each 12.5% of the Stroop task (eight blocks), subjects received a CAF-MALT mouth rinse (MR: 0.3 g/25 ml CAF: 1.6g/25 ml MALT) or placebo (PLAC: 25 ml artificial saliva).

    Results
    Self-reported mental fatigue was lower in MR (p?=?0.017) compared to PLAC. Normalized accuracy (accuracy first block?=?100%) was higher in the last block of the Stroop in MR (p?=?0.032) compared to PLAC. P2 amplitude in the dorsolateral prefrontal cortex (DLPFC) decreased over time only in PLAC (p?=?0.017).

    Conclusion
    Frequent mouth rinsing during a prolonged and demanding cognitive task reduces mental fatigue compared to mouth rinsing with artificial saliva.
  • Saville, C., de Morree, H., Dundon, N., Marcora, S. and Klein, C. (2017). Effects of caffeine on reaction time are mediated by attentional rather than motor processes. Psychopharmacology [Online] 235:749-759. Available at: https://doi.org/10.1007/s00213-017-4790-7.
    Background
    Caffeine has a well-established effect on reaction times (RTs) but the neurocognitive mechanisms underlying this
    are unclear.

    Methods
    In the present study, 15 female participants performed an oddball task after ingesting caffeine or a placebo, and
    electroencephalographic data were obtained. Single-trial P3b latencies locked to the stimulus and to the response were extracted
    and mediation models were fitted to the data to test whether caffeine’s effect on RTs was mediated by its effect on either type of
    P3b latencies.

    Results
    Stimulus-locked latencies showed clear evidence of mediation, with approximately a third of the effect of caffeine on RTs
    running through the processes measured by stimulus-locked latencies. Caffeine did not affect response-locked latencies, so could
    not mediate the effect.

    Discussion
    These findings are consistent with caffeine’s effect on RTs being a result of its effect on perceptual-attentional
    processes, rather than motor processes. The study is the first to apply mediation analysis to single-trial P3b data and this technique
    holds promise for mental chronometric studies into the effects of psychopharmacological agents. The R code for performing the
    single trial analysis and mediation analysis are included as supplementary materials.
  • Salam, H., Marcora, S. and Hopker, J. (2017). The Effect of Mental Fatigue on Critical Power during cycling exercise. European Journal of Applied Physiology [Online] 118:85-92. Available at: https://doi.org/10.1007/s00421-017-3747-1.
    Purpose: Time-to-exhaustion (TTE) tests used in the determination of critical power (CP) and curvature constant (W) of the power-duration relationship are strongly influenced by the perception of effort (PE). This study aimed to investigate whether manipulation of the PE alters the CP and W. Methods: Eleven trained cyclists completed a series of TTE tests to establish CP and W under two conditions, following a mentally fatiguing (MF), or a control (CON) task. Both cognitive tasks lasted 30 min followed by a TTE test. Ratings of PE and heart rate (HR) were measured during each TTE. Blood lactate was taken pre and post each TTE test. Ratings of perceived mental and physical fatigue were taken pre- and post-cognitive task, and following each TTE test. Results: Perceived MF significantly increased as a result of the MF task compared to baseline and the CON task (P<0.05), without a change in perceived physical fatigue (P>0.05). PE was significantly higher during TTE in the MF condition (P<0.05). Pre-post blood lactate accumulation was significantly lower after each TTE in MF condition (P<0.05). HR was not significant different between conditions (P>0.05). Neither cognitive task induced any change in CP (MF 253±51 vs. CON 247±58W; P>0.05), although W was significantly reduced in the MF condition (MF 2.3±4.5 vs. CON 2.9±6.3kJ; P<0.01). Conclusion: MF has no effect of CP, but reduces the W in trained cyclists. Lower lactate accumulation during TTE tests following MF, suggests that cyclists were not be able to fully expend W even though they exercised to volitional exhaustion.
  • Angius, L., Mauger, A., Hopker, J., Pascual-Leone, A., Santarnecchi E, E. and Marcora, S. (2017). Bilateral extracephalic transcranial direct current stimulation improves endurance performance in healthy individuals. Brain stimulation [Online] 11:108-117. Available at: http://dx.doi.org/10.1016/j.brs.2017.09.017.
    Background: Transcranial direct current stimulation (tDCS) has been used to enhance endurance performance but its precise mechanisms and effects remain unknown.
    Objective: To investigate the effect of bilateral tDCS on neuromuscular function and performance during a cycling time to task failure (TTF) test.
    Methods: Twelve participants in randomized order received a placebo tDCS (SHAM) or real tDCS with two cathodes (CATHODAL) or two anodes (ANODAL) over bilateral motor cortices and the opposite electrode pair over the ipsilateral shoulders. Each session lasted 10 min and current was set at 2mA. Neuromuscular assessment was performed before and after tDCS and was followed by a cycling time to task failure (TTF) test. Heart rate (HR), ratings of perceived exertion (RPE), leg muscle pain (PAIN) and blood lactate accumulation (?B[La-]) in response to the cycling TTF test were measured.
    Results: Corticospinal excitability increased in the ANODAL condition (P < 0.001) while none of the other neuromuscular parameters showed any change. Neuromuscular parameters did not change in the SHAM and CATHODAL conditions. TTF was significantly longer in the ANODAL (P = 0.003) compared to CATHODAL and SHAM conditions (12.61 ± 4.65 min; 10.61 ± 4.34 min; 10.21 ± 3.47 min respectively), with significantly lower RPE and higher ?B[La-] (P < 0.001). No differences between conditions were found for HR (P = 0.803) and PAIN during the cycling TTF test (P = 0.305).
    Conclusion: Our findings demonstrate that tDCS with the anode over both motor cortices using a bilateral extracephalic reference improves endurance performance.
  • NicolòA., Marcora, S., Bazzucchi, I. and Sacchetti, M. (2017). Differential control of respiratory frequency and tidal volume during high-intensity interval training. Experimental Physiology [Online] 102:934-949. Available at: http://dx.doi.org/10.1113/EP086352.
    New Findings: What is the central question of this study?
    By manipulating recovery intensity and exercise duration during high-intensity interval training (HIIT), we tested the hypothesis that fast inputs contribute more than metabolic stimuli to respiratory frequency (fR) regulation.

    What is the main finding and its importance?
    Respiratory frequency, but not tidal volume, responded rapidly and in proportion to changes in workload during HIIT, and was dissociated from some markers of metabolic stimuli in response to both experimental manipulations, suggesting that fast inputs contribute more than metabolic stimuli to fR regulation. Differentiating between fR and tidal volume may help to unravel the mechanisms underlying exercise hyperpnoea.

    Given that respiratory frequency (fR) has been proposed as a good marker of physical effort, furthering the understanding of how fR is regulated during exercise is of great importance. We manipulated recovery intensity and exercise duration during high-intensity interval training (HIIT) to test the hypothesis that fast inputs (including central command) contribute more than metabolic stimuli to fR regulation. Seven male cyclists performed an incremental test, a 10 and a 20 min continuous time trial (TT) as preliminary tests. Subsequently, recovery intensity and exercise duration were manipulated during HIIT (30 s work and 30 s active recovery) by performing four 10 min and one 20 min trial (recovery intensities of 85, 70, 55 and 30% of the 10 min TT mean workload; and 85% of the 20 min TT mean workload). The work intensity of the HIIT sessions was self-paced by participants to achieve the best performance possible. When manipulating recovery intensity, fR, but not tidal volume (VT), showed a fast response to the alternation of the work and recovery phases, proportional to the extent of workload variations. No association between fR and gas exchange responses was observed. When manipulating exercise duration, fR and rating of perceived exertion were dissociated from VT, carbon dioxide output and oxygen uptake responses. Overall, the rating of perceived exertion was strongly correlated with fR (r = 0.87; P < 0.001) but not with VT. These findings may reveal a differential control of fR and VT during HIIT, with fast inputs appearing to contribute more than metabolic stimuli to fR regulation. Differentiating between fR and VT may help to unravel the mechanisms underlying exercise hyperpnoea.
  • McCormick, A., Meijen, C. and Marcora, S. (2017). Effects of a Motivational Self-Talk Intervention for Endurance Athletes Completing an Ultramarathon. The Sport Psychologist [Online] 32:42-50. Available at: https://dx.doi.org/10.1123/tsp.2017-0018.
    This study examined the effects of strategic, motivational self-talk for runners completing a 60-mile, overnight ultramarathon using a randomised, controlled experiment. Data were collected before, during, and after an annual ultramarathon. Twenty-nine ultramarathon runners were randomly allocated to a motivational self-talk group or an alternative control group. A condition-by-time mixed ANOVA indicated that learning to use motivational self-talk did not affect pre-event self-efficacy or perceived control. A t-test and magnitude-based inference indicated that motivational self-talk did not affect performance. Nevertheless, follow-up data suggested that most participants found the intervention helpful and continued to use it six months after their research commitment, particularly in endurance events and to a lesser extent in training. Participants continued to use self-talk to cope with exertion, as well as other stressors such as blister discomfort and adverse conditions. Suggestions are offered for future research examining the effects of psychological interventions on performance in endurance events.
  • Van Cutsem, J., De Pauw, K., Buyse, L., Marcora, S., Meeusen, R. and Roelands, B. (2017). Effects of Mental Fatigue on Endurance Performance in the Heat. Medicine and science in sports and exercise [Online] 49:1677-1687. Available at: http://dx.doi.org/10.1249/MSS.0000000000001263.
    PURPOSE

    Mental fatigue is a psychobiological state caused by prolonged periods of demanding cognitive activity and has been observed to decrease time-trial (TT) endurance performance by ~3,5% in normal ambient temperatures. Recently it has been suggested that heat may augment the negative effect of mental fatigue on cognitive performance, raising the question whether it may also amplify the effect of mental fatigue on TT-performance.

    METHODS

    In 30 °C and 30% relative humidity, ten endurance-trained male athletes (Age: 22 ± 3 y; Wmax: 332 ± 41 W) completed two experimental conditions: intervention (I; 45-min Stroop task) and control (C; 45-min documentary). Pre and post intervention/control, cognitive performance was followed up with a 5-min Flanker task. Thereafter subjects cycled for 45 min at a fixed pace equal to 60%-Wmax, immediately followed by a self-paced TT in which they had to produce a fixed amount of work (equal to cycling 15 min at 80%-Wmax) as fast as possible.

    RESULTS

    Self-reported mental fatigue was significantly higher after I compared to C (P<0.05). Moreover electroencephalographic measures also indicated the occurrence of mental fatigue during the Stroop (P<0.05). TT-time did not differ between conditions (I: 906 ± 30 s, C: 916 ± 29 s). Throughout exercise, physiological (heart rate, blood lactate, core and skin temperature) and perceptual measures (perception of effort and thermal sensation) were not affected by mental fatigue.

