Carbohydrate in the mouth enhances activation of brain circuitry involved in motor performance and sensory perception

Carbohydrate mouth rinse failed to reduce central fatigue, lower perceived exertion, and improve performance during incremental exercise

We examined if carbohydrate (CHO) mouth rinse may reduce central fatigue and perceived exertion, thus improving maximal incremental test (MIT) performance. Nine recreational cyclists warmed up for 6 min before rinsing a carbohydrate (CHO) or placebo (PLA) solution in their mouth for 10 s in a double-blind, counterbalanced manner. Thereafter, they performed the MIT (25 W·min-1 increases until exhaustion) while cardiopulmonary and ratings of perceived exertion (RPE) responses were obtained. Pre- to post-MIT alterations in voluntary activation (VA) and peak twitch torque (Tw) were determined. Time-to-exhaustion (p = 0.24), peak power output (PPO; p = 0.45), and V̇O2MAX (p = 0.60) were comparable between conditions. Neither treatment main effect nor time-treatment interaction effect were observed in the first and second ventilatory threshold when expressed as absolute or relative V̇O2 (p = 0.78 and p = 0.96, respectively) and power output (p = 0.28 and p = 0.45, respectively) values, although with moderate-to-large effect sizes. RPE increased similarly throughout the tests and was comparable at the ventilatory thresholds (p = 0.56). Despite the time main effect revealing an MIT-induced central and peripheral fatigue as indicated by the reduced VA and Tw, CHO mouth rinse was ineffective in attenuating both fatigues. Hence, rinsing the mouth with CHO was ineffective in reducing central fatigue, lowering RPE, and improving MIT performance expressed as PPO and time-to-exhaustion. However, moderate-to-large effect sizes in power output values at VT1 and VT2 may suggest some beneficial CHO mouth rinse effects on these MIT outcomes.

Carbohydrate mouth rinse improves performance of mentally fatigued cyclists despite null effects on psychological responses

Mental fatigue reduces exercise performance through an impaired psychological response such as increased perceived exertion. Carbohydrate (CHO) mouth rinses improve exercise performance and perceived exertion likely due to an improved activation in cerebral reward areas, then we investigated if the CHO mouth rinse-improved exercise performance in mentally fatigued individuals was associated with ameliorated reward-related psychological responses. We hypothesised that CHO mouth rinse would be beneficial for mentally fatigued cyclists mainly in high-metabolic disturbance intensities. After familiarization and baseline sessions, well trained cyclists (n = 20) performed a maximal incremental test (MIT) after mental fatigue induction. They completed the MIT either without mouth rinse (MF) or rinsing their mouth with CHO (MF+CHO) or placebo (FM+PLA) solutions at every 25 % of the MIT. Psychological responses such as ratings of perceived exertion (RPE), affective valence, emotional arousal, and motivation were assessed throughout the MIT, while performance was assessed as peak power output and time of exercise. Mental fatigue reduced MIT performance (P < 0.05), but CHO mouth rinse was effective to counteract this deleterious mental fatigue effect (P < 0.05). However, we found null effects of CHO mouth rinses in psychological responses above the VT2 (P > 0.05) such as RPE, affective valence, emotional arousal, and motivation. Correlational analysis showed a significant, but moderate negative correlation between motivation and time of exercise above the VT2 when participants used CHO mouth rinse. In conclusion, the ergogenic CHO mouth rinse effects on MIT performance of mentally fatigued cyclists were irrespective of ameliorated psychological responses to exercise.

