Portrait of Dr James Hopker

Dr James Hopker

Acting Head of School
Reader
Director of Graduate Studies (PGR)

About

Dr James Hopker received his BSc (Hons) in Sports Rehabilitation and Sports Science from St. Mary's University College, Twickenham in 1999, and his MSc. in Sport and Exercise Science from Canterbury Christ Church University in 2003. James began his post at the University of Kent in 2004 and completed his PhD thesis on the influence of training on cycling efficiency and performance in 2009. Currently James is a Reader in Exercise Physiology, Director of Postgraduate Research, and a supervisor to PhD students.

Research interests

James' main research interest is concerned with responses to exercise and training. Specifically, his current research is concerned with the optimization of the exercise training process and how this can be considered on an individual basis from both applied practical, and mathematical/statistical perspectives. He has published an extensive number of research papers on the physiological adaptations to training using both cross-sectional and longitudinal approaches.

James' other research interests are concerned with examining the determinants to endurance exercise performance and he has published studies involving the role of the brain, neuromuscular system, and muscle physiology. 

James has also successfully obtained funding from a range of sources to support his work on exercise training, as well as from the NHS to translate some of his work on fit healthy individuals, into clinical populations. James also regularly provides scientific advice to athletes from amateur to professional level in cycling, triathlon, athletics and football.

Teaching

James' teaching focuses on high-performance physiology, assessment and training for optimal performance and contemporary perspectives in sport research. He teaches at undergraduate and postgraduate level.

Publications

Showing 50 of 111 total publications in the Kent Academic Repository. View all publications.

Article

  • Ebreo, R., Passfield, L. and Hopker, J. (2020). The reliability of measuring gross efficiency during high intensity cycling exercise. International Journal of Sports Physiology and Performance [Online] 15:126-132. Available at: https://doi.org/10.1123/ijspp.2018-0949.
    Purpose: To evaluate the reliability of calculating gross efficiency (GE) conventionally and using a back extrapolation (BE) method during high-intensity exercise (HIE).

    Methods: A total of 12 trained participants completed 2 HIE bouts (P1 = 4 min at 80% maximal aerobic power [MAP]; P2 = 4 min at 100%MAP). GE was calculated conventionally in the last 3 minutes of submaximal (50%MAP) cycling bouts performed before and after HIE (Pre50%MAP and Post50%MAP). To calculate GE using BE (BGE), a linear regression of GE submaximal values post-HIE were back extrapolated to the end of the HIE bout.

    Results: BGE was significantly correlated with Post50%MAP GE in P1 (r = .63; P = .01) and in P2 (r = .85; P = .002). Reliability data for P1 and P2 BGE demonstrate a mean coefficient of variation of 7.8% and 9.8% with limits of agreement of 4.3% and 4.5% in relative GE units, respectively. P2 BGE was significantly lower than P2 Post50%MAP GE (18.1% [1.6%] vs 20.3% [1.7%]; P = .01). Using a declining GE from the BE method, there was a 44% greater anaerobic contribution compared with assuming a constant GE during 4-minute HIE at 100%MAP.