    CONCLUSION

    No negative effects of mild mental fatigue were observed on performance and the physiological and perceptual responses to endurance exercise in the heat. Most plausibly mild mental fatigue does not reduce endurance performance when the brain is already stressed by a hot environment.
  • Van Cutsem, J., Marcora, S., De Pauw, K., Bailey, S., Meeusen, R. and Roelands, B. (2017). The Effects of Mental Fatigue on Physical Performance: A Systematic Review. Sports medicine (Auckland, N.Z.) [Online]:1-20. Available at: http://dx.doi.org/10.1007/s40279-016-0672-0.
    BACKGROUND
    Mental fatigue is a psychobiological state caused by prolonged periods of demanding cognitive activity. It has recently been suggested that mental fatigue can affect physical performance.

    OBJECTIVE
    Our objective was to evaluate the literature on impairment of physical performance due to mental fatigue and to create an overview of the potential factors underlying this effect.

    METHODS
    Two electronic databases, PubMed and Web of Science (until 28 April 2016), were searched for studies designed to test whether mental fatigue influenced performance of a physical task or influenced physiological and/or perceptual responses during the physical task. Studies using short (<30 min) self-regulatory depletion tasks were excluded from the review.

    RESULTS
    A total of 11 articles were included, of which six were of strong and five of moderate quality. The general finding was a decline in endurance performance (decreased time to exhaustion and self-selected power output/velocity or increased completion time) associated with a higher than normal perceived exertion. Physiological variables traditionally associated with endurance performance (heart rate, blood lactate, oxygen uptake, cardiac output, maximal aerobic capacity) were unaffected by mental fatigue. Maximal strength, power, and anaerobic work were not affected by mental fatigue.

    CONCLUSION
    The duration and intensity of the physical task appear to be important factors in the decrease in physical performance due to mental fatigue. The most important factor responsible for the negative impact of mental fatigue on endurance performance is a higher perceived exertion.
  • McCormick, A., Meijen, C. and Marcora, S. (2016). Psychological Demands Experienced by Recreational Endurance Athletes. International Journal of Sport and Exercise Psychology [Online]. Available at: http://dx.doi.org/10.1080/1612197X.2016.1256341.
    This study aimed to identify psychological demands that are commonly experienced by endurance athletes so that these demands could inform the design of performance-enhancement psychological interventions for endurance athletes. Focus group interviews were conducted with 30 recreational endurance athletes of various sports (running, cycling, and triathlon), distances, and competitive levels to explore the psychological demands of training, competition preparation, and competition participation. An inductive thematic analysis was used to identify psychological demands that were experienced across sports, distances, and competitive levels. Seven themes captured demands that were commonly experienced away from the competitive environment (time investment and lifestyle sacrifices, commitment to training sessions, concerns about optimising training, and exercise sensations during training), preceding an endurance event (pre-event stressors), or during an event (exercise sensations, optimising pacing, and remaining focused despite adversity). Interventions that could be delivered to recreational athletes, who do not typically have access to a sport psychologist, are suggested. Experimental research examining the efficacy of interventions that help endurance athletes to cope with the reported psychological demands is encouraged.
  • Martin, K., Staiano, W., Menaspà, P., Hennessey, T., Marcora, S., Keegan, R., Thompson, K., Martin, D., Halson, S. and Rattray, B. (2016). Superior Inhibitory Control and Resistance to Mental Fatigue in Professional Road Cyclists. PLoS ONE [Online]. Available at: http://dx.doi.org/10.1371/journal.pone.0159907.
    Purpose
    Given the important role of the brain in regulating endurance performance, this comparative study sought to determine whether professional road cyclists have superior inhibitory control and resistance to mental fatigue compared to recreational road cyclists.

    Methods
    After preliminary testing and familiarization, eleven professional and nine recreational road cyclists visited the lab on two occasions to complete a modified incongruent colour-word Stroop task (a cognitive task requiring inhibitory control) for 30 min (mental exertion condition), or an easy cognitive task for 10 min (control condition) in a randomized, counterbalanced cross-over order. After each cognitive task, participants completed a 20-min time trial on a cycle ergometer. During the time trial, heart rate, blood lactate concentration, and rating of perceived exertion (RPE) were recorded.

    Results
    The professional cyclists completed more correct responses during the Stroop task than the recreational cyclists (705±68 vs 576±74, p = 0.001). During the time trial, the recreational cyclists produced a lower mean power output in the mental exertion condition compared to the control condition (216±33 vs 226±25 W, p = 0.014). There was no difference between conditions for the professional cyclists (323±42 vs 326±35 W, p = 0.502). Heart rate, blood lactate concentration, and RPE were not significantly different between the mental exertion and control conditions in both groups.

    Conclusion
    The professional cyclists exhibited superior performance during the Stroop task which is indicative of stronger inhibitory control than the recreational cyclists. The professional cyclists also displayed a greater resistance to the negative effects of mental fatigue as demonstrated by no significant differences in perception of effort and time trial performance between the mental exertion and control conditions. These findings suggest that inhibitory control and resistance to mental fatigue may contribute to successful road cycling performance. These psychobiological characteristics may be either genetic and/or developed through the training and lifestyle of professional road cyclists.
  • Smirmaul, B., de Moraes, A., Angius, L. and Marcora, S. (2016). Effects of caffeine on neuromuscular fatigue and performance during high-intensity cycling exercise in moderate hypoxia. European Journal of Applied Physiology [Online]. Available at: http://dx.doi.org/10.1007/s00421-016-3496-6.
    Purpose
    To investigate the effects of caffeine on performance, neuromuscular fatigue and perception of effort during high-intensity cycling exercise in moderate hypoxia.

    Methods
    Seven adult male participants firstly underwent an incremental exercise test on a cycle ergometer in conditions of acute normobaric hypoxia (fraction inspired oxygen = 0.15) to establish peak power output (PPO). In the following two visits, they performed a time to exhaustion test (78 ± 3% PPO) in the same hypoxic conditions after caffeine ingestion (4 mg kg?1) and one after placebo ingestion in a double-blind, randomized, counterbalanced cross-over design.

    Results
    Caffeine significantly improved time to exhaustion by 12%. A significant decrease in subjective fatigue was found after caffeine consumption. Perception of effort and surface electromyographic signal amplitude of the vastus lateralis were lower and heart rate was higher in the caffeine condition when compared to placebo. However, caffeine did not reduce the peripheral and central fatigue induced by high-intensity cycling exercise in moderate hypoxia.

