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General Neural Process in Cycling Exercise
Abstract
Performance in cycling is frequently related to metabolic or biomechanical factors. Overall, the contribution of the neurophysiological
system during cycling is often poorly considered in performance optimization. Yet, cycling is a complex
whole-body physical exercise that necessitates specific coordination and fine control of motor output to manage the different
intensities. The ability to produce different levels of intensity of exercise would require optimizing many functions
of the central nervous system from the brain’s treatment of sensory signals to complex motor command execution via the
corticospinal pathway. This review proposes an integrative approach to the factors that could influence cycling performance,
based on neurophysiological and cognitive markers. First, we report data relying on brain activity signals, to account for
the different brain areas and cognitive functions involved. Then, because the motor command is highly dependent upon its
regulation along the corticospinal pathway, we expose the modulation of corticospinal and spinal excitabilities during cycling.
We present these later by reviewing the literature of studies using transcranial magnetic or percutaneous nerve stimulations.
Finally, we describe a model of neural and cognitive adjustments that occur with acute and chronic cycling practices, with
several areas of improvement focusing on these factors, including mental and cognitive training.
Background
Information on acute traumatic cycling injuries (ATCIs) in the 12 months prior to entry in a cycling race and the predisposing factors have not been well-researched.
Objective
Determine factors associated with a history of ATCIs sustained in the previous 12 months by race entrants of a 109 km cycling race.
Methods
Descriptive, cross-sectional study on 60 941 Cape Town Cycle Tour race entrants from 2016 to 2020. Data on a history of ATCIs sustained in the previous 12 months were obtained through an online pre-race medical screening questionnaire (mandatory in 2016, and voluntary in 2017–2020). Factors investigated were demographics, cycling/training history and history of chronic disease, collapse, cramping, allergies and regular chronic prescription medication usage. We calculated the prevalence ratio (PR) for reporting a history of an ATCI in the previous 12 months for each category (multiple regression model).
Results
Factors associated with an increased PR for a history of ATCIs gathered from race entrants (34% of the total entrants) were: increased years of participation in distance cycling events >2 hours (PR=1.05 per 5 years of distance cycling, p<0.0001), increased weekly average training/racing distance of a cyclist in the past 12 months (PR=1.11 per 50 km increase in weekly cycling). Other factors were: increased number of chronic diseases reported (PR=1.53, per two additional chronic diseases reported, p<0.0001), history of collapse (PR=1.75, p=0.0005), history of cramping (PR=1.65, p<0.0001) and history of allergies (PR=1.49, p<0.0001).
Conclusions
Subgroups of recreational cyclists at higher risk for ATCIs were identified. This information could assist in developing and implementing future strategies to mitigate ATCIs.
This study aimed to investigate the relationship between neural efficiency and the ability of an athlete to produce accurate efforts in different perceived intensity zones during a racing scenario. The α/β ratio was used to quantify the neural efficiency during cycling, as it traduced the degree of participants information processing activity with lower cortical activity possible. Twelve trained competitive male cyclists delimited their perceived intensity zones 2 to 6 on a scale to assess the rating of exercise intensity. Then, they performed a 30 min racing scenario during which they had to produce different perceived intensities. The ability of athletes to produce perceived effort with accuracy and their neural efficiency was quantified during the racing scenario. The increase in the neural efficiency with the increase in the effort intensity could partly explain the improvement in athletes’ ability to produce accurately perceived efforts from intensity zones 3 to 6. Moreover, the neural efficiency during the racing scenario was significantly correlated to the ability to produce perceived effort with accuracy at submaximal intensities.
Although endurance running (ER) seems to be a simple repetitive exercise, good ER performance also requires and relies on multiple cognitive and motor control processes. Most of previous neuroimaging studies on ER were conducted by using a single MRI modality, yet no multimodal study to our knowledge has been performed in this regard. In this study, we used multimodal MRI data to investigate the brain structural and functional differences between endurance runners (n=22; age = 26.27 ± 6.07 years; endurance training = 6.23 ± 2.41 years) and healthy controls (HCs; n =20; age = 24.60 ± 4.14 years). Compared with the HCs, the endurance runners showed
greater gray matter volume (GMV) and cortical surface area in the left precentral gyrus, which at the same time had higher functional connectivity (FC) with the right postcentral and precentral gyrus. Subcortically, the endurance runners showed greater GMV in the left hippocampus and regional inflation in the right hippocampus. Using the bilateral hippocampi as seeds, further seed-based FC analyses showed higher hippocampal FC with the supplementary motor area, middle cingulate cortex, and left posterior lobe of the cerebellum. Moreover, compared with the HCs, the endurance runners also showed higher fractional anisotropy in several white matter regions, involving the corpus callosum, left internal capsule, left corona radiata, left external capsule, left posterior lobe of cerebellum and bilateral precuneus. Taken together, our findings provide several lines of evidence for the brain structural and functional differences between endurance runners and HCs. The current data suggest that these
brain characteristics may have arisen as a result of regular ER training, however, whether they represent the neural correlates underlying the good ER performances of the endurance runners requires further investigations.
Immersive technologies in transport research are gaining popularity, allowing for data collection in a controlled dynamic setting. Nonetheless, their ecological validity is still to be established hence their use in mathematical modelling in a transport setting has been scarce. We aim to fill this gap by conducting a study of cycling behaviour where non-immersive and immersive presentation methods are used in a virtual reality setting. The results confirm our hypothesis that participants behave differently when shown a choice scenario in non-immersive and immersive settings. In particular, cycling in an immersive setting is characterised by a higher degree of engagement. We also captured neural activity during task performance. We focussed on oscillations in the alpha (α) band where we found increased suppression in this signal in response to the immersive condition relative to the non-immersive. These results complement the behavioural findings and indicate that immersive environments may increase levels of task-engagement.
The fact that a single bout of acute physical exercise has a positive impact on cognition is well-established in the literature, but the neural correlates that underlie these cognitive improvements are not well understood. Here, the use of neuroimaging techniques, such as functional magnetic resonance imaging (fMRI), offers great potential, which is just starting to be recognized. This review aims at providing an overview of those studies that used fMRI to investigate the effects of acute physical exercises on cerebral hemodynamics and cognition. To this end, a systematic literature survey was conducted by two independent reviewers across five electronic databases. The search returned 668 studies, of which 14 studies met the inclusion criteria and were analyzed in this systematic review. Although the findings of the reviewed studies suggest that acute physical exercise (e.g., cycling) leads to profound changes in functional brain activation, the small number of available studies and the great variability in the study protocols limits the conclusions that can be drawn with certainty. In order to overcome these limitations, new, more well-designed trials are needed that (i) use a more rigorous study design, (ii) apply more sophisticated filter methods in fMRI data analysis, (iii) describe the applied processing steps of fMRI data analysis in more detail, and (iv) provide a more precise exercise prescription.
Background
Core affect is defined as the most general affective construct consciously accessible that is experienced constantly. It can be experienced as free-floating (mood) or related to prototypical emotional episodes. The aim of this study was to examine the influence of pleasant and unpleasant core affect on cyclo-ergometer endurance performance. Specifically, we considered the influence of pleasant and unpleasant core affect on performance outcomes (i.e., time to task completion) and rate of perceived exertion (RPE; Borg Scale, category ratio-10) collected during the task.
Methods
Thirty-one participants aged 20–28 years were recruited. Core affect was randomly elicited by 2 sets of pleasant and unpleasant pictures chosen from the international affective picture system. Pictures were displayed to participants during a cyclo-ergometer performance in 2 days in a counterbalanced order. RPE was collected every minute to detect volunteers’ exhaustion.
