Portrait of Dr Lex Mauger

Dr Lex Mauger

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About

Lex completed his BSc in Sport and Exercise Science at Exeter University and graduated with First Class honours in 2006. He then went on to complete his PhD at Exeter University in 2010. Between 2009 and 2011 Lex worked as a Lecturer at the University of Bedfordshire, before joining the University of Kent in 2011. Lex teaches on a variety of physiology modules in the School of Sport and Exercise Sciences, regularly publishes his research in leading journals and supervises several PhD students. He has led and worked on several large externally funded projects, including those funded by Research Council, NHS, charities and private companies.

Lex's current research involves improving our understanding of how exercise-induced pain affects the performance of exercise, and the use of non-invasive brain stimulation as an ergogenic aid.

Externally, Lex has acted as an External Examiner for a number of PhD and MRes students, and for postgraduate and undergraduate taught academic courses. He has also worked as a Panel member for course Planned Periodic Reviews and Course Accreditation events.


Research interests

Lex's principal research focuses on the regulation of work rate during exercise, and specifically how conscious sensations arising from intense exercise influences this process. This overarching theme influences his two main areas of study: the role of exercise-induced pain in fatigue and endurance performance, and the use of non-invasive brain stimulation in sport and exercise. To study these areas, Lex employs a variety of techniques and methods, including; transcranial magnetic stimulation, peripheral nerve stimulation, electromyography, experimental pain induction, online gas analysis and a variety of exercise paradigms including isometric muscle contraction, cycling and running ergometry and training studies. Lex has presented his work in this area at invited talks at a variety of conferences, seminars and symposiums, and has discussed his work with journalists through features on BBC Horizon, BBC Radio 4, NBC Today, Stade 2, Runner's World and Men's Health. Lex is an active member for the School's Endurance Research Group (ERG) and Health Research Group. 

Publications

Showing 50 of 71 total publications in the Kent Academic Repository. View all publications.

Article

  • Smith, S., Micklewright, D., Winter, S. and Mauger, A. (2020). Muscle pain induced by hypertonic saline in the knee extensors decreases single-limb isometric time to task failure. European journal of applied physiology [Online]. Available at: https://dx.doi.org/10.1007/s00421-020-04425-2.
    Purpose: Increased nociceptive activity and the experience of exercise-induced pain (EIP) may contribute to fatigue during endurance exercise. To investigate this, a pain model that produces pain similar to EIP and decouples its’ relationship to exercise intensity is required. This study 1) compared the quality of pain caused by a hypertonic saline injection into the vastus lateralis in resting and exercise conditions, and 2) investigated whether this pain contributes to changes in time to task failure. Methods: On separate days, eighteen participants completed a time to task failure at 20% maximal voluntary torque (MVT), a resting hypertonic saline intramuscular injection, and in a further three visits a time to task failure at 10% MVT following injection of isotonic saline, hypertonic saline or a control (no injection). Results: In a subset of eligible participants (n = 12), the hypertonic saline combined with 10% MVT produced a qualitative experience of pain (assessed by the McGill Pain Questionnaire) that felt similar to EIP. 10% MVT with hypertonic saline significantly elevated pain intensity in the first 20% of the time to task failure and caused a significantly (P < 0.05) shorter time to task failure (448 ± 240 s) compared with the isotonic saline (605 ± 285 s) and control (514 ± 197 s) conditions. Conclusion: These findings demonstrate that hypertonic saline increases the intensity of pain during exercise, which results in a faster occurrence of exercise-induced fatigue. These results provide important evidence supporting pain as a limiting factor in endurance performance.
  • Machado, D., Unal, G., Andrade, S., Moreira, A., Altimari, L., Brunoni, A., Perrey, S., Mauger, A., Bikson, M. and Okano, A. (2018). Effect of transcranial direct current stimulation on exercise performance: a systematic review and meta-analysis. Brain Stimulation [Online]. Available at: https://doi.org/10.1016/j.brs.2018.12.227.
    Background: Transcranial direct current stimulation (tDCS) has been used to improve exercise performance, though the protocols used, and results found are mixed.
    Objective: We aimed to analyze the effect of tDCS on improving exercise performance.
    Methods: A systematic search was performed on the following databases, until December 2017: PubMed/MEDLINE, Embase, Web of Science, SCOPUS, and SportDiscus. Full-text articles that used tDCS for exercise performance improvement in adults were included. We compared the effect of anodal (anode near nominal target) and cathodal (cathode near nominal target) tDCS to a sham/control condition on the outcome measure (performance in isometric, isokinetic or dynamic strength exercise and whole-body exercise).
    Results: 22 studies (393 participants) were included in the qualitative synthesis and 11 studies (236 participants) in the meta-analysis. The primary motor cortex (M1) was the main nominal tDCS target (n = 16; 72.5%). A significant effect favoring anodal tDCS (a-tDCS) applied before exercise over M1 was found on cycling time to exhaustion (mean difference = 93.41 s; 95%CI = 27.39 s to 159.43 s) but this result was strongly influenced by one study (weight = 84%), no effect was found for cathodal tDCS (c-tDCS). No significant effect was found for a-tDCS applied on M1 before or during exercise on isometric muscle strength of the upper or lower limbs. Studies regarding a-tDCS over M1 on isokinetic muscle strength presented mixed results. Individual results of studies using a-tDCS applied over the prefrontal and motor cortices either before or during dynamic muscle strength testing showed positive results, but performing meta-analysis was not possible.
    Conclusion: For the protocols tested, a-tDCS but not c-tDCS vs. sham over M1 improved exercise performance in cycling only. However, this result was driven by a single study, which when removed was no longer significant. Further well-controlled studies with larger sample sizes and broader exploration of the tDCS montages and doses are warranted.
  • 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.
  • Matsangidou, M., Ang, C., Mauger, A., Intarasirisawat, J., Otkhmezuri, B. and Avraamides, M. (2018). Is Your Virtual Self as Sensational as Your Real? Virtual Reality: The Effect of Body Consciousness on the Experience of Exercise Sensations. Psychology of Sport & Exercise [Online]. Available at: https://doi.org/10.1016/j.psychsport.2018.07.004.
    Objectives: Past research has shown that Virtual Reality (VR) is an effective method for reducing the perception of pain and effort associated with exercise. As pain and effort are subjective feelings, they are influenced by a variety of psychological factors, including one’s awareness of internal body sensations, known as Private Body Consciousness (PBC). The goal of the present study was to investigate whether the effectiveness of VR in reducing the feeling of exercise pain and effort is moderated by PBC.
    Design and Methods: Eighty participants were recruited to this study and were randomly assigned to a VR or a non-VR control group. All participants were required to maintain a 20% 1RM isometric bicep curl, whilst reporting ratings of pain intensity and perception of effort. Participants in the VR group completed the isometric bicep curl task whilst wearing a VR device which simulated an exercising environment. Participants in the non-VR group completed a conventional isometric bicep curl exercise without VR. Participants’ heart rate was continuously monitored along with time to exhaustion. A questionnaire was used to assess PBC.
    Results: Participants in the VR group reported significantly lower pain and effort and exhibited longer time to exhaustion compared to the non-VR group. Notably, PBC had no effect on these measures and did not interact with the VR manipulation.
    Conclusions: Results verified that VR during exercise could reduce negative sensations associated with exercise regardless of the levels of PBC.
  • Viana, B., Oliveira, B., Santos, T., Pinheiro, F., Cerqueira, L., Inoue, A., Micklewright, D., Mauger, A. and Pires, F. (2018). Psychophysiological And Pacing Strategy Responses To A Sprint Exercise Performed With Different Exercise Expectations. Medicine & Science in Sports & Exercise [Online] 50:324. Available at: https://dx.doi.org/10.1249/01.mss.0000536148.33766.69.
  • Hogg, J., Hopker, J., Coakley, S. and Mauger, A. (2018). Prescribing 6-weeks of running training using parameters from a self-paced maximal oxygen uptake protocol. European Journal of Applied Physiology [Online] 118:911-918. Available at: https://doi.org/10.1007/s00421-018-3814-2.
  • Stevens, C., Mauger, A., Hassmèn, P. and Taylor, L. (2018). Author’s Reply to Cheung et al. Comment on: "Endurance Performance is Influenced by Perceptions of Pain and Temperature: Theory, Applications and Safety Considerations". Sports Medicine [Online] 48:2675-2676. Available at: https://dx.doi.org/10.1007/s40279-018-0921-5.
  • Angius, L., Mauger, A., Hopker, J., Pascual-Leone, A., Santarnecchi E, E. and Marcora, S. (2018). 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.
  • Esh, C., Mauger, A., Palfreeman, R., Al-Janubi, H. and Taylor, L. (2017). Acetaminophen (paracetamol): use beyond pain management and dose variability. Frontiers in Physiology [Online]. Available at: http://dx.doi.org/10.3389/fphys.2017.01092.
  • Stevens, C., Mauger, A., Hassmen, P. and Taylor, L. (2017). Endurance performance is influenced by perceptions of pain and temperature: Theory, applications and safety considerations. Sports Medicine [Online] 48:525-537. Available at: https://doi.org/10.1007/s40279-017-0852-6.
    Models of endurance performance now recognise input from the brain, including an athlete’s ability to cope with various non-pleasurable perceptions during exercise, such as pain and temperature. Exercise training can reduce perceptions of both pain and temperature over time, partly explaining why athletes generally have a higher pain tolerance, despite a similar pain threshold, compared with active controls. Several strategies with varying efficacy may ameliorate the perceptions of pain (e.g. acetaminophen, transcranial direct current stimulation and transcutaneous electrical stimulation) and temperature (e.g. menthol beverages, topical menthol products and other cooling strategies, especially those targeting the head) during exercise to improve athletic performance. This review describes both the theory and practical applications of these interventions in the endurance sport setting, as well as the potentially harmful health consequences of their use.
  • Hettinga, F., Renfree, A., Pageaux, B., Jones, H., Corbett, J., Micklewright, D. and Mauger, A. (2017). Editorial: Regulation of Endurance Performance: New Frontiers. Frontiers in Physiology [Online] 8. Available at: http://dx.doi.org/10.3389/fphys.2017.00727.
  • Foster, J., Mauger, A., Govus, A., Hewson, D. and Taylor, L. (2017). Acetaminophen (Paracetamol) Induces Hypothermia During Acute Cold Stress. Clinical drug investigation [Online]:1-11. Available at: https://doi.org/10.1007/s40261-017-0560-x.
    BACKGROUND

