Carbohydrate Mouth Rinse Mitigates Mental Fatigue Effects on Maximal Incremental Test Performance, but Not in Cortical Alterations

Detrimental mental fatigue effects on exercise performance have been documented in constant workload and time trial exercises, but effects on a maximal incremental test (MIT) remain poorly investigated. Mental fatigue-reduced exercise performance is related to an increased effort sensation, likely due to a reduced prefrontal cortex (PFC) activation and inhibited spontaneous behavior. Interestingly, only a few studies verified if centrally active compounds may mitigate such effects. For example, carbohydrate (CHO) mouth rinse potentiates exercise performance and reduces effort sensation, likely through its effects on PFC activation. However, it is unknown if this centrally mediated effect of CHO mouth rinse may mitigate mental fatigue-reduced exercise performance. After a proof-of-principle study, showing a mental fatigue-reduced MIT performance, we observed that CHO mouth rinse mitigated MIT performance reductions in mentally fatigued cyclists, regardless of PFC alterations. When compared to placebo, mentally fatigued cyclists improved MIT performance by 2.24–2.33 when rinsing their mouth with CHO during MIT. However, PFC and motor cortex activation during MIT in both CHO and placebo mouth rinses were greater than in mental fatigue. Results showed that CHO mouth rinse mitigated the mental fatigue-reduced MIT performance, but challenged the role of CHO mouth rinse on PFC and motor cortex activation

Efeito placebo aplicado a ambientes clínicos e de desempenho físico

Introdução: Placebo é considerado uma substância ou um procedimento inerte que pode proporcionar um efeito positivo ou negativo dependendo da condição em que é aplicado. É bem documentado que o placebo promove resultados positivos em condições patológicas e em condições de desempenho físico. Objetivo: Sendo assim, objetivo desse estudo é revisar em duas sessões, trabalhos que tenham abordado: 1) o efeito placebo e nocebo aplicado à clínica no tratamento da doença de Parkinson, depressão e dor, e 2) o uso do placebo como recurso ergogênico no desempenho físico. Metodologia: Para tal, uma busca foi realizada na base de dados “Pubmed” e “Web of Science”. Resultados e discussão: Nesta revisão narrativa, discutimos como o efeito placebo atua em diversas condições como a dor, depressão, doença de Parkinson, e no desempenho físico, além disso, foram abordados possíveis mecanismos que possam atuar neste fenômeno. Conclusão: Podemos concluir que em condição clínica e de desempenho físico, o placebo compartilha regiões cerebrais semelhantes, que geram respostas positivas ao tratamento

Commentaries on viewpoint : physiology and fast marathons

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Effects of carbohydrate mouth rinse on physical performance, psychophysiological and cerebral responses of mentally fatigued cyclists during a maximal incremental test

