149 research outputs found
Practitioner Perspectives on the Association Between Mental Fatigue and Injury Risk in High-Performance Sport: A Mixed Methods Study
No full textThis study aimed to investigate the perceptions of practitioners involved in injury management within high-performance sport on the potential interaction between mental fatigue and injury risk, including perceived mechanisms. A sequential explanatory design was used, with phase one implementing a cross-sectional survey and phase two utilising semi-structured interviews. An electronic survey of multi-disciplinary practitioners working in high-performance sport, specifically invasion-based team sports, was conducted. Topics included the mechanisms by which mental fatigue may influence risk of injury, potential sex differences, mental fatigue and injury prevention and areas for future research. Preliminary data analysis guided the development of the phase two interview schedule, which aimed to gain a deeper understanding of the association and perceived mechanisms. Forty-five participants completed the phase one survey, and eight participants completed the phase two semi-structured interviews. The primary findings of this study suggest that practitioners working in high-performance sport perceive a link between mental fatigue and risk of injury, primarily acute noncontact injuries. Proposed mechanisms include impaired motor control, poor biomechanics and reduced cognitive function. However, isolating mental fatigue as a direct factor is difficult, due to challenges distinguishing between mental and physical fatigue. The findings of this study indicate practitioners perceive an association between mental fatigue and risk of injury. Future research focused on the mechanisms linking mental fatigue to injury risk is required to empirically examine and determine the validity of this perception. However, athlete management strategies regarding mental fatigue may be incorporated into practice to potentially limit the risk of athlete injury.The practitioners who volunteered their time to complete the survey and semi‐structured interviews are thanked for their support and valuable insights. Bart Roelands is a Collen‐Francqui research professor and a member of the Strategic Research Programme Exercise and the Brain in Health and Disease: The Added Value of Human‐Centred Robotics (SRP77)
A shared robot control system combining augmented reality and motor imagery brain-computer interfaces with eye tracking
No full textThis research was made possible thanks to the EUTOIA alliance of universities supporting the PhD of AD and the Strategic Research Program 'Exercise and the Brain in Health and Disease: The Added Value of Human-Centered Robotics'. Bart Roelands is a Collen-Francqui research professor. We thank all the participants of the user study for their participation and for their motivation which ensured a thorough assessment of the capabilities of our control system. We also gratefully acknowledge the undergrad students and interns who assisted with the evaluation study
Subjective thermal strain impairs endurance performance in a temperate environment
No full textPurpose: The aim of this study was to test the hypothesis that subjective thermal strain can reduce endurance performance independently from the general physiological strain normally associated with impaired endurance performance in the heat. Methods: In 20 °C and 44% relative humidity, 12 endurance-trained athletes (1♀ 11♂; mean ± SD; age: 27 ± 6 y; VO 2max : 61 ± 6 ml/kg/min) performed a time to exhaustion (TTE) test in two different experimental conditions: with an electric heat pad applied to the subjects' upper back (HP) and control (CON: without heat pad). In both conditions, subjects cycled to volitional exhaustion at 70% of their VO 2max . Cardiorespiratory, metabolic, thermoregulatory and perceptual responses were measured throughout the TTE test and compared at 0%, 50% and 100% isotime and at exhaustion. Results: TTE was reduced by 9% in HP (2092 ± 305 s) compared to CON (2292 ± 344 s; p =.023). The main effect of condition on thermal discomfort at isotime (p =.002), the effect of condition on thermal sensation at 0% isotime (p =.004) and the condition by isotime interaction on rating of perceived exertion (p =.036) indicated higher subjective thermal strain in HP compared to CON. None of the measured cardiorespiratory, metabolic and thermoregulatory variables differed significantly between conditions. Conclusion: Our novel experimental manipulation (HP) was able to induce significant subjective thermal strain and reduce endurance performance in a temperate environment without inducing the general physiological strain normally associated with impaired endurance performance in the heat. These results suggest that subjective thermal strain is an important and independent mediator of the heat-induced impairment in endurance performance
Prolonged cognitive effort impairs inhibitory control and causes significant mental fatigue after an endurance session with an auditive distractor in professional soccer players
No full textBackground
Throughout official soccer matches, the presence of cheer by the crowd could be considered a critical auditive distraction that could further impair the cognitive interference control system, multiple object tracking (MOT) skill, heart rate variability (HRV), and increase mental fatigue. As the resource is not immediately replenished, the impairment of the cognitive interference control system may be delayed following a soccer game. Then, evaluating the recovery time course of the cognitive interference control system, MOT skill, HRV, and mental fatigue after prolonged tasks combining physical, endurance, and cognitive effort are essential.