Results
The study sample was split into 2 groups. Group 1 comprised participants who performed better with pleasant core affect, whereas Group 2 included participants who performed better with unpleasant core affect. Mixed between-within subjects analysis of variance revealed a significant 2 (group) × 2 (condition) × 5 (isotime) interaction (p = 0.002, ηp² = 0.158). Post hoc comparisons showed that participants who obtained better performance with pleasant core affect (pleasant pictures; Group 1) reported lower RPE values at 75% of time to exhaustion in a pleasant core affect condition compared to an unpleasant core affect condition. On the other hand, participants who obtained better performance with unpleasant core affect (unpleasant pictures; Group 2) reported lower RPE values at 75% and 100% of time to exhaustion in an unpleasant core affect condition.
Conclusion
Findings suggest differential effects of pleasant and unpleasant core affect on performance. Moreover, core affect was found to influence perceived exertion and performance according to participants’ preferences for pleasant or unpleasant core affect.
Electroencephalography research surrounding maximal exercise testing has been limited to male subjects. Additionally, studies have used open-looped protocols, meaning individuals do not know the exercise endpoint. Closed-loop protocols are often shown to result in optimal performance as self-pacing is permitted. The purpose of this study was to compare brain activity during open- and closed-loop maximal exercise protocols, and to determine if any sex differences are present. Twenty-seven subjects (12 males, ages 22.0 ± 2.5 years) participated in this study. A pre-assembled EEG sensor strip was used to collect brain activity from specific electrodes (F3/F4: dorsolateral prefrontal cortex, or dlPFC; and C3/Cz/C4: motor cortex, or MC). Alpha (8–12 Hz) and beta (12–30 Hz) frequency bands were analyzed. Subjects completed two maximal exercise tests on a cycle ergometer, separated by at least 48 h: a traditional, open-loop graded exercise test (GXT) and a closed-loop self-paced VO2max (SPV) test. Mixed model ANOVAs were performed to compare power spectral density (PSD) between test protocols and sexes. A significant interaction of time and sex was shown in the dlPFC for males, during the GXT only (p = 001), where a peak was reached and then a decrease was shown. A continuous increase was shown in the SPV. Sex differences in brain activity during exercise could be associated with inhibitory control, which is a function of the dlPFC. Knowledge of an exercise endpoint could be influential towards cessation of exercise and changes in cortical brain activity.
It is well known that endurance exercise modulates the cardiovascular, pulmonary, and musculoskeletal system. However, knowledge about its effects on brain function and structure is rather sparse. Hence, the present study aimed to investigate exercise-dependent adaptations in neurovascular coupling to different intensity levels in motor-related brain regions. Moreover, expertise effects between trained endurance athletes (EA) and active control participants (ACP) during a cycling test were investigated using multi-distance functional near-infrared spectroscopy (fNIRS). Initially, participants performed an incremental cycling test (ICT) to assess peak values of power output (PPO) and cardiorespiratory parameters such as oxygen consumption volume (VO2max) and heart rate (HRmax). In a second session, participants cycled individual intensity levels of 20, 40, and 60% of PPO while measuring cardiorespiratory responses and neurovascular coupling. Our results revealed exercise-induced decreases of deoxygenated hemoglobin (HHb), indicating an increased activation in motor-related brain areas such as primary motor cortex (M1) and premotor cortex (PMC). However, we could not find any differential effects in brain activation between EA and ACP. Future studies should extend this approach using whole-brain configurations and systemic physiological augmented fNIRS measurements, which seems to be of pivotal interest in studies aiming to assess neural activation in a sports-related context.
Background: We examined corticospinal and spinal excitability across multiple power outputs during arm cycling using a weak and strong stimulus intensity. Methods: We elicited motor evoked potentials (MEPs) and cervicomedullary motor evoked potentials (CMEPs) in the biceps brachii using magnetic stimulation over the motor cortex and electrical stimulation of corticospinal axons during arm cycling at six different power outputs (i.e., 25, 50, 100, 150, 200 and 250 W) and two stimulation intensities (i.e., weak vs. strong). Results: In general, biceps brachii MEP and CMEP amplitudes (normalized to maximal M-wave (Mmax)) followed a similar pattern of modulation with increases in cycling intensity at both stimulation strengths. Specifically, MEP and CMEP amplitudes increased up until ~150 W and ~100 W when the weak and strong stimulations were used, respectively. Further increases in cycling intensity revealed no changes on MEP or CMEP amplitudes for either stimulation strength. Conclusions: In general, MEPs and CMEPs changed in a similar manner, suggesting that increases and subsequent plateaus in overall excitability are likely mediated by spinal factors. Interestingly, however, MEP amplitudes were disproportionately larger than CMEP amplitudes as power output increased, despite being initially matched in amplitude, particularly with strong stimulation. This suggests that supraspinal excitability is enhanced to a larger degree than spinal excitability as the power output of arm cycling increases.
Introduction The brain plays a key role in the perceptual regulation of exercise, yet neuroimaging techniques have only demonstrated superficial brain areas responses during exercise, and little is known about the modulation of the deeper brain areas at different intensities.
Objectives/methods Using a specially designed functional MRI (fMRI) cycling ergometer, we have determined the sequence in which the cortical and subcortical brain regions are modulated at low and high ratings perceived exertion (RPE) during an incremental exercise protocol.
Results Additional to the activation of the classical motor control regions (motor, somatosensory, premotor and supplementary motor cortices and cerebellum), we found the activation of the regions associated with autonomic regulation (ie, insular cortex) (ie, positive blood-oxygen-level-dependent (BOLD) signal) during exercise. Also, we showed reduced activation (negative BOLD signal) of cognitive-related areas (prefrontal cortex), an effect that increased during exercise at a higher perceived intensity (RPE 13–17 on Borg Scale). The motor cortex remained active throughout the exercise protocol whereas the cerebellum was activated only at low intensity (RPE 6–12), not at high intensity (RPE 13–17).
Conclusions These findings describe the sequence in which different brain areas become activated or deactivated during exercise of increasing intensity, including subcortical areas measured with fMRI analysis.
Long-term exercise interventions have been shown to be a potent trigger for both neurogenesis and vascular plasticity. However, little is known about the underlying temporal dynamics and specifically when exercise-induced vascular adaptations first occur, which is vital for therapeutic applications. In this study, we investigated whether a single session of moderate-intensity exercise was sufficient to induce changes in the cerebral vasculature. We employed arterial spin labeling magnetic resonance imaging to measure global and regional cerebral blood f low (CBF) before and after 20 min of cycling. The blood vessels' ability to dilate, measured by cerebrovascular reactivity (CVR) to CO 2 inhalation, was measured at baseline and 25-min postexercise. Our data showed that CBF was selectively increased by 10-12% in the hippocampus 15, 40, and 60 min after exercise cessation, whereas CVR to CO 2 was unchanged in all regions. The absence of a corresponding change in hippocampal CVR suggests that the immediate and transient hippocampal adaptations observed after exercise are not driven by a mechanical vascular change and more likely represents an adaptive metabolic change, providing a framework for exploring the therapeutic potential of exercise-induced plasticity (neural, vascular, or both) in clinical and aged populations.