Psychological effect of acute creatine pre-workout supplementation induces performance improvement in resistance exercise

The purpose of this study was to test whether believed versus actual acute creatine ingestion impacted resistance exercise performance. Fifteen men (21.9 ± 2.7 years old) completed four bouts of three sets each of squat and bench press to volitional fatigue at a 10RM load with 1-min between-sets rest interval. Thirty minutes prior to each exercise bout, they received the following treatments in a randomized order: 1) nothing (CON); 2) 0.3 g·kg-1 dextrose placebo (PLC); 3) 0.3 g·kg-1 dextrose, identified as creatine (Cr-False); 4) 0.3 g·kg 20 -1 creatine, identified as creatine (CrTrue). Between-treatments comparisons included the total repetitions completed and the rate of perceived exertion. Results revealed (p < 0.05) higher repetitions performed for all treatments versus CON for both squat and bench press. In the squat, more repetitions were performed with Cr-True (p < 0.001) and CrFalse (p < 0.001) than with either CON or PLC. Bayes Factor analyses revealed strong (PLC to Cr-True BF = 19.1) and very strong (PLC to CrFalse BF = 45.3) posterior probability favouring positive effects for both "creatine" conditions over PLC for the squat. In conclusion, in acute measures, belief versus ingestion of creatine yields similar exercise performance.

Carbohydrate Nutrition and Skill Performance in Soccer

In soccer, players must perform a variety of sport-specific skills usually during or immediately after running, often at sprint speed. The quality of the skill performed is likely influenced by the volume of work done in attacking and defending over the duration of the match. Even the most highly skilful players succumb to the impact of fatigue both physical and mental, which may result in underperforming skills at key moments in a match. Fitness is the platform on which skill is performed during team sport. With the onset of fatigue, tired players find it ever more difficult to successfully perform basic skills. Therefore, it is not surprising that teams spend a large proportion of their training time on fitness. While acknowledging the central role of fitness in team sport, the importance of team tactics, underpinned by spatial awareness, must not be neglected. It is well established that a high-carbohydrate diet before a match and, as a supplement during match play, helps delay the onset of fatigue. There is some evidence that players ingesting carbohydrate can maintain sport-relevant skills for the duration of exercise more successfully compared with when ingesting placebo or water. However, most of the assessments of sport-specific skills have been performed in a controlled, non-contested environment. Although these methods may be judged as not ecologically valid, they do rule out the confounding influences of competition on skill performance. The aim of this brief review is to explore whether carbohydrate ingestion, while delaying fatigue during match play, may also help retain sport soccer-specific skill performance.

How Attention Changes in Response to Carbohydrate Mouth Rinsing

Research investigating the effects of carbohydrate (CHO) mouth rinsing on neurocognitive functions is currently limited and has yielded inconsistent results. In this study, we employed the event-related potential (ERP) electroencephalography technique to investigate the effect of CHO mouth rinsing on electrophysiological correlates of visuospatial attention. Using a double-blind, non-nutritive sweetener (NNS)-controlled, within-subjects design, 53 young adults performed a standard cognitive task (modified Simon task) on two separate days in a fasted state (16 h). Intermittently, mouth rinsing was performed either with a CHO (glucose, 18%, 30 mL) or an NNS solution (aspartame, 0.05%, 30 mL). Results revealed that relative to NNS, electrophysiological correlates of both more bottom-up controlled visuospatial attention (N1_pc-ERP component) were decreased in response to CHO rinsing. In contrast, compared to NNS, more top-down controlled visuospatial attention (N2_pc-ERP component) was increased after CHO rinsing. Behavioral performance, however, was not affected by mouth rinsing. Our findings suggest that orosensory signals can impact neurocognitive processes of visuospatial attention in a fasted state. This may suggest a central mechanism underlying the ergogenic effects of carbohydrate mouth rinsing on endurance performance could involve modulations of attentional factors. Methodologically, our study underlines that understanding the effects of carbohydrate mouth rinsing at the central level may require combining neuroscientific methods and manipulations of nutritional states.

