Incorporating methods and findings from neuroscience to better understand placebo and nocebo effects in sport

Placebo and nocebo effects are a factor in sports performance. However, the majority of published studies in sport science are descriptive and speculative regarding mechanisms. It is therefore not unreasonable for the sceptic to argue that placebo and nocebo effects in sport are illusory, and might be better explained by variations in phenomena such as motivation. It is likely that, in sport at least, placebo and nocebo effects will remain in this empirical grey area until researchers provide stronger mechanistic evidence. Recent research in neuroscience has identified a number of consistent, discrete and interacting neurobiological and physiological pathways associated with placebo and nocebo effects, with many studies reporting data of potential interest to sport scientists, for example relating to pain, fatigue and motor control. Findings suggest that placebos and nocebos result in activity of the opioid, endocannabinoid and dopamine neurotransmitter systems, brain regions including the motor cortex and striatum, and measureable effects on the autonomic nervous system. Many studies have demonstrated that placebo and nocebo effects associated with a treatment, for example an inert treatment presented as an analgesic or stimulant, exhibit mechanisms similar or identical to the verum or true treatment. Such findings suggest the possibility of a wide range of distinct placebo and nocebo mechanisms that might influence sports performance. In the present paper, we present some of the findings from neuroscience. Focussing on fatigue as an outcome and caffeine as vehicle, we propose three approaches that researchers in sport might incorporate in their studies in order to better elucidate mechanisms of placebo/nocebo effects on performance

From the midnight sun to the longest night: sleep in Antarctica

Sleep disturbances are the main health complaints from personnel deployed in Antarctica. The current paper presents a systematic review of research findings on sleep disturbances in Antarctica. The available sources were divided in three categories: results based on questionnaire surveys or sleep logs, studies using actigraphy, and data from polysomnography results. Other areas relevant to the issue were also examined. These included chronobiology, since the changes in photoperiod have been known to affect circadian rhythms; mood disturbances; exercise, sleep and hypoxia; countermeasure investigations in Antarctica; and other locations lacking a normal photoperiod

A caffeine-maltodextrin mouth rinse counters mental fatigue

Introduction: Mental fatigue is a psychobiological state caused by prolonged periods of demanding cognitive activity that has negative implications on many aspects in daily life. Caffeine and carbohydrate ingestion have been shown to be able to reduce these negative effects of mental fatigue. Intake of these substances might however be less desirable in some situations (e.g., restricted caloric intake, Ramadan). Rinsing caffeine or glucose within the mouth has already been shown to improve exercise performance. Therefore, we sought to evaluate the effect of frequent caffeine-maltodextrin (CAF-MALT) mouth rinsing on mental fatigue induced by a prolonged cognitive task. Methods: Ten males (age 23?±?2 years, physical activity 7.3?±?4.3 h/week, low CAF users) performed two trials. Participants first completed a Flanker task (3 min), then performed a 90-min mentally fatiguing task (Stroop task), followed by another Flanker task. Before the start and after each 12.5% of the Stroop task (eight blocks), subjects received a CAF-MALT mouth rinse (MR: 0.3 g/25 ml CAF: 1.6g/25 ml MALT) or placebo (PLAC: 25 ml artificial saliva). Results: Self-reported mental fatigue was lower in MR (p?=?0.017) compared to PLAC. Normalized accuracy (accuracy first block?=?100%) was higher in the last block of the Stroop in MR (p?=?0.032) compared to PLAC. P2 amplitude in the dorsolateral prefrontal cortex (DLPFC) decreased over time only in PLAC (p?=?0.017). Conclusion: Frequent mouth rinsing during a prolonged and demanding cognitive task reduces mental fatigue compared to mouth rinsing with artificial saliva