    Conclusion
    The caffeine-induced improvement in time to exhaustion during high-intensity cycling exercise in moderate hypoxia seems to be mediated by a reduction in perception of effort, which occurs despite no reduction in neuromuscular fatigue.
  • Inzlicht, M. and Marcora, S. (2016). The Central Governor Model of Exercise Regulation Teaches Us Precious Little about the Nature of Mental Fatigue and Self-Control Failure. Frontiers in psychology [Online] 7:656. Available at: https://doi.org/10.3389/fpsyg.2016.00656.
    Self-control is considered broadly important for many domains of life. One of its unfortunate features, however, is that it tends to wane over time, with little agreement about why this is the case. Recently, there has been a push to address this problem by looking to the literature in exercise physiology, specifically the work on the central governor model of physical fatigue. Trying to explain how and why mental performance wanes over time, the central governor model suggests that exertion is throttled by some central nervous system mechanism that receives information about energetic bodily needs and motivational drives to regulate exertion and, ultimately, to prevent homeostatic breakdown, chiefly energy depletion. While we admire the spirit of integration and the attempt to shed light on an important topic in psychology, our concern is that the central governor model is very controversial in exercise physiology, with increasing calls to abandon it altogether, making it a poor fit for psychology. Our concerns are threefold. First, while we agree that preservation of bodily homeostasis makes for an elegant ultimate account, the fact that such important homeostatic concerns can be regularly overturned with even slight incentives (e.g., a smile) renders the ultimate account impotent and points to other ultimate functions for fatigue. Second, despite the central governor being thought to take as input information about the metabolic needs of the body, there is no credible evidence that mental effort actually consumes inordinate amounts of energy that are not already circulating in the brain. Third, recent modifications of the model make the central governor appear like an all-knowing homunculus and unfalsifiable in principle, thus contributing very little to our understanding of why people tend to disengage from effortful tasks over time. We note that the latest models in exercise physiology have actually borrowed concepts and models from psychology to understand physical performance.
  • Smith, M., Coutts, A., Merlini, M., Deprez, D., Lenoir, M. and Marcora, S. (2016). Mental Fatigue Impairs Soccer-Specific Physical and Technical Performance. Medicine & Science in Sports & Exercise [Online] 48:267-276. Available at: https://doi.org/10.1249/MSS.0000000000000762.
    Purpose: To investigate the effects of mental fatigue on soccer-specific physical and technical performance. Methods: This investigation consisted of
    two separate studies. Study 1 assessed the soccer-specific physical performance of 12 moderately trained soccer players using the Yo-Yo
    Intermittent Recovery Test, Level 1 (Yo-Yo IR1). Study 2 assessed the soccer-specific technical performance of 14 experienced soccer
    players using the Loughborough Soccer Passing and Shooting Tests (LSPT, LSST). Each test was performed on two occasions and
    preceded, in a randomized, counterbalanced order, by 30 min of the Stroop task (mentally fatiguing treatment) or 30 min of reading
    magazines (control treatment). Subjective ratings of mental fatigue were measured before and after treatment, and mental effort and
    motivation were measured after treatment. Distance run, heart rate, and ratings of perceived exertion were recorded during the Yo-Yo IR1.
    LSPT performance time was calculated as original time plus penalty time. LSST performance was assessed using shot speed, shot accuracy,
    and shot sequence time. Results: Subjective ratings of mental fatigue and effort were higher after the Stroop task in both studies
    (P G 0.001), whereas motivation was similar between conditions. This mental fatigue significantly reduced running distance in the Yo-Yo
    IR1 (P G 0.001). No difference in heart rate existed between conditions, whereas ratings of perceived exertion were significantly higher at
    iso-time in the mental fatigue condition (P G 0.01). LSPT original time and performance time were not different between conditions;
    however, penalty time significantly increased in the mental fatigue condition (P = 0.015). Mental fatigue also impaired shot speed (P = 0.024)
    and accuracy (P G 0.01), whereas shot sequence time was similar between conditions. Conclusions: Mental fatigue impairs soccer-specific
    running, passing, and shooting performance.
  • Morales-Alamo, D., Martin-Rincon, M., Perez-Valera, M., Marcora, S. and Calbet, J. (2016). No functional reserve at exhaustion in endurance-trained men?. Journal of Applied Physiology [Online] 120:476-476. Available at: https://doi.org/10.1152/japplphysiol.01006.2015.
  • NicolòA., Marcora, S. and Sacchetti, M. (2016). Respiratory frequency is strongly associated with perceived exertion during time trials of different duration. Journal of sports sciences [Online] 34:1199-1206. Available at: http://dx.doi.org/10.1080/02640414.2015.1102315.
    In order to provide further insight into the link between respiratory frequency (fR) and the rating of perceived exertion (RPE), the present study investigated the effect of exercise duration on perceptual and physiological responses during self-paced exercise. Nine well-trained competitive male cyclists (23 ± 3 years) performed a preliminary incremental ramp test and three randomised self-paced time trials (TTs) differing in exercise duration (10, 20 and 30 min). Both RPE and fR increased almost linearly over time, with a less-pronounced rate of increase when absolute exercise duration increased. However, when values were expressed against relative exercise duration, no between-trial differences were found in either RPE or fR. Conversely, between-trial differences were observed for minute ventilation (.VE), .VO2 and heart rate (HR), when values were expressed against relative exercise duration. Unlike the relationship between RPE and both .VE and HR, the relationship between RPE and fR was not affected by exercise duration. In conclusion, fR, but not .VE, HR or [.VO2, shows a strong relationship to RPE and a similar time course, irrespective of exercise duration. These findings indicate that fR is the best correlate of RPE during self-paced exercise, at least among the parameters and for the range of durations herein investigated.
  • Pageaux, B., Lepers, R. and Marcora, S. (2016). Reliability of a Novel High Intensity One Leg Dynamic Exercise Protocol to Measure Muscle Endurance. PloS one [Online] 11:e0163979. Available at: http://dx.doi.org/10.1371/journal.pone.0163979.
    We recently developed a high intensity one leg dynamic exercise (OLDE) protocol to measure muscle endurance and investigate the central and peripheral mechanisms of muscle fatigue. The aims of the present study were to establish the reliability of this novel protocol and describe the isokinetic muscle fatigue induced by high intensity OLDE and its recovery. Eight subjects performed the OLDE protocol (time to exhaustion test of the right leg at 85% of peak power output) three times over a week period. Isokinetic maximal voluntary contraction torque at 60 (MVC60), 100 (MVC100) and 140 (MVC140) deg/s was measured pre-exercise, shortly after exhaustion (13 ± 4 s), 20 s (P20) and 40 s (P40) post-exercise. Electromyographic (EMG) signal was analyzed via the root mean square (RMS) for all three superficial knee extensors. Mean time to exhaustion was 5.96 ± 1.40 min, coefficient of variation was 8.42 ± 6.24%, typical error of measurement was 0.30 min and intraclass correlation was 0.795. MVC torque decreased shortly after exhaustion for all angular velocities (all P < 0.001). MVC60 and MVC100 recovered between P20 (P < 0.05) and exhaustion and then plateaued. MVC140 recovered only at P40 (P < 0.05). High intensity OLDE did not alter maximal EMG RMS of the three superficial knee extensors during MVC. The results of this study demonstrate that this novel high intensity OLDE protocol could be reliably used to measure muscle endurance, and that muscle fatigue induced by high intensity OLDE should be examined within ~ 30 s following exhaustion.
  • Hopker, J., Caporaso, G., Azzalin, A., Carpenter, R. and Marcora, S. (2016). Locomotor muscle fatigue does not alter oxygen uptake kinetics during high intensity exercise. Frontiers in Physiology [Online]. Available at: http://dx.doi.org/10.3389/fphys.2016.00463.
    The slow component (sc) that develops during high-intensity aerobic exercise is thought to be strongly associated with locomotor muscle fatigue. We sought to experimentally test this hypothesis by pre-fatiguing the locomotor muscles used during subsequent high-intensity cycling exercise. Over two separate visits, eight healthy male participants were asked to either perform a non-metabolically stressful 100 intermittent drop-jumps protocol (pre fatigue condition) or rest for 33 minutes (control condition) according to a random and counterbalanced order. Locomotor muscle fatigue was quantified with 6-second maximal sprints at a fixed pedaling cadence of 90 rev·min-1. Oxygen kinetics and other responses (heart rate, capillary blood lactate concentration and rating of perceived exertion, RPE) were measured during two subsequent bouts of 6 min cycling exercise at 50% of the delta between the lactate threshold and max determined during a preliminary incremental exercise test. All tests were performed on the same cycle ergometer. Despite significant locomotor muscle fatigue (P = 0.03), the sc was not significantly different between the pre fatigue (464 ± 301 mL·min-1) and the control (556 ± 223 mL·min-1) condition (P = 0.50). Blood lactate response was not significantly different between conditions (P = 0.48) but RPE was significantly higher following the pre-fatiguing exercise protocol compared with the control condition (P < 0.01) suggesting higher muscle recruitment. These results demonstrate experimentally that locomotor muscle fatigue does not significantly alter the kinetic response to high intensity aerobic exercise, and challenge the hypothesis that thesc is strongly associated with locomotor muscle fatigue.
  • Angius, L., Pageaux, B., Hopker, J., Marcora, S. and Mauger, A. (2016). Transcranial Direct Current Stimulation Improves Isometric Time to Exhaustion of the Knee Extensors. Neuroscience [Online] 339:363-375. Available at: http://dx.doi.org/10.1016/j.neuroscience.2016.10.028.
    Transcranial direct current stimulation (tDCS) can increase cortical excitability of a targeted brain area, which may affect endurance exercise performance. However, optimal electrode placement for tDCS remains unclear. We tested the effect of two different tDCS electrode montages for improving exercise performance. Nine subjects underwent a control (CON), placebo (SHAM) and two different tDCS montage sessions in a randomized design. In one tDCS session, the anodal electrode was placed over the left motor cortex and the cathodal on contralateral forehead (HEAD), while for the other montage the anodal electrode was placed over the left motor cortex and cathodal electrode above the shoulder (SHOULDER). tDCS was delivered for 10min at 2.0mA, after which participants performed an isometric time to exhaustion (TTE) test of the right knee extensors. Peripheral and central neuromuscular parameters were assessed at baseline, after tDCS application and after TTE. Heart rate (HR), ratings of perceived exertion (RPE), and leg muscle exercise-induced muscle pain (PAIN) were monitored during the TTE. TTE was longer and RPE lower in the SHOULDER condition (P<0.05). Central and peripheral parameters, and HR and PAIN did not present any differences between conditions after tDCS stimulation (P>0.05). In all conditions maximal voluntary contraction (MVC) significantly decreased after the TTE (P<0.05) while motor-evoked potential area (MEP) increased after TTE (P<0.05). These findings demonstrate that SHOULDER montage is more effective than HEAD montage to improve endurance performance, likely through avoiding the negative effects of the cathode on excitability.
  • Dyer, J., Davison, G., Marcora, S. and Mauger, A. (2016). Effect of a Mediterranean type diet on inflammatory and cartilage degradation biomarkers in patients with osteoarthritis. The Journal of Nutrition, Health and Aging [Online]. Available at: http://link.springer.com/article/10.1007/s12603-016-0806-y.
    Objectives: To investigate the effects of a Mediterranean type diet on patients with osteoarthritis (OA). Participants: Ninety-nine volunteers with OA (aged 31 - 90 years) completed the study (83% female). Setting: Southeast of England, UK. Design: Participants were randomly allocated to the dietary intervention (DIET, n = 50) or control (CON, n = 49). The DIET group were asked to follow a Mediterranean type diet for 16 weeks whereas the CON group were asked to follow their normal diet. Measurements: All participants completed an Arthritis Impact Measurement Scale (AIMS2) pre-, mid- and post- study period. A subset of participants attended a clinic at the start and end of the study for assessment of joint range of motion, ROM (DIET = 33, CON = 28), and to provide blood samples (DIET = 29, CON = 25) for biomarker analysis (including serum cartilage oligomeric matrix protein (sCOMP) (a marker of cartilage degradation) and a panel of other relevant biomarkers including pro- and anti-inflammatory cytokines). Results: There were no differences between groups in the response of any AIMS2 components and most biomarkers (p > 0.05), except the pro-inflammatory cytokine IL-1?, which decreased in the DIET group (~47%, p = 0.010). sCOMP decreased in the DIET group by 1 U/L (~8%, p = 0.014). There was a significant improvement in knee flexion and hip rotation ROM in the DIET group (p < 0.05). Conclusions: The average reduction in sCOMP in the DIET group (1 U/L) represents a meaningful change, but the longer term effects require further study.
  • Pageaux, B., Angius, L., Hopker, J., Lepers, R. and Marcora, S. (2015). Central alterations of neuromuscular function and feedback from group III-IV muscle afferents following exhaustive high intensity one leg dynamic exercise. American journal of physiology - Regulatory, integrative and comparative physiology [Online] 308:R1008-R1020. Available at: http://dx.doi.org/10.1152/ajpregu.00280.2014.
    The aims of this investigation were to describe the central alterations of neuromuscular function induced by exhaustive high intensity one leg dynamic exercise (OLDE, study 1), and to indirectly quantify feedback from group III-IV muscle afferents via muscle occlusion (MO, study 2) in healthy adult male humans. We hypothesized that these central alterations and their recovery are associated with changes in afferent feedback. Both studies consisted of two time to exhaustion tests at 85% peak power output. In study 1, voluntary activation level (VAL), M-wave (M), cervicomedullary motor evoked potential (CMEP), motor evoked potential (MEP) and MEP cortical silent period (CSP) of the knee extensor muscles were measured. In study 2, mean arterial pressure (MAP) and leg muscle pain were measured during MO. Measurements were performed pre-exercise, at exhaustion and after three minutes recovery. Compared to pre-exercise values, VAL was lower at exhaustion (-13±13%, P<0.05) and after three minutes recovery (-6±6%, P=0.05). CMEParea/Marea was lower at exhaustion (-38±13%, P<0.01) and recovered after three minutes. MEParea/Marea was higher at exhaustion (+25±27%, P<0.01) and after three minutes recovery (+17±20%, P<0.01). CSP was higher (+19±9%, P<0.01) only at exhaustion and recovered after three minutes. Markers of afferent feedback (MAP and leg muscle pain during MO) were significantly higher only at exhaustion. These findings suggest that the alterations in spinal excitability and CSP induced by high intensity OLDE are associated with an increase in afferent feedback at exhaustion, whilst central fatigue does not fully recover even when significant afferent feedback is no longer present.
  • Smith, M., Marcora, S. and Coutts, A. (2015). Mental Fatigue Impairs Intermittent Running Performance. Medicine and science in sports and exercise [Online] 47:1682-1690. Available at: http://dx.doi.org/10.1249/MSS.0000000000000592.
    PURPOSE

    The purpose of the study was to investigate the effects of mental fatigue on intermittent running performance.

    METHODS

    Ten male intermittent team sports players performed two identical self-paced, intermittent running protocols. The two trials were separated by 7 d and preceded, in a randomized-counterbalanced order, by 90 min of either emotionally neutral documentaries (control) or the AX-continuous performance test (AX-CPT; mental fatigue). Subjective ratings of fatigue and vigor were measured before and after these treatments, and motivation was recorded before the intermittent running protocol. Velocity, heart rate, oxygen consumption, blood glucose and lactate concentrations, and ratings of perceived exertion (RPE) were measured throughout the 45-min intermittent running protocol. Session RPE was recorded 30 min after the intermittent running protocol.