Formulation of Ready-to-Eat Soup for the Elderly: Nutritional Composition and Storage Stability Study

Lack of appetite is a common problem in elderly people which could lead to the risk of malnutrition. Soup-based product formulation and supplementation for the elderly is an interesting and convenient way to maintain nutritional status. Hence, this study aims to develop ready-to-eat (RTE) soup and instant soup powder using common agricultural commodities. The results indicated that among all formulations, the F7 formula comprised brown rice (15 g), pumpkin (32.5 g), sweetcorn (12.5 g), red tilapia (17.5 g), rice bran oil (1.0 g), and water (21.5 g) with energy ratio (C:P:F) of 58:23:20 receiving the highest sensory scores. The selected formulation (F7) was also transformed into instant powder and both RTE soup and instant powder were evaluated for nutritional composition and storage stabilities at 5 °C and 25 °C, respectively. The nutritional composition analyses indicate that 100 g of RTE soup consists of 13.8 g carbohydrates, 4.9 g proteins, 1.8 g fats, and 1.5 g dietary fibers; the soup is also a rich source of antioxidants and β-carotene. Storage studies suggested that the content of β-carotene and antioxidant activity of both (ready-to-eat and instant powder) types of soup decreased with increasing storage time, while a slight increase in yeast and mold count (<50 cfu/g) was noted. Most importantly, no pathogenic bacteria were detected in ready-to-eat and instant soup during the storage study of 6 weeks at 5 °C and 6 months at 25 °C, respectively. In terms of the high nutritional composition and functional value of the product, 4 weeks of storage at 5 °C and 4 months of storage at room temperature were suggested for ready-to-eat and instant powder soup product, respectively.

Carbohydrate mouth rinse is no more effective than placebo on running endurance of dehydrated and heat acclimated athletes

PURPOSE

To determine whether carbohydrate mouth rinsing would improve endurance running performance of tropical natives in a warm-humid (30 °C and 70% relative humidity) environment.

METHOD

Twelve endurance male runners [age 25 ± 3 years; peak aerobic capacity ([Formula: see text]O_2peak) 57.6 ± 3.6 mL^.kg^-1.min^-1] completed three time-to-exhaustion (TTE) trials at ~ 70% [Formula: see text]O_2peak while swilling 25 ml of a 6% carbohydrate (CHO) or taste-matched placebo (PLA) as well as no mouth rinse performed in the control (CON) trial.

RESULTS

TTE performance was significantly longer in both CHO and PLA trials when compared with the CON trial (54.7 ± 5.4 and 53.6 ± 5.1 vs. 48.4 ± 3.6 min, respectively; p < 0.001 and p = 0.012, respectively), but was not significantly different between CHO and PLA trials (p = 1.000). The rating of perceived exertion was not different between the CHO and PLA trials, however, was significantly affected when compared to the CON trial (p < 0.001). A similar effect was observed for perceived arousal level between the CHO and PLA trials to the CON trial. Core temperature, mean skin temperature and skin blood flow were not significantly different between the three trials (all p > 0.05). Similarly, plasma lactate and glucose as well as exercise heart rate were not influenced by the trials.

CONCLUSIONS

The present study demonstrates that mouth rinsing, whether carbohydrate or placebo, provides an ergogenic benefit to running endurance when compared to CON in a heat stress environment. Nevertheless, the results do not support the notion that rinsing a carbohydrate solution provides a greater advantage as previously described among non-heat acclimated individuals within a temperate condition.

Mouth rinsing and ingesting salty or bitter solutions does not influence corticomotor excitability or neuromuscular function

PURPOSE

To explore the effect of tasting unpleasant salty or bitter solutions on lower limb corticomotor excitability and neuromuscular function.

METHODS

Nine females and eleven males participated (age: 27 ± 7 years, BMI: 25.3 ± 4.0 kg m^-2). Unpleasant salty (1 M) and bitter (2 mM quinine) solutions were compared to water, sweetened water, and no solution, which functioned as control conditions. In a non-blinded randomized cross-over order, each solution was mouth rinsed (10 s) and ingested before perceptual responses, instantaneous heart rate (a marker of autonomic nervous system activation), quadricep corticomotor excitability (motor-evoked potential amplitude) and neuromuscular function during a maximal voluntary contraction (maximum voluntary force, resting twitch force, voluntary activation, 0-50 ms impulse, 0-100 impulse, 100-200 ms impulse) were measured.