The effects of acute dopamine reuptake inhibition on performance

Introduction: Acute bupropion (BUP; dopamine/noradrenaline reuptake inhibitor) administration significantly improved time trial performance and increased core temperature in the heat (30°C). Purpose: The present study was performed to examine the effect of a dopaminergic reuptake inhibitor on exercise capacity and thermoregulation during prolonged exercise in temperate and warm conditons. Methods: Eight healthy well-trained male cyclists participated in this study. Subjects ingested either a placebo (PLAC; lactose; 20mg) or Ritalin (RIT; methylphenidate (MPH); 20mg) one hour before the start of exercise in temperate (18°C) or warm (30°C) conditions and cycled for 60 min at 55% Wmax, immediately followed by a time trial (TT; pla18 and rit18; pla30 and rit30) to measure exercise performance. Results: Ritalin did not influence TT performance at 18oC (P=0.397). TT was completed 16% faster in rit30 (38.1±6.4min) than in pla30 (45.4±7.3min; p=0.049). Power output was higher in rit30, compared to pla30 (p<0.05). In the heat Tcore was significantly higher at rest (p=0.009), at the start of exercise and throughout rit30 (p<0.05). Throughout rit30 heart rates were significantly higher (p<0.05). Prolactin concentrations decreased after one hour cycling in 18°C (p=0,036) and at rest in 30°C (p=0,007) after RIT administration. Conclusions: These results show that RIT has a clear ergogenic effect that was not apparent in 18°C. The combination of a dopamine reuptake inhibitor and exercise in the heat clearly improved performance and appeared to increase metabolic heat production, suggesting an important role for dopamine in the fatigue process

Effects of Mental Fatigue on Endurance Performance in the Heat

PURPOSE: Mental fatigue is a psychobiological state caused by prolonged periods of demanding cognitive activity and has been observed to decrease time-trial (TT) endurance performance by ~3,5% in normal ambient temperatures. Recently it has been suggested that heat may augment the negative effect of mental fatigue on cognitive performance, raising the question whether it may also amplify the effect of mental fatigue on TT-performance. METHODS: In 30 °C and 30% relative humidity, ten endurance-trained male athletes (Age: 22 ± 3 y; Wmax: 332 ± 41 W) completed two experimental conditions: intervention (I; 45-min Stroop task) and control (C; 45-min documentary). Pre and post intervention/control, cognitive performance was followed up with a 5-min Flanker task. Thereafter subjects cycled for 45 min at a fixed pace equal to 60%-Wmax, immediately followed by a self-paced TT in which they had to produce a fixed amount of work (equal to cycling 15 min at 80%-Wmax) as fast as possible. RESULTS: Self-reported mental fatigue was significantly higher after I compared to C (P<0.05). Moreover electroencephalographic measures also indicated the occurrence of mental fatigue during the Stroop (P<0.05). TT-time did not differ between conditions (I: 906 ± 30 s, C: 916 ± 29 s). Throughout exercise, physiological (heart rate, blood lactate, core and skin temperature) and perceptual measures (perception of effort and thermal sensation) were not affected by mental fatigue. CONCLUSION: No negative effects of mild mental fatigue were observed on performance and the physiological and perceptual responses to endurance exercise in the heat. Most plausibly mild mental fatigue does not reduce endurance performance when the brain is already stressed by a hot environment

Repeated-sprints exercise in daylight fasting: carbohydrate mouth rinsing does not affect sprint and reaction time performance

To determine the effect of carbohydrate mouth rinsing (CHO-MR) on physical and cognitive performance during repeated-sprints (RS) after 3 days of intermittent fasting (abstaining from food and fluid 14 h per day). In a randomized and counter-balanced manner 15 active healthy males in a fasted state performed a RS-protocol [RSP; 2 sets (SET1 and SET2) of 5×5 s maximal sprints, with each sprint interspersed with 25 s rest and 3 min of recovery between SET1 and SET2] on an instrumented non-motorized treadmill with embedded force sensors under three conditions: i) Control (CON; no-MR), ii) Placebo-MR (PLA-MR; 0% maltodextrin) and iii) CHO-MR (10% maltodextrin). Participants rinsed their mouth with either 10 mL of PLA-MR or CHO-MR solution for 5 s before each sprint. Sprint kinetics were measured for each sprint and reaction time (RTI) tasks (simple and complex) were assessed pre-, during- and post-RSP. There was no statistical main effect of CHO-MR on mean power, mean speed, and vertical stiffness during the sprints between the PLA-MR and CON condition. Additionally, no statistical main effect for CHO-MR on accuracy, movement time and reaction time during the RTI tasks was seen. CHO-MR did not affect physical (RSP) or cognitive (RTI) performance in participants who had observed 3 days of intermittent fasting (abstaining from food and fluid 14 h per day)