The purpose of this study was to evaluate corticospinal excitability to the biceps and triceps brachii during forward (FWD) and backward (BWD) arm cycling. Corticospinal and spinal excitability were assessed using transcranial magnetic stimulation and transmastoid electrical stimulation to elicit motor evoked potentials (MEPs) and cervicomedullary evoked potentials (CMEPs), respectively. MEPs and CMEPs were recorded from the biceps and triceps brachii during FWD and BWD arm cycling at 2 positions, 6 and 12 o’clock. The 6 o’clock position corresponded to mid-elbow flexion and extension during FWD and BWD cycling, respectively, while 12 o’clock corresponded to mid-elbow extension and flexion during FWD and BWD cycling, respectively. During the flexion phase, MEP and CMEP amplitudes of the biceps brachii were higher during FWD cycling. However, during the extension phase, MEP and CMEP amplitudes were higher during BWD cycling. For the triceps brachii, MEP amplitudes were higher during FWD cycling regardless of phase. However, CMEP amplitudes were phase-dependent. During the flexion phase, CMEPs of the triceps brachii were higher during FWD cycling compared with BWD, but during the extension phase CMEPs were higher during BWD cycling compared with FWD. The data suggest that corticospinal and spinal excitability to the biceps brachii is phase- and direction-dependent. In the triceps brachii, spinal, but not corticospinal, excitability is phase-dependent when comparing FWD and BWD cycling.
NoveltyThis is the first study to assess corticospinal excitability during FWD and BWD locomotor output.
Corticospinal excitability during arm cycling depends on the direction, phase, and muscle being assessed.
What is the topic of this review? The origin, interpretation and methodological constraints of the silent period induced by transcranial magnetic stimulation are reviewed.
What advances does it highlight? The silent period is generated by both cortical and spinal mechanisms. Therefore, it seems inappropriate to preface silent period with ‘cortical’ unless additional measures are employed. Due to many confounding variables, a standardised approach to the silent period measurement cannot be suggested. Rather, recommendations of best practice are provided based on the available evidence and the context of the research question.
Transcranial magnetic stimulation of the motor cortex evokes a response in the muscle that can be recorded via electromyography (EMG). One component of this response, when elicited during a voluntary contraction, is a period of EMG silence, termed the silent period (SP), which follows a motor evoked potential (MEP). Modulation of SP duration was long thought to reflect the degree of intracortical inhibition. However, the evidence presented in this review suggests that both cortical and spinal mechanisms contribute to generation of the SP, which makes prefacing SP with ‘cortical’ misleading. Further investigations with multi‐methodological approaches, such as TMS‐EEG coupling or interaction of TMS with neuroactive drugs, are needed to make such inferences with greater confidence. A multitude of methodological factors can influence SP and thus confound the interpretation of this measure; namely, background muscle activity, instructions given to the participant, stimulus intensity and the size of the MEP preceding the SP, and the approach to analysis. A systematic understanding of how the confounding factors influence the interpretation of SP is lacking, making standardisation of the methodology difficult to conceptualise. Rather, the methodology should be guided through the lens of the research question and the population studied, ensuring greater reproducibility, repeatability and comparability of datasets. Recommendations are provided for the best practice within a given context of the experimental design.
It is understood that withholding information during exercise can alter performance during self-paced exercise, though less is known about neural activity during such exercise. The aim of this study was to compare the effects of withholding versus providing distance feedback on perception, muscular activation, and cerebral activity during cycling time trials (TT). Nine well-trained male cyclists randomly completed 2 x 30-km TT, with provision of performance information and distance feedback (known; KTT), and without performance information and remaining distance (unknown; UTT). Prefrontal cortex (PFC) hemoglobin concentration, electroencephalogy (EEG) responses of the parietal lobe (PL) and motor cortex (MC), and surface electromyogram (EMG) of the right thigh were monitored throughout the TTs, in addition to heart rate (HR), rating of perceived exertion (RPE), and power output (PO). Time to completion was shorter for the KTT compared to UTT (51.04 ± 3.26 vs. 49.25 ± 3.57 min, P = 0.01). There were no differences evident for RPE between conditions (P > 0.50). However, during the final 2 km, the KTT presented higher PO (P ≤ 0.05), HR (P = 0.03) and MC, and PL EEG activity (d = 0.51-0.71) in addition to increased tissue hemoglobin index (nTHI) and oxygen extraction (HHb) (d = 0.55-0.65) compared to the UTT. In conclusion, when withholding information pertaining to remaining distance, performance was reduced due to the application of a conservative pacing strategy. In addition, the increase in HHb across the PFC was strongly correlated with PO (r = 0.790; P < 0.001) suggesting knowledge about remaining distance may increase activation across the PFC. Further, it appears that changes within the PFC may play a role in the regulation of cycling performance.
Key points
While a consensus has now been reached on the effect of motor imagery (MI) – the mental simulation of an action – on motor cortical areas, less is known about its impact on spinal structures.
The current study, using H‐reflex conditioning paradigms, examined the effect of a 20 min MI practice on several spinal mechanisms of the plantar flexor muscles.
We observed modulations of spinal presynaptic circuitry while imagining, which was even more pronounced following an acute session of MI practice.
We suggested that the small cortical output generated during MI may reach specific spinal circuits and that repeating MI may increase the sensitivity of the spinal cord to its effects.
The short‐term plasticity induced by MI practice may include spinal network modulation in addition to cortical reorganization.
Abstract
Kinesthetic motor imagery (MI) is the mental simulation of a movement with its sensory consequences but without its concomitant execution. While the effect of MI practice on cortical areas is well known, its influence on spinal circuitry remains unclear. Here, we assessed plastic changes in spinal structures following an acute MI practice. Thirteen young healthy participants accomplished two experimental sessions: a 20 min MI training consisting of four blocks of 25 imagined maximal isometric plantar flexions, and a 20 min rest (control session). The level of spinal presynaptic inhibition was assessed by conditioning the triceps surae spinal H‐reflex with two methods: (i) the stimulation of the common peroneal nerve that induced D1 presynaptic inhibition (HPSI response), and (ii) the stimulation of the femoral nerve that induced heteronymous Ia facilitation (HFAC response). We then compared the effects of MI on unconditioned (HTEST) and conditioned (HPSI and HFAC) responses before, immediately after and 10 min after the 20 min session. After resting for 20 min, no changes were observed on the recorded parameters. After MI practice, the amplitude of rest HTEST was unchanged, while HPSI and HFAC significantly increased, showing a reduction of presynaptic inhibition with no impact on the afferent‐motoneuronal synapse. The current results revealed the acute effect of MI practice on baseline spinal presynaptic inhibition, increasing the sensitivity of the spinal circuitry to MI. These findings will help in understanding the mechanisms of neural plasticity following chronic practice.
Pacing during exercise performance is well-established; however, little is known about the neural responses associated with changes in power output and the effect of exercise end-point knowledge. Therefore, the aim of this study was to examine the effect of deception of cycling distance on pacing, cerebral oxy- (O2Hb) and deoxy-haemoglobin concentrations, and alpha (α) wave activity. Ten well-trained male cyclists (23.7 ± 6.6 years) completed three cycling time trials (TT) on a stationary air-braked cycle ergometer and were informed the study was to examine the reliability of 3 × 30-km TT. Participants unknowingly completed three distances (24, 30, and 36 km) in a randomised order. Performance (power output; PO), physiological (heart rate; HR), perceptual (rating of perceived exertion; RPE), and neurological (O2Hb, HHb, and α activity) measures were recorded throughout each TT. Data were converted to a percentage relative to the total distance covered. At 100% completion, HR and PO were lower during the 36 km compared to the 30 km trial (P ≤ 0.01). Compared to the 24 km trial, α waves were reduced at 100% (effect size; ES = 1.01), while O2Hb was greater at 70% of completion in the 36 km trial (ES = 1.39). RPE was also higher for 36 km compared to 30-km trial at 80% and the 24-km trial at 10% and 40–100% of completion (P ≤ 0.02). We conclude that the increase in O2Hb and RPE during the 36-km trial, while a reduction in HR and PO is present, may indicate that the pre-frontal cortex may influence the regulation of exercise performance when deceived of the duration end-point by increasing perception of effort to reduce premature onset of physiological strain.