    Conclusion: HIE acutely reduced BGE at 100%MAP. A greater anaerobic contribution to exercise as well as excess postexercise oxygen consumption at 100%MAP may contribute to this decline in efficiency. The BE method may be a reliable and valid tool in both estimating GE during HIE and calculating aerobic and anaerobic contributions.
  • Hopker, J., Griffin, J., Brookhouse, J., Peters, J., Yorck Olaf, S. and Sergei, I. (2019). Performance profiling as an intelligence-led approach to anti-doping in sports. Drug Testing and Analysis [Online]. Available at: https://dx.doi.org/10.1002/dta.2748.
    The efficient use of testing resources is crucial in the fight against doping in sports. The athlete biological passport relies on the need to identify the right athletes to test, and the right time to test them. Here we present an approach to longitudinal tracking of athlete performance to provide an additional, more intelligence‐led approach to improve targeted antidoping testing. The performance results of athletes (male shot putters, male 100 m sprinters, and female 800 m runners) were obtained from a performance results database. Standardized performances, which adjust for average career performance, were calculated to determine the volatility in performance over an athlete's career. We then used a Bayesian spline model to statistically analyse changes within an athlete's standardized performance over the course of a career both for athletes who were presumed “clean” (not doped), and those previously convicted of doping offences. We used the model to investigate changes in the slope of each athlete's career performance trajectory and whether these changes can be linked to doping status. The model was able to identify differences in the standardized performance of clean and doped athletes, with the sign of the change able to provide some discrimination. Consistent patterns of standardized performance profile are seen across shot put, 100 m and 800 m for both the clean and doped athletes we investigated. This study demonstrates the potential for modeling athlete performance data to distinguish between the career trajectories of clean and doped athletes, and to enable the risk stratification of athletes on their risk of doping.
  • Almquist, N., Ettema, G., Hopker, J., Sandbakk, O. and Ronnestad, B. (2019). The effect of 30-second sprints during prolonged exercise on gross efficiency, electromyography, and pedaling technique in elite cyclists. International Journal of Sports Physiology and Performance [Online]. Available at: https://doi.org/10.1123/ijspp.2019-0367.
    Background: Cycling competitions are often of long duration and include repeated high-intensity efforts. Purpose: To investigate the effect of repeated maximal sprints during 4 hours of low-intensity cycling on gross efficiency (GE), electromyography patterns, and pedaling technique compared with work-matched low-intensity cycling in elite cyclists. Methods: Twelve elite, male cyclists performed 4 hours of cycling at 50% of maximal oxygen uptake either with 3 sets of 3 × 30-second maximal sprints (E&S) during the first 3 hours or a work-matched cycling without sprints (E) in a randomized order. Oxygen uptake, electromyography, and pedaling technique were recorded throughout the exercises. Results: GE was reduced from start to the end of exercise in both conditions (E&S: 19.0 [0.2] vs 18.1 [0.2], E: 19.1% [0.2%] vs 18.1% [0.2%], both P = .001), with no difference in change between conditions (condition × time interaction, P = .8). Integrated electromyography increased from start to end of exercise in m. vastus lateralis and m. vastus medialis (m. vastus medialis: 9.9 [2.4], m. vastus lateralis: 8.5 [4.0] mV, main effect of time: P < .001 and P = .03, respectively) and E&S increased less than E in m. vastus medialis (mean difference −3.3 [1.5] mV, main effect of condition: P = .03, interaction, P = .06). The mechanical effectiveness only decreased in E&S (E&S: −2.2 [0.7], effect size = 0.24 vs E: −1.3 [0.8] percentage points: P = .04 and P = .8, respectively). The mean power output during each set of 3 × 30-second sprints in E&S did not differ (P = .6). Conclusions: GE decreases as a function of time during 4 hours of low-intensity cycling. However, the inclusion of maximal repeated sprinting does not affect the GE changes, and the ability to sprint is maintained throughout the entire session.
  • Matta, G., Bossi, A., Millet, G., Lima, P., Lima, J. and Hopker, J. (2019). Influence of a Slow-Start on Overall Performance and Running Kinematics During 6-H Ultramarathon Races. European Journal of Sport Science [Online]. Available at: https://doi.org/10.1080/17461391.2019.1627422.
    The aim of this study was to describe the pacing during a 6-h ultramarathon (race 1) and to
    investigate whether a slow-start affects performance, running kinematic changes, ratings
    of perceived exertion (RPE) and fatigue (ROF) (race 2). After a critical speed test,
    participants completed two 6-h ultramarathons. Race 1 (n = 16) was self-paced, whereas in
    race 2 (n = 10), athletes performed the initial 36 min at speeds 18% below the mean speed
    of the initial 36 min of race 1. In race 1, participants adopted an inverse sigmoid pacing.
    Contact times increased after 1 h, and flight times decreased after 30 min (all P ≤ 0.009);
    stride length reduced after 1 h 30 min (all P = 0.022), and stride frequency did not change.
    Despite the lower speeds during the first 10% of race 2, and higher speeds at 50% and 90%,
    performance remained unchanged (57.5 ± 10.2 vs. 56.3 ± 8.5 km; P = 0.298). However,
    RPE and ROF were lowered for most of race 2 duration (all P < 0.001). For the comparison
    of kinematic variables between races, data were normalised by absolute running speed at
    each time point from 1 h onwards. No differences were found for any of the kinematic
    variables. In conclusion, decreasing initial speed minimises RPE and ROF, but does not
    necessarily affect performance. In addition, running kinematic changes do not seem to be
    affected by pacing manipulation.
  • Bossi, A., Timmerman, W. and Hopker, J. (2019). Energy Expenditure Equation Choice: Effects on Cycling Efficiency and Its Reliability. International Journal of Sports Physiology and Performance [Online]:1-14. Available at: https://doi.org/10.1123/ijspp.2018-0818.
    Purpose:
    There are several published equations to calculate energy expenditure (EE) from gas exchanges. We assessed whether using different EE equations would affect gross efficiency (GE) estimates and their reliability.

    Methods:
    Eleven male and three female cyclists (age: 33 ± 10 years; height: 178 ± 11 cm; body mass: 76.0 ± 15.1 kg; maximal oxygen uptake: 51.4 ± 5.1 ml·kg-1·min-1; peak power output: 4.69 ± 0.45 W·kg-1) completed five visits to the laboratory on separate occasions. In the first visit, participants completed a maximal ramp test to characterize their physiological profile. In visits two to five, participants performed four identical submaximal exercise trials to assess GE and its reliability. Each trial included three 7-min bouts at 60%, 70% and 80% of the gas exchange threshold. EE was calculated with four equations by Péronnet & Massicotte, Lusk, Brouwer and Garby & Astrup.

    Results:
    All four EE equations produced GE estimates that differed from each other (all P < 0.001). Reliability parameters were only affected when the typical error was expressed in absolute GE units, suggesting a negligible effect—related to the magnitude of GE produced by each EE equation. The mean coefficient of variation for GE across different exercise intensities and calculation methods was 4.2%.

    Conclusions:
    Although changing the EE equation does not affect GE reliability, exercise scientists and coaches should be aware that different EE equations produce different GE estimates. Researchers are advised to share their raw data to allow for GE recalculation, enabling comparison between previous and future studies.
  • Mierau, A., Holgado, D., Zandonai, T., Ciria, L., Zabala, M., Hopker, J. and Sanabria, D. (2019). Transcranial direct current stimulation (tDCS) over the left prefrontal cortex does not affect time-trial self-paced cycling performance: Evidence from oscillatory brain activity and power output. PLOS ONE [Online] 14:e0210873. Available at: https://doi.org/10.1371/journal.pone.0210873.
    Objectives
    To test the hypothesis that transcranial direct current stimulation (tDCS) over the left dorsolateral prefrontal cortex (DLPFC) influences performance in a 20-min time-trial self-paced exercise and electroencephalographic (EEG) oscillatory brain activity in a group of trained male cyclists.