Estudos têm demonstrado separadamente, a redução do desempenho aeróbio após uma tarefa de alta demanda cognitiva, e a melhora do desempenho físico através da suplementação com bochecho de carboidrato (CHO), levando à hipótese de que o bochecho com CHO possa atenuar a redução do desempenho aeróbio induzida pela fadiga mental. Portanto, nosso objetivo foi investigar se o uso do bochecho com CHO pode melhorar o desempenho físico, atividade cortical e respostas psicofisiológicas em ciclistas mentalmente fadigados submetidos a um teste incremental máximo (TIM). Métodos: 19 ciclistas treinados (7,56 ± 5,89 anos de experiência, 4,43 ± 0,45 VO2PICO, 359,61 ± 22,92 WPICO) realizaram 5 visitas ao laboratório, sendo as duas primeiras em ordem sequencial e as últimas três balanceadas de acordo com a descrição a seguir: 1) familiarização com TIM (teste preliminar), instrumentos e protocolo de FM; 2) TIM controle (CON) e segunda familiarização com o protocolo de FM; 3) TIM+FM; 4) TIM+FM+CHO; 5) TIM+FM+placebo (PLA). Respostas cardiopulmonares, potencia, percepção subjetiva de esforço (PSE) e valências afetivas foram analisadas durante o TIM, enquanto a atividade de córtex pré-frontal (CPF) e córtex motor primário (CMP) foram analisadas em intervalos regulares (a cada 25 % do TIM preliminar). As respostas psicológicas e atividade de CPF em repouso foram comparadas através do teste t de student, enquanto todas as respostas durante o TIM foram comparadas através de uma de modelos mistos. Resultados: os ciclistas mentalmente fadigados atingiram WPICO ~ 2,18 % e ~ 2.23 % maior na manipulação FM+CHO do que na manipulação FM (P = 0,09) e FM+PLA (P = 0,02). Além disso, o tempo até a exaustão na manipulação FM+CHO foi ~ 2,01 % e ~ 2,14 % maior do que na manipulação FM (P = 0,05) e FM+PLA (P = 0,03), com tamanho de efeito grande em ambos os resultados. A atividade cerebral em CPF foi maior na manipulação MF+CHO e MF+PLA do que na manipulação MF (P = 0,00). Além disso a ativação de CMP também foi maior na manipulação MF+CHO (P = 0,00) e MF+PLA (P = 0,01) do que na manipulação FM, mas nenhuma diferença foi encontrada entre os bochechos. As respostas psicofisiológicas não tiveram diferenças significantes entre as manipulações. Conclusão: O bochecho com CHO foi capaz de atenuar a perda de desempenho comparado à manipulação FM+PLA, mas não comparado à FM. Alémdisso, tanto FM+CHO quanto FM+PLA induziram maior atividade de CPF e CMP comparados à FMIndependent studies have shown a decrease in endurance performance after a high-demand cognitive task, but an improvement on endurance performance with carbohydrate (CHO) mouth rinse, thus leading to a hypothesis that the CHO mouth rinse could attenuate the mental fatiguereduced endurance performance. Therefore, our aim was to investigate if the use of CHO mouth rinse may improve physical performance, cortical activity and psychophysiological responses in mentally fatigued cyclists underwent to a maximal incremental test (MIT). Methods: 19 endurance trained cyclists (7.56 ± 5.89 years of cycling experience, 4.43 ± 0.45 VO2PEAK, 359.61 ± 22.92 WPEAK) performed 5 trials, being the two first visits in sequential and the last three in a counterbalanced order, as it follow: 1) familiarization with MIT protocol (preliminary trial), instruments and MF task; 2) MIT control (CON) and second familiarization with MF task; 3) MIT+CHO; 4) MIT+placebo (PLA). Cardiopulmonary responses, power output, ratings of perceived exertion (RPE) and affective valences were assessed through the MIT, while prefrontal cortex (PFC) and primary motor cortex (PMC) activation were obtained at regular intervals (every 25 % of the preliminary MIT). Psychological responses and PFC activation at rest were compared as using t student test, while the responses during the MIT were compared through a number of mixed model. Results: Mentally fatigued cyclists reached a WPEAK ~ 2.18 % and ~ 2.23 % higher in MF+CHO than MF (P = 0.09) and MF+PLA (P = 0.02), respectively. Moreover, time to exhaustion in MF+CHO manipulation was ~ 2.01 % and ~ 2.14 % greater in MF+CHO than in MF (P = 0.05) and MF+PLA (P = 0.03), respectively. Both performance results showed a large effect size. Cerebral activation in CPF was greater in MF+CHO and MF+PLA than in MF (P = 0.00). Accordingly, PMC activation was also greater in MF+CHO (P = 0.00) and MF+PLA (P = 0.01) than in MF, but no differences have been observed between bouth rinses. Psychophysiological responses has no significant differences between the manipulations. Conclusion: CHO mouth rinse could attenuate the reduced performance compared to MF+PLA but not compared to MF. Moreover, both MF+CHO and MF+PLA induced greater cerebral activity in PFC and PMC compared do M

Effects of carbohydrate mouth rinse on physical performance, psychophysiological and cerebral responses of mentally fatigued cyclists during a maximal incremental test