Recent psychophysiological models of endurance performance explained that pacing strategies and exercise intensity regulation influence cyclists' ability to produce high mean power output (PO) during time-trial. However, the relationships between these pacing strategies and psychological parameters of the athletes remain unknown.
Purpose:
The aims of this study were to 1) determine the impact of pacing strategies on cyclists' mean PO during an elite time-trial championship and 2) identify the relationships between these pacing strategies and psychological parameters.
Methods:
Mean power output, projected frontal area, attentional focus and pleasure were recorded for nine male cyclists during an official ITT national championship. Pacing regulations were quantified from PO using the new Exposure Variation Analysis (EVA), which determines times spent at adapted PO (APO) and inaccurate PO (IPO) for optimal constant pacing strategy. Relationships between mean PO, times spent at APO and IPO and psychological variables were analysed.
Results:
Significant relationships were found between mean PO and EVA pacing parameters (r2 from 0.56 to 0.86; p > 0.05). Time spent at IPO was negatively related to pleasure during the ITT (r = -0.746; p = 0.016). Conversely, time spent at APO was significantly related to cyclists' attentional focus (r = 0.827; p = 0.006).
Conclusions:
Mean PO during elite ITT is directly related to the athletes' ability to optimally regulate pace throughout the event. This pacing regulation is influenced by attentional focus and pleasure, underlining that coaches and athletes should devote greater attention to these psychological parameters in order to improve their performances.
This study investigated the effects of 9-week endurance cycling training on central fatigability and corticomotor excitability of the locomotor muscles. Fourteen healthy participants undertook three incremental fatiguing cycling tests to volitional exhaustion (EXH): (i) before training (PRE), (ii) after training at the same absolute power output as PRE (POSTABS) and (iii) after training at the same percentage of V̇O2max as PRE (POSTREL). At baseline (i.e. before cycling), every 5 min during cycling and immediately at EXH, a neuromuscular evaluation including a series of 5-s knee extensions at 100, 75 and 50% of maximal voluntary knee extension (MVC) was performed. During each contraction, transcranial magnetic and peripheral nerve stimuli were elicited to obtain motor evoked potential (MEP), silent period (SP) and compound muscle action potential (Mmax) and to calculate voluntary activation (VA). The MEP·Mmax⁻¹ ratio recorded from vastus lateralis at 100 and 50% MVC did not show any difference between conditions. At 75% MVC, MEP exhibited significantly lower values in POSTABS and POSTREL compared to PRE at baseline (P = 0.022 and P = 0.011, respectively) as well as at 25% of time to EXH of PRE (P = 0.022) for POSTREL. No adaptations, either at baseline or during cycling, were observed for VA and SPs. In conclusion, endurance training may result in some adaptations in the corticomotor responses when measured at rest or with low level of fatigue, yet these adaptations do not translate into attenuation of central fatigue at a similar cycling workload or at exhaustion.
The aim of this study was to examine EEG coherence before, during, and after time to exhaustion (TTE) trials in an endurance cycling task, as well as the effect of effort level and attentional focus (i.e., functional external, functional internal, and dysfunctional internal associative strategies−leading to Type 1, Type 2, and Type 3 performances) on brain functional connectivity. Eleven college-aged participants performed the TTE test on a cycle-ergometer with simultaneous EEG and rate of perceived exertion (RPE) monitoring. EEG data from 32 electrodes were divided into five effort level periods based on RPE values (Baseline, RPE 0-4, RPE 5-8, RPE 9-MAX, and Recovery). Within subjects RM-ANOVA was conducted to examine time to task completion across Type 1, Type 2, and Type 3 performance trials. RM-ANOVA (3 performance types × 5 effort levels) was also performed to compare the EEG coherence matrices in the alpha and beta bands for 13 pairs of electrodes (F3-F4, F3-P3, F4-P4, T7-T8, T7-P3, C3-C4, C3-P3, C4-P4, T8-P4, P3-P4, P3-O1, P4-O2, O2-O1). Significant differences were observed on TTE performance outcomes between Type 1 and Type 3, and between Type 2 and Type 3 performance states (p < 0.05), whereas Type 1 and Type 2 performance states did not differ. No significant main effects were observed on performance type (p > 0.05) for all frequency bands in any pair of electrodes of the coherence matrices. Higher EEG coherence values were observed at rest (Baseline) than during cycling (RPE 0–4, 5–8, 9–MAX) for all pairs of electrodes and EEG frequency bands irrespective of the type of performance (main effect of effort, p < 0.05). Interestingly, we observed a performance × effort interaction in C3–C4 in beta 3 band [F (4, 77) = 2.62, p = 0.038] during RPE 9-MAX for Type 3 performance as compared to Type 1 and Type 2 performances. These findings may have practical implications in the development of performance optimization strategies in cycling, as we found that focusing attention on a core component of the action could stimulate functional connectivity among specific brain areas and lead to enhanced performance.
Generally, in sports performance, the relationship between movement science and physiological function has been conducted integrating neuronal mechanism over the past decades. However, understanding those interaction between neural network and motor performance comprehensively in achieving optimal performance is still lacking, mainly in cycling. The purpose of this study was to discuss the issues in neuroscience related to brain activity, physiology and biomechanics in achieving optimal performance in cycling. As sports technology improves, more objective measurement can be demonstrated in solving specific issue in cycling, with optimization of performance as the main focus. In this review, the focus on brain activity will be based on the evaluation of the alpha and beta brainwaves as well as the alpha/beta ratio since they are biomarkers of EEG specifically related to cycling performance. Further in-depth understanding of the mechanism and interaction between brain activity, physiology and biomechanics in competitive cycling were acquired and discussed. Moreover, the biomarkers of brain activity related to cycling performance from previous studies were clearly identified and discussed and recommendations to be incorporated in future research were proposed.
The modulation of spinal cord excitability during rhythmic limb movement reflects the neuronal coordination underlying actions of the arms and legs. Integration of network activity in the spinal cord can be assessed by reflex variability between the limbs, an approach so far very little studied. The present work addresses this question by eliciting Hoffmann (H-) reflexes in both limbs to assess if common drive onto bilateral pools of motoneurons influence spinal cord excitability simultaneously or with a delay between sides. A cross-covariance (CCV) sequence between reflexes in both arms or legs was evaluated under conditions providing common drive bilaterally through voluntary muscle contraction and/or rhythmic movement of the remote limbs. For H-reflexes in the flexor carpi radialis (FCR) muscle, either contraction of the FCR or leg cycling induced significant reduction in the amplitude of the peak at the zero lag in the CCV sequence, indicating independent variations in spinal excitability between both sides. In contrast, for H-reflexes in the soleus (SO) muscle, arm cycling revealed no reduction in the amplitude of the peak in the CCV sequence at the zero lag. This suggests a more independent control of the arms compared with the legs. These results provide new insights into the organization of human limb control in rhythmic activity and the behavior of bilateral reflex fluctuations under different motor tasks. From a functional standpoint, changes in the co-variability might reflect dynamic adjustments in reflex excitability that are subsumed under more global control features during locomotion.