    Design
    The study consisted of a pre-registered (https://osf.io/rf95j/), randomised, sham-controlled, single-blind, within-subject design experiment.

    Methods
    36 trained male cyclists, age 27 (6.8) years, weight 70.1 (9.5) Kg; VO2max: 54 (6.13) ml.min-1.kg-1, Maximal Power output: 4.77 (0.6) W/kg completed a 20-min time-trial self-paced exercise in three separate sessions, corresponding to three stimulation conditions: anodal, cathodal and sham. tDCS was administered before each test during 20-min at a current intensity of 2.0 mA. The anode electrode was placed over the DLPFC and the cathode in the contralateral shoulder. In each session, power output, heart rate, sRPE and EEG (at baseline and during exercise) was measured.

    Results
    There were no differences (F = 0.31, p > 0.05) in power output between the stimulation conditions: anodal (235 W [95%CI 222–249 W]; cathodal (235 W [95%CI 222–248 W] and sham (234 W [95%CI 220–248 W]. Neither heart rate, sRPE nor EEG activity were affected by tDCS (all Ps > 0.05).

    Conclusion
    tDCS over the left DLFC did not affect self-paced exercise performance in trained cyclists. Moreover, tDCS did not elicit any change on oscillatory brain activity either at baseline or during exercise. Our data suggest that the effects of tDCS on endurance performance should be taken with caution.
  • Jackson, A., Allen, H., Hull, J., Hopker, J., Backhouse, S., Price, O. and Dickinson, J. (2019). Diagnosing exercise‐induced bronchoconstriction: Over‐or under‐detection?. Allergy [Online]. Available at: https://doi.org/10.1111/all.14005.
  • 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.
  • Montagna, S. and Hopker, J. (2018). A Bayesian approach to the use of athlete performance data within anti-doping. Frontiers in Physiology [Online] 9. Available at: https://doi.org/10.3389/fphys.2018.00884.
    The World Anti-doping Agency currently collates the results of all doping tests for
    athletes involved in elite sporting competition with the aim of improving the fight against
    doping. Existing anti-doping strategies involve either the direct detection of use of
    banned substances, or abnormal variation in metabolites or biological markers related
    to their use. As the aim of any doping regime is to enhance athlete competitive
    performance, it is interesting to consider whether performance data could be used within
    the fight against doping. In this regard, the identification of unexpected increases in
    athlete performance could be used as a trigger for their closer scrutiny via a targeted
    anti-doping testing programme. This study proposes a Bayesian framework for the
    development of an “athlete performance passport” and documents some initial findings
    and limitations of such an approach. The Bayesian model was retrospectively applied to
    the competitive results of 1,115 shot put athletes from 1975 to 2016 in order establish
    the interindividual variability of intraindividual performance in order to create individualized
    career performance trajectories for a large number of presumed clean athletes. Data
    from athletes convicted for doping violations (3.69% of the sample) was used to assess
    the predictive performance of the Bayesian framework with a probit model. Results
    demonstrate the ability to detect performance differences (?1 m) between doped and
    presumed clean athletes, and achieves good predictive performance of doping status
    (i.e., doped vs. non-doped) with a high area under the curve (AUC = 0.97). However, the
    model prediction of doping status was driven by the correct classification of presume
    non-doped athletes, misclassifying doped athletes as non-doped. This lack of sensitivity
    is likely due to the need to accommodate additional longitudinal covariates (e.g., aging
    and seasonality effects) potentially affecting performance into the framework. Further
    research is needed in order to increase the framework structure and improve its accuracy
    and sensitivity.
  • Holgado, D., Zandonai, T., Zabala, M., Hopker, J., Perakakis, P., Luque-Casado, A., Ciria, L., Guerra-Hernandez, E. and Sanabria, D. (2018). Tramadol effects on physical performance and sustained attention during a 20-min indoor cycling time-trial: A randomised controlled trial. Journal of Science and Medicine in Sport [Online] 21:654-660. Available at: https://doi.org/10.1016/j.jsams.2017.10.032.
    Objectives: To investigate the effect of tramadol on performance during a 20-min cycling time-trial (Experiment 1), and to test whether sustained attention would be impaired during cycling after tramadol intake (Experiment 2). Design: randomized, double-blind, placebo controlled trial. Methods: In Experiment 1, participants completed a cycling time-trial, 120-min after they ingested either tramadol or placebo. In Experiment 2, participants performed a visual Oddball task during the time-trial. Electroencephalography measures (EEG) were recorded throughout the session. Results: In Experiment 1, average time-trial power output was higher in the tramadol vs. placebo condition (tramadol: 220 watts vs. placebo: 209 watts; p < 0.01). In Experiment 2, no differences between conditions were observed in the average power output (tramadol: 234 watts vs. placebo: 230 watts; p > 0.05). No behavioural differences were found between conditions in the Oddball task. Crucially, the time frequency analysis in Experiment 2 revealed an overall lower target-locked power in the beta-band (p < 0.01), and higher alpha suppression (p < 0.01) in the tramadol vs. placebo condition. At baseline, EEG power spectrum was higher under tramadol than under placebo in Experiment 1 while the reverse was true for Experiment 2. Conclusions: Tramadol improved cycling power output in Experiment 1, but not in Experiment 2, which may be due to the simultaneous performance of a cognitive task. Interestingly enough, the EEG data in Experiment 2 pointed to an impact of tramadol on stimulus processing related to sustained attention. Trial registration: EudraCT number: 2015-005056-96.