    Acetaminophen is an over-the-counter drug used to treat pain and fever, but it has also been shown to reduce core temperature (T c) in the absence of fever. However, this side effect is not well examined in humans, and it is unknown if the hypothermic response to acetaminophen is exacerbated with cold exposure.

    OBJECTIVE

    To address this question, we mapped the thermoregulatory responses to acetaminophen and placebo administration during exposure to acute cold (10 °C) and thermal neutrality (25 °C).

    METHODS

    Nine healthy Caucasian males (aged 20-24 years) participated in the experiment. In a double-blind, randomised, repeated measures design, participants were passively exposed to a thermo-neutral or cold environment for 120 min, with administration of 20 mg/kg lean body mass acetaminophen or a placebo 5 min prior to exposure. T c, skin temperature (T sk), heart rate, and thermal sensation were measured every 10 min, and mean arterial pressure was recorded every 30 min. Data were analysed using linear mixed effects models. Differences in thermal sensation were analysed using a cumulative link mixed model.

    RESULTS

    Acetaminophen had no effect on T c in a thermo-neutral environment, but significantly reduced T c during cold exposure, compared with a placebo. T c was lower in the acetaminophen compared with the placebo condition at each 10-min interval from 80 to 120 min into the trial (all p < 0.05). On average, T c decreased by 0.42 ± 0.13 °C from baseline after 120 min of cold exposure (range 0.16-0.57 °C), whereas there was no change in the placebo group (0.01 ± 0.1 °C). T sk, heart rate, thermal sensation, and mean arterial pressure were not different between conditions (p > 0.05).

    CONCLUSION

    This preliminary trial suggests that acetaminophen-induced hypothermia is exacerbated during cold stress. Larger scale trials seem warranted to determine if acetaminophen administration is associated with an increased risk of accidental hypothermia, particularly in vulnerable populations such as frail elderly individuals.
  • Jenkins, L., Mauger, A. and Hopker, J. (2017). Evaluation of Risk in Research must be Judged on Evidence, not Personal Opinion. International Journal of Sports Medicine [Online] 38:646-647. Available at: https://dx.doi.org/10.1055/s-0043-112615.
    Letter to editor - response.
  • Dyer, J., Davison, G., Marcora, S. and Mauger, A. (2017). Effect of a Mediterranean type diet on inflammatory and cartilage degradation biomarkers in patients with osteoarthritis. The Journal of Nutrition, Health and Aging [Online] 21:562-566. Available at: https://doi.org/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.
  • Jenkins, L., Mauger, A. and Hopker, J. (2017). Inconsistent approach to evaluating studies and selective interpretation of data reveals lack of objectivity and undermines repeated attempts to discredit SPV. European Journal of Applied Physiology [Online] 117:1057-1058. Available at: https://dx.doi.org/10.1007/s00421-017-3579-z.
  • Jenkins, L., Mauger, A., Fisher, J. and Hopker, J. (2017). Reliability and Validity of a Self-paced Cardiopulmonary Exercise Test in Post-MI Patients. International Journal of Sports Medicine [Online] 38:300-306. Available at: http://dx.doi.org/10.1055/s-0042-122818.
    A self-paced peak oxygen uptake (V?O2peak) test (SPV) has been shown to produce higher V?O2peak values compared to standard cardiopulmonary exercise tests (sCPET), but has not been tested on any clinical population. This study aimed to assess the reliability of the SPV in a healthy population (study 1), and the validity and reliability of the SPV in post Myocardial Infarction (post-MI) patients (study 2). For study 1, twenty-five healthy participants completed three SPV’s. For study 2, twenty-eight post-MI patients completed one sCPET and two SPV’s. The SPV consisted of 5 x 2- min stages where participants were able to self-regulate their effort by using incremental ‘clamps’ in ratings of perceived exertion. The sCPET consisted of a 20 W/min ramp. Results demonstrated the SPV to have a coefficient of variation for V?O2peak of 4.7% for the healthy population, and 8.2% for the post-MI patients. Limits of agreement ranged between ± 4.22-5.86 ml·kg-1·min-1, with the intraclass correlation coefficient ranging between 0.89-0.95. In study 2, there was a significantly higher V?O2peak achieved in the SPV (23.07 ± 4.90 ml·kg-1·min-1) against the sCPET (21.29 ± 4.93 ml·kg-1·min-1). It is concluded that these results provide initial evidence that the SPV may be a safe, valid and reliable method for determining exercise capacity in post-MI patients.
  • Angius, L., Hopker, J. and Mauger, A. (2017). The ergogenic effects of transcranial direct current stimulation on exercise performance. Frontiers in Physiology [Online] 8:1-7. Available at: http://dx.doi.org/10.3389/fphys.2017.00090.
    The physical limits of the human performance have been the object of study for a considerable time. Most of the research has focused on the locomotor muscles, lungs and heart. As a consequence, much of the contemporary literature has ignored the importance of the brain in the regulation of exercise performance. With the introduction and development of new non-invasive devices, the knowledge regarding the behaviour of the central nervous system during exercise has advanced. A first step has been provided from studies involving neuroimaging techniques where the role of specific brain areas have been identified during isolated muscle or whole-body exercise. Furthermore, a new interesting approach has been provided by studies involving non-invasive techniques to manipulate specific brain areas. These techniques most commonly involve the use of an electrical or magnetic field crossing the brain. In this regard, there has been emerging literature demonstrating the possibility to influence exercise outcomes in healthy people following stimulation of specific brain areas. Specifically, transcranial direct current stimulation (tDCS) has been recently used prior to exercise in order to improve exercise performance under a wide range of exercise types. In this review article, we discuss the evidence provided from experimental studies involving tDCS. The aim of this review is to provide a critical analysis of the experimental studies investigating the application of tDCS prior to exercise and how it influences brain function and performance. Finally, we provide a critical opinion of the usage of tDCS for exercise enhancement. This will consequently progress the current knowledge base regarding the effect of tDCS on exercise and provides both a methodological and theoretical foundation on which future research can be based.
  • Astokorki, A. and Mauger, A. (2017). Transcutaneous electrical nerve stimulation reduces exercise-induced perceived pain and improves endurance exercise performance. European Journal of Applied Physiology [Online] 117:483-492. Available at: http://dx.doi.org/10.1007/s00421-016-3532-6.
    Purpose. Muscle pain is a natural consequence of intense and prolonged exercise and has been suggested to be a limiter of performance. Transcutaneous electrical nerve stimulation (TENS) and interferential current (IFC) have been shown to reduce both chronic and acute pain in a variety of conditions. This study sought to ascertain whether TENS and IFC could reduce exercise-induced pain (EIP) and whether this would affect exercise performance. It was hypothesised that TENS and IFC would reduce EIP and result in an improved exercise performance.
    Methods. In two parts, 18 (Part I) and 22 (Part II) healthy male and female participants completed an isometric contraction of the dominant bicep until exhaustion (Part I) and a 16.1 km cycling time trial as quickly as they could (Part II) whilst receiving TENS, IFC and a SHAM placebo in a repeated measures, randomized cross-over, and placebo controlled design. Perceived EIP was recorded in both tasks using a validated subjective scale.
    Results. In Part I, TENS significantly reduced perceived EIP (mean reduction of 12%) during the isometric contraction (P = 0.006) and significantly improved participants’ time to exhaustion by a mean of 38% (P = 0.02). In Part II, TENS significantly improved (P = 0.003) participants’ time trial completion time (~2% improvement) through an increased mean power output.
    Conclusion. These findings demonstrate that TENS can attenuate perceived EIP in a healthy population and that doing so significantly improves endurance performance in both submaximal isometric single limb exercise and whole-body dynamic exercise.
  • Jenkins, L., Mauger, A. and Hopker, J. (2016). Age differences in physiological responses to self?paced and incremental VO2max testing. European Journal of Applied Physiology [Online]. Available at: http://dx.doi.org/10.1007/s00421-016-3508-6.
    Purpose