High-intensity exercise induces significant central and peripheral fatigue, however the effect of endurance training on these mechanisms of fatigue is poorly understood. We compared the effect of cycling endurance training of disparate intensities on high-intensity exercise endurance capacity and the associated limiting central and peripheral fatigue mechanisms. Twenty adults were randomly assigned to 6 weeks of either high-intensity interval training (HIIT, 6-8 × 5 min at halfway between lactate threshold and maximal oxygen uptake [50%Δ]) or volume matched moderate-intensity continuous training (CONT, ~60-80 min at 90% lactate threshold). Two time to exhaustion (TTE) trials at 50%Δ were completed pre- and post-training to assess endurance capacity; the two post-training trials were completed at the pre-training 50%Δ (same absolute intensity) and the 'new' post-training 50%Δ (same relative intensity). Pre- and post-exercise responses to femoral nerve and motor cortex stimulation were examined to determine peripheral and central fatigue, respectively. HIIT resulted in greater increases in TTE at the same absolute and relative intensities as pre-training (148% and 43%, respectively) compared with CONT (38% and -4%, respectively). Compared with pre-training, HIIT increased the level of potentiated quadriceps twitch reduction (-34% vs -43%, respectively) and attenuated the level of voluntary activation reduction (-7% vs -3%, respectively) following the TTE trial at the same relative intensity. There were no other training effects on neuromuscular fatigue development. This suggests that central fatigue resistance contributes to enhanced high-intensity exercise endurance capacity after HIIT by allowing greater performance to be extruded from the muscle. This article is protected by copyright. All rights reserved.
Executive functioning and attention require mental effort. In line with the resource conservation principle, we hypothesized that mental effort would be saved when individuals expected to exercise for a long period. Twenty-two study participants exercised twice on a cycle ergometer for 10 min at 60% of their maximal aerobic power, with the expectation of exercising for either 10 min or 60 min. Changes in activity in the right dorsolateral prefrontal cortex (rdlPFC) and right medial frontal cortex (rmPFC) were investigated by measuring oxyhemoglobin using near-infrared spectroscopy. Attentional focus and ratings of perceived exertion were assessed at three time points (200, 400, and 600 s). The oxyhemoglobin concentration was lower in the rdlPFC and higher in the rmPFC under the 60-min than under the 10-min condition. Also, attention was less focused in the 60-min than in the 10-min condition. We discuss these results as possible evidence of a disengagement of the brain regions associated with mental effort (executive network), in favor of brain regions linked to resting activity (the default network), in order to save mental resources for the maintenance of exercise.
Objective:
To investigate the influence of group III/IV muscle afferents on the development of central fatigue and corticospinal excitability during exercise.
Methods:
Fourteen males performed cycling-exercise both under control-conditions (CTRL) and with lumbar intrathecal fentanyl (FENT) impairing feedback from leg muscle afferents. Transcranial magnetic- and cervicomedullary stimulation was used to monitor cortical versus spinal excitability.
Results:
While fentanyl-blockade during non-fatiguing cycling had no effect on motor-evoked potentials (MEPs), cervicomedullary-evoked motor potentials (CMEPs) were 13±3% higher (P<0.05), resulting in a decrease in MEP/CMEP (P<0.05). Although the pre- to post-exercise reduction in resting twitch was greater in FENT vs. CTRL (-53±3% vs. -39±3%; P<0.01), the reduction in voluntary muscle activation was smaller (-2±2% vs. -10±2%; P<0.05). Compared to the start of fatiguing exercise, MEPs and CMEPs were unchanged at exhaustion in CTRL. In contrast, MEPs and MEP/CMEP increased 13±3% and 25±6% in FENT (P<0.05).
Conclusion:
During non-fatiguing exercise, group III/IV muscle afferents disfacilitate, or inhibit, spinal motoneurons and facilitate motor cortical cells. In contrast, during exhaustive exercise, group III/IV muscle afferents disfacilitate/inhibit the motor cortex and promote central fatigue.
Significance:
Group III/IV muscle afferents influence corticospinal excitability and central fatigue during whole-body exercise in humans.
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 randomised 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 10 min at 2.0 mA, 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 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 MVC significantly decreased after the TTE (P < 0.05) whilst 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.
Exercise-induced fatigue influences the excitability of the motor pathway during single-joint isometric contractions. This study sought to investigate the influence of fatigue on corticospinal excitability during cycling-exercise. Eight males performed fatiguing constant-load (80% Wpeak, 241±13W) cycling to exhaustion during which the percent increase in quadriceps electromyography [∆EMG; vastus-lateralis (VL) and rectus-femoris (RF)] was quantified. During a separate trial, subjects performed two brief (~45-s) non-fatiguing cycling bouts (244±15W and 331±23W) individually chosen to match the ∆EMG across bouts to that observed during fatiguing cycling. Corticospinal excitability during exercise was quantified by transcranial magnetic, electric transmastoid, and femoral nerve stimulation to elicit motor-evoked potentials (MEP), cervicomedullary-evoked potentials (CMEP), and M-waves in the quadriceps. Peripheral and central fatigue were expressed as pre- to post-exercise reductions in quadriceps twitch-force (∆Qtw) and voluntary quadriceps activation (∆VA). While non-fatiguing cycling caused no measureable fatigue, fatiguing-cycling resulted in significant peripheral (ΔQtw: 42±6%) and central (ΔVA: 4±1%) fatigue. During non-fatiguing cycling, the area of MEPs and CMEPs, normalized to M-waves, similarly increased in the quadriceps (~40%, P<0.05). In contrast, there was no change in normalized MEPs or CMEPs during fatiguing-cycling. As a consequence, the MEP/CMEP ratio was unchanged during both trials (P>0.5). Therefore, although increases in muscle activation promote corticospinal excitability via motoneuronal facilitation during non-fatiguing cycling, this effect is abolished during fatigue. We conclude that the unaltered excitability of the corticospinal pathway from start of intense cycling exercise to exhaustion is, in part, determined by inhibitory influences on spinal motoneurons obscuring the facilitating effects of muscle activation.
Perception of effort, also known as perceived exertion or sense of effort, can be described as a cognitive feeling of work associated with voluntary actions. The aim of the present review is to provide an overview of what is perception of effort in Exercise Science. Due to the addition of sensations other than effort in its definition, the neurophysiology of perceived exertion remains poorly understood. As humans have the ability to dissociate effort from other sensations related to physical exercise, the need to use a narrower definition is emphasised. Consequently, a definition and some brief guidelines for its measurement are provided. Finally, an overview of the models present in the literature aiming to explain its neurophysiology, and some perspectives for future research are offered.
The main goal of the present study was to explore theta and alpha event-related desynchronization/synchronization (ERD/ERS) activity during shooting performance. We adopted the idiosyncratic framework of the multi-action plan (MAP) model to investigate different processing modes underpinning four types of performance. In particular, we were interested in examining the neural activity associated with optimal-automated (Type 1) and optimal-controlled (Type 2) performances.
Methods.