    RESULTS

    Subjective ratings of fatigue were higher after the AX-CPT (P = 0.005). This mental fatigue significantly reduced velocity at low intensities (1.28 ± 0.18 m·s vs 1.31 ± 0.17 m·s; P = 0.037), whereas high-intensity running and peak velocities were not significantly affected. Running velocity at all intensities significantly declined over time in both conditions (P < 0.001). Oxygen consumption was significantly lower in the mental fatigue condition (P = 0.007). Other physiological variables, vigor and motivation, were not significantly affected. Ratings of perceived exertion during the intermittent running protocol were not significantly different between conditions despite lower overall velocity in the mental fatigue condition. Session RPE was significantly higher in the mental fatigue condition (P = 0.013).

    CONCLUSION

    Mental fatigue impairs intermittent running performance. This negative effect of mental fatigue seems to be mediated by higher perception of effort.
  • Pageaux, B., Marcora, S., Rozand, V. and Lepers, R. (2015). Mental fatigue induced by prolonged self-regulation does not exacerbate central fatigue during subsequent whole-body endurance exercise. Frontiers in human neuroscience [Online] 9:67. Available at: https://doi.org/10.3389/fnhum.2015.00067.
    It has been shown that the mental fatigue induced by prolonged self-regulation increases perception of effort and reduces performance during subsequent endurance exercise. However, the physiological mechanisms underlying these negative effects of mental fatigue are unclear. The primary aim of this study was to test the hypothesis that mental fatigue exacerbates central fatigue induced by whole-body endurance exercise. Twelve subjects performed 30 min of either an incongruent Stroop task to induce a condition of mental fatigue or a congruent Stroop task (control condition) in a random and counterbalanced order. Both cognitive tasks (CTs) were followed by a whole-body endurance task (ET) consisting of 6 min of cycling exercise at 80% of peak power output measured during a preliminary incremental test. Neuromuscular function of the knee extensors was assessed before and after CT, and after ET. Rating of perceived exertion (RPE) was measured during ET. Both CTs did not induce any decrease in maximal voluntary contraction (MVC) torque (p = 0.194). During ET, mentally fatigued subjects reported higher RPE (mental fatigue 13.9 ± 3.0, control 13.3 ± 3.2, p = 0.044). ET induced a similar decrease in MVC torque (mental fatigue -17 ± 15%, control -15 ± 11%, p = 0.001), maximal voluntary activation level (mental fatigue -6 ± 9%, control -6 ± 7%, p = 0.013) and resting twitch (mental fatigue -30 ± 14%, control -32 ± 10%, p < 0.001) in both conditions. These findings reject our hypothesis and confirm previous findings that mental fatigue does not reduce the capacity of the central nervous system to recruit the working muscles. The negative effect of mental fatigue on perception of effort does not reflect a greater development of either central or peripheral fatigue. Consequently, mentally fatigued subjects are still able to perform maximal exercise, but they are experiencing an altered performance during submaximal exercise due to higher-than-normal perception of effort.
  • Angius, L., Hopker, J., Marcora, S. and Mauger, A. (2015). The effect of transcranial direct current stimulation of the motor cortex on exercise-induced pain. European Journal of Applied Physiology [Online] 115:2311-2319. Available at: http://dx.doi.org/10.1007/s00421-015-3212-y.
    Purpose

    Transcranial direct current stimulation (tDCS) provides a new exciting means to investigate the role of the brain during exercise. However, this technique is not widely used in exercise science, with little known regarding effective electrode montages. This study investigated whether tDCS of the motor cortex (M1) would elicit an analgesic response to exercise-induced pain (EIP).
    Methods

    Nine participants completed a VO2max test and three time to exhaustion (TTE) tasks on separate days following either 10 min 2 mA tDCS of the M1, a sham or a control. Additionally, seven participants completed 3 cold pressor tests (CPT) following the same experimental conditions (tDCS, SHAM, CON). Using a well-established tDCS protocol, tDCS was delivered by placing the anodal electrode above the left M1 with the cathodal electrode above dorsolateral right prefrontal cortex. Gas exchange, blood lactate, EIP and ratings of perceived exertion (RPE) were monitored during the TTE test. Perceived pain was recorded during the CPT.
    Results

    During the TTE, no significant differences in time to exhaustion, RPE or EIP were found between conditions. However, during the CPT, perceived pain was significantly (P < 0.05) reduced in the tDCS condition (7.4 ± 1.2) compared with both the CON (8.6 ± 1.0) and SHAM (8.4 ± 1.3) conditions.
    Conclusion

    These findings demonstrate that stimulation of the M1 using tDCS does not induce analgesia during exercise, suggesting that the processing of pain produced via classic measures of experimental pain (i.e., a CPT) is different to that of EIP. These results provide important methodological advancement in developing the use of tDCS in exercise.
  • Marcora, S. (2015). Can Doping be a Good Thing? Using Psychoactive Drugs to Facilitate Physical Activity Behaviour. Sports Medicine [Online] 46:1-5. Available at: https://doi.org/10.1007/s40279-015-0412-x.
  • McCormick, A., Meijen, C. and Marcora, S. (2015). Psychological determinants of whole-body endurance performance. Sports Medicine [Online] 45:997-1015. Available at: http://dx.doi.org/10.1007/s40279-015-0319-6.
    Background: No literature reviews have systematically identified and evaluated research on the psychological determinants of endurance performance, and sport psychology performance-enhancement guidelines for endurance sports are not founded on a systematic appraisal of endurance-specific research.

    Objective: A systematic literature review was conducted to identify practical psychological interventions that improve endurance performance and to identify additional psychological factors that affect endurance performance. Additional objectives were to evaluate the research practices of included studies, to suggest theoretical and applied implications, and to guide future research.

    Methods: Electronic databases, forward-citation searches, and manual searches of reference lists were used to locate relevant studies. Peer-reviewed studies were included when they chose an experimental or quasi-experimental research design, a psychological manipulation, endurance performance as the dependent variable, and athletes or physically-active, healthy adults as participants.

    Results: Consistent support was found for using imagery, self-talk, and goal setting to improve endurance performance, but it is unclear whether learning multiple psychological skills is more beneficial than learning one psychological skill. The results also demonstrated that mental fatigue undermines endurance performance, and verbal encouragement and head-to-head competition can have a beneficial effect. Interventions that influenced perception of effort consistently affected endurance performance.

    Conclusions: Psychological skills training could benefit an endurance athlete. Researchers are encouraged to compare different practical psychological interventions, to examine the effects of these interventions for athletes in competition, and to include a placebo control condition or an alternative control treatment. Researchers are also encouraged to explore additional psychological factors that could have a negative effect on endurance performance. Future research should include psychological mediating variables and moderating variables. Implications for theoretical explanations of endurance performance and evidence-based practice are described.
  • Pageaux, B., Anguis, L., Hopker, J., Lepers, R. and Marcora, S. (2014). On the Importance of Testing Time Delay to Assess Central Fatigue Induced by Endurance Exercise. Medicine and Science in Sports and Exercise 46:6-6.
  • Rozand, V., Pageaux, B., Marcora, S., Papaxanthis, C. and Lepers, R. (2014). Does mental exertion alter maximal muscle activation?. Frontiers in human neuroscience [Online] 8:755. Available at: https://doi.org/10.3389/fnhum.2014.00755.
    Mental exertion is known to impair endurance performance, but its effects on neuromuscular function remain unclear. The purpose of this study was to test the hypothesis that mental exertion reduces torque and muscle activation during intermittent maximal voluntary contractions of the knee extensors. Ten subjects performed in a randomized order three separate mental exertion conditions lasting 27 min each: (i) high mental exertion (incongruent Stroop task), (ii) moderate mental exertion (congruent Stroop task), (iii) low mental exertion (watching a movie). In each condition, mental exertion was combined with 10 intermittent maximal voluntary contractions of the knee extensor muscles (one maximal voluntary contraction every 3 min). Neuromuscular function was assessed using electrical nerve stimulation. Maximal voluntary torque, maximal muscle activation and other neuromuscular parameters were similar across mental exertion conditions and did not change over time. These findings suggest that mental exertion does not affect neuromuscular function during intermittent maximal voluntary contractions of the knee extensors.
  • Pageaux, B., Lepers, R., Dietz, K. and Marcora, S. (2014). Response inhibition impairs subsequent self-paced endurance performance. European Journal of Applied Physiology [Online] 114:1095-1105. Available at: http://dx.doi.org/10.1007/s00421-014-2838-5.
    Purpose
    The aim of this study was to test the effects of mental exertion involving response inhibition on pacing and endurance performance during a subsequent 5-km running time trial.

    Methods
    After familiarization, 12 physically active subjects performed the time trial on a treadmill after two different cognitive tasks: (i) an incongruent Stroop task involving response inhibition (inhibition task) and (ii) a congruent Stroop task not involving response inhibition (control task). Both cognitive tasks were performed for 30 min.

    Results
    Neither the inhibition nor the control task induced subjective feelings of mental fatigue. Nevertheless, time trial performance was impaired following the inhibition task (24.4 ± 4.9 min) compared to the control task (23.1 ± 3.8 min) because of a significant reduction in average running speed chosen by the subject. The response inhibition task did not affect pacing strategy, which was negative in both conditions. Heart rate and blood lactate responses to the time trial were not affected by the inhibition task, but subjects rated perceived exertion higher compared to the control condition (13.5 ± 1.3 vs 12.4 ± 1.3).