    A self-paced maximal exercise protocol has demonstrated higher V?O2maxV?O2max values when compared against traditional tests. The aim was to compare physiological responses to this self-paced V?O2maxV?O2max protocol (SPV) in comparison to a traditional ramp V?O2maxV?O2max (RAMP) protocol in young (18–30 years) and old (50–75 years) participants.

    Methods

    Forty-four participants (22 young; 22 old) completed both protocols in a randomised, counter-balanced, crossover design. The SPV included 5 × 2 min stages, participants were able to self-regulate their power output (PO) by using incremental ‘clamps’ in ratings of perceived exertion. The RAMP consisted of either 15 or 20 W min?1.

    Results

    Expired gases, cardiac output (Q), stroke volume (SV), muscular deoxyhaemoglobin (deoxyHb) and electromyography (EMG) at the vastus lateralis were recorded throughout. Results demonstrated significantly higher V?O2maxV?O2max in the SPV (49.68 ± 10.26 ml kg?1 min?1) vs. the RAMP (47.70 ± 9.98 ml kg?1 min?1) in the young, but not in the old group (>0.05). Q and SV were significantly higher in the SPV vs. the RAMP in the young (<0.05) but not in the old group (>0.05). No differences seen in deoxyHb and EMG for either age groups (>0.05). Peak PO was significantly higher in the SPV vs. the RAMP in both age groups (<0.05).