Ten elite shooters (6 male and 4 female) with extensive international experience participated in the study. ERD/ERS analysis was used to investigate cortical dynamics during performance. A 4 × 3 (performance types × time) repeated measures analysis of variance was performed to test the differences among the four types of performance during the three seconds preceding the shots for theta, low alpha, and high alpha frequency bands. The dependent variables were the ERD/ERS percentages in each frequency band (i.e., theta, low alpha, high alpha) for each electrode site across the scalp. This analysis was conducted on 120 shots for each participant in three different frequency bands and the individual data were then averaged.
Results.
We found ERS to be mainly associated with optimal-automatic performance, in agreement with the “neural efficiency hypothesis.” We also observed more ERD as related to optimal-controlled performance in conditions of “neural adaptability” and proficient use of cortical resources.
Discussion.
These findings are congruent with the MAP conceptualization of four performance states, in which unique psychophysiological states underlie distinct performance-related experiences. From an applied point of view, our findings suggest that the MAP model can be used as a framework to develop performance enhancement strategies based on cognitive and neurofeedback techniques.
Self-regulation reflects an individual's efforts to bring behavior and thinking into line with often consciously desired goals. During endurance activity, self-regulation requires an athlete to balance their speed or power output appropriately to achieve an optimal level of performance. Considering that both behavior and thinking are core elements of self-regulation, this article provides a cognitive perspective on the processes required for effective pace-regulation during endurance performance. We also integrate this viewpoint with physiological and performance outcomes during activity. As such, evidence is presented to suggest that what an athlete thinks about has an important influence on effort perceptions, physiological outcomes, and, consequently, endurance performance. This article also provides an account of how an athlete might control their cognition and focus attention during an endurance event. We propose that effective cognitive control during performance requires both proactive, goal-driven processes and reactive, stimulus-driven processes. In addition, the role of metacognition—or thinking about thinking—in pace-regulation will also be considered. Metacognition is an essential component of self-regulation and its primary functions are to monitor and control the thoughts and actions required for task completion. To illustrate these processes in action, a metacognitive framework of attentional focus and cognitive control is applied to an endurance performance setting: specifically, Bradley Wiggins' successful 2015 Hour record attempt in cycling. Finally, future perspectives will consider the potentially deleterious effects of the sustained cognitive effort required during prolonged and strenuous endurance tasks.
Purpose:
Effort sense has been suggested to be involved in the hyperventilatory response during intense exercise (IE). However, the mechanism by which effort sense induces an increase in ventilation during IE has not been fully elucidated. The aim of this study was to determine the relationship between effort-mediated ventilatory response and corticospinal excitability of lower limb muscle during IE.
Methods:
Eight subjects performed 3 min of cycling exercise at 75-85 % of maximum workload twice (IE1st and IE2nd). IE2nd was performed after 60 min of resting recovery following 45 min of submaximal cycling exercise at the workload corresponding to ventilatory threshold. Vastus lateralis muscle response to transcranial magnetic stimulation of the motor cortex (motor evoked potentials, MEPs), effort sense of legs (ESL, Borg 0-10 scale), and ventilatory response were measured during the two IEs.
Results:
The slope of ventilation (l/min) against CO2 output (l/min) during IE2nd (28.0 ± 5.6) was significantly greater than that (25.1 ± 5.5) during IE1st. Mean ESL during IE was significantly higher in IE2nd (5.25 ± 0.89) than in IE1st (4.67 ± 0.62). Mean MEP (normalized to maximal M-wave) during IE was significantly lower in IE2nd (66 ± 22 %) than in IE1st (77 ± 24 %). The difference in mean ESL between the two IEs was significantly (p < 0.05, r = -0.82) correlated with the difference in mean MEP between the two IEs.
Conclusions:
The findings suggest that effort-mediated hyperventilatory response to IE may be associated with a decrease in corticospinal excitability of exercising muscle.
During exercise, there is a progressive reduction in the ability to produce muscle forces. Processes within the nervous system, as well as within the muscles contribute to this fatigue. In addition to impaired function of the motor system, sensations associated with fatigue, and impairment of homeostasis can contribute to impairment of performance during exercise. This review discusses some of the neural changes that accompany exercise and the development of fatigue. The role of brain monoaminergic neurotransmitter systems in whole-body endurance performance is discussed, particularly with regard to exercise in hot environments. Next, fatigue-related alterations in the neuromuscular pathway are discussed in terms of changes in motor unit firing, motoneuron excitability and motor cortical excitability. These changes have mostly been investigated during single-limb isometric contractions. Finally, the small-diameter muscle afferents that increase firing with exercise and fatigue are discussed. These afferents have roles in cardiovascular and respiratory responses to exercise, and in impairment of exercise performance through interaction with the motor pathway, as well as providing sensations of muscle discomfort. Thus, changes at all levels of the nervous system including the brain, spinal cord, motor output, sensory input and autonomic function occur during exercise and fatigue. The mix of influences and the importance of their contribution varies with the type of exercise being performed.
Brain dynamics is at the basis of top performance accomplishment in sports. The search for neural biomarkers of performance remains a challenge in movement science and sport psychology. The non-invasive nature of high-density electroencephalography (EEG) recording has made it a most promising avenue for providing quantitative feedback to practitioners and coaches. Here, we review the current relevance of the main types of EEG oscillations in order to trace a perspective for future practical applications of EEG and event-related potentials (ERP) in sport. In this context, the hypotheses of unified brain rhythms and continuity between wake and sleep states should provide a functional template for EEG biomarkers in sport. The oscillations in the thalamo-cortical and hippocampal circuitry including the physiology of the place cells and the grid cells provide a frame of reference for the analysis of delta, theta, beta, alpha (incl.mu), and gamma oscillations recorded in the space field of human performance. Based on recent neuronal models facilitating the distinction between the different dynamic regimes (selective gating and binding) in these different oscillations we suggest an integrated approach articulating together the classical biomechanical factors (3D movements and EMG) and the high-density EEG and ERP signals to allow finer mathematical analysis to optimize sport performance, such as microstates, coherency/directionality analysis and neural generators.
Objectives
Few studies have directly investigated changes in cortical haemodynamics during a self-paced interval endurance activity, while collecting conscious cognition and physiological performance data. This pilot study used functional Near Infrared Spectroscopy (fNIRS), while capturing conscious cognition using Think Aloud (TA) during an incremental paced cycling exercise.
Methods
A mixed design was implemented with cycling expertise (untrained vs. trained) as the between groups variable and incremental self-paced stage (5 stages of increasing effort) and site (12 optodes across the PFC) as the within groups variables. Dependent measures were the changes in cortical O2Hb, and physiological indicators (% heart rate max (%HRmax), average power output (APO), peak power output (PPO), rate of perceived exertion (RPE) and blood lactate (Bla)) over time. Participants used TA throughout their second interval trial.
Results
Trained cyclists had higher APO and maximum power output (MPO) from stages 2 to 5, in addition to a greater increase in PPO over the whole trial. There were significant main effects of stage on %HRmax, Bla and RPE. Differences in cortical haemodynamics were found specifically in areas in the mid left and right PFC. TA data demonstrated that untrained participants verbalised more irrelevant information and feelings of pain and fatigue, in addition to both groups verbalising significantly more motivation-related thoughts during the final stage.
Conclusion
This pilot is the first to capture changes in Cox, physiological measures and conscious cognition through the use of TA. We demonstrate the potential role of mid- PFC, and how conscious cognition may change over time. This study has implications for coaches and sport psychologists who may want to understand the cognitions of their athlete during an event and support low level athletes in developing a better understanding of the own cognitions.