    Conclusion
    These findings show for the first time that 30 min of mental exertion involving response inhibition reduces subsequent self-paced endurance performance despite no overt mental fatigue. The impairment in endurance performance observed after the incongruent Stroop task seems to be mediated by the higher perception of effort as predicted by the psychobiological model of endurance performance.
  • Blanchfield, A., Hardy, J. and Marcora, S. (2014). Non-conscious visual cues related to affect and action alter perception of effort and endurance performance. Frontiers in Human Neuroscience [Online] 8. Available at: https://doi.org/10.3389/fnhum.2014.00967.
    The psychobiological model of endurance performance proposes that endurance performance is determined by a decision-making process based on perception of effort and potential motivation. Recent research has reported that effort-based decision-making during cognitive tasks can be altered by non-conscious visual cues relating to affect and action. The effects of these non-conscious visual cues on effort and performance during physical tasks are however unknown. We report two experiments investigating the effects of subliminal priming with visual cues related to affect and action on perception of effort and endurance performance. In Experiment 1 thirteen individuals were subliminally primed with happy or sad faces as they cycled to exhaustion in a counterbalanced and randomized crossover design. A paired t-test (happy vs. sad faces) revealed that individuals cycled significantly longer (178 s, p = 0.04) when subliminally primed with happy faces. A 2 × 5 (condition × iso-time) ANOVA also revealed a significant main effect of condition on rating of perceived exertion (RPE) during the time to exhaustion (TTE) test with lower RPE when subjects were subliminally primed with happy faces (p = 0.04). In Experiment 2, a single-subject randomization tests design found that subliminal priming with action words facilitated a significantly longer TTE (399 s, p = 0.04) in comparison to inaction words. Like Experiment 1, this greater TTE was accompanied by a significantly lower RPE (p = 0.03). These experiments are the first to show that subliminal visual cues relating to affect and action can alter perception of effort and endurance performance. Non-conscious visual cues may therefore influence the effort-based decision-making process that is proposed to determine endurance performance. Accordingly, the findings raise notable implications for individuals who may encounter such visual cues during endurance competitions, training, or health related exercise.
  • de Morree, H., Klein, C. and Marcora, S. (2014). Cortical substrates of the effects of caffeine and time-on-task on perception of effort. Journal of Applied Physiology [Online] 117:1514-1523. Available at: http://dx.doi.org/10.1152/japplphysiol.00898.2013.
    Caffeine intake results in a decrease in perception of effort, but the cortical substrates of this perceptual effect of caffeine are unknown. The aim of this randomized counterbalanced double-blind crossover study was to investigate the effect of caffeine on the motor-related cortical potential (MRCP) and its relationship with rating of perceived effort (RPE). We also investigated whether MRCP is associated with the increase in RPE occurring over time during submaximal exercise. Twelve healthy female volunteers performed 100 intermittent isometric knee extensions at 61 ± 5% of their maximal torque 1.5 h after either caffeine (6 mg/kg) or placebo ingestion, while RPE, vastus lateralis electromyogram (EMG), and MRCP were recorded. RPE and MRCP amplitude at the vertex during the first contraction epoch (0–1 s) were significantly lower after caffeine ingestion compared with placebo (P < 0.05) and were significantly higher during the second half of the submaximal intermittent isometric knee-extension protocol compared with the first half (P < 0.05). No significant effects of caffeine and time-on-task were found for EMG amplitude and submaximal force output variables. The covariation between MRCP and RPE across both caffeine and time-on-task (r10 = ?0.335, P < 0.05) provides evidence in favor of the theory that perception of effort arises from neurocognitive processing of corollary discharges from premotor and motor areas of the cortex. Caffeine seems to reduce perception of effort through a reduction in the activity of cortical premotor and motor areas necessary to produce a submaximal force, and time-on-task has the opposite effect.
  • Blanchfield, A., Hardy, J., de Morree, H., Staiano, W. and Marcora, S. (2014). Talking yourself out of exhaustion: the effects of self-talk on endurance performance. Medicine and Science in Sports and Exercise [Online] 46:998-1007. Available at: http://journals.lww.com/acsm-msse/Fulltext/2014/05000/Talking_Yourself_Out_of_Exhaustion___The_Effects.19.aspx.
    PURPOSE:
    The psychobiological model of endurance performance proposes that the perception of effort is the ultimate determinant of endurance performance. Therefore, any physiological or psychological factor affecting the perception of effort will affect endurance performance. Accordingly, this novel study investigated the effects of a frequently used psychological strategy, motivational self-talk (ST), on RPE and endurance performance.
    METHODS:
    In a randomized between-group pretest-posttest design, 24 participants (mean ± SD age = 24.6 ± 7.5 yr, VO2max = 52.3 ± 8.7 mL·kg·min) performed two constant-load (80% peak power output) cycling time-to-exhaustion (TTE) tests, punctuated by a 2-wk ST intervention or a control phase.
    RESULTS:
    A group (ST vs Control) × test (pretest vs posttest) mixed-model ANOVA revealed that ST significantly enhanced TTE test from pretest to posttest (637 ± 210 vs 750 ± 295 s, P < 0.05) with no change in the control group (486 ± 157 vs 474 ± 169 s). Moreover, a group × test × isotime (0%, 50%, and 100%) mixed-model ANOVA revealed a significant interaction for RPE, with follow-up tests showing that motivational self-talk significantly reduced RPE at 50% isotime (7.3 ± 0.6 vs 6.4 ± 0.8, P < 0.05), with no significant difference in the control group (6.9 ± 1.9 vs 7.0 ± 1.7).
    CONCLUSIONS:
    This study is the first to demonstrate that ST significantly reduces RPE and enhances endurance performance. The findings support the psychobiological model of endurance performance and illustrate that psychobiological interventions designed to specifically target favorable changes in the perception of effort are beneficial to endurance performance. Consequently, this psychobiological model offers an important and novel perspective for future research investigations.
  • de Morree, H., Klein, C. and Marcora, S. (2012). Perception of effort reflects central motor command during movement execution. Psychophysiology [Online] 49:1242-1253. Available at: http://dx.doi.org/10.1111/j.1469-8986.2012.01399.x.
    It is thought that perception of effort during physical tasks is the conscious awareness of the central motor command sent to the active muscles. The aim of this study was to directly test this hypothesis by experimentally varying perception of effort and measuring movement-related cortical potential (MRCP). Sixteen healthy, recreationally active men made unilateral dynamic elbow flexions to lift a light (20% one repetition maximum, 1RM) and a heavier (35% 1RM) weight with a fatigued arm and a nonfatigued arm while rating of perceived effort (RPE), biceps brachii electromyogram (EMG), and MRCP were recorded. RPE, EMG amplitude, and MRCP amplitude at Cz during weight raising increased with weight and with muscle fatigue. There was a significant correlation between RPE and MRCP amplitude at the vertex during the weight raising epoch. This study provides direct neurophysiological evidence that perception of effort correlates with central motor command during movement execution.

Book section

  • de Morree, H. and Marcora, S. (2015). Psychobiology of Perceived Effort During Physical Tasks. In: Handbook of Biobehavioral Approaches to Self-Regulation. New York, NY: Springer New York, pp. 255-270. Available at: http://dx.doi.org/10.1007/978-1-4939-1236-0_17.
    Perception of effort is the conscious sensation of the effort exerted during a physical task, and it is one of the subjective experiences that accompany voluntary actions. Perception of effort has an important role in the self-regulation of behavior. In physical tasks requiring endurance, perception of effort is one of the main determinants of pacing and performance and it is one of the barriers that prevent sedentary individuals from adopting an active lifestyle. Furthermore, high perception of effort is one of the main features of the disabling fatigue affecting patients with cancer and other medical conditions. The afferent feedback model postulates that perception of effort arises from sensory signals produced by peripheral receptors (e.g., group III–IV afferents). According to the corollary discharge model, perception of effort arises from corollary discharges of the central motor command to the working muscles (including the respiratory muscles). Current electrophysiological evidence, showing that motor-related brain activity correlates with perception of effort, corroborates the corollary discharge model of perception of effort. Preliminary evidence from neuroimaging studies suggests that the cingulate and insular cortices, and possibly the thalamus and precuneus, are brain areas that might be involved in perception of effort. Future research should focus on targets for interventions aimed at reducing perception of effort. Such interventions might benefit athletes involved in endurance performance, patients suffering from fatigue, and sedentary individuals wishing to adopt a more active lifestyle.

Conference or workshop item

  • McCormick, A., Meijen, C., Pageaux, B. and Marcora, S. (2016). Application of the Facial Feedback Hypothesis to Endurance Performance: Does Frowning Modulate Perception of Effort?. In: British Psychological Society Division of Sport and Exercise Psychology Conference, Cardiff, Wales 2016. Available at: https://www.bps.org.uk/events/conferences/division-sport-and-exercise-psychology-conference-0.
    Objectives: People frown during strenuous exercise. Research on the facial feedback hypothesis raises the intriguing
    possibility that frowning may modulate (i.e., amplify/soften) perception of effort during endurance performance and
    therefore play a causal role in endurance performance. This study examined whether intentionally frowning
    throughout a cycling time-to-exhaustion test increased perception of effort and, consequently, reduced time to
    exhaustion. This study also examined the effects of frowning on affective states experienced during performance
    and after exhaustion.
    Design: A randomised, controlled, crossover experimental design was used to compare (within-subjects) the effects
    of frowning with control conditions.
    Methods: Ten recreational endurance athletes performed cycling time-to-exhaustion tests in three conditions. In a
    frowning condition, participants frowned throughout the time-to-exhaustion test. In a matched-workload control
    condition, participants pressed their thumb against the ergometer handlebar throughout the test. Electromyography
    biofeedback was used to deliver these interventions. There was also a no-intervention control condition. Perception
    of effort and exercise-related affect were measured throughout the time-to-exhaustion test, and positive and
    negative affective states were measured before and after the test.
    Results: Intentionally frowning did not affect perception of effort, affective states experienced while cycling or after
    exhaustion, or time to exhaustion.
    Conclusions: Frowning may not modulate perception of effort or affective responses during endurance exercise to
    exhaustion. Although additional research using different methods would allow firmer conclusions to be drawn, these
    findings suggest that interventions that target the expression of a frown would be unlikely to offer an efficacious
    method of improving endurance performance.
  • Merlini, M., Whyte, G., Chester, N., Loosemore, M., Marcora, S. and Dickinson, J. (2016). The Long-Term Ergogenic Effect of Long Acting ?2-Agonists. In: 21st Annual Congress of European College of Sport Science.
    Background: The WADA List of Banned Substances and Methods stipulates that athletes can use up to 54 µg inhaled Formoterol and inhaled Salmeterol as directed by the manufacturer. It is unknown whether large daily therapeutic doses of Formoterol and Salmeterol can improve sprint and strength performance.
    Purpose: To investigate the impact of inhaling 100 µg of Salmeterol (SAL) or 12 µg of Formoterol (FOR) twice daily over a 5 week period on sprint, strength and power performance.
    Methods: In a randomised single blind study 24 male and 15 female non-asthmatic and active participants were recruited (mean ± SD; Males age 28.0 ± 5.5 years; weight 72.1 ± 10.5 Kg; height 164.7 ± 7.1 cm; Females age 24.1 ± 4.1 years; weight 65.4 ± 9.5 Kg; height 168.0 ± 4.3 cm). Participants completed three standardised whole body strength and power training sessions per week for five weeks. All the training sessions were supervised by a personal trainer who recorded work performed in each session. During the five week training period participants were assigned to either SAL, FOR or a placebo (PLA) group. Participants took their inhaler twice per day as instructed. Participants completed assessments of sprint, strength and power at week 0 and after 5 weeks of strength and power training. The assessments included 30 m sprint, vertical jump, 1 RM bench press, 1 RM leg press, peak torque flexion and extension, anthropometric evaluation and Rest-Q questionnaires. Mixed Model Repeated Measures ANOVA were performed to investigate the changes in the sprint, strength and power assessments between groups over the course of the 5 week training session.
    Results: 30 m Sprint time was significantly lower in FOR group (– 0.29 ± 0.11 s; p=0.049) and SAL (– 0.35 ± 0.05 s; p=0.04) when compared with compared with Placebo (+0.01 ± 0.11 s; P=0.000). No significant change was found in 1RM Leg, Squat and Bench Press or during Isokinetic evaluation performed at 60° range in flex/ext movement. Jump performance as well as anthropometric measures didn’t differ between groups.