    Conclusion

    Findings demonstrate that the SPV produces higher V?O2maxV?O2max , peak Q and SV values in the young group. However, older participants achieved similar V?O2maxV?O2max values in both protocols, mostly likely due to age-related differences in cardiovascular responses to incremental exercise, despite them achieving a higher physiological workload in the SPV.
  • Bacon, C. and Mauger, A. (2016). Prediction of overuse injuries in professional U18-U21 footballers using metrics of training distance and intensity. Journal of Strength & Conditioning Research [Online]. Available at: http://dx.doi.org/10.1519/JSC.0000000000001744.
    The most common injury in professional football is an overuse injury to the lower limb. A significant external risk factor of this injury is the mismanagement of training and match loads. The aim of the current study was to examine the predictability of overuse injuries in professional youth soccer players using volume and intensity variables derived from Global Positioning Systems (GPS). A total of 41 players (Age - 17.8 yrs±1.1 yrs) training and match loads were assessed. These external loads were measured over two competitive seasons for every training session and match for each individual. A linear regression was used to test the predictability of the injury based on load, which were grouped using loading groups calculated from squad weekly averages. The load groupings assigned were: Low load = 1 SD below the squad mean score; Normal load = ±1 SD from the squad mean; High load = 1 SD above squad mean. The analysis demonstrated that total distance significantly predicted overuse injury incidence rates (F(1, 39) = 6.482, p = 0.015), whereas high speed running meters could not (F(1, 39) = 1.003, p = 0.323). This study demonstrated that distance covered in training and matches can impact on the incidence of overuse injury in youth soccer players. Coaches should seek to monitor player training loads and incorporate this metric into their decision making for protecting players from overuse injury.
  • 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.
  • Lim, W., Lambrick, D., Mauger, A., Woolley, B. and Faulkner, J. (2016). The effect of trial familiarisation on the validity and reproducibility of a field-based self-paced VO2max test. Biology of sport [Online] 33:269-275. Available at: http://dx.doi.org/10.5604/20831862.1208478.
    The self-paced maximal oxygen uptake (VO2max) test (SPV), which is based on the Borg 6-20 Ratings of Perceived Exertion (RPE) scale, allows participants to self-regulate their exercise intensity during a closed-loop incremental maximal exercise test. As previous research has assessed the utility of the SPV test within laboratory conditions, the purpose to this study was to assess the effect of trial familiarisation on the validity and reproducibility of a field-based, SPV test. In a cross-sectional study, fifteen men completed one laboratory-based graded exercise test (GXT) and three field-based SPV tests. The GXT was continuous and incremental until the attainment of VO2max. The SPV, which was completed on an outdoor 400m athletic track, consisted of five x 2 min perceptually-regulated (RPE11, 13, 15, 17 and 20) stages of incremental exercise. There were no differences in the VO2max reported between the GXT (63.5±10.1 ml·kg(-1)·min(-1)) and each SPV test (65.5±8.7, 65.4±7.0 and 66.7±7.7 ml·kg(-1)·min(-1) for SPV1, SPV2 and SPV3, respectively; P>.05). Similar findings were observed when comparing VO2max between SPV tests (P>.05). High intraclass correlation coefficients were reported between the GXT and the SPV, and between each SPV test (?.80). Although participants ran faster and further during SPV3, a similar pacing strategy was implemented during all tests. This study demonstrated that a field-based SPV is a valid and reliable VO2max test. As trial familiarisation did not moderate VO2max values from the SPV, the application of a single SPV test is an appropriate stand-alone protocol for gauging VO2max.
  • Taylor, L., Lee, B., Gibson, O., Midgley, A., Watt, P., Mauger, A. and Castle, P. (2016). Effective microorganism - X attenuates circulating superoxide dismutase following an acute bout of intermittent running in hot, humid conditions. Research in Sports Medicine [Online] 24:130-44. Available at: http://dx.doi.org/10.1080/15438627.2015.1126279.
    This study determined the effectiveness of antioxidant supplementation on high-intensity exercise-heat stress. Six males completed a high-intensity running protocol twice in temperate conditions (TEMP; 20.4°C), and twice in hot conditions (HOT; 34.7°C). Trials were completed following7 days supplementation with 70 ml·day(-1) effective microorganism-X (EM-X; TEMPEMX or HOTEMX) or placebo (TEMPPLA or HOTPLA). Plasma extracellular Hsp72 (eHsp72) and superoxide dismutase (SOD) were measured by ELISA. eHsp72 and SOD increased pre-post exercise (p < 0.001), with greater eHsp72 (p < 0.001) increases observed in HOT (+1.5 ng·ml(-1)) compared to TEMP (+0.8 ng·ml(-1)). EM-X did not influence eHsp72 (p > 0.05). Greater (p < 0.001) SOD increases were observed in HOT (+0.22 U·ml(-1)) versus TEMP (+0.10 U·ml(-1)) with SOD reduced in HOTEMX versus HOTPLA (p = 0.001). Physiological and perceptual responses were all greater (p < 0.001) in HOT versus TEMP conditions, with no difference followed EM-X (p > 0.05). EM-X supplementation attenuated the SOD increases following HOT, potentiating its application as an ergogenic aid to ameliorate oxidative stress.
  • Foster, J., Mauger, A., Thomasson, K., White, S. and Taylor, L. (2016). Effect of Acetaminophen Ingestion on Thermoregulation of Normothermic, Non-febrile Humans. Frontiers in Pharmacology [Online] 7. Available at: http://dx.doi.org/10.3389/fphar.2016.00054.
    In non-febrile mouse models, high dose acetaminophen administration causes profound hypothermia. However, this potentially hazardous side-effect has not been confirmed in non-febrile humans. Thus, we sought to ascertain whether an acute therapeutic dose (20 mg⋅kg lean body mass) of acetaminophen would reduce non-febrile human core temperature in a sub-neutral environment. Ten apparently healthy (normal core temperature, no musculoskeletal injury, no evidence of acute illness) Caucasian males participated in a preliminary study (Study 1) to determine plasma acetaminophen concentration following oral ingestion of 20 mg⋅kg lean body mass acetaminophen. Plasma samples (every 20 min up to 2-hours post ingestion) were analyzed via enzyme linked immunosorbent assay. Thirteen (eight recruited from Study 1) apparently healthy Caucasian males participated in Study 2, and were passively exposed to 20°C, 40% r.h. for 120 min on two occasions in a randomized, repeated measures, crossover design. In a double blind manner, participants ingested acetaminophen (20 mg⋅kg lean body mass) or a placebo (dextrose) immediately prior to entering the environmental chamber. Rectal temperature, skin temperature, heart rate, and thermal sensation were monitored continuously and recorded every 10 min. In Study 1, the peak concentration of acetaminophen (14 ± 4 μg/ml) in plasma arose between 80 and 100 min following oral ingestion. In Study 2, acetaminophen ingestion reduced the core temperature of all participants, whereas there was no significant change in core temperature over time in the placebo trial. Mean core temperature was significantly lower in the acetaminophen trial compared with that of a placebo (p < 0.05). The peak reduction in core temperature in the acetaminophen trial was reached at 120 min in six of the thirteen participants, and ranged from 0.1 to 0.39°C (average peak reduction from baseline = 0.19 ± 0.09°C). There was no significant difference in skin temperature, heart rate, or thermal sensation between the acetaminophen and placebo trials (p > 0.05). The results indicate oral acetaminophen reduces core temperature of humans exposed to an environment beneath the thermal neutral zone. These results suggest that acetaminophen may inhibit the thermogenic mechanisms required to regulate core temperature during exposure to sub-neutral environments.
  • Astokorki, A. and Mauger, A. (2016). Tolerance of exercise-induced pain at a fixed rating of perceived exertion predicts time trial cycling performance. Scandinavian Journal of Medicine & Science in Sports [Online] 27:309-317. Available at: http://dx.doi.org/10.1111/sms.12659.
    To compare the predictive capacity of experimental pain and exercised-induced pain (EIP) on exercise performance. Thirty-two recreationally active male (n = 23) and female (n = 9) participants were recruited. Participants completed measures of pain tolerance by cold pressor test (CPT), pain pressure threshold via algometry (PPT), and EIP tolerance using an RPE clamp trial. A VO2max test provided traditional predictors of performance [VO2max , gas-exchange threshold? (GET), peak power output (PPO)]. Finally, participants completed a 16.1-km cycling time trial (TT). No correlation was found between experimental pain measures (CPT, PPT) and TT performance. However, there was a significant correlation between EIP tolerance and TT performance (R = -0.83, P < 0.01). Regression analysis for pain and physiological predictor variables (mean pain in CPT, PPT, EIP tolerance, VO2max , PPO, GET) revealed that a significant model (P < 0.01) emerged when only PPO (Adjusted R(2)  = 0.739) and EIP tolerance (?R(2)  = 0.075) were used to predict TT performance. These findings suggest that EIP tolerance is an important factor in endurance performance. However, PPT and CPT have limited ability to assess this relationship, and so their use in EIP research should be treated with caution.
  • 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.
  • Foster, J., Mauger, A., Chrismas, B., Thomasson, K. and Taylor, L. (2015). Is prostaglandin E2 (PGE2) involved in the thermogenic response to environmental cooling in healthy humans?. Medical hypotheses [Online] 85:607-611. Available at: http://dx.doi.org/10.1016/j.mehy.2015.07.022.
    Prostaglandin E2 (PGE2) is an eicosanoid derived from cyclooxygenase, an enzyme responsible for the cyclisation and oxygenation of arachidonic acid. In response to bacterial infection, PGE2 binds to EP3 receptors on a population of GABAergic neurons in the pre-optic area. Activation of the EP3 receptor decreases the intracellular cyclic adenosine monophosphate (cAMP) concentrations of these neurons, and the resulting dis-inhibition activates spinal motor outputs responsible for shivering thermogenesis, tachycardia, and brown adipose tissue activation. These involuntary responses increase core body temperature to varying degrees depending on the magnitude of infection; an immune response which is crucial for the survival of the host. However, evidence in animal and human models, primarily through the use of cyclooxygenase inhibitors (which block the production of PGE2), suggests that PGE2 may also be an important molecule for the defence of core temperature against body cooling and cold stress (in the absence of fever). In this paper, evidence within human and animal models is discussed which supports the hypothesis that the eicosanoid PGE2 has a role in maintaining human core temperature during environmental cooling. Given that over-the-counter PGE2 inhibiting drugs [i.e. Non-Steroidal Anti Inflammatory Drugs (NSAIDS)] are frequently used worldwide, it is possible that the use of such medication during environmental cooling could impair one's ability to thermoregulate. Support for such findings could have major implications in the pathology of hypothermia, thus, we suggest that future researchers investigate this specific hypothesis in vivo, using healthy human models. Suggestions for the implementation of such experiments are provided in the present work.
  • Taylor, L., Chrismas, B., Mauger, A., Thomasson, K., White, S. and Foster, J. (2015). Paracetamol (Acetaminophen) Ingestion and Core Body Temperature within Normothermic and Hot Conditions at Rest. Medicine & Science in Sports & Exercise [Online] 47:492. Available at: https://dx.doi.org/10.1249/01.mss.0000477783.29645.5d.
  • Hogg, J., Hopker, J. and Mauger, A. (2015). The self-paced VO2max test to assess maximal oxygen uptake in highly trained runners. International journal of sports physiology and performance [Online] 10:172-177. Available at: http://dx.doi.org/10.1123/ijspp.2014-0041.
    PURPOSE

    The novel self-paced maximal-oxygen-uptake (VO2max) test (SPV) may be a more suitable alternative to traditional maximal tests for elite athletes due to the ability to self-regulate pace. This study aimed to examine whether the SPV can be administered on a motorized treadmill.