Purpose:
Previous studies report memory and functional connectivity of memory systems improve acutely after a single aerobic exercise session or with training, suggesting the acute effects of aerobic exercise may reflect initial changes that adapt over time. In this trial, for the first time, we test the proof-of-concept of whether the acute and training effects of aerobic exercise on working memory and brain network connectivity are related in the same participants.
Methods:
Cognitively normal older participants (N=34) were enrolled in a randomized clinical trial (NCT02453178). Participants completed fMRI resting state and a face working memory N-back task acutely after light and moderate intensity exercise and after a 12-week aerobic training intervention.
Results:
Functional connectivity did not change more after moderate compared with light intensity training. However, both training groups showed similar changes in cardiorespiratory fitness (maximal exercise oxygen uptake, VO2peak), limiting group-level comparisons. Acute effects of moderate intensity aerobic exercise on hippocampal-cortical connections in the default network predicted training enhancements in the same connections. Working memory also improved acutely, especially following moderate intensity, and greater acute improvements predicted greater working memory improvement with training. Exercise effects on functional connectivity of right lateralized fronto-parietal connections were related to both acute and training gains in working memory.
Conclusion:
Our data support the concept of acute aerobic exercise effects on functional brain systems and performance as an activity-evoked biomarker for exercise training benefits in the same outcomes. These findings may lead to new insights and methods for improving memory outcomes with aerobic exercise training.
International Journal of Exercise Science 12(3): 800-810, 2019. Electroencephalography (EEG) is a non-invasive method of measuring electrical activity of the brain during exercise. There is conflicting evidence as to how neural activity changes in relation to incremental exercise testing (IET), or if age has any effect. The purpose of this study was to determine 1) how brain activity changes throughout an IET, and 2) if age affects this response. 13 younger (age: 24.9 ± 2.6 years, 9 males) and 10 middle-aged (49.1 ± 3.2 years, 3 males) recreationally active individuals volunteered for this study. A self-paced, perceptually regulated IET was performed, while subjects wore an EEG electrode strip. Power spectral density (PSD) was calculated; alpha (8-13 Hz) and beta (13-30 Hz) activity from the prefrontal and motor cortices was compared to baseline measures. A one-way repeated-measures ANOVA with age as a between-subjects factor was used to determine the effect of test stage and age on PSD. Relative PSD in both the alpha and beta frequency bands increased with exercise intensity. In the prefrontal and motor cortices there was a main effect of stage (both p < .05), and PSD increased markedly at the end of the test. There was no difference between age groups (all p > .05). The lack of a downregulation in neural activity in the final stage of the test is in contrast to some studies but corroborates others. A likely cause for the differences between studies is exercise modality preference. There was no age effect, which may be due to the subjects used (middle-aged regular exercisers).
Objectives:
A growing body of research suggests that regular participation in long-term exercise is associated with enhanced cognitive function. However, less is known about the beneficial effects of acute exercise on semantic memory. This study investigated brain activation during a semantic memory task after a single session of exercise in healthy older adults using functional magnetic resonance imaging (fMRI).
Methods:
Using a within-subjects counterbalanced design, 26 participants (ages, 55-85 years) underwent two experimental visits on separate days. During each visit, participants engaged in 30 min of rest or stationary cycling exercise immediately before performing a Famous and Non-Famous name discrimination task during fMRI scanning.
Results:
Acute exercise was associated with significantly greater semantic memory activation (Famous>Non-Famous) in the middle frontal, inferior temporal, middle temporal, and fusiform gyri. A planned comparison additionally showed significantly greater activation in the bilateral hippocampus after exercise compared to rest. These effects were confined to correct trials, and as expected, there were no differences between conditions in response time or accuracy.
Conclusions:
Greater brain activation following a single session of exercise suggests that exercise may increase neural processes underlying semantic memory activation in healthy older adults. These effects were localized to the known semantic memory network, and thus do not appear to reflect a general or widespread increase in brain blood flow. Coupled with our prior exercise training effects on semantic memory-related activation, these data suggest the acute increase in neural activation after exercise may provide a stimulus for adaptation over repeated exercise sessions. (JINS, 2019, 00, 1-12).
Purpose:
To verify whether caffeine (CAF) could increase the prefrontal cortex (PFC) activation and improve 20 km cycling time trial (TT20km) performance in mentally fatigued cyclists.
Methods:
After preliminary TT20km, twelve recreational cyclists (VO2MAX of 58.9 ± 6.2 mL kg min-1) performed a familiarization with a cognitive test to induce mental fatigue (MF) and psychological scales. Thereafter, they performed: 2) a baseline TT20km; 3) a mentally fatigued TT20km (MF); 4 and 5) a mentally fatigued TT20km after CAF (MF + CAF) or placebo (MF + PLA) ingestion, in a double-blind, counterbalanced design. Performance and psychological responses were obtained throughout the TT20km, while PFC electroencephalography (EEG) theta wave was obtained before and after the mental fatigue test.
Results:
The mental fatigue-induced increase in EEG theta wave (↑ ~ 4.8%) was reverted with CAF (↓ 8.8%) and PLA ingestion (↓ 4.8%). CAF improved TT20km performance in mentally fatigued cyclists by reducing time (p = .00; ↓ ~ 1.7%) and increasing WMEAN (p = .00; ↑ ~ 3.6%), when compared to MF + PLA. The RPE-power output ratio was lower (p = .01), but affect (p = .018), motivation (p = .033) and emotional arousal (p = .001) were greater throughout the TT20km in MF + CAF than in MF + PLA.
Conclusions:
CAF ingestion improved TT20km performance and psychological responses in mentally fatigued cyclists, despite the unaltered PFC activation.
The locomotor role of meso-diencephalic dopaminergic (DA) neurons is traditionally associated with their ascending pathways to the basal ganglia, which project to the Mesencephalic Locomotor Region (MLR), a brainstem region controlling locomotion. However, descending DA projections to the MLR were recently reported in lamprey, where they promote locomotion through the activation of D1 receptors in the MLR. In rodents, the DA innervation of the MLR is conserved and originates from the substantia nigra pars compacta (A9) and medial zona incerta (A13). Intriguingly, the DA innervation of the MLR degenerates in a monkey model of Parkinson's disease. Here, we review the current knowledge on these newly uncovered descending DA pathways to brainstem circuits and discuss their possible roles in locomotor control.
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.
Understanding the interactions between brain activity and behavior comprehensively in achieving optimal exercise performance in sports is still lacking. The existent research in this area has been limited by the constraints of sports environments and the robustness of the most suitable non-invasive functional neuroimaging methods (electroencephalography, EEG and functional near-infrared spectroscopy, fNIRS) to motion artifacts and noise. However, recent advances in brain mapping technology should improve the capabilities of the future brain imaging devices to assess and monitor the level of adaptive cognitive-motor performance during exercise in sports environments. The purpose of this position manuscript is to discuss the contributions and issues in behavioral neuroscience related to brain activity measured during exercise and in various sports. A first part aims to give an overview of EEG and fNIRS neuroimaging methods assessing electrophysiological activity and hemodynamic responses of the acute and chronic relation of physical exercise on the human brain. Then, methodological issues, such as the reliability of brain data during physical exertion, key limitations and possible prospects of fNIRS and EEG methods are provided. While the use of such methods in sports environments remains scarce and limited to controlled cycling task, new generation of wearable, whole-scalp EEG and fNIRS technologies could open up a range of new applications in sports sciences for providing neuroimaging-based biomarkers (hemodynamic and/or neural electrical signals) to various types of exercise and innovative training.