  • 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.
  • Jackson, A., Hull, J., Hopker, J. and Dickinson, J. (2018). Impact of detecting and treating exercise-induced bronchoconstriction in elite footballers. European Respiratory Journal Open Research [Online] 4. Available at: http://dx.doi.org/10.1183/23120541.00122-2017.
    Our aim was to evaluate the prevalence of exercise-induced bronchoconstriction (EIB) in elite football players and assess subsequent impact of therapy on airway health and exercise performance. 97 male professional football players completed an airway health assessment with a eucapnic voluntary hyperpnoea (EVH) challenge to diagnose EIB. Players demonstrating a positive result (EVH+) were prescribed inhaler therapy depending on severity, including inhaled corticosteroids and inhaled short-acting β2-agonists, and underwent repeat assessment after 9 weeks of treatment. Eight players (EVH+ n=3, EVH− n=5) completed a peak oxygen uptake (V′O2peak) test at initial and follow-up assessment. Out of the 97 players, 27 (28%) demonstrated a positive EVH result. Of these, 10 had no prior history (37%) of EIB or asthma. EVH outcome was not predictable by respiratory symptoms. Seven (24%) of the 27 EVH+ players attended follow-up and demonstrated improved post-challenge spirometry (forced expiratory volume in 1 s pre-test −22.9±15.4%, post-test −9.0±1.6%; p=0.018). At follow-up V′O2peak improved by 3.4±2.9 mL·kg−1·min−1 in EVH+ players compared to 0.1±2.3 mL·kg−1·min−1 in EVH− players. Magnitude of inference analysis indicated treatment was possibly beneficial (74%) for exercise capacity.
    Elite football players have a high EIB prevalence. Treatment with inhaler therapy reduces EIB severity.
  • Bossi, A., O’Grady, C., Ebreo, R., Passfield, L. and Hopker, J. (2018). Pacing strategy and tactical positioning during cyclo-cross races. International Journal of Sports Physiology and Performance [Online]. Available at: https://doi.org/10.1123/ijspp.2017-0183.
    Purpose: To describe pacing strategy and competitive behaviour in elite-level cyclo-cross races. Methods: Data from 329 men and women competing in 5 editions (2012–2016) of UCI Cyclo-cross World Championships were compiled. Individual mean racing speeds from each lap were normalised to the mean speeds of the whole race. Lap-by-lap and final rankings were also explored. Pacing strategy was compared between sexes and between top- and bottom-placed cyclists. Results: A significant main effect of laps was found in 8 out of 10 races (4 positive, 3 variable, 2 even and 1 negative pacing strategies) and an interaction effect of ranking-based groups was found in 2 (2016, male and female races). Kendall's tau-b correlations revealed an increasingly positive relationship between intermediate and final rankings throughout the races. The number of overtakes during races decreased from start to finish, as suggested by significant Friedman tests. In the first lap, normalised cycling speeds were different in 3 out of 5 editions—men were faster in 1 and slower in 2 editions. In the last lap, however, normalised cycling speeds of men were lower than those of women in 4 editions. Conclusions: Elite cyclo-cross competitors adopt slightly distinct pacing strategies in each race, but positive pacing strategies are highly probable in most events, with more changes in rankings during the first laps. Sporadically, top- and bottom-placed groups might adopt different pacing strategies during either male or female races. Men and women seem to distribute their efforts differently, but this effect is of small magnitude.
  • Hopker, J., Schumacher, Y., Fedoruk, M., Morkeberg, J., Bermon, S., Iljukov, S., Aikin, R. and Sottas, P. (2018). Athlete performance monitoring in anti-doping. Frontiers in Physiology [Online] 9:Article 232. Available at: http://dx.doi.org/10.3389/fphys.2018.00232.
  • 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.
  • 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.
  • Holgado, D., Hopker, J., Sanabria, D. and Zabala, M. (2017). Analgesics and Sport Performance: Beyond the Pain Modulating Effects. PM&R [Online]. Available at: http://dx.doi.org/10.1016/j.pmrj.2017.07.068.
    Analgesics are widely used in sport to treat pain and inflammation associated with injury. However, there is growing evidence that some athletes might be taking these substances in an attempt to enhance performance. While the pharmacological action of analgesics and their use in treating pain with and without anti-inflammatory effect is well established, their effect on sport performance is debated. The aim of this review was to evaluate the evidence of whether analgesics are capable of enhancing exercise performance, and if so, to what extent. Paracetamol has been suggested to improve endurance and repeated sprint exercise performance by reducing the activation of higher brain structures involved in pain and cognitive/affective processing. Non-steroidal anti-inflammatory drugs (NSAIDs) affect both central and peripheral body systems, but investigation on their ergogenic effect on muscle strength development have provided equivocal results. The therapeutic use of glucocorticoids is indubitable, but clear evidence exists for a performance enhancing effect following short-term oral administration. Based upon the evidence presented in this review article, the ergogenic benefit of analgesics may warrant further consideration by regulatory bodies. In contrast to the aforementioned analgesics, there is a paucity of research on the use opioids such as tramadol on sporting performance.