    METHODS

    Fourteen highly trained male distance runners performed a standard graded exercise test (GXT), an incline-based SPV (SPVincline), and a speed-based SPV (SPVspeed). The GXT included a plateau-verification stage. Both SPV protocols included 5×2-min stages (and a plateau-verification stage) and allowed for self-pacing based on fixed increments of rating of perceived exertion: 11, 13, 15, 17, and 20. The participants varied their speed and incline on the treadmill by moving between different marked zones in which the tester would then adjust the intensity.

    RESULTS

    There was no significant difference (P=.319, ES=0.21) in the VO2max achieved in the SPVspeed (67.6±3.6 mL·kg(-1)·min(-1), 95%CI=65.6-69.7 mL·kg(-1)·min(-1)) compared with that achieved in the GXT (68.6±6.0 mL·kg(-1)·min(-1), 95%CI=65.1-72.1 mL·kg(-1)·min(-1)). Participants achieved a significantly higher VO2max in the SPVincline (70.6±4.3 mL·kg(-1)·min(-1), 95%CI=68.1-73.0 mL·kg(-1)·min(-1)) than in either the GXT (P=.027, ES=0.39) or SPVspeed (P=.001, ES=0.76).

    CONCLUSIONS

    The SPVspeed protocol produces VO2max values similar to those obtained in the GXT and may represent a more appropriate and athlete-friendly test that is more oriented toward the variable speed found in competitive sport.
  • Faulkner, J., Mauger, A., Woolley, B. and Lambrick, D. (2015). The efficacy of a self-paced VO2max test during motorized treadmill exercise. International Journal of Sports Physiology and Performance [Online] 10:99-105. Available at: http://dx.doi.org/10.1123/ijspp.2014-0052.
    PURPOSE

    To assess the utility of a self-paced maximal oxygen uptake (VO2max) test (SPV) in eliciting an accurate measure of VO2max in comparison with a traditional graded exercise test (GXT) during motorized treadmill exercise.

    DESIGN

    This was a cross-sectional experimental study whereby recreationally trained men (n = 13, 25.5 ± 4.6 y) completed 2 maximal exercise tests (SPV, GXT) separated by a 72-h recovery period.

    METHODS

    The GXT was continuous and incremental, with prescribed 1-km/h increases every 2 min until the attainment of VO2max. The SPV consisted of 5 × 2-min stages of incremental exercise, which were self-selected and adjusted according to 5 prescribed RPE levels (RPE 11, 13, 15, 17, and 20).

    RESULTS

    Although no significant differences in VO2max were observed between the SPV and GXT (63.9 ± 3.3 cf 60.9 ± 4.6 mL · kg-1 · min-1, respectively, P > .05), the apparent 4.7% mean difference may be practically important. The 95% limits-of-agreement analysis was 3.03 ± 11.49 mL · kg-1 · min-1. Therefore, in the worst-case scenario, the GXT may underestimate measured VO2max as ascertained by the SPV by up to 19%. Conversely, the SPV could underestimate the GXT by 14%.

    CONCLUSIONS

    The current study has shown that the SPV is an accurate measure of VO2max during exercise on a motorized treadmill and may provide a slightly higher VO2max value than that obtained from a traditional GXT. The higher VO2max during the SPV may be important when prescribing training or monitoring athlete progression.
  • Taylor, L., Mauger, A., Watkins, S., Fitch, N., Brewer, J., Maxwell, N., Webborn, N. and Castle, P. (2014). Precooling does not improve 2,000-m rowing performance of females in hot, humid conditions. Journal of strength and conditioning research [Online] 28:3416-3424. Available at: http://dx.doi.org/10.1519/JSC.0000000000000558.
    Precooling lowers skin (Tsk) and core temperature (Tre) and can improve performance in hot conditions, but has predominantly been studied in males. This study investigated the effects of precooling on self-paced 2,000-m rowing performance, within females, in hot, humid conditions. Eight physically active females (19.9 ± 1.5 years, 66.8 ± 3.1 kg, 30.0 ± 5.0% body fat) performed 2,000-m rows in a randomized order within 3 conditions {control (CONT) (20° C, 40% relative humidity [RH]); hot (HOT) (35° C, 60% RH); precooling (PREC) (35° C, 60% RH, preceded by precooling)}. The precooling condition consisted of 20-minute precooling with a cold water shower, followed by a 2,000-m row. In contrast, CONT and HOT consisted of 20-minute passive rest in place of precooling. Tre, Tsk, and power output were recorded every 100 m of the rows. Muscle temperature (Tmu) was recorded at baseline, after 20-minute passive rest/precooling and post-row. No differences were observed between conditions for performance time (CONT, 8.89 ± 0.45 minutes; HOT, 9.01 ± 0.55 minutes; PREC, 8.87 ± 0.48 minutes; p = 0.42). Mean Tre during the row was not different between conditions (CONT, 37.8 ± 0.2° C; HOT, 37.7 ± 0.3° C; PREC, 37.5 ± 0.2° C; p = 0.12; main effect), although lower Tre was observed at 1,600 and 1,800 m in PREC compared with HOT (p ? 0.05). Tmu was significantly reduced after precooling (p = 0.03). Precooling did not enhance 2,000-m rowing performance, despite differences in Tre, Tsk, and Tmu. The lack of observed improvement in rowing performance after cold shower precooling may have been due to the short exercise time. An improvement in performance may have been observed using an alternate method of precooling, which has been shown to be ergogenic in other sports.
  • Coull, N., Watkins, S., Aldous, J., Warren, L., Chrismas, B., Dascombe, B., Mauger, A., Abt, G. and Taylor, L. (2014). Effect of tyrosine ingestion on cognitive and physical performance utilising an intermittent soccer performance test (iSPT) in a warm environment. European Journal of Applied Physiology [Online] 115:373-386. Available at: http://dx.doi.org/10.1007/s00421-014-3022-7.
    Purpose
    The aim of this study was to investigate the effect of tyrosine (TYR) ingestion on cognitive and physical performance during soccer-specific exercise in a warm environment.

    Methods
    Eight male soccer players completed an individualised 90 min soccer-simulation intermittent soccer performance test (iSPT), on a non-motorised treadmill, on two occasions, within an environmental chamber (25 °C, 40 % RH). Participants ingested tyrosine (TYR; 250 mL sugar free drink plus 150 mg kg body mass?1 TYR) at both 5 h and 1 h pre-exercise or a placebo control (PLA; 250 mL sugar free drink only) in a double-blind, randomised, crossover design. Cognitive performance (vigilance and dual-task) and perceived readiness to invest physical effort (RTIPE) and mental effort (RTIME) were assessed: pre-exercise, half-time, end of half-time and immediately post-exercise. Physical performance was assessed using the total distance covered in both halves of iSPT.

    Results
    Positive vigilance responses (HIT) were significantly higher (12.6 ± 1.7 vs 11.5 ± 2.4, p = 0.015) with negative responses (MISS) significantly lower (2.4 ± 1.8 vs 3.5 ± 2.4, p = 0.013) in TYR compared to PLA. RTIME scores were significantly higher in the TYR trial when compared to PLA (6.7 ± 1.2 vs 5.9 ± 1.2, p = 0.039). TYR had no significant (p > 0.05) influence on any other cognitive or physical performance measure.