RESULTS

Hedonic value (water: 47 ± 8%, sweet: 23 ± 17%, salt: 71 ± 8%, bitter: 80 ± 10%), taste intensity, unpleasantness and increases in heart rate (no solution: 14 ± 5 bpm, water: 18 ± 5 bpm, sweet: 20 ± 5 bpm, salt: 24 ± 7 bpm, bitter: 23 ± 6 bpm) were significantly higher in the salty and bitter conditions compared to control conditions. Nausea was low in all conditions (< 15%) but was significantly higher in salty and bitter conditions compared to water (water: 3 ± 5%, sweet: 6 ± 13%, salt: 7 ± 9%, bitter: 14 ± 16%). There was no significant difference between conditions in neuromuscular function or corticomotor excitability variables.

CONCLUSION

At rest, unpleasant tastes appear to have no influence on quadricep corticomotor excitability or neuromuscular function. These data question the mechanisms via which unpleasant tastes are proposed to influence exercise performance.

A Narrative Review of Current Concerns and Future Perspectives of the Carbohydrate Mouth Rinse Effects on Exercise Performance

Previous systematic reviews have confirmed that carbohydrate (CHO) mouth rinse may boost physical exercise performance, despite some methodological aspects likely affecting its ergogenic effect. In this review, we discussed if the exercise mode, pre-exercise fasting status, CHO solutions concentration, CHO solutions temperature, mouth rinse duration, and CHO placebo effects may potentially reduce the CHO mouth rinse ergogenic effect, suggesting possible solutions to manage these potential confounders. The effectiveness of CHO mouth rinse as a performance booster is apparently related to the origin of the exercise-induced neuromuscular fatigue, as CHO mouth rinse unequivocally potentiates endurance rather than sprint and strength exercises performance. Furthermore, ergogenic effects have been greater in fasting than fed state, somehow explaining the varied magnitude of the CHO mouth rinse effects in exercise performance. In this regard, the CHO solution concentration and temperature, as well as the mouth rinse duration, may have increased the variability observed in CHO mouth rinse effects in fasting and fed state. Finally, placebo effects have challenged the potential of the CHO mouth rinse as an ergogenic aid. Therefore, we suggest that future studies should consider methodological controls such as sample size and sample homogeneity, proper familiarization with experimental procedures, and the use of alternative placebo designs to provide unbiased evidence regarding the potential of the CHO mouth rinse as an ergogenic aid.

How to Tackle Mental Fatigue: A Systematic Review of Potential Countermeasures and Their Underlying Mechanisms

INTRODUCTION

Mental fatigue (MF) is a psychobiological state that impairs cognitive as well as physical performance in different settings. Recently, numerous studies have sought ways to counteract these negative effects of MF. An overview of the explored countermeasures for MF is, however, lacking.

OBJECTIVES

The objective of this review is to provide an overview of the different MF countermeasures currently explored in literature. Countermeasures were classified by the timing of application (before, during or after the moment of MF) and type of intervention (behavioural, physiological and psychological).

METHODS

The databases of PubMed (MEDLINE), Web of Science and PsycINFO were searched until March 7, 2022. Studies were eligible when MF was induced using a task with a duration of at least 30 min, when they assessed MF markers in at least two out of the three areas wherein MF markers have been defined (i.e., behavioural, subjective and/or [neuro]physiological) and used a placebo or control group for the countermeasure.

RESULTS

A total of 33 studies investigated one or more countermeasures against MF. Of these, eight studies assessed a behavioural countermeasure, 22 a physiological one, one a psychological countermeasure and two a combination of a behavioural and psychological countermeasure. The general finding was that a vast majority of the countermeasures induced a positive effect on behavioural (e.g., task or sport performance) and/or subjective MF markers (e.g., visual analogue scale for MF or alertness). No definitive conclusion could be drawn regarding the effect of the employed countermeasures on (neuro)physiological markers of MF as only 19 of the included studies investigated these measures, and within these a large heterogeneity in the evaluated (neuro)physiological markers was present.