  • Passfield, L. and Hopker, J. (2017). A mine of information: can sports analytics provide wisdom from your data?. International journal of sports physiology and performance [Online] 12:851-855. Available at: http://dx.doi.org/10.1123/ijspp.2016-0644.
    This paper explores the notion that the availability and analysis of large datasets has the capacity to improve practice and change the nature of science in the sport and exercise setting. The increasing use of data and information technology in sport is giving rise to this change. Websites hold large data repositories and the development of wearable technology, mobile phone applications and related instruments for monitoring physical activity, training and competition, provide large data sets of extensive and detailed measurements. Innovative approaches conceived to exploit more fully these large datasets could provide a basis for more objective evaluation of coaching strategies and new approaches to how science is conducted. The emergence of a new discipline, sports analytics, could help overcome some of the challenges involved in obtaining knowledge and wisdom from these large datasets. Examples of where large datasets have been analyzed, to evaluate the career development of elite cyclists, and to characterize and optimize the training load of well-trained runners are discussed. Careful verification of large datasets is time consuming and imperative before useful conclusions can be drawn. Consequently, it is recommended that prospective studies are preferred to retrospective analyses of data. It is concluded that rigorous analysis of large datasets could enhance our knowledge in the sport and exercise sciences, inform competitive strategies, and allow innovative new research and findings.
  • 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.
  • Cole, M., Hopker, J., Wiles, J. and Coleman, D. (2017). The effects of acute carbohydrate and caffeine feeding strategies on cycling efficiency. Journal of Sports Sciences [Online]. Available at: https://dx.doi.org/10.1080/02640414.2017.1343956.
    To assess the effect of carbohydrate and caffeine on gross efficiency (GE), 14 cyclists (V? O2max 57.6 ± 6.3 ml.kg?1.min?1) completed 4 × 2-hour tests at a submaximal exercise intensity (60% Maximal Minute Power). Using a randomized, counter-balanced crossover design, participants con- sumed a standardised diet in the 3-days preceding each test and subsequently ingested either caffeine (CAF), carbohydrate (CHO), caffeine+carbohydrate (CAF+CHO) or water (W) during exercise whilst GE and plasma glucose were assessed at regular intervals (~30 mins). GE progressively decreased in the W condition but, whilst caffeine had no effect, this was significantly attenuated in both trials that involved carbohydrate feedings (W = ?1.78 ± 0.31%; CHO = ?0.70 ± 0.25%, p = 0.008; CAF+CHO = ?0.63 ± 0.27%, p = 0.023; CAF = ?1.12 ± 0.24%, p = 0.077). Blood glucose levels were significantly higher in carbohydrate ingestion conditions (CHO = 4.79 ± 0.67 mmol·L?1, p < 0.001; CAF +CHO = 5.05 ± 0.81 mmol·L?1, p < 0.001; CAF = 4.46 ± 0.75 mmol·L?1; W = 4.20 ± 0.53 mmol·L?1). Carbohydrate ingestion has a small but significant effect on exercise-induced reductions in GE, indicat- ing that cyclists’ feeding strategy should be carefully monitored prior to and during assessment.
  • Bossi, A., Matta, G., Millet, G., Lima, P., Pertence, L., de Lima, J. and Hopker, J. (2017). Pacing Strategy During 24-hour Ultramarathon-Distance Running. International Journal of Sports Physiology and Performance [Online] 12:590-596. Available at: http://dx.doi.org/10.1123/ijspp.2016-0237.
    Purpose: This study aimed to describe pacing strategy in a 24-h ultramarathon-distance running race held on a flat course and its interaction with sex, age group and athletes’ performance group. Methods: Data from 398 male and 103 female participants in 5 consecutive editions were obtained based on a minimum 19.2-h (80% duration) active-running cut-off. Mean running speeds from each hour were percentage normalized to the total 24-h mean speed in order to eliminate the effect of between-runner differences in absolute speed. Results: Mean performance of all editions was 135.5 ± 33 km with a mean active-running time of 22.4 ± 1.3 h. Overall data showed a reverse J-shaped pacing strategy with the exception of a significant reduction in speed during the last hour. Two-way mixed ANOVA showed no significant interactions between racing time and sex (F = 1.57; P = 0.058) and racing time and age group (F = 1.25; P = 0.053), but significant interactions were found between racing time and performance group (F = 7.01; P < 0.001). Person’s product-moment correlations showed a moderate association between total running distance and normalized mean running speed in the first two hours (r = -0.58; P < 0.001) but not in the last two (r = 0.03; P = 0.480). Conclusions: In 24-h ultramarathons, while the general behaviour represents a reverse J-shaped pattern, the fastest
    runners started at lower normalized mean running speed, displaying a more even pacing strategy compared to the slower counterparts, regardless of sex and age group.
  • 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.
  • 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.
  • Arkesteijn, M., Jobson, S., Hopker, J. and Passfield, L. (2016). The effect of cycling intensity on cycling economy during seated and standing cycling. International journal of sports physiology and performance [Online] 11:907-912. Available at: http://www.dx.doi.org/10.1123/ijspp.2015-0441.
    BACKGROUND:
    Previous research has shown that cycling in a standing position reduces cycling economy compared with seated cycling. It is unknown whether the cycling intensity moderates the reduction in cycling economy while standing.