    Conclusion
    The results show that TYR ingestion is associated with improved vigilance and RTIME when exposed to individualised soccer-specific exercise (iSPT) in a warm environment. This suggests that increasing the availability of TYR may improve cognitive function during exposure to exercise-heat stress.
  • Watkins, S., Castle, P., Mauger, A., Sculthorpe, N., Fitch, N., Aldous, J., Brewer, J., Midgley, A. and Taylor, L. (2014). The effect of different environmental conditions on the decision-making performance of soccer goal line officials. Research in sports medicine (Print) [Online] 22:425-437. Available at: http://dx.doi.org/10.1080/15438627.2014.948624.
    Goal line officials (GLO) are exposed to extreme environmental conditions when employed to officiate in professional European soccer cup competitions. The present study aimed to investigate the effect of such environments on GLO decision-making ability. Thirteen male participants were exposed to three conditions: cold (-5°C, 50% relative humidity (RH)); temperate (18°C, 50% RH); and hot (30°C, 50% RH) for 90 min per condition, with a 15 min half-time break after 45 min. Decision-making ability was assessed throughout the 90 min exposure. Core and skin temperatures were recorded throughout. Decision making was improved during exposure to the temperate condition when compared with the cold (mean difference = 12.5%; 95% CI = 1.1%, 23.9%; P = 0.031). Regression analysis indicated that as skin temperature increases so does decision-making ability. Exposure to cold conditions diminished the decision-making ability of GLO.
  • Mauger, A. (2014). Factors affecting the regulation of pacing: current perspectives. Open Access Journal of Sports Medicine [Online] 5:209-14. Available at: http://dx.doi.org/10.2147/OAJSM.S38599.
    During prolonged dynamic and rhythmic exercise, muscular pain and discomfort arises as a result of an increased concentration of deleterious metabolites. Sensed by peripheral nociceptors and transmitted via afferent feedback to the brain, this provides important information regarding the physiological state of the muscle. These sensations ultimately contribute to what is termed "exercise-induced pain". Despite being well recognized by athletes and coaches, and suggested to be integral to exercise performance, this construct has largely escaped attention in experimental work. This perspective article highlights the current understanding of pacing in endurance performance, and the causes of exercise-induced pain. A new perspective is described, which proposes how exercise-induced pain may be a contributing factor in helping individuals to regulate their work rate during exercise and thus provides an important construct in pacing.
  • Hogg, J., Hopker, J. and Mauger, A. (2014). The Self-Paced VO2max Test to Assess Maximal Oxygen Uptake in Highly Trained Runners. International journal of sports physiology and performance [Online] 10:172-177. Available at: http://dx.doi.org/10.1123/ijspp.2014-0041.
    PURPOSE

    The novel self-paced maximal oxygen uptake (VO2max) test (SPV) may be a more suitable alternative to traditional maximal tests for elite athletes due to the ability to self-regulate pace. This study aimed to examine whether the SPV can be administered on a motorised treadmill.

    METHODS

    Fourteen highly trained male distance runners performed a standard GXT, an incline-based SPV (SPVinc) and a speed-based SPV (SPVsp). The GXT included a plateau verification stage. Both SPV protocols included 5 x 2 minute stages [and a plateau verification stage] and allowed for self-pacing based on fixed increments of rating of perceived exertion (RPE): 11, 13, 15, 17 and 20. The participants varied their speed/incline on the treadmill by moving between different marked 'zones', in which the tester would then adjust the intensity.

    RESULTS

    There was no significant difference (p=0.319, ES=0.21) in the VO2max achieved in the SPVsp (67.6 ± 3.6 mL·kg-1·min-1, 95%CI = 65.6 - 69.7 mL·kg-1·min-1) compared to that achieved in the GXT (68.6 ± 6.0 mL·kg-1·min-1, CI = 65.1 - 72.1 mL·kg-1·min-1). Participants achieved a significantly higher VO2max in the SPVinc (70.6 ± 4.3 mL·kg-1·min-1, 95%CI = 68.1 - 73.0 mL·kg-1·min-1) compared to both the GXT (p=0.027, ES=0.39) and SPVsp (p=0.001, ES=0.76).

    CONCLUSIONS

    The SPVsp protocol produces similar VO2max values to those obtained in the GXT and may represent a more appropriate and athlete-friendly test which is more orientated towards the variable speed found in competitive sport.
  • Aldous, J., Akubat, I., Chrismas, B., Watkins, S., Mauger, A., Midgley, A., Abt, G. and Taylor, L. (2014). The reliability and validity of a soccer-specific nonmotorised treadmill simulation (intermittent soccer performance test). Journal of Strength and Conditioning Research [Online] 28:1971-1980. Available at: http://dx.doi.org/10.1519/JSC.0000000000000310.
    This study investigated the reliability and validity of a novel nonmotorised treadmill (NMT)-based soccer simulation using a novel activity category called a "variable run" to quantify fatigue during high-speed running. Twelve male University soccer players completed 3 familiarization sessions and 1 peak speed assessment before completing the intermittent soccer performance test (iSPT) twice. The 2 iSPTs were separated by 6-10 days. The total distance, sprint distance, and high-speed running distance (HSD) were 8,968 ± 430 m, 980 ± 75 m and 2,122 ± 140 m, respectively. No significant difference (p > 0.05) was found between repeated trials of the iSPT for all physiological and performance variables. Reliability measures between iSPT1 and iSPT2 showed good agreement (coefficient of variation: <4.6%; intraclass correlation coefficient: >0.80). Furthermore, the variable run phase showed HSD significantly decreased (p ? 0.05) in the last 15 minutes (89 ± 6 m) compared with the first 15 minutes (85 ± 7 m), quantifying decrements in high-speed exercise compared with the previous literature. This study validates the iSPT as a NMT-based soccer simulation compared with the previous match-play data and is a reliable tool for assessing and monitoring physiological and performance variables in soccer players. The iSPT could be used in a number of ways including player rehabilitation, understanding the efficacy of nutritional interventions, and also the quantification of environmentally mediated decrements on soccer-specific performance.
  • Mauger, A., Faulkner, J., Woolley, B. and Lambrick, D. (2014). The Efficacy Of The Self-paced VO2max Test Design In Motorised Treadmill Running. Medicine and Science in Sports and Exercise [Online]. Available at: https://dx.doi.org/10.1249/01.mss.0000495999.48885.64.
  • Taylor, L., Watkins, S., Aldous, J., Warren, L., Chrismas, B., Dascombe, B., Mauger, A. and Coull, N. (2014). Effect Of Tyrosine Ingestion On Physical And Cognitive Performance During iSPT In A Warm Environment. Medicine & Science in Sports & Exercise [Online] 46:187. Available at: http://dx.doi.org/10.1249/01.mss.0000493741.30759.34.
  • Taylor, L., Fitch, N., Castle, P., Watkins, S., Aldous, J., Sculthorpe, N., Midgely, A., Brewer, J. and Mauger, A. (2014). Exposure to hot and cold environmental conditions does not affect the decision making ability of soccer referees following an intermittent sprint protocol. Frontiers in Physiology [Online] 5:185. Available at: http://dx.doi.org/10.3389/fphys.2014.00185.
    Soccer referees enforce the laws of the game and the decisions they make can directly affect match results. Fixtures within European competitions take place in climatic conditions that are often challenging (e.g., Moscow ~ -5°C, Madrid ~30°C). Effects of these temperatures on player performance are well-documented; however, little is known how this environmental stress may impair cognitive performance of soccer referees and if so, whether exercise exasperates this. The present study aims to investigate the effect of cold [COLD; -5°C, 40% relative humidity (RH)], hot (HOT; 30°C, 40% RH) and temperate (CONT; 18°C, 40% RH) conditions on decision making during soccer specific exercise. On separate occasions within each condition, 13 physically active males; either semi-professional referees or semi-professional soccer players completed three 90 min intermittent treadmill protocols that simulated match play, interspersed with 4 computer delivered cognitive tests to measure vigilance and dual task capacity. Core and skin temperature, heart rate, rating of perceived exertion (RPE) and thermal sensation (TS) were recorded throughout the protocol. There was no significant difference between conditions for decision making in either the dual task (interaction effects: FALSE p = 0.46; MISSED p = 0.72; TRACKING p = 0.22) or vigilance assessments (interaction effects: FALSE p = 0.31; HIT p = 0.15; MISSED p = 0.17) despite significant differences in measured physiological variables (skin temperature: HOT vs. CONT 95% CI = 2.6 to 3.9, p < 0.001; HOT vs. COLD 95% CI = 6.6 to 9.0, p < 0.001; CONT vs. COLD 95% CI = 3.4 to 5.7, p < 0.01). It is hypothesized that the lack of difference observed in decision making ability between conditions was due to the exercise protocol used, as it may not have elicited an appropriate and valid soccer specific internal load to alter cognitive functioning.
  • Mauger, A., Huntley, T. and Fletcher, I. (2014). RPE-derived work rates can be accurately produced without external feedback or reference to the RPE Scale. Perceptual and Motor Skills [Online] 118:507-521. Available at: http://dx.doi.org/10.2466/27.06.PMS.118k19w7.
    Ratings of perceived exertion (RPE) are used to prescribe exercise intensity. This study assessed whether the accurate production of exercise intensity is affected when the rater cannot see the RPE scale. After completing a graded exercise test, 15 active, male participants (M age = 34, SD = 6.7 yr.; M mass = 73.9, SD = 14.8kg, M height = 1.74, SD = 0.08m) completed 3 x 4 min. cycling trials at four randomised RPE-based intensities (RPEs 11, 13, 15, and 17). Participants were allocated to a Full feedback group or a No feedback group (RPEs not in view). On the third trial, No feedback conditions were imposed on the Full feedback group. No statistically significant differences between groups' mean work rates were observed. Changing from Full feedback to No feedback conditions led to a significant overestimation between the trials for power output at RPE 11. Intra-class correlations were significant at RPEs 11, 13, and 17 between all trials for both conditions. Provided adequate familiarisation, active participants can accurately produce RPE derived work rates, even when RPE is not in view.
  • Mauger, A., Metcalfe, A., Taylor, L. and Castle, P. (2014). Reply to "Discussion: The efficacy of the self-paced V?O2max test to measure maximal oxygen uptake in treadmill running". Applied Physiology, Nutrition and Metabolism (Physiologie appliquee, nutrition et metabolisme) [Online] 39:589-591. Available at: http://dx.doi.org/10.1139/apnm-2013-0587.