Objective: Numerous previous studies have suggested that physical activity or exercise may play an important role in both structural integrity of the brain and cognitive function. However, it is unclear what effect exercise has on cognitive related brain structure. The present study comprehensively reviews the effect of exercise on cognitive related brain regions of the healthy elderly by using activation likelihood estimation (ALE).
Materials and methods: Seven electronic databases were searched for randomized controlled trials published up to September 2017. The quality of the selected studies was evaluated using the Cochrane Collaboration’s tool for assessing the risk of bias. GingerALE version 2.3.6 was used to perform the coordinate-based ALE meta-analysis.
Results and conclusions: Nine randomized controlled trials (RCTs) with 50 distinct foci were analyzed for structural changes, containing 412 healthy older subjects. ALE showed significant regional increases in regions including the left superior temporal gyrus, left medial temporal gyrus, left inferior frontal gyrus, right medial frontal gyrus, right and left superior frontal gyrus, left cingulate gyrus, right anterior cingulate and left lentiform nucleus in subjects with the exercise intervention compared to controls. However, considering the quantity and limitations of the included studies, the conclusion could not yet be drawn. Additional randomized controlled trials with rigorous designs and longer intervention periods are needed in the future.
The present study investigated whether changes in oxyhemoglobin (O2Hb) concentration over time differed across brain regions according to differences in gross movement intensity. Thirteen healthy adults (21.2 ± 1.0 years, 8 women) participated in this study. After 180 s of rest, the participants performed 600 s of exercise on a cycle ergometer. Exercise intensity was set at 30%VO2peak and 50%VO2peak. The prefrontal cortex (PFC) and primary motor cortex (M1) were chosen as regions of interest. In addition, mean arterial pressure (MAP) and scalp blood flow (SBF) were measured simultaneously. O2Hb concentration in PFC and M1 was significantly decreased in initial phase of the exercise, while it was significantly increased from the mid to final phase for both intensities compared with resting state values (p < 0.01). The O2Hb concentrations in the PFC and M1 were significantly decreased in the initial exercise phase. However, the MAP and SBF values did not exhibit a similar pattern. The main findings of our study were the follows: (1) During cycle ergometer exercise at the 30% and 50% O2Hb peak, the after O2Hb concentrations were transiently decreased in the initial exercise phase, and the concentrations then steadily increased in both the PFC and M1; and (2) the duration of the transient decreases in the O2Hb concentrations varied according to the brain region and exercise intensity.
Physical activity may play a role in both the prevention and slowing of brain volume loss and may be beneficial in terms of improving the functional connectivity of brain regions. But much less is known about the potential benefit of aerobic exercise for the structure and function of the default mode network (DMN) brain regions. This systematic review examines the effects of aerobic exercise on the structure and function of DMN brain regions in human adulthood. Seven electronic databases were searched for prospective controlled studies published up to April 2015. The quality of the selected studies was evaluated with the Cochrane Collaboration's tool for assessing the risk of bias. RevMan 5.3 software was applied for data analysis. Finally, 14 studies with 631 participants were identified. Meta-analysis revealed that aerobic exercise could significantly increase right hippocampal volume (SMD = 0.26, 95% CI 0.01 to 0.51, P = 0.04, I(2) = 7%, 4 studies), and trends of similar effects were observed in the total (SMD = 0.12, 95% CI -0.17 to 0.41, P = 0.43, I(2) = 0%, 5 studies), left (SMD = 0.12, 95% CI -0.13 to 0.37, P = 0.33, I(2) = 14%, 4 studies), left anterior (SMD = 0.12, 95% CI -0.16 to 0.40, P = 0.41, I(2) = 74%, 2 studies) and right anterior (SMD = 0.10, 95% CI -0.17 to 0.38, P = 0.46, I(2) = 76%, 4 studies) hippocampal volumes compared to the no-exercise interventions. A few studies reported that relative to no-exercise interventions, aerobic exercise could significantly decrease the atrophy of the medial temporal lobe, slow the anterior cingulate cortex (ACC) volume loss, increase functional connectivity within the hippocampus and improve signal activation in the cingulate gyrus and ACC. The current review suggests that aerobic exercise may have positive effects on the right hippocampus and potentially beneficial effects on the overall and other parts of the hippocampus, the cingulate cortex and the medial temporal areas of the DMN. Moreover, aerobic exercise may increase functional connectivity or activation in the hippocampus, cingulate cortex and parahippocampal gyrus regions of the DMN. However, considering the quantity and limitations of the included studies, the conclusion could not be drawn so far. Additional RCTs with rigorous designs and longer intervention periods are needed in the future.
Although elbow extensors (EE) have a great role in cross-country skiing (XC) propulsion, previous studies on neuromuscular fatigue in long-distance XC have investigated only knee extensor (KE) muscles. In order to investigate the origin and effects of fatigue induced by long-distance XC race, 16 well-trained XC skiers were tested before and after a 56-km classical technique race. Maximal voluntary isometric contraction (MVC) and rate of force development (RFD) were measured for both KE and EE. Furthermore, electrically evoked double twitch during MVC and at rest were measured. MVC decreased more in KE (-13%) than in EE (-6%, P = 0.016), whereas the peak RFD decreased only in EE (-26%, P = 0.02) but not in KE. The two muscles showed similar decrease in voluntary activation (KE -5.0%, EE -4.8%, P = 0.61) and of double twitch amplitude (KE -5%, EE -6%, P = 0.44). A long-distance XC race differently affected the neuromuscular function of lower and upper limbs muscles. Specifically, although the strength loss was greater for lower limbs, the capacity to produce force in short time was more affected in the upper limbs. Nevertheless, both KE and EE showed central and peripheral fatigue, suggesting that the origins of the strength impairments were multifactorial for the two muscles.
Purpose:
We tested the hypothesis that central and peripheral fatigue after constant-load cycling exercise would vary with exercise intensity and duration.
Methods:
Twelve, well-trained male cyclists (V[Combining Dot Above]O2max, 4.49±0.35 L·min) completed three constant-load cycling trials to the limit of tolerance in a randomized, crossover design. Exercise intensities were set according to the respiratory responses to a preliminary ramp test to elicit cardiorespiratory and metabolic responses consistent with exercise in the severe and heavy exercise domains; 1) at power at V[Combining Dot Above]O2max (S+, 379±31 W), 2) at 60% of the difference between gas exchange threshold and V[Combining Dot Above]O2max (S-, 305±23 W) and 3) at the respiratory compensation point (RCP, 254±26 W). Pre- and post-exercise twitch responses from the quadriceps to electrical stimulation of the femoral nerve and magnetic stimulation of the motor cortex were recorded to assess neuromuscular and corticospinal function, respectively.
Results:
Exercise time was 3.14±0.59 min, 11.11±1.86 min and 42.14±9.09 min for S+, S- and RCP respectively. All trials resulted in similar reductions in maximum voluntary force (P=0.61). However, the degree of peripheral fatigue varied in an intensity-dependent manner, with greater reductions in potentiated twitch force after S+ (-33±9%) compared to both S- (-16±9%, P<0.001) and RCP trials (-11±9%, P<0.001) and greater after S- compared to RCP (P<0.05). For central fatigue this trend was reversed, with smaller reductions in voluntary activation after S+ compared to RCP (-2.7±2.2% vs. -9.0±4.7%, P<0.01).
Conclusion:
These data suggest the magnitude of peripheral and central fatigue after locomotor cycling exercise is exacerbated with exercise intensity and duration, respectively.