    Discussion: The significant changes in FOR and SAL 30m sprint time when compared to PLA suggest the long term use of inhaled ?2-agonnists may provide ergogenic advantage. This finding suggests a review of the use of inhaled doses of FOR and SAL by athletes in training and official competition may be necessary.
  • Angius, L., Marcora, S., Hopker, J. and Mauger, A. (2016). Transcranial direct current stimulation improves cycling performance in healthy individuals. In: Physiology 2016. Physiological Society.
    Central motor command originating from motor and premotors areas have been shown to correlate with the intensity of perception of effort (RPE) (1). Recently, non-invasive brain stimulation techniques able to change excitability of targeted area have been shown to improve exercise capacity on single joint exercise (2) and to alter perception of effort (3). In the present study we monitored whether stimulation of both motor cortexes can alter perception of effort and exercise capacity of whole body cycling exercise. Twelve healthy volunteers were recruited and underwent a placebo (SHAM), anodal tDCS (ANODAL) and cathodal tDCS (CATHODAL) condition in a double-blind, randomised and counterbalanced experimental design. tDCS stimulation was delivered for 10 min at 2.0 mA by using two extracephalic montages with the active electrode placed over the motor cortex and the reference electrode over the shoulder. Neuromuscular assessment was performed before and after tDCS stimulation to monitor central and peripheral parameters. This consisted on a maximal voluntary contraction (MVC) of knee extensor muscles with superimposed doublet followed by a resting potentiated doublet. Then, four brief submaximal contractions at 10% MVC with superimposed transcranial magnetic stimulation and one at 10% MVC with superimposed femoral nerve stimulation were executed. Volunteers then underwent a cycling time to exhaustion (TTE) at 70% of peak power output previously assessed. Heart rate (HR), ratings of perceived exertion (RPE) and leg muscle pain (PAIN) were monitored during the TTE while blood lactate (BLa-) was measured immediately after the TTE. TTE was significantly longer in the ANODAL (P=0.003) compared to the CATHODAL and SHAM conditions (13.24 ± 4.34 min; 11.1 ± 4.28 min; 10.75 ± 3.03 min). A significant reduction of RPE (P<0.001) and higher increase of BLa- (P<0.001) were found in the ANODAL condition. No differences were found for HR (P=0.80) and PAIN between conditions (P=0.27) (Fig. 1). MVC, voluntary activation level (VAL) and doublet were not affected by tDCS stimulation. However, an increase in cortical excitability was found following ANODAL tDCS as demonstrated by the increased motor evoked potential (MEParea/Mwave ratio) response (Fig 2). None of the monitored parameters were significantly affected in the SHAM and CATHODAL conditions. This experiments demonstrated that ANODAL tDCS stimulation improves constant cycling performance. Moreover, the increased excitability of the motor cortex might facilitate the central command required and consequently reduced the perception of effort during exercise. These findings further demonstrate that the motor cortex plays an important role in the generation of perception of effort.
  • Davison, G., Dyer, J., Marcora, S. and Mauger, A. (2015). Effect of a Mediterranean diet on inflammatory and cartilage degradation markers in osteoarthritis. In: 20th Annual Congress of the European College of Sport Science. Available at: http://ecss-congress.eu/2015/15/.
  • Angius, L., Pageaux, B., Hopker, J., Marcora, S. and Mauger, A. (2015). Transcranial direct current stimulation improves isometric time to exhaustion performance of lower limbs. In: Physiology 2015. Physiological society.
    Supraspinal fatigue is defined as the inability of the motor cortex (M1) to produce an adequate neural drive to excite and drive motoneurons adequately, and could contribute to the decrease in force production capacity (2). Recently, research studies have applied the use of transcranial direct current stimulation (tDCS) to manipulate corticospinal excitability in order to improve endurance performance (1). These interventions can be inhibitory (cathodal) or excitatory (anodal). Since there is no consensus on the standard placement of electrodes for improving endurance performance, we therefore tested the effect of two electrodes configurations. Nine subjects underwent a control (CON), placebo (SHAM) and two different tDCS configurations sessions in a double blind, randomised and counterbalanced design. In one tDCS session, the anodal electrode was placed over the left M1 and the cathodal on contralateral forehead (HEAD) while for the other montage, the anodal electrode was placed over the left M1 and cathodal electrode above the contralateral shoulder (SHOULDER). tDCS was delivered for 10 min at 2.0 mA, after which participants performed an isometric time to exhaustion (TTE) of the right knee extensors at 20% of the maximal voluntary contraction (MVC). Peripheral and central parameters were examined respectively by femoral nerve stimulation and M1 excitability via TMS at baseline, after tDCS application and immediately after TTE. Heart rate (HR), ratings of perceived exertion (RPE), and leg muscle PAIN were monitored during the TTE. A one-way ANOVA with repeated measures was used to assess TTE duration, while two-way ANOVA with repeated measures was used to analyse central and peripheral parameters, HR, PAIN, and RPE. None of the central and peripheral parameters showed any difference between conditions after tDCS stimulation (p>0.05). MVC significantly decreased after TTE (p<0.05) due to presence of central and peripheral fatigue, whilst motor evoked potential area (MEP) and cortical silent period increased after TTE (p<0.05) independently of the experimental condition. TTE was longer in the SHOULDER condition (p<0.05) although HR and PAIN did not present any difference between conditions (p>0.05). However, RPE was significantly lower in the SHOULDER condition (p<0.05). This is the first study showing an improvement of isometric TTE performance of the lower limbs after tDCS stimulation and further demonstrates that anodal tDCS over M1 improves isometric endurance performance of the knee extensors. Our findings suggest that SHOULDER montage is more effective than HEAD montage to improve endurance performance.
  • Li, L., Witon, A., Marcora, S., Bowman, H. and Mandic, D. (2014). EEG-based brain connectivity analysis of states of unawareness. In: Engineering in Medicine and Biology Society (EMBC), 2014 36th Annual International Conference of the IEEE. IEEE, pp. 1002-1005. Available at: http://doi.org/10.1109/EMBC.2014.6943762.
    This work investigates phase synchrony as a neuro-marker for the identification of two brain states: coma and quasi-brain-death. Scalp electroencephalography (EEG) data of 34 patients were recorded in an intensive care unit (ICU), with 17 recordings for patients in a coma state, and 17 recordings for patients in a quasi-brain-death state. Phase synchrony was used for feature extraction from EEG recording by comparing the phase value between pairs of electrodes using an entropy based measure. In particular, we performed phase synchrony analysis in five standard frequency bands and provide visualization of the phase synchronies in matrices. The effectiveness of the phase synchrony features in each of the frequency bands are evaluated with statistical analysis. Results suggest phase synchrony for coma patients has a significant increase in the theta / alpha band compared to quasi-brain-death patients. Hence, we propose phase synchrony as a candidate for the identification of consciousness states between coma and quasi-brain-death.
  • Angius, L., Hopker, J., Marcora, S. and Mauger, A. (2014). Transcranial current direct stimulation reduces cold pain perception but not acute muscle pain. In: Physiology 2014. Physiological society. Available at: http://www.physoc.org/proceedings/abstract/Proc%20Physiol%20Soc%2031PCA157.
    Stimulation of muscle pain receptors by release of algesic substances during high intensity exercise is the cause of acute muscle pain. Peripheral signals are processed in the brain and then perceived as pain sensation. Some authors have proposed that an athletes' ability to tolerate exercise-induced muscle pain could represent an important factor in long lasting, high intensity exercise (5, 6). Non-invasive techniques such as the transcranial direct current stimulation (tDCS) have been previously shown to relieve pain perception (1, 4), and so we investigated whether tDCS administration would lead to an improvement in exercise performance. Pain response was monitored during exercise (PAIN-EXE) and a cold pressor test (CPT), (PAIN-CPT) in two separate studies (A and B respectively). In study A, following full ethical approval, 9 participants performed a cycling time to exhaustion (TTE) at a 70% of their peak power output while in study B, 7 subjects underwent a CPT with an 8 min cut-off time. Both studies involved a control (CON), placebo (SHAM) and experimental (tDCS) session in a single-blind, randomised, counter-balanced design. tDCS stimulation for 10 min at 2.0 mA was delivered by placing anodal electrode above the left motor cortex (M1) with the cathodal electrode placed above dorsolateral right prefrontal cortex (1). Ratings of perceived exertion (RPE) were monitored during the TTE using Borg 6-20 scale. PAIN-EXE and PAIN-CPT were assessed using the 10 points numerical Cook scale (3). An isotime of 6 min, plus the final min, for both the TTE and CPT were used in order to include all participants in the subsequent analyses. A one-way ANOVA with repeated measures was used to assess TTE duration. Two-way ANOVA with repeated measures was used to analyse RPE, PAIN-EXE and PAIN-CPT data. All data are presented as means ± SD in Fig. 1.No significant differences (p>0.05) in exercise duration, RPE and PAIN-EXE were found in the TTE. However, PAIN-CPT in the tDCS session was significantly lower (p<0.05) compared with the other conditions (5.6±2.8 CON, 6.0±3.0 SHAM, 5.5±2.7 tDCS).These findings demonstrate that tDCS is capable of inducing an analgesic effect in response to cold pain stimuli but not for exercise-induced muscle pain.
  • Angius, L., Pageaux, B., Hopker, J. and Marcora, S. (2013). Muscle ischemic preconditioning reduces feedback from group iii and iv muscle afferents. In: European College of Sports Sciences.
    INTRODUCTION The primary aim of this study was to test the hypothesis that muscle ischemic preconditioning (MIP) reduces feedback from group III and IV muscle afferents measured indirectly by muscle metaboreflex. The second aim was to investigate whether the hypothesized reduction in afferent feedback (Crisafulli et al, 2011) causes a reduction of rating of perceived exertion (RPE) as predicted by the afferent feedback model of PE (Marcora, 2009) MATERIAL AND METHODS Nine healthy subjects visited the laboratory three times in a single-blind, randomized and counterbalanced experimental design. In a preliminary day they underwent a one leg incremental test up to exhaustion to detect Wmax then an experimental (EXP) and control (SHAM) session in separated days. To test muscle afferent activity, two post-exercise muscle ischemia (PEMI) were executed. PEMI involved: 3 min of baseline, 3 min of exercise at 70% of Wmax, 3 min of thigh occlusion followed by 3 min of recovery. MIP treatment during EXP or SHAM was executed between the two PEMI sessions. MIP involved 3 cycles of occlusion of 5 min at 220 mmHg separated by 5 min of reperfusion. During the SHAM session, occlusion was 20 mmHg. Cardiac output (CO), mean arterial pressure (MAP) and RPE during exercise were monitored during both PEMI sessions. RESULTS CO and MAP responses were significantly reduced after MIP (CO = 6.92 ± 1.81 vs 5.79 ± 1.39 l•min-1 and MAP= 109.25 ± 9.85 vs 103.70 ±10.43 mmHg). RPE was not affected by MIP (15.67 ± 1.87 vs 15.56 ± 2.07). None of the parameters reported any statistical changes in the SHAM condition. DISCUSSION This study shows for the first time that MIP reduces feedback from group III and IV muscle afferents as indicated by a significant reduction in muscle metabo-reflex. Despite this reduced afferent feedback, RPE was unchanged. This finding provides further experimental evidence that feedback from III and IV muscle afferents is not a sensory signal for PE. REFERENCES Crisafulli A. et al J Appl Physiol. 2011 Aug;111(2):530-6. Marcora S. J Appl Physiol. 2009 Jun;106(6):2060-2.