    PURPOSE:
    The aim was to determine whether the negative effect of standing on cycling economy would be decreased at a higher intensity.

    METHODS:
    Ten cyclists cycled in 8 different conditions. Each condition was either at an intensity of 50% or 70% of maximal aerobic power, at a gradient of 4% or 8% and in the seated or standing cycling position. Cycling economy and muscle activation level of 8 leg muscles were recorded.

    RESULTS:
    There was an interaction between cycling intensity and position for cycling economy (P = 0.03), the overall activation of the leg muscles (P = 0.02) and the activation of the lower leg muscles (P = 0.05). The interaction showed decreased cycling economy when standing compared with seated cycling, but the difference was reduced at higher intensity. The overall activation of the leg muscles and the lower leg muscles respectively increased and decreased, but the differences between standing and seated cycling were reduced at higher intensity.

    CONCLUSIONS:
    Cycling economy was lower during standing cycling than seated cycling, but the difference in economy diminishes when cycling intensity increases. Activation of the lower leg muscles did not explain the lower cycling economy while standing. The increased overall activation therefore suggests that increased activation of the upper leg muscles explains part of the lower cycling economy while standing.
  • 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.
  • 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.
  • Karsten, B., Hopker, J., Jobson, S., Baker, J., Petringa, L., Klose, A. and Beedie, C. (2016). Comparison of inter-trial recovery times for the determination of critical power and W’ in cycling. Journal of Sports Sciences [Online] 35:1420-1425. Available at: http://dx.doi.org/10.1080/02640414.2016.1215500.
    Critical Power (CP) and W’ are often determined using multi-day testing protocols. To investigate this cumbersome testing method, the purpose of this study was to compare the differences between the conventional use of a 24-h inter-trial recovery time with those of 3 h and 30 min for the determination of CP and W’. Methods: 9 moderately trained cyclists performed an incremental test to exhaustion to establish the power output associated with the maximum oxygen uptake (pmax), and 3 protocols requiring time-to-exhaustion trials at a constant work-rate performed at 80%, 100% and 105% of pmax. Design: Protocol A utilised 24-h inter-trial recovery (CP24/W’24), protocol B utilised 3-h inter-trial recovery (CP3/W’3), and protocol C used 30-min inter-trial recovery period (CP0.5/W’0.5). CP and W’ were calculated using the inverse time (1/t) versus power (P) relation (P = W’(1/t) + CP). Results: 95% Limits of Agreement between protocol A and B were ?9 to 15 W; ?7.4 to 7.8 kJ (CP/W’) and between protocol A and protocol C they were ?27 to 22 W; ?7.2 to 15.1 kJ (CP/W’). Compared to criterion protocol A, the average prediction error of protocol B was 2.5% (CP) and 25.6% (W’), whilst for protocol C it was 3.7% (CP) and 32.9% (W’). Conclusion: 3-h and 30-min inter-trial recovery time protocols provide valid methods of determining CP but not W’ in cycling.
  • Passfield, L., Hopker, J., Jobson, S., Friel, D. and Zabala, M. (2016). Knowledge is Power: Issues of Measuring Training and Performance in Cycling. Journal of Sports Sciences [Online] 35:1426-1434. Available at: http://dx.doi.org/10.1080/02640414.2016.1215504.
    Mobile power meters provide a valid means of measuring cyclists’ power output in the field. These field measurements can be performed with very good accuracy and reliability making the power meter a useful tool for monitoring and evaluating training and race demands. This study examines power meter data from a Grand Tour cyclist’s training and racing and explores the inherent complications created by its stochastic nature. Simple summary methods cannot reflect a session’s variable distribution of power output or indicate its likely metabolic stress. Binning power output data, into training zones for example, provides information on the detail but not the length of efforts within a session. An alternative approach is to track changes in cyclists’ modelled training and racing performances. Both Critical Power and Record Power Profiles have been used for monitoring training-induced changes in this manner. Ultimately, new methods for quantifying the effects of training loads and modelling their implications for future performance are required. Although first proposed 40 years ago, our ability to model the effects of training on performance remain limited and merits further research.
  • Bossi, A. and Hopker, J. (2016). Twilight: filter the blue light of your device and sleep better. British Journal of Sports Medicine [Online] 51. Available at: http://www.dx.doi.org/10.1136/bjsports-2016-096315.
  • Bossi, A., Lima, P., Lima, J. and Hopker, J. (2016). Laboratory predictors of uphill cycling performance in trained cyclists. Journal of Sports Sciences [Online]. Available at: http://www.dx.doi.org/10.1080/02640414.2016.1182199.
    This study aimed to assess the relationship between an uphill time-trial (TT) performance and both aerobic and anaerobic parameters obtained from laboratory tests. Fifteen cyclists performed a Wingate anaerobic test, a graded exercise test (GXT) and a field-based 20-min TT with 2.7% mean gradient. After a 5-week non-supervised training period, 10 of them performed a second TT for analysis of pacing reproducibility. Stepwise multiple regressions demonstrated that 91% of TT mean power output variation (W kg-1) could be explained by peak oxygen uptake (ml kg-1.min-1) and the respiratory compensation point (W kg-1), with standardised beta coefficients of 0.64 and 0.39, respectively. The agreement between mean power output and power at respiratory compensation point showed a bias ± random error of 16.2 ± 51.8 W or 5.7 ± 19.7%. One-way repeated-measures analysis of variance revealed a significant effect of the time interval (123.1 ± 8.7; 97.8 ± 1.2 and 94.0 ± 7.2% of mean power output, for epochs 0-2, 2-18 and 18-20 min, respectively; P < 0.001), characterising a positive pacing profile. This study indicates that an uphill, 20-min TT-type performance is correlated to aerobic physiological GXT variables and that cyclists adopt reproducible pacing strategies when they are tested 5 weeks apart (coefficients of variation of 6.3; 1 and 4%, for 0-2, 2-18 and 18-20 min, respectively).
  • Richardson, K. and Hopker, J. (2016). One minute to assess frailty, but what should we do next?. Anaesthesia [Online] 71:622-626. Available at: http://onlinelibrary.wiley.com/doi/10.1111/anae.13321/abstract.
  • Hopker, J., OGrady, C. and Pageaux, B. (2016). Prolonged constant load cycling exercise is associated with reduced gross efficiency and increased muscle oxygen uptake. Scandinavian journal of medicine & science in sports [Online] 27:408-417. Available at: http://dx.doi.org/10.1111/sms.12673.
    This study investigated the effects of prolonged constant load cycling exercise on cycling efficiency and local muscle oxygen uptake responses. Fourteen well-trained cyclists each completed a 2-h steady-state cycling bout at 60% of their maximal minute power output to assess changes in gross cycling efficiency (GE) and muscle oxygen uptake (mVO2) at time points 5, 30, 60, 90, and 120 min. Near-infrared spatially resolved spectroscopy (NIRS) was used to continually monitor tissue oxygenation of the Vastus Lateralis muscle, with arterial occlusions (OCC) applied to assess mVO2 . The half-recovery time of oxygenated hemoglobin (HbO2 ) was also assessed pre and post the 2-h cycling exercise by measuring the hyperemic response following a 5-min OCC. GE significantly declined during the 2-h cycling bout (18.4 ± 1.6 to 17.4 ± 1.4%; P < 0.01). Conversely, mVO2 increased, being significantly higher after 90 and 120 min than at min 5 (+0.04 mlO2 /min/100 g; P = 0.03). The half-recovery time for HbO2 was increased comparing pre and post the 2-h cycling exercise (+7.1 ± 19s), albeit not significantly (d: 0.48; P = 0.27). This study demonstrates that GE decreases during prolonged constant load cycling exercise and provides evidence of an increased mVO2 , suggestive of progressive mitochondrial or contractile inefficiency.
  • 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.
  • 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.
  • Galbraith, A., Hopker, J. and Passfield, L. (2015). Modeling Intermittent Running from a Single-visit Field Test. International journal of sports medicine [Online] 36:365-370. Available at: http://dx.doi.org/10.1055/s-0034-1394465.
    This study assessed whether the distance-time relationship could be modeled to predict time to exhaustion (TTE) during intermittent running. 13 male distance runners (age: 33±14 years) completed a field test and 3 interval tests on an outdoor 400?m athletic track. Field-tests involved trials over 3?600?m, 2?400?m and 1?200?m with a 30-min rest between each run. Interval tests consisted of: 1?000?m at 107% of CS with 200?m at 95% CS; 600?m at 110% of CS with 200?m at 90% CS; 200?m at 150% of CS with 200?m at 80% CS. Interval sessions were separated by 24?h recovery. Field-test CS and D' were applied to linear and non-linear models to estimate the point of interval session termination. Actual and predicted TTE using the linear model were not significantly different in the 1?000?m and 600?m trials. Actual TTE was significantly lower (P=0.01) than predicted TTE in the 200?m trial. Typical error was high across the trials (range 334-1?709?s). The mean balance of D' remaining at interval session termination was significantly lower when estimated from the non-linear model (-21.2 vs. 13.4?m, P<0.01), however no closer to zero than the linear model. Neither the linear or non-linear model could closely predict TTE during intermittent running.