DISCUSSION

Within the physiological countermeasures it seems that the use of odours during a MF task or caffeine before the MF task are the most promising interventions in combating MF. Promising behavioural (e.g., listening to music) and psychological (e.g., extrinsic motivation) countermeasures of MF have also been reported. The most assumed mechanism through which these countermeasures operate is the dopaminergic system. However, this mechanism remains speculative as (neuro)physiological markers of MF have been scarcely evaluated to date.

CONCLUSION

The present systematic review reveals that a wide range of countermeasures have been found to successfully counteract MF on a subjective, (neuro)physiological and/or behavioural level. Of these, caffeine, odours, music and extrinsic motivation are the most evidenced for countering MF. To provide in-detail practical guidelines for the real-life application of MF countermeasures, more research must be performed into the underlying mechanisms and into the optimal dosage and time of application/intake.

Carbohydrate Mouth Rinse and Spray Improve Prolonged Exercise Performance in Recreationally Trained Male College Students

Mouth rinsing with a carbohydrate (CHO) solution has emerged as a sports nutrition strategy to increase endurance performance. This study aimed to clarify the effects of two forms of CHO sensing in the mouth (i.e., CHO mouth rinse (CMR) and CHO mouth spray (CMS)) on exercise performance during prolonged exercise, including ultra-high intensity intermittent exercise over time. We conducted the following experimental trials: (1) 6% glucose solution (G), (2) 6% CMR, (3) 6% CMS, and (4) water (WAT). These trials were conducted at least 1 week apart in a randomized crossover design. Eight male college students performed constant-load exercise for 60 min (intensity 40% VO2peak), four sets of the Wingate test (three 30 s Wingate tests with a 4 min recovery between each test), and a constant-load exercise for 30 min (intensity 40% VO2peak). The mean exercise power output (Watt), ratings of perceived exertion, and blood glucose levels were measured. We found that the mean power values of the CMR and CMS in the third and fourth sets was significantly higher than that of WAT (p < 0.05), and that the G trial did not show a significant difference from any other trial. Thus, when compared to G or WAT, CMR and CMS can help improve endurance exercise performance.

What Is the Evidence That Dietary Macronutrient Composition Influences Exercise Performance? A Narrative Review

The introduction of the needle muscle biopsy technique in the 1960s allowed muscle tissue to be sampled from exercising humans for the first time. The finding that muscle glycogen content reached low levels at exhaustion suggested that the metabolic cause of fatigue during prolonged exercise had been discovered. A special pre-exercise diet that maximized pre-exercise muscle glycogen storage also increased time to fatigue during prolonged exercise. The logical conclusion was that the athlete's pre-exercise muscle glycogen content is the single most important acutely modifiable determinant of endurance capacity. Muscle biochemists proposed that skeletal muscle has an obligatory dependence on high rates of muscle glycogen/carbohydrate oxidation, especially during high intensity or prolonged exercise. Without this obligatory carbohydrate oxidation from muscle glycogen, optimum muscle metabolism cannot be sustained; fatigue develops and exercise performance is impaired. As plausible as this explanation may appear, it has never been proven. Here, I propose an alternate explanation. All the original studies overlooked one crucial finding, specifically that not only were muscle glycogen concentrations low at exhaustion in all trials, but hypoglycemia was also always present. Here, I provide the historical and modern evidence showing that the blood glucose concentration-reflecting the liver glycogen rather than the muscle glycogen content-is the homeostatically-regulated (protected) variable that drives the metabolic response to prolonged exercise. If this is so, nutritional interventions that enhance exercise performance, especially during prolonged exercise, will be those that assist the body in its efforts to maintain the blood glucose concentration within the normal range.