Purpose
We aimed to analyze the acute effect of cognitive effort and auditive distractor with 24-h follow-up throughout a prolonged endurance session on inhibitory control, subjective mental fatigue, MOT skill, and HRV in professional soccer players.
Methods
Twenty professional male soccer players were recruited (23.56 ± 3.8 years, 78.1 ± 6.9 kg, 1.77 ± 0.06 m, and 12.5 ± 5.3% body fat). The sessions were performed in a randomized and counterbalanced crossover design, divided into four experimental conditions: endurance, endurance + MOT, endurance + MOT + AD, and endurance + AD. The soccer players completed the incongruent Stroop task utilizing an eye-tracker to assess cognitive effort. MOT task, subjective mental fatigue, and HRV were evaluated before the endurance training (60%Δ of maximal aerobic velocity during 40-min) and after 30-min and 24-h of recovery. These sessions were designed to investigate the acute effect of prolonged cognitive effort (repeated MOT throughout the endurance task) and AD (constant crowd noise and coach's voice each 15–40 s, totalizing = 80 voices) on inhibitory control, MOT skills, HRV, and subjective mental fatigue after a fixed endurance training session.
Results
There was no condition × time interaction for accuracy of inhibitory control (p > 0.05, ηp2 = 0.001). There was a significant condition × time interaction for inhibitory control response time (p < 0.05, ηp2 = 0.16). A higher response time of inhibitory control was found for the endurance + MOT + AD and endurance + MOT experimental sessions (p < 0.05). There was a significant condition × time interaction for subjective mental fatigue (p < 0.05, ηp2 = 0.46). A higher subjective mental fatigue was found for the endurance + MOT + AD and endurance + MOT experimental sessions (p < 0.05). There was no condition × time interaction for HRV (p > 0.05, ηp2 = 0.02).
Conclusion
We concluded that cognitive effort throughout a prolonged endurance session impaired inhibitory control and increased mental fatigue without promoting greater MOT skill and HRV changes in professional soccer players
A caffeine-maltodextrin mouth rinse counters mental fatigue
No full textIntroduction: Mental fatigue is a psychobiological state caused by prolonged periods of demanding cognitive activity that has negative implications on many aspects in daily life. Caffeine and carbohydrate ingestion have been shown to be able to reduce these negative effects of mental fatigue. Intake of these substances might however be less desirable in some situations (e.g., restricted caloric intake, Ramadan). Rinsing caffeine or glucose within the mouth has already been shown to improve exercise performance. Therefore, we sought to evaluate the effect of frequent caffeine-maltodextrin (CAF-MALT) mouth rinsing on mental fatigue induced by a prolonged cognitive task. Methods: Ten males (age 23?±?2 years, physical activity 7.3?±?4.3 h/week, low CAF users) performed two trials. Participants first completed a Flanker task (3 min), then performed a 90-min mentally fatiguing task (Stroop task), followed by another Flanker task. Before the start and after each 12.5% of the Stroop task (eight blocks), subjects received a CAF-MALT mouth rinse (MR: 0.3 g/25 ml CAF: 1.6g/25 ml MALT) or placebo (PLAC: 25 ml artificial saliva). Results: Self-reported mental fatigue was lower in MR (p?=?0.017) compared to PLAC. Normalized accuracy (accuracy first block?=?100%) was higher in the last block of the Stroop in MR (p?=?0.032) compared to PLAC. P2 amplitude in the dorsolateral prefrontal cortex (DLPFC) decreased over time only in PLAC (p?=?0.017). Conclusion: Frequent mouth rinsing during a prolonged and demanding cognitive task reduces mental fatigue compared to mouth rinsing with artificial saliva
Characterization of mixing in T- and Y-shaped mixing chambers using computational dynamics