Book section

  • Hopker, J. and Jobson, S. (2017). Assessing cycling fitness. In: Zabala, M. and Cheung, S. eds. Cycling Science. Illinois, USA: Human Kinetics.

Conference or workshop item

  • Gowers, W., Jackson, A., Hull, J., Hopker, J. and Dickinson, J. (2018). Indirect airway challenges and asthma related conditions in healthy active individuals. In: European Respiratory Society International Congress.
  • Hull, J., Jackson, A., Hopker, J., Greenwell, J. and Dickinson, J. (2017). Maximizing Respiratory Health in Elite Swimmers – A systematic approach to optimize total airway health. In: American College of Sports Medicine Annual Conference (May 2017). Available at: https://journals.lww.com/acsm-msse/Fulltext/2017/05001/Maximizing_Respiratory_Health_In_Elite_Swimmers__.933.aspx.
  • 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.
  • Hopker, J. and Passfield, L. (2016). Modelling of Cycling Power Output Data and its applicability for anti-doping. In: Science & Cycling 2016.
  • Jackson, A., Hopker, J. and Dickinson, J. (2016). Exercise-Induced Bronchoconstriction: Impact on Health and Performance. In: XXV International Conference on Sports Rehabilitation and Traumatology. Football Medicine Strategies. Return to Play. Available at: http://www.footballmedicinestrategies.com/all/doc/upl/s1/RTP%202016%20-%20Abstract%20Book.pdf.

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.
  • 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.