Conference or workshop item

  • Matsangidou, M., Ang, C., Mauger, L., Otkhmezuri, B. and Tabbaa, L. (2017). How Real is Unreal? Virtual Reality and the Impact of Visual Imagery on the Experience of Exercise-Induced Pain. In: INTERACT 2017 Conference. Springer. Available at: https://doi.org/10.1007/978-3-319-68059-0_18.
    As a consequence of prolonged muscle contraction, acute pain arises during exercise due to a build-up of noxious biochemicals in and around the muscle. Specific visual cues, e.g., the size of the object in weight lifting exercises, may reduce acute pain experienced during exercise. In this study, we examined how Virtual Reality (VR) can facilitate this “material-weight illusion”, influencing perception of task difficulty, which may reduce perceived pain. We found that when vision understated the real weight, the time to exhaustion was 2 minutes longer. Furthermore, participants’ heart rate was significantly lower by 5-7 bpm in the understated session. We concluded that visual-proprioceptive information modulated the individual’s willingness to continue to exercise for longer, primarily by reducing the intensity of negative perceptions of pain and effort associated with exercise. This result could inform the design of VR aimed at increasing the level of physical activity and thus a healthier lifestyle.
  • 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.
  • Jenkins, L., Mauger, A. and Hopker, J. (2014). Validity and reliability of an alternative CPET protocol. In: 7th National Perioperative CPET Forum.

Thesis

  • Hogg, J. (2018). The Use of the Self-Paced Exercise Test in Assessing Cardiorespiratory Fitness in Runners.
    The aim of this thesis was to investigate the utility of the self-paced exercise test (SPXT) in assessing the cardiorespiratory fitness of runners. Traditionally, cardiorespiratory fitness is assessed via an open-ended graded exercise test (GXT) which utilises fixed increments of work-rate and involves the participant continuing until volitional exhaustion. The SPXT is a closed-looped 10 minute (min) test which is made up of 5 x 2 min stages in which intensity is clamped by ratings of perceived exertion (RPE). The test starts at RPE 11, and this increases in an incremental fashion to encompass RPE 13, 15, 17, and finally 20. The test is more time-efficient than traditional protocols due to not requiring a known starting speed. Additionally, the SPXT may be more valid for runners compared to the GXT in which test duration is unknown.

    In study one, gradient and speed-based SPXT protocols were compared to a laboratory based GXT to investigate the validity of the SPXT in producing maximal oxygen uptake (V?O2max). The gradient-based SPXT [which has not previously been investigated] produced higher V?O2max than the GXT (71 ± 4.3 vs. 68.6 ± 6.0 mL·kg-1·min-1, P = .03, ES = .39) but the speed-based SPXT produced similar V?O2max to the GXT (67.6 ± 3.6 vs. 68.6 ± 6.0 mL·kg-1·min-1, P = .32, ES = .21). Results also demonstrated that the oxygen (O2) cost of ventilation may differ between the SPXT and GXT (26.4 ± 2.8 vs. 28.2 ± 2.8 mL.min-1, respectively) (P = .02).

    In study two, the oxygen cost of breathing during the SPXT was investigated. When assessed via separate ventilation trials, there were no differences in the oxygen cost of breathing between the SPXT and GXT (26.1 ± 5.3 vs. 26.9 ± 4.2 mL.min-1, respectively) (t7 = -1.00, P = .34,), and V?O2max was again similar between the SPXT and GXT (Z = -.43, P = .67,). The mean velocity at RPE20 (vRPE20) measured via the SPXT was also similar to the maximal velocity (Vmax) derived from the GXT (t8 = .74, P = .48).

    In study three, the ability of the SPXT to provide novel parameters that could be used to prescribe six-weeks of running training for recreationally active runners was investigated. Results demonstrated that vRPE20 was effective in improving V?O2max (6 ± 6 %), critical speed (3 ± 3 %) and lactate threshold (7 ± 8%) and these improvements were similar to a separate group who trained using GXT-derived parameters including Vmax (4 ± 8, 7 ± 7, 5 ± 4 %, for V?O2max, critical speed, and lactate threshold, respectively). Prescribing training via the SPXT may be beneficial as it does not require additional testing that is usually associated with the GXT.

    In study four, the ability of the SPXT to accurately determine ventilatory thresholds (VT) was investigated. The first and second VT (VT1 and VT2, respectively) were not significantly different when measured as V?O2 between the SPXT (4.03 ± 0.5 and 4.37 ± 0.6 L.min-1, for VT1 and VT2, respectively) and GXT (4.18 ± 0.5 and 4.54 ± 0.7 L.min-1, respectively) in highly trained runners. In recreationally trained runners VT1 was significantly different when measured via the SPXT and GXT (2.78 ± 0.5 vs. 2.99 ± 0.5 L.min-1, respectively) (t23 = -4.51, P < .01, ES = .42) whilst VT2 was also significantly different (3.10 ± 0.6 vs. 3.22 ± 0.6 L.min-1) (t21 = -2.35, P = .03, ES = .20). However, when calculated using different variables such as velocity, RPE, and HR, VT1 and VT2 were similar between protocols. This demonstrated that the SPXT can provide valid VT for runners.