Estudos têm demonstrado separadamente, a redução do desempenho aeróbio após uma tarefa de alta demanda cognitiva, e a melhora do desempenho físico através da suplementação com bochecho de carboidrato (CHO), levando à hipótese de que o bochecho com CHO possa atenuar a redução do desempenho aeróbio induzida pela fadiga mental. Portanto, nosso objetivo foi investigar se o uso do bochecho com CHO pode melhorar o desempenho físico, atividade cortical e respostas psicofisiológicas em ciclistas mentalmente fadigados submetidos a um teste incremental máximo (TIM). Métodos: 19 ciclistas treinados (7,56 ± 5,89 anos de experiência, 4,43 ± 0,45 VO2PICO, 359,61 ± 22,92 WPICO) realizaram 5 visitas ao laboratório, sendo as duas primeiras em ordem sequencial e as últimas três balanceadas de acordo com a descrição a seguir: 1) familiarização com TIM (teste preliminar), instrumentos e protocolo de FM; 2) TIM controle (CON) e segunda familiarização com o protocolo de FM; 3) TIM+FM; 4) TIM+FM+CHO; 5) TIM+FM+placebo (PLA). Respostas cardiopulmonares, potencia, percepção subjetiva de esforço (PSE) e valências afetivas foram analisadas durante o TIM, enquanto a atividade de córtex pré-frontal (CPF) e córtex motor primário (CMP) foram analisadas em intervalos regulares (a cada 25 % do TIM preliminar). As respostas psicológicas e atividade de CPF em repouso foram comparadas através do teste t de student, enquanto todas as respostas durante o TIM foram comparadas através de uma de modelos mistos. Resultados: os ciclistas mentalmente fadigados atingiram WPICO ~ 2,18 % e ~ 2.23 % maior na manipulação FM+CHO do que na manipulação FM (P = 0,09) e FM+PLA (P = 0,02). Além disso, o tempo até a exaustão na manipulação FM+CHO foi ~ 2,01 % e ~ 2,14 % maior do que na manipulação FM (P = 0,05) e FM+PLA (P = 0,03), com tamanho de efeito grande em ambos os resultados. A atividade cerebral em CPF foi maior na manipulação MF+CHO e MF+PLA do que na manipulação MF (P = 0,00). Além disso a ativação de CMP também foi maior na manipulação MF+CHO (P = 0,00) e MF+PLA (P = 0,01) do que na manipulação FM, mas nenhuma diferença foi encontrada entre os bochechos. As respostas psicofisiológicas não tiveram diferenças significantes entre as manipulações. Conclusão: O bochecho com CHO foi capaz de atenuar a perda de desempenho comparado à manipulação FM+PLA, mas não comparado à FM. Alémdisso, tanto FM+CHO quanto FM+PLA induziram maior atividade de CPF e CMP comparados à FMIndependent studies have shown a decrease in endurance performance after a high-demand cognitive task, but an improvement on endurance performance with carbohydrate (CHO) mouth rinse, thus leading to a hypothesis that the CHO mouth rinse could attenuate the mental fatiguereduced endurance performance. Therefore, our aim was to investigate if the use of CHO mouth rinse may improve physical performance, cortical activity and psychophysiological responses in mentally fatigued cyclists underwent to a maximal incremental test (MIT). Methods: 19 endurance trained cyclists (7.56 ± 5.89 years of cycling experience, 4.43 ± 0.45 VO2PEAK, 359.61 ± 22.92 WPEAK) performed 5 trials, being the two first visits in sequential and the last three in a counterbalanced order, as it follow: 1) familiarization with MIT protocol (preliminary trial), instruments and MF task; 2) MIT control (CON) and second familiarization with MF task; 3) MIT+CHO; 4) MIT+placebo (PLA). Cardiopulmonary responses, power output, ratings of perceived exertion (RPE) and affective valences were assessed through the MIT, while prefrontal cortex (PFC) and primary motor cortex (PMC) activation were obtained at regular intervals (every 25 % of the preliminary MIT). Psychological responses and PFC activation at rest were compared as using t student test, while the responses during the MIT were compared through a number of mixed model. Results: Mentally fatigued cyclists reached a WPEAK ~ 2.18 % and ~ 2.23 % higher in MF+CHO than MF (P = 0.09) and MF+PLA (P = 0.02), respectively. Moreover, time to exhaustion in MF+CHO manipulation was ~ 2.01 % and ~ 2.14 % greater in MF+CHO than in MF (P = 0.05) and MF+PLA (P = 0.03), respectively. Both performance results showed a large effect size. Cerebral activation in CPF was greater in MF+CHO and MF+PLA than in MF (P = 0.00). Accordingly, PMC activation was also greater in MF+CHO (P = 0.00) and MF+PLA (P = 0.01) than in MF, but no differences have been observed between bouth rinses. Psychophysiological responses has no significant differences between the manipulations. Conclusion: CHO mouth rinse could attenuate the reduced performance compared to MF+PLA but not compared to MF. Moreover, both MF+CHO and MF+PLA induced greater cerebral activity in PFC and PMC compared do M