Thesis

  • Salam, H. (2017). The Role of Perception of Effort in Endurance Performance Testing and Training.
    The role of endurance performance measurements have been an important theme, cycling time trials are main elements of Grand Tour cycling events, such as the Tour de France. Normally time trials within road cycling championships cover distances between 10 and 44 km over periods of 10 min to 60 min. afterward, success in these individual tests of human endurance is widely determined by the cyclist's level of aerobic fitness. Furthermore, focussing on all endurance performance methods to assess athlete's level, there is not only physiological assessment for endurance performance. Perceived exertion, defined as "the conscious sensation of hard, heavy and strenuous exercise", is identified to regulate human behaviour and endurance exercise performance, moreover, rating perceived exertion has been valid tool to demonstrated endurance performance as well as physiological parameters (heart rate and blood lactate concentration, and exercise economy) during submaximal exercise performance. As there are a numerous studies suggested that perception of effort can determine endurance exercise performance independently of alterations in cardiorespiratory, metabolic and neuromuscular parameters. Therefore, it is possible that perception of effort plays a major role in determining endurance performance. Therefore, from these perceptive the idea for first study has been developed

    However, to date, not only to clarify RPE's correlation to endurance performance but also how manipulations of perceived exertion might influence endurance performance remain not well understood. The secondary aim of this thesis was to examine how manipulations of perception of effort might affect endurance performance. This manipulation is divided in two parts: The effect of mental fatigue on critical power and the anaerobic work capacity and Does chronic use of caffeine reduce its acute ergogenic effects during high intensity interval training? We firstly investigated the effect of impairing perception of effort via mental fatigue involving the response inhibition process on critical power endurance performance. These studies have demonstrated higher perceptions of effort and reduced exercise performance independently of alterations in cardiorespiratory or metabolic responses to exercise. Therefore, higher PE may limit TTE and subsequently alter the CP and W' independently of changes within the underlying muscle physiology. We found that contrary to endurance exercise performance, so the outcomes of this study were, mental fatigue induced by a response inhibition stroop task reduced time to exhaustion at fixed power outputs, the reduced time to exhaustion does not alter the resultant critical power. However, the development of mental fatigue did significantly reduce the supposed anaerobic work capacity, mental fatigue induced by a response inhibition stroop task significantly increased RPE during the TTE trials. Therefore, these findings provides strong evidence that the proposed physiological critical power model can be affected by purely psychological factors i.e. mental fatigue.
    On the other hand, in second part the thesis investigated on the effect of caffeine on endurance performance based on extensive research showing positive effects on performance many athletes use caffeine before and during competitions, however, the use of caffeine during training is not well understood. As the study outcomes shows, no significant changes in VO2max were observed in either groups after 4 weeks of training. As hypothesised, caffeine acutely increased power output, HR and blood lactate during HIIT at both the baseline and follow-up assessments. There were no significant interactions and main effects of time suggesting the development of tolerance to these acute ergogenic effects of caffeine during HIIT after 4 weeks of chronic supplementation. Caffeine ingestion one hour prior to HIIT acutely increases power output, HR and blood lactate for the same RPE. Frequent use of caffeine before training (3 times a week for 4 weeks) does not reduce these acute ergogenic effects of caffeine during HIIT. This observation argues against the development of tolerance and suggests that pre-training caffeine ingestion is a useful strategy to increase training intensity, whether this increase in training intensity leads to greater gains in performance needs to be investigated in future studies with more controlled training programs and longer follow up periods.

    Overall, when merging all experimental parts, provides new vision on how perception of effort a valid and effective regulates of endurance performance. Specially, it proves how muscle fatigue is one of the contributor of the constant increase in perception of effort during endurance exercise, however, there are other contributors play a role in this increase and decrease in perceived exertion. In contrast, we demonstrated for the first time that i) perception of effort can be endurance performance regulator, ii) alterations in the attendance of mental fatigue does decrease endurance performance and increase perception of effort, iii) endurance performance can be improved by caffeine ingestion one hour prior to HIIT acutely increases power output, HR and blood lactate for the same intensity. Frequent use of caffeine before training does not reduce these acute ergogenic effects of caffeine during HIIT.
  • Santos MagalhãesA. (2016). Subjective and Objective Assessment of Physically Active People With Knee Injury.
    Knee injuries are highly prevalent in physically active individuals and are frequently associated with sport participation. Independently of the nature of the injury, subjective and objective clinical measures are used to assess, monitor and evaluate treatment outcomes in this population. To be clinically meaningful, these outcome measures should be relevant to the condition, the anatomical area, the individual or population, and importantly, possess adequate psychometric properties. Despite a high prevalence of knee injuries, there are several aspects of the subjective and objective knee evaluation in physically active individuals that remain unclear or have not been considered in previous research.The main aim of the present thesis was to fill some of the gaps identified in the literature regarding both subjective and objective knee measures in physically active individuals. Therefore, this thesis was divided into two distinct parts. The first part looked at the patient-reported outcome (PRO) measures of the knee and physical activity, and consisted of two studies. The first study was a systematic review conducted to explore the PRO measures that are commonly used in the evaluation of physical activity and return to sport following autologous chondrocyte implantation (ACI). Aiming as well, to provide a critical analysis of these instruments from a rehabilitative perspective. This review revealed not only the heterogeneity in the selection, but also in the timing and reporting of patient-reported activity scoring instruments following ACI, which makes a systematic comparison difficult and introduces bias into the interpretation of these outcomes. Another important finding of this review, was that the instruments currently used to evaluate postoperative outcomes in an articular cartilage repair population do not always fulfil the rehabilitative needs of physically active individuals. The second study was conducted in recreational marathon runners and aimed to provide normative values for a widely used knee specific PRO measure in athletes with knee injury, the Knee Injury Osteoarthritis Outcome Score (KOOS). Alongside the normative KOOS subscales values stratified by age group and history of knee injury that were presented, this study also showed that recent history of knee running-related injury (RRI) has a negative impact on the KOOS scores. In runners with no history of knee RRI, the results observed suggested a lack of interaction between KOOS subscale values and age. Furthermore, the KOOS values seen were substantially higher compared to previously published normative population-based KOOS values.
    The second part of the present thesis comprised three experimental studies concerning single-leg cycling (SLC) exercise testing, in particular assessing the potential use of the self-paced test (SPT) concept as an objective measure following knee surgery. The first study analysed the reliability of a 5x2 min stages SPT anchored to the rate of perceived exertion (RPE) for SLC exercise testing. This study showed that this test protocol elicits reliable cardiorespiratory and metabolic responses. The second study examined the validity of the SPT protocol used in the previous study, through a concurrent comparison against a conventional fixed power incremental SLC exercise test. This investigation showed that the 5x2 min SPT provides a valid objective means for assessing peak aerobic capacity in SLC exercise testing. Moreover, it may be associated with increased activity enjoyment comparatively to conventional testing. The third and last experimental study investigated the effect of a 10 kg counterweight device (CW10) on cardiorespiratory, metabolic and perceptual responses to SLC exercise testing. The results of this study demonstrated that the CW10 despite eliciting an improvement in the activity enjoyment, did not affect peak cardiorespiratory and metabolic responses to SLC exercise testing. When matched for test duration the SPT elicited higher peak power output and peak oxygen consumption than conventional incremental testing, regardless of the CW10 usage or not. In conclusion, the original work of the present thesis increases the body of knowledge of two distinct, but complementary fields in the subjective and objective knee assessment of physically active individuals. The outcomes provided both on PRO measures and SLC exercise testing, may have impact on the clinical practice of clinicians, sport rehabilitation professionals and researchers.
  • McCormick, A. (2016). Psychologically-Informed Methods of Enhancing Endurance Performance.
    The main focus of this thesis was to determine psychologically-informed methods of enhancing endurance performance, particularly in endurance sport events. There were three main research aims. First, this thesis aimed to synthesise research conducted to date on the psychological determinants of endurance performance. A systematic literature review was conducted to identify psychological interventions that affect endurance performance in experimental research. Learning psychological skills, verbal encouragement, and head-to-head competition enhanced endurance performance, whereas mental fatigue undermined endurance performance. Second, this thesis aimed to inform the design of performance-enhancement psychological interventions for endurance sports. In the first study addressing this aim, focus group interviews were conducted with recreational endurance athletes of various endurance sports, distances, and competitive levels to identify psychological demands that are commonly experienced by endurance athletes. Seven common psychological demands were identified using a thematic analysis. These demands were commonly encountered away from the competitive environment (time investment and lifestyle sacrifices, commitment to training sessions, concerns about optimising training, and exercise sensations during training), preceding an event (pre-event stressors), and during an event (exercise sensations, optimising pacing, and remaining focused despite adversity). Psychological interventions that help endurance athletes to cope with these psychological demands could potentially enhance performance in endurance events. In the second study that aimed to inform the design of an intervention, a psychophysiology experiment applied research on the facial feedback hypothesis to determine whether frowning modulates perception of effort during endurance performance. Contrary to hypotheses, intentionally frowning throughout a cycling time-to-exhaustion test did not influence perception of effort or time to exhaustion. This finding suggests that novel interventions that are informed by the facial feedback hypothesis and that target the expression of a frown would be unlikely to enhance endurance performance. Finally, this thesis aimed to examine the effect of a psychological skills training intervention on performance in a real-life endurance event. A randomised, controlled experiment was conducted to examine the effect of learning motivational self-talk on performance in a 60-mile, overnight ultramarathon. Although performance times indicated that motivational self-talk possibly produced a performance enhancement that might benefit ultramarathon runners, additional data will be collected at the same ultramarathon in 2016 to draw firmer conclusions. Overall, the findings of this thesis draw attention to psychological factors that influence performance in endurance events and demonstrate that psychologically-informed interventions can enhance endurance performance. People involved in endurance sports, such as athletes and coaches, are therefore encouraged to systematically work on the psychological aspects of training, preparing for a competition, and competing. Suggestions for how to approach this practically are scrutinised throughout the thesis.
  • Angius, L. (2015). The Effect of Transcranial Direct Current Stimulation on Exercise Performance.
    The physical limits of the human being have been the object of study for a considerable time. Human and exercise physiology, in combination with multiple other related disciplines, studied the function of the organs and their relationship during exercise. When studying the mechanisms causing the limits of the human body, most of the research has focused on the locomotor muscles, lungs and heart. Therefore, it is not surprising that the limit of the performance has predominantly been explained at a "peripheral" level. Many studies have successfully demonstrated how performance can be improved (or not) by manipulating a "peripheral" parameter. However, in most cases it is the brain that regulates and integrates these physiological functions, and much of the contemporary literature has ignored its potential role in exercise performance. This may be because moderating brain function is fraught with difficulty, and challenging to measure. However, with the recent introduction and development of new non-invasive devices, the knowledge regarding the behaviour of the central nervous system during exercise can be advanced. Transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS) are two such methods. These methods can transiently moderate the activity of a targeted brain area, potentially altering the regulation of a particular physiological (or psychological) system, and consequently eliciting a change in exercise performance.
    Despite the promising theory, there is little or no experimental data regarding the potential to moderate neurophysiological mechanisms through tDCS to improve exercise performance. Consequently, the experiments performed as part of this thesis investigated the capacity for tDCS to alter physical performance. The ability of tDCS as a targeted and selective intervention at the brain level provides the unique opportunity to reduce many methodological constraints that might limit or confound understanding regarding some of the key physiological mechanisms during exercise. Therefore, the primary aim of this thesis was to investigate how tDCS may moderate both central and peripheral neurophysiological mechanisms, and how this may effect various exercise tasks.
    The first study investigated the effect of a well-documented analgesic tDCS montage on exercise-induced muscle pain. This study demonstrated for the first time, that although anodal tDCS of the motor cortex (M1) reduces pain in a cold pressor task, it does not elicit any reduction in exercise-induced muscle pain and consequently has no effect on exercise performance. As reductions in exercise-induced pain have previously been documented to improve performance, probably the lack of effect was due to either the M1 having a limited processing role in exercise-induced pain, or that the cathodal stimulation of the prefrontal cortex negated any positive impact of anodal M1 stimulation.
    Given the lack of guidelines for tDCS electrode montage for exercise, the second study examined the effect of different electrode montages on isometric performance and the neuromuscular response of knee extensor muscle. Given that the anode increases excitability and the cathode decreases excitability, the placement of these has the potential to elicit significant effects on exercise performance. The results showed that exercise performance improved only when an extrachepalic tDCS montage was applied to the M1, but in the absence of changes to the measured neuromuscular parameters. These results suggest that tDCS can have a positive effect on single limb submaximal exercise, but not on maximal muscle contraction. The improvement in performance was probably the consequence of the reduction in perceived exertion for a given load. This is the first experiment showing an improvement in exercise performance on single joint exercise of the lower limbs following tDCS. The results suggest that the extrachepalic set-up is recommended for exercise studies in order to avoid any potential negative effect of the cathodal electrode.
    Previous studies investigating tDCS have shown its potential to alter autonomic activity, and in some circumstances reduce the cardiovascular response during exercise. Considering the emerging studies and applications of tDCS on exercise and the potential benefits of tDCS in the treatment of cardiovascular diseases, the third study monitored multiple cardiovascular variables following tDCS in a group of healthy volunteers. Using more advanced techniques and methods compared to previous research, including the post exercise ischemia technique and transthoracic bioimpedance, the results suggest that tDCS administration has no significant effect on the cardiovascular response in healthy individuals.
    The final study sought to apply the findings obtained in the study 2 to whole body exercise. The same extrachepalic set up was applied over both the motor cortices, with both anodal and cathodal stimulation conditions. The neuromuscular response and cycling performance was also monitored. Following anodal tDCS, time to exhaustion and motor cortex excitability of lower limbs increased. Interestingly, cathodal stimulation did not induce any change in cycling performance or neuromuscular response. This study demonstrated for the first time the ability of anodal tDCS to improve performance of a constant load cycling task, and highlights the inability of cathodal tDCS to decrease cortical activation during muscle contraction.
    Taken together, the experiments performed as part of this thesis provide new insights on how brain stimulation influences exercise performance, with notable findings regarding the role of M1 excitability and perception of effort. Furthermore, considering the lack of knowledge regarding the use of tDCS on exercise, these findings will help further understanding of how to apply tDCS in exercise science. This consequently improves the knowledge base regarding the effect of tDCS on exercise and provides both a methodological and theoretical foundation on which future research can be based.
  • Richardson, K. (2015). The Effect of Preoperative Exercise and Training on Postoperative Outcome.
    The overall aim of this thesis was to investigate the effect of preoperative exercise and training on postoperative outcome. Poor cardiorespiratory fitness has been associated with poor postoperative outcome including increased length of hospital stay and postoperative complications. Thus, increasing cardiorespiratory capacity prior to surgery via preoperative exercise training could potentially alter postoperative outcome. High intensity exercise training (HIIT) has been demonstrated to be an efficient training intervention to increase cardiorespiratory capacity in as little as 2 weeks. It was hypothesised that chronic preoperative exercise training (i.e. 2 weeks HIIT) would improve postoperative outcome measures (i.e. length of stay, complications and mortality) in urology cancer resection patients in comparison to a usual-care-only group (UC). Thirty-five urology cancer resection patients voluntarily enrolled into the study, of these thirty completed the study (15 UC, 15 EXP). There was a significant increase in length of stay (LOS) in the EXP group in comparison to the UC group (4.0 ±6.0 versus 3.0 ±1.5 days, P=0.03), respectively. However, after accounting for covariates (surgical severity, number of operations) LOS was not significantly different between groups (5.8 ±0.8 versus 5.0 ±0.8 days; P=0.24) for UC and EXP patients, respectively). There were no significant differences between groups for postoperative complications on days 1-8 post-surgery (P>0.05), despite significant differences between groups for VO2peak change data (-2.2 ±0.8 ml.kg-1.min-1 versus +1.3 ±0.8ml.kg-1.min-1; Eta2:0.24; P=0.02) for UC and EXP patients). Overall, two weeks preoperative HIIT does not appear to alter postoperative outcome in urology cancer resection patients.