Consensus recommendations on training and competing in the heat

Exercising in the heat induces thermoregulatory and other physiological strain that can lead to impairments in endurance exercise capacity. The purpose of this consensus statement is to provide up-to-date recommendations to optimize performance during sporting activities undertaken in hot ambient conditions. The most important intervention one can adopt to reduce physiological strain and optimize performance is to heat acclimatize. Heat acclimatization should comprise repeated exercise–heat exposures over 1–2 weeks. In addition, athletes should initiate competition and training in an euhydrated state and minimize dehydration during exercise. Following the development of commercial cooling systems (e.g., cooling vests), athletes can implement cooling strategies to facilitate heat loss or increase heat storage capacity before training or competing in the heat. Moreover, event organizers should plan for large shaded areas, along with cooling and rehydration facilities, and schedule events in accordance with minimizing the health risks of athletes, especially in mass participation events and during the first hot days of the year. Following the recent examples of the 2008 Olympics and the 2014 FIFA World Cup, sport governing bodies should consider allowing additional (or longer) recovery periods between and during events for hydration and body cooling opportunities when competitions are held in the heat

The Effects of Mental Fatigue on Physical Performance: A Systematic Review.

Background: Mental fatigue is a psychobiological state caused by prolonged periods of demanding cognitive activity. It has recently been suggested that mental fatigue can affect physical performance. Objective: Our objective was to evaluate the literature on impairment of physical performance due to mental fatigue and to create an overview of the potential factors underlying this effect. \ud Methods: Two electronic databases, PubMed and Web of Science (until 28 April 2016), were searched for studies designed to test whether mental fatigue influenced performance of a physical task or influenced physiological and/or perceptual responses during the physical task. Studies using short (<30 min) self-regulatory depletion tasks were excluded from the review. Results: A total of 11 articles were included, of which six were of strong and five of moderate quality. The general finding was a decline in endurance performance (decreased time to exhaustion and self-selected power output/velocity or increased completion time) associated with a higher than normal perceived exertion. Physiological variables traditionally associated with endurance performance (heart rate, blood lactate, oxygen uptake, cardiac output, maximal aerobic capacity) were unaffected by mental fatigue. Maximal strength, power, and anaerobic work were not affected by mental fatigue. Conclusion: The duration and intensity of the physical task appear to be important factors in the decrease in physical performance due to mental fatigue. The most important factor responsible for the negative impact of mental fatigue on endurance performance is a higher perceived exertion

Topic 3. Nutrition and the brain

The brain and body are constantly exchanging to ensure that the former receives information on the energy status and metabolic requirements of the latter. Most nutrients influence the brain’s metabolic signal pathways. The constant interaction between the peripheral nervous system and the brain is controlled by the somatic, autonomic and neurohumoral pathways which are involved in the contribution, expenditure and storage of energy reserves. Brain cells are sensitive and responsive not only to fluctuations in blood sugar concentration, but also to metabolites that provide information on the body’s metabolic status. The constant interaction between the peripheral system and the brain is also present during prolonged exercise. In this context, disruptions to the supply of neurotransmitter precursors might be responsible for the occurrence of fatigue. The “central fatigue” theory is mainly based on an increase in the concentration of the neurotransmitter serotonin (5-HT). According to the scientific literature, physical performance would be little influenced, if at all, by the intake of tryptophan (TRP) or branched chain amino acid (BCAA) substrates. In contrast, the beneficial effect of carbohydrate intake during prolonged exercise is unquestionable and could be related to the increase (or maintaining of) the supply of substrates to the brain. Numerous studies indicate that hypoglycemia affects brain function and cognitive performance. The positive effect of glucose intake on athletic performance is clearly illustrated by several investigations using a carbohydrate mouth rinse compared to a placebo. Studies have clearly shown an improvement in performance even when the carbohydrate drink was not ingested. Interestingly, research has shown that a mouth rince activates multiple areas of the brain involved in the control of reward, emotion and motor output

Thème 3. La nutrition et le cerveau

Le 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