The reward for placebos: mechanisms underpinning placebo-induced effects on motor performance

Different from the most popular thinking, the placebo effect is not a purely psychological phenomenon. A body of knowledge from multidisciplinary fields has shown that the expectation of a potential benefit when receiving a treatment induces a cascade of neurochemical-electrophysiological alterations in brain reward areas, including motor-related ones. Alterations in the dopamine, opioid, and glutamate metabolism are the neural representation converting reward-derived declarative forms into an attractive and wanted behavior, thereby changing the activation in reward subcortical and cortical structures involved in motor planning, motor execution, and emotional-cognitive attributes of decision-making. We propose that the expectation of receiving a treatment that is beneficial to motor performance triggers a cascade of activations in brain reward areas that travels from motor planning and motor command areas, passing through corticospinal pathways until driving the skeletal muscles, therefore facilitating the motor performance. Although alternative explanations cannot be totally ruled out, this mechanistic route is robust in explaining the results of placebo-induced effects on motor performance and could lead to novel insights and applications in the exercise sciences. Factors such as sex differences in reward-related mechanisms and aversion-induced nocebo effects should also be addressed

Caffeine improved cycling trial performance in mentally fatigued cyclists, regardless of alterations in prefrontal cortex activation

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 doubleblind, 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 = 0.00; ↓ ~1.7 %) and increasing WMEAN (p = 0.00; ↑ ~3.6%), when compared to MF+PLA. The RPE-power output ratio was lower (p = 0.01), but affect (p = 0.018), motivation (p = 0.033) and emotional arousal (p = 0.001) 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

Carbohydrate Mouth Rinse Fails to Improve Four-Kilometer Cycling Time Trial Performance

We investigated if a carbohydrate (CHO) mouth rinse may attenuate global fatigue and improve 4-km cycling time trial (TT4km) performance. After a preliminary session, cyclists (n = 9) performed a TT4km after a CHO or placebo (PLA) mouth rinse. Mean power output, time, and ratings of perceived exertion (RPE) were recorded throughout the TT4km. Twitch interpolation responses (%VA; voluntary activation and ∆Tw; delta peak twitch torque) were compared pre and post TT4km with traditional statistics and effect size (ES) analysis. Time-to-complete the 4 km and mean power output were comparable between CHO (386.4 ± 28.0 s) and PLA (385.4 ± 22.4 s). A lower central (p = 0.054) and peripheral (p = 0.02) fatigue in CHO than in PLA were suggested by an extremely-large ES in %VA (manipulation main effect: p = 0.052, d = 1.18; manipulation-by-time interaction effect: p = 0.08, d = 1.00) and an extremely, very-large ES in ∆Tw (manipulation main effect: p = 0.07, d = 0.97; time-by-manipulation interaction effect: p = 0.09, d = 0.89). The RPE increased slower in CHO than in PLA (p = 0.051; d = 0.7). The apparent reduction in global fatigue (central and peripheral) and RPESLOPE with only one CHO mouth rinse were not translated into improved TT4km performance. Further tests may be required to verify if these likely differences in global fatigue might represent an edge in the short-lasting cycling time trial performance