    The effect of two weeks preoperative HIIT was investigated in colorectal cancer resection patients. It was hypothesised that chronic preoperative exercise training (i.e. 2 weeks HIIT) would improve postoperative outcome measures (i.e. LOS, complications and mortality) in colorectal cancer resection patients in comparison to the UC group. Twenty-one colorectal patients voluntarily enrolled into the study and completed the study (12 UC, 9 EXP). There were no significant differences between groups for LOS, (7.0 ±8.5 versus 6.0 ±2.0 days, Eta2:0.04; P=0.38) for UC and EXP patients, respectively). The Cox Regression hazard ratio was 1.55, suggesting that there was a 55% increased likelihood of being discharged on any given postoperative time point in the EXP group when compared to the UC group (95% CI: 0.25 to 1.65; P=0.36). There were no significant differences between groups for postoperative complications for days 1-10 post-surgery (P>0.05). Though, there was a moderate to large effect size for a reduction in postoperative complications on the 2nd (Eta2: 0.09), 4th and 8th postoperative day (Eta2: 0.07), in favour of the EXP group. There were no significant differences between groups for cardiorespiratory measures (i.e. AT, VO2peak) (P0.05). Thus, 2 hours hypoxia (O2: 14.5%) did not appear to significantly alter salivary stress markers. Therefore, the role of the cross-stressor adaptation hypothesis in exercise induced cardioprotection is unclear.

    The overall conclusion of this thesis is that preoperative exercise appears to improve postoperative outcome measures in AAA patients. However, the benefits of preoperative exercise training on postoperative outcome in colorectal and urology patients is equivocal. Though, there was a group effect on postoperative complications on days 2, 4 and 8 post-surgery in colorectal patients, in favour of the EXP group. Lastly, an acute bout of exercise did not appear to attenuate the stress response to a subsequent stressor.
  • Mohammad Amin, A. (2014). The Psychobiological Model of Pacing in Endurance Performance.
    Abstract
    Pacing is the mechanism that athletes use in order to attempt to control their speed in such a manner that they can cover a specific distance or perform in a set time without failing. Several theories and models have been proposed on pacing and the regulation of pacing strategies. The aim of this thesis was to present a new prominent model of endurance performance for pacing, the Psychobiological model for pacing and analyse its single factors.
    The Psychobiological model for pacing has based its theory on five factors to explain pacing and performance: i) the perception of effort, defined as “the conscious sensation of how hard, heavy and strenuous the exercise is”; ii) the potential motivation that represents the individual’s willingness to exert effort; iii) the distance- or time trial duration to cover; iv) the time/distance elapsed/remaining and; v) the previous experience/memory of perceived exertion during exercise of varying intensity and duration.
    In chapter 2 we elucidated the influence of VO2max during a 30 min running time trial. Results showed that runners of different VO2max, pace themselves using different speed in order to avoid reaching maximal RPE and, thus, exhaustion, before the end of the time trial. However, no difference has been found in pacing strategy which does not depend on VO2max.
    In chapter 3 we discussed the effect of knowledge of distance to cover on pacing and performance during a 5 km running time trial. Results showed that knowledge of distance to cover and learning from previous experience is an important determinant in pacing and pacing strategy. Individuals when informed of the correct knowledge of distance to cover where able to pace themselves faster and complete the performance test significantly faster than when the knowledge of distance to cover was incorrectly provided.
    In chapter 4 we assessed the effect of knowledge of distance/time remaining on pacing by using a 5 km time trial to account for knowledge of
    distance and a 30 min cycling time trial to account for knowledge of time remaining. Results demonstrated that time/distance feedback plays an important role for performance. The significant difference in distance/time to complete the performance test showed that participants who were aware of the remaining time/distance to be covered were able to choose a pace during the time trial compared to when they were blind to the distance/time feedback.
    Finally, in chapter 5 we analysed the efficacy of motivational verbal encouragement provided at different phases during a 30 min cycling time trial. Results showed the determinant role of verbal encouragement in relation with RPE and the importance of the timing at which to provide it. Individuals who were verbally encouraged at the end of the cycling performance showed a faster pace and overall they covered a greater distance compared to when they were encouraged at the beginning of the time trial.
    Overall, this thesis demonstrated that the psychobiological model of endurance performance for pacing proposed in the recent years is, indeed, a valid and effective model to explain human performance and it provides new insights in the study of pacing, compared to other existing models of pacing.

Forthcoming

  • Meijen, C., McCormick, A. and Marcora, S. (2016). Psychological Demands in Endurance Performance: Shared Experiences of Recreational Endurance Athletes. In: 9th Annual Meeting of the Society for the Study of Motivation. Available at: http://www.thessm.org/SSM2016_Abstracts.pdf.
    We aimed to identify psychological demands that are commonly experienced by recreational athletes of various endurance sports, distances, and competitive levels away from the competitive environment, preceding an event, or during an event. Four focus groups were held. Inductive thematic analysis resulted in the identification of seven themes; time investment and lifestyle sacrifices; commitment to training sessions; concerns about optimising training; pre-event stressors; exercise sensations; optimising pacing; and remaining focused despite adversity. The potential of designing psychological skills interventions aimed at managing these demands will be discussed, particularly in terms of regulation processes such as emotion control.
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