Carbohydrate Mouth-Rinsing Improves Overtime Physical Performance in Male Ice Hockey Players During On-Ice Scrimmages

Purpose

This randomized, double-blind, crossover study examined the effects of mouth-rinsing (MR) with a carbohydrate (CHO) vs. a placebo (PLA) solution on external and internal loads in hydrated ice hockey players during regulation and overtime (OT) periods of an on-ice scrimmage.

Methods

Twelve skilled male hockey players (22.6 [3.4] years, 178.9 [4.7] cm, 84.0 [6.5] kg) played three 20-min regulation periods and one 12-min OT period of small-sided 3-on-3 scrimmage. Skaters repeated 2 min shift and rest intervals. Participants mouth rinsed with 25 mL of CHO or PLA solution approximately every 10 min for a total of 7 rinses. A local positioning system (LPS) tracked external load variables including speed, distance, acceleration, and deceleration. Internal load was monitored with heart rate (HR) sensors and a rating of perceived exertion (RPE).

Results

During regulation play, both the conditions developed similar fatigue, with significantly decreased high-intensity distance, average speed and decelerations, and increased RPE, from period 1 to 2 and 3. In OT, CHO MR increased the distance skated at high-intensity (224 [77], 185 [66] m, p = 0.042), peak speed (24.6 [1.6], 23.7 [1.3] km·h⁻¹, p = 0.016), number of sprints (1.9 [1.2], 1.2 [0.9], p = 0.011), and decreased distance skated at slow speed (300 [33], 336 [47], p = 0.034) vs. PLA MR. OT RPE was similar between the two conditions in spite of more work done in CHO MR.

Conclusions

CHO MR may be a valuable practice to protect against decrements in external load with increased playing time in ice hockey, and possibly allows athletes to perform more work relative to perceived levels of exertion.

No independent or synergistic effects of carbohydrate-caffeine mouth rinse on repeated sprint performance during simulated soccer match play in male recreational soccer players

The study examined the synergistic and independent effects of carbohydrate-caffeine mouth rinse on repeated sprint performance during simulated soccer match play. Nine male soccer players (21 ± 3 years, 1.75 ± 0.05 m, 68.0 ± 9.0 kg) completed four trials with either 6 mg·kg^-1 caffeine + 10% maltodextrin (CHO+CAFMR), 6 mg·kg^-1 caffeine (CAFMR), 10% maltodextrin (CHOMR), water (PLA) in a block randomised, double-blinded, counterbalanced and crossover manner separated by minimum 96 h. All solutions were taste-matched and a carbohydrate-rich meal (2 g·kg^-1body mass) was provided 2 h before each trial. Each trial consisted of a 90-min soccer-specific aerobic field test (SAFT⁹⁰) and two bouts of repeated sprint ability tests (RSAT; 6 × 6 s sprints with 24 s recovery) completed at 0 min and 75^th min of SAFT⁹⁰. A 25 ml solution of either CHO+CAFMR, CAFMR, CHOMR or PLA was rinsed immediately before the second RSAT (75 min). Mean power output, peak power output (PPO) or fatigue index (FI) was not impacted by any treatment during the 75^th min RAST (p > 0.05). These results suggest that carbohydrate and/or caffeine mouth rinses do not have an ergogenic effect during simulated soccer exercise after a high carbohydrate meal.

Effects of Carbohydrate Mouth Rinsing on Upper Body Resistance Exercise Performance