No full textIn this research project, two mixer types were compared: a T-shaped mixer and a Y-shaped one. The mixers wih be used in precipitation experiments where it is important to achieve fast micromixing. By using CFD (computational fluid dynamics) simulations, the mixers were characterized. The flow in the mixers was turbulent; the Reynolds number at the inlet was 9,000 and at the outlet i t was 18,000. First the simulation data of a straight pipe with a Reynolds number of 9,000 were compared to literature to validate the simulation method. Then simulations with the mixers were performed. The velocity field, kinetic energy and energy dissipation profiles for the mixers were compared. Also a model for macromixing was used and the concentrations of species A and B were calculated. The simulations show that macromixing is not yet completed at the outlet. To check whether mixing on molecular scale was good or not, mixing times were calculated, both being dependent on the energy dissipation. Particle tracking was performed to obtain a history of the energy dissipation rates along their flow trajectories. The energy dissipation histories could be translated to these mixing times. Mixing times are a measure for the level of mixedness. Two mixing time equations were used and compared to the residence time in the reactor.Kramers Laboratorium voor Fysische TechnologieApplied Science
Polymorphism in precipitation processes
No full textPolymorphism is the phenomenon that molecules of a compound are able to form more than one crystal structure. These structures possess different properties that are of considerable interest to industry, for example, the solubility and hence bio-availability of pharmaceuticals. Only one of the polymorphic structures is thermodynamically stable but the formation of a metastable structure may be kinetically favoured eventually followed by transformation to the stable structure. To relieve the high supersaturation that is generally created in precipitation processes molecules may follow different polymorphic pathways for nucleation and growth. Apart from the formation of a metastable crystalline phase evidence is presented that also a highly metastable liquid-liquid separation may occur. Control over the formation of polymorphs therefore requires control over their relative nucleation rates. This research offers guidelines to achieve control over the polymorphic pathways in precipitation processes.Applied Science
Correlational aspects of the viscosity-temperature-pressure relationship of lubricating oils
No full textMijnbouwkundeCivil Engineering and Geoscience
Thème 3. La nutrition et le cerveau
No full textLe cerveau et l’ensemble du corps humain entretiennent des échanges constants, nécessaires au premier pour obtenir des informations sur le statut énergétique et les besoins métaboliques de l’organisme. La plupart des nutriments ont une influence sur les voies de signalisation métabolique du cerveau. L’interaction constante entre la périphérie et le cerveau est contrôlée par les voies somato-motrices, autonomes, et neuro-humorales impliquées dans l’apport, la dépense et la mise en réserve énergétique. Les cellules du cerveau sont sensibles et répondent aux variations de la glycémie, mais aussi aux métabolites qui les renseignent sur le statut métabolique du corps.L’interaction constante entre la périphérie et le cerveau est aussi présente au cours de l’exercice de longue durée. Dans ce cadre, des perturbations dans la fourniture en précurseurs des neurotransmetteurs pourraient être responsables de la fatigue. Cette hypothèse de la « fatigue centrale » est principalement basée sur une augmentation de la concentration d’un neurotransmetteur, la sérotonine (5-HT). Selon la littérature, la performance physique serait peu, ou pas, influencée par la prise alimentaire de tryptophane (TRP) ou d’acides aminés branchés (BCAA). En revanche, l’effet bénéfique d’un apport en glucides au cours d’exercices prolongés est incontestable et pourrait être lié à l’augmentation (ou au maintien) de la fourniture de substrats au cerveau, de nombreuses études indiquant qu’un épisode d’hypoglycémie affecte la fonction cérébrale et la performance cognitive.Le fait que la sensibilité au glucose puisse influencer la performance physique a été parfaitement illustré par plusieurs études utilisant le rinçage de la bouche avec du glucose ou un placebo. Ces études montrent clairement une amélioration de la performance, même lorsque la boisson glucosée n’est pas ingérée. De manière intéressante, il a été montré que ce type de méthode permet d’activer plusieurs zones du cerveau qui contrôlent la récompense, l’émotion et les aires motrices
The Effects of Cognitive Training on Executive Function and Cognition
No full textCognitive training has emerged as a promising approach to enhancing executive function and cognition across various populations from children to older adults [...
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