Forthcoming

  • Bossi, A., Mesquida, C., Passfield, L., Rønnestad, B. and Hopker, J. (2019). Optimizing interval training through power output variation within the work intervals. International Journal of Sports Physiology and Performance [Online]. Available at: https://doi.org/10.1123/ijspp.2019-0260.
    Maximal oxygen uptake (V̇O2max) is a key determinant of endurance performance. Therefore, devising high-intensity interval training (HIIT) that maximizes stress of the oxygen transport and utilization systems may be important to stimulate further adaptation in athletes. We compared physiological and perceptual responses elicited by work intervals matched for duration and mean power output, but differing in power output distribution. Methods. Fourteen cyclists (V̇O2max: 69.2 ± 6.6 ml·kg-1·min-1) completed three laboratory visits for a performance assessment and two HIIT sessions using either varied- or constant-intensity work intervals. Results. Cyclists spent longer time at >90%V̇O2max during HIIT with varied-intensity work intervals (410 ± 207 vs. 286 ± 162 s; P = 0.02), but there were no differences between sessions in heart rate- or perceptual-based training load metrics (all P ≥ 0.1). When considering individual work intervals, minute ventilation (V̇E) was higher in the varied-intensity mode (F = 8.42; P = 0.01), but not respiratory frequency, tidal volume, blood lactate concentration [La], ratings of perceived exertion, or cadence (all F ≤ 3.50; P ≥ 0.08). Absolute changes (Δ) between HIIT sessions were calculated per work interval, and Δ total oxygen uptake was moderately associated with ΔV̇E (r = 0.36; P = 0.002). Conclusions. In comparison to a HIIT session with constant-intensity work intervals, well-trained cyclists sustain higher fractions of V̇O2max when work intervals involve power output variations. This effect is partially mediated by an increased oxygen cost of hyperpnoea, and not associated with a higher [La], perceived exertion or training load metrics.
  • Fennell, C. (2019). The Impact of Recovery Interval Duration and Intensity on the Acute Physiological Responses to Interval Training During Cycling Exercise.
    The current thesis aimed to investigate the impact of the recovery interval duration and intensity on the acute physiological and perceptual responses to high intensity interval training (HIIT) during cycling exercise. Two studies were completed to examine the effects of the recovery interval duration and intensity in isolation. In Study One, sixteen participants completed a 6 x 4-min and 3 x 8-min HIIT session twice, with a standardised (STD) and individualised (IND) recovery duration based upon a resolution of muscle oxygen consumption (mV̇O2) to pre-exercise levels. In Study Two, fourteen participants completed a 6 x 4-min and 3 x 8-min HIIT session three times, with a passive (PA) and two active (ACT) recovery intensities. Results of Study One found there were no significant differences between the IND and STD recovery durations for any of the physiological or performance parameters assessed. Study Two results demonstrated that ACT recovery intensities increased the overall accumulation of central and peripheral physiological stress, without increasing the total training time commitment of the HIIT session, when compared to PA recovery intensity. Recovery intensity did not affect the time spent above 90 and 95% of V̇O2max during the HIIT sessions. In conclusion, full recovery of mV̇O2 and a return of the exercising muscle to metabolic homeostasis may not be required to maintain work interval performance and to generate the desired acute physiological responses during HIIT. Moreover, evidence within this thesis highlights the importance of the optimisation of the recovery interval components to the specific individual and HIIT protocol when seeking to maximising the training stimulus, and time efficiency of the training session. However, at present, the 2:1 work recovery ratio and a moderate ACT recovery intensity appear to be the most practical recovery component prescription when programming the recovery intervals during long work interval HIIT across a broad range of individuals.
  • Jackson, A., Hull, J., Hopker, J. and Dickinson, J. (2017). Diagnosing Exercise Induced Bronchoconstriction: A comparison of Eucapnic Voluntary Hyperpnoea and Exercise in low humidity. In: American College of Sports Medicine Annual Conference (May 2017).
    In athletic individuals, a secure diagnosis of exercise-induced bronchoconstriction (EIB) is dependent on objective testing. Indirect bronchoprovocation testing is often used in this context and eucapnic voluntary hyperpnea (EVH) testing is recommended for this purpose, yet the short-term reproducibility of EVH is yet to be appropriately established. The aim of this study was to evaluate the reproducibility of EVH in a cohort of recreational athletes. A cohort of recreational athletes (n = 32) attended the laboratory on two occasions to complete an EVH challenge, separated by a period of 14 or 21 days. Spirometry and impulse oscillometry was performed before and after EVH. Training load was maintained between visits. Prechallenge lung function was similar at both visits (P > .05). No significant difference was observed in maximum change in FEV1 (?FEV1max) after EVH between visits (P > .05), and test-retest ?FEV1max was correlated (intraclass correlation coefficient = 0.81; r(2) = 0.66; P = .001). Poor diagnostic reliability was observed between tests; 11 athletes were diagnosed with EIB (on the basis of ?FEV1max ?10%) at visit 1 and at visit 2. However, only 7 athletes were positive at both visits. Although there was a small mean difference in ?FEV1max between tests (-0.6%), there were wide limits of agreement (-10.7% to 9.5%). Likewise, similar results were observed for impulse oscillometry between visits. In a cohort of recreational athletes, EVH demonstrated poor clinical reproducibility for the diagnosis of EIB. These findings highlight a need for caution when confirming or refuting EIB on the basis of a single indirect bronchoprovocation challenge. When encountering patients with mild or borderline EIB, we recommend that more than one EVH test is performed to exclude or confirm a diagnosis. Copyright © 2014 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.

    Diagnosing Exercise-Induced Bronchoconstriction With Eucapnic Voluntary Hyperpnea: Is One Test Enough? | Request PDF. Available from: https://www.researchgate.net/publication/268924411_Diagnosing_Exercise-Induced_Bronchoconstriction_With_Eucapnic_Voluntary_Hyperpnea_Is_One_Test_Enough [accessed Sep 26 2018].
  • Jackson, A., Greenwell, J., Hopker, J., Hull, J. and Dickinson, J. (2016). Total Airway Health in Elite Swimmers. Allergy.
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