Carbohydrate mouth rinsing has been shown to enhance aerobic exercise performance, but there is limited research with resistance exercise (RE). Therefore, the purpose of this investigation was to examine the effects of carbohydrate mouth rinsing during a high-volume upper body RE protocol on performance, heart rate responses, ratings of perceived exertion, and felt arousal. Recreationally experienced resistance-trained males (N = 17, age: 21 ± 1 years, height: 177.3 ± 5.2 cm, mass: 83.5 ± 9.3 kg) completed three experimental sessions, with the first serving as familiarization to the RE protocol. During the final two trials, the participants rinsed a 25-ml solution containing either a 6% carbohydrate solution or an artificially flavored placebo in a randomized, counterbalanced, and double-blinded fashion. The participants rinsed a total of nine times immediately before beginning the protocol and 20 s before repetitions to failure with the exercises bench press, bent-over row, incline bench press, close-grip row, hammer curls, skull crushers (all completed at 70% one-repetition maximum), push-ups, and pull-ups. Heart rate, ratings of perceived exertion, and felt arousal were measured at the baseline and immediately after each set of repetitions to failure. There were no differences for the total repetitions completed (carbohydrate = 203 ± 25 repetitions vs. placebo = 201 ± 23 repetitions, p = .46, Cohen's d = 0.10). No treatment differences were observed for heart rate, ratings of perceived exertion, or felt arousal (p > .05). Although carbohydrate mouth rinsing has been shown to be effective in increasing aerobic performance, the results from this investigation show no benefit in RE performance in resistance-trained males.

Impact of a Carbohydrate Mouth Rinse on Corticomotor Excitability after Mental Fatigue in Healthy College-Aged Subjects

Mental Fatigue (MF) has been associated with reduced physical performance but the mechanisms underlying this result are unclear. A reduction in excitability of the corticomotor system is a way mental fatigue could negatively impact physical performance. Carbohydrate (CHO) mouth rinse (MR) has been shown to increase corticomotor excitability. PURPOSE: The purpose of this study was to determine if CHO MR impacts corticomotor excitability after MF. METHODS: Fifteen subjects (nine females, six males; age = 23 ± 1 years; height = 171 ± 2 cm; body mass = 69 ± 3 kg; BMI = 23.8 ± 0.7) completed two sessions under different MR conditions (Placebo (PLAC), 6.4% glucose (CHO)) separated by at least 48 h and applied in a double-blinded randomized fashion. Motor-evoked potential (MEP) of the left first dorsal interosseous (FDI) was determined by transcranial magnetic stimulation (TMS) before and after MF. Perceived MF was recorded before and after the MF task using a 100 mm visual analog scale (VAS). RESULTS: MF was greater following PLAC (+30.4 ± 4.0 mm) than CHO (+19.4 ± 3.9 mm) (p = 0.005). MEP was reduced more following PLAC (−16.6 ± 4.4%) than CHO (−3.7 ± 4.7%) (p < 0.001). CONCLUSIONS: CHO MR was successful at attenuating the reduction in corticomotor excitability after MF. Carbohydrate mouth rinse may be a valuable tool at combating the negative consequences of mental fatigue.

Good taste or gut feeling? A new method in rats shows oro-sensory stimulation and gastric distention generate distinct and overlapping brain activation patterns

Satiation is influenced by a variety of signals including gastric distention and oro-sensory stimulation. Here we developed a high-field (9.4 T) functional magnetic resonance imaging (fMRI) protocol to test how oro-sensory stimulation and gastric distention, as induced with a block-design paradigm, affect brain activation under different states of energy balance in rats. Repeated tasting of sucrose induced positive and negative fMRI responses in the ventral tegmental area and septum, respectively, and gradual neural activation in the anterior insula and the brain stem nucleus of the solitary tract (NTS), as revealed using a two-level generalized linear model-based analysis. These unique findings align with comparable human experiments, and are now for the first time identified in rats, thereby allowing for comparison between species. Gastric distention induced more extensive brain activation, involving the insular cortex and NTS. Our findings are largely in line with human studies that have shown that the NTS is involved in processing both visceral information and taste, and anterior insula in processing sweet taste oro-sensory signals. Gastric distention and sucrose tasting induced responses in mesolimbic areas, to our knowledge not previously detected in humans, which may reflect the rewarding effects of a full stomach and sweet taste, thereby giving more insight into the processing of sensory signals leading to satiation. The similarities of these data to human neuroimaging data demonstrate the translational value of the approach and offer a new avenue to deepen our understanding of the process of satiation in healthy people and those with eating disorders.