    The conclusion from this thesis is that the SPXT is a valid protocol for measuring V?O2max and can also be used to prescribe a programme of endurance training, and provide an accurate marker of VT.
  • Jenkins, L. (2017). The Use of a Self-Paced Cardiopulmonary Exercise Test in the Pre and Post-Operative Care of Patients With Cardiovascular Disease.
    The aim of this thesis was to assess the ability of a self-paced (SPV) cardiopulmonary exercise test (CPET) in assessing patient fitness prior to elective surgery, and its ability to predict postoperative outcomes. The SPV is a 10 minute test which is comprised of 5 × 2 minute stages. Each stage is fixed to a level on the ratings of perceived exertion (RPE) scale, in an incremental format (RPE: 11, 13, 15, 17 and 20). This test eliminates the need of practitioners having to choose the most appropriate work rate increments to ensure a patient reaches volitional exhaustion within the recommended time period (8-12 min).
    Study 1 aimed to assess the reliability of the maximal exercise test parameters obtained from the SPV. Twenty-five (12 females, 13 males) healthy participants completed three SPV tests on three separate occasions. Results demonstrated a coefficient of variation (CV) for V?O2peak (ml·kg-1·min-1) of 4.2% (95% CI: 3.4-5.6%) for trials 2-1, and 5.1% (95% CI: 4.2-6.8%) for trials 3-2. Repeated measures ANOVA analysis demonstrated no significant difference in V?O2peak across the repeated tests (p > 0.05). The limits of agreement (LOA) were ± 5.59 ml·kg-1·min-1 for trials 2-1, and ± 5.86 ml·kg-1·min-1 for trials 3-2. The mean intraclass correlation coefficient (ICC) was 0.95, which represents good reproducibility. It was concluded that the SPV is a reliable indicator of the main CPET derived variables in a healthy population, with comparable values to previous work on standard CPET protocols.
    Study 2 investigated the physiological responses between the SPV and a standard CPET (sCPET) protocol between a young (18-30 years) and a middle aged to older adult (50-75 years) population. This was in the attempt to gain an understanding of the response to the protocol and whether these responses differ with age. Expired gases, Q, SV, muscular deoxyhaemoglobin (deoxyHb) and electromyography (EMG) at the vastus lateralis were recorded throughout both tests. Results demonstrated a significantly higher V?O2max in the SPV (49.68 ± 10.26 ml·kg-1·min-1) vs. a sCPET (47.70 ± 9.98 ml·kg-1·min-1) in the young, but no differences in the middle aged to older adult group (> 0.05). Q and SV were significantly higher in the SPV vs. a sCPET in the young (< 0.05) but no differences in the middle aged to older adult group (> 0.05). No differences were seen in both age groups in the deoxyHb and EMG response (> 0.05). Findings from this study suggest that in the young group, the SPV produces higher V?O2max values as a result of an increase in oxygen delivery (enhanced Q). However, likely due to age-related differences, particularly in the cardiovascular response to exercise, the middle aged to older adult group achieved similar V?O2max values regardless of them reaching a higher physiological workload.
    Study 3 aimed to assess the validity and reliability of the SPV in post myocardial infarction (post-MI) patients, this was the first study to assess the use of the SPV in a clinical population. Twenty-eight post-MI patients completed one sCPET and two SPVs in a randomised, counterbalanced crossover design. Each patient completed one sCPET and two SPVs. Results demonstrated the SPV to have a coefficient of variation for V?O2peak of 8.2%. The limits of agreement were ± 4.22 ml·kg-1·min-1, with intraclass correlation coefficient of 0.89. There was a significantly higher V?O2peak achieved in the SPV (23.07 ± 4.90 ml·kg-1·min-1) against the sCPET (21.29 ± 4.93 ml·kg-1·min-1). It was concluded that the SPV is a safe and valid test of exercise capacity in post-MI patients, with acceptable levels of reliability when compared to previous work on sCPET protocols.
    Study 4 aimed to determine if the SPV can assess patient's preoperative risk similar to sCPET and if exercise variables obtained from the test can accurately predict post-operative outcome. Fifty patients with cardiovascular related co-morbidities completed one sCPET and one SPV, although only thirty of those patients when ahead with surgery. Post-surgery, patients were monitored for incidence of morbidity on postoperative days 3 and 5, length of hospital stay, and incidence of mortality in the 30 days after surgery. Patients achieved a significantly higher V?O2peak, HR, V?E, peak PO and TTE in the SPV compared to the sCPET (P < 0.05). Logistic regression analysis demonstrated that for the thirty patients who had surgery, none of the CPET variables were associated with postoperative morbidity at either day 3 or 5 (P > 0.05). Although when combining postoperative morbidity at days 3 and 5, logistic regression analysis showed that oxygen pulse at AT obtained from the SPV was significantly related to postoperative complications (P < 0.05). ROC curve analysis demonstrated oxygen pulse at AT to provide an AUC of 0.72 a.u. (95%CI 0.51 to 0.92), with an optimal cut-off point of 8.5 ml/beat-1 which provided 72.7% sensitivity and 71.4% specificity. It was concluded that the SPV was able to assess preoperative fitness comparable to the sCPET. Although none of the CPET variable from either test were associated with postoperative morbidity, which is likely a result of the small sample size.
    The conclusion for this thesis is that a self-paced CPET test is able to reliably assess cardiovascular patient's fitness comparable to traditional methods. This type of test may be seen as advantageous, this is because the SPV takes away the need of clinicians having to choose the most appropriate work rate increments, it allows patients to have full control over the test, and it ensures that regardless of fitness all patients will be exercise for the recommended test time. The fixed test duration of 10 minutes may also help to improve the efficiency of running busy CPET clinics. There are clear benefits to using the SPV, although further research is required first to assess its ability of predicting postoperative outcome in a much larger sample, and to determine if it can be used to the same advantages sCPET protocols have previously demonstrated.
  • 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.

Forthcoming

  • Hunt, A. (2019). An Investigation into the Test-Retest Reliability of the Pain Response to Hypertonic Saline Injections and the Impact of Added Muscle Contraction.
    Background/Aims: Intramuscular Hypertonic Saline (HS) injections induce pain that resembles exercise-induced pain. The reliability and the impact that parallel exercise may have on this pain sensation is unestablished. Therefore, the aims of this research were to assess the test-retest reliability of this model's pain response and the influence of additional muscle contractions to the pain experience, in terms of both Pain Intensity (PI) and Pain Quality (PQ). Methodology: 8 male and 6 female participants (25 ± 5 years, 172.9 ± 8.5 cm, 71.9 ± 12.7 kg) completed the two studies. Study 1.1 assessed test-retest reliability with 3 separate visits, in which 1 ml of 5.85% HS was injected into the right vastus lateralis and differences in PI and PQ were measured. In Study 1.2, participants attended 3 separate visits, where they completed an isometric exercise task with 3 separate 10-second contractions at different intensities (10%/15%/20%). This was done with either HS, a placebo or no injection as control. Results: Study 1.1: Intraclass Correlation Coefficient scores for all PI measures indicated at least 'moderate' to 'good' test-retest reliability (0.68 - 0.814). Cronbach's Alpha scores for all PQ measures indicated 'acceptable' to 'good' test-retest reliability (0.806 - 0.933), except for the affective dimension (0.397 - 0.601). Study 1.2: Paired samples t-tests revealed no differences between exercise and rest, for any of the PI measures or PQ measures, except for the Present Pain Index (PPI) of the Long-form McGill Pain Questionnaire (P = 0.048). ANOVA analyses revealed no differences in PI or PQ measures between contraction intensities. Discussion: In Summary, HS provides a 'moderate' to 'good' reliable pain response, except for the affective dimension of pain. PI response is not affected by the addition of exercise or exercise intensity. PQ response is only affected in terms of different descriptive words, when exercise is introduced.
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