Carbohydrate mouth rinsing does not affect 6-min walk test performance and blood glucose responses in older adults

PURPOSE

Carbohydrate (CHO) mouth rinsing (MR) prior to exercise has been shown to elicit enhanced performance and energy availability in some studies. Previous literature has concentrated on examining CHO MR strategies for improving aerobic endurance performance in younger athletic adults. Knowledge of the impact of CHO MR on functional performance in older adults is scarce. The purpose of this investigation was to determine if CHO MR would improve 6-min walk test (6MWT) performance, perceived exertion, and blood glucose responses in older adults.

METHOD

Thirty-three individuals (16 males, 17 females), age ≥ 70 years performed two 6MWT trials, one of which utilized a 6.4% maltodextrin CHO MR and one of which utilized a placebo MR. Participants held the MR in their mouth for 20 s prior to the 6MWT, and trials occurred in a counterbalanced fashion. Total distance walked and rating of perceived exertion (RPE) were recorded upon completion of each 6MWT. Heart rate (HR), peripheral blood oxygen saturation (SpO₂), systolic and diastolic blood pressures (BP), blood glucose, and blood lactate were measured before and after each 6MWT.

RESULT

CHO MR did not alter the response of any study parameter compared to the placebo MR (p = 0.13-0.94). HR, systolic BP, and blood lactate increased and SpO₂ decreased across time (p < 0.01).

CONCLUSION

A 6.4% maltodextrin CHO MR did not alter total distance walked, perceived exertion, or other physiological responses elicited by the 6MWT in older adults.

Effects of carbohydrate and caffeine combination mouth rinse on anaerobic performance of highly trained male athletes

The ergogenic effects of carbohydrate (CHO) and caffeine (CAF) mouth rinse (MR) methods on anaerobic performance remains unclear. Therefore, the aim of this study was to investigate the effects of CHO, CAF, and CHO + CAF combination solutions in mouth on repeated vertical jumping (RVJ) performance in highly trained male athletes. Eight male athletes (mean age: 22 years) underwent test sessions four times with minimum 24-h intervals under fasting conditions. Participants rinsed their mouths with four different 25-ml solutions, namely, CHO (6.4% maltodextrin = 1.6 g), CAF (1.2% caffeine = 300 mg), placebo (PLA, saccharin), or CHO + CAF (6.4%+1.2%) combination, for 10 s and performed a 30-s RVJ test twice with a 5-min interval. Peak power output, vertical jump height, blood lactate level, fatigue index, and rate of perceived exertion of the RVJ tests for different intervention sessions were compared. The statistical significance level was set at p ≤ 0.05. Analyses demonstrated that CHO- (Δ: 3.4), CAF- (Δ: -0.8), and CHO + CAF-MR (Δ: -1.8) interventions led to similar RVJ performance changes compared to PLA. All differences in the dependent variables were statistically insignificant and had moderate and lower effect sizes between interventions (p > 0.05, g < 0.94). Our study did not elicit sufficient evidence to recommend highly trained male athletes the use of CHO- and CAF-MR separately or in combination to enhance jump performance. However, the fact that some differences have medium to large effect sizes suggests that the issue is still worth to be a potential topic for further research.Highlights Effects of CHO + CAF-MR on anaerobic performance in highly trained athletes have not been investigated using performance tasks requiring high technical skills.There is not enough evidence to suggest that CHO, CAF and CHO + CAF-MR interventions have beneficial effects on RVJ performance compared to PLA in highly trained male athletes.Some statistically insignificant differences have medium to large effect sizes. Therefore, the issue is still worth to be a potential topic for further research.

Primary, Secondary, and Tertiary Effects of Carbohydrate Ingestion During Exercise

The purpose of this current opinion paper is to describe the journey of ingested carbohydrate from 'mouth to mitochondria' culminating in energy production in skeletal muscles during exercise. This journey is conveniently described as primary, secondary, and tertiary events. The primary stage is detection of ingested carbohydrate by receptors in the oral cavity and on the tongue that activate reward and other centers in the brain leading to insulin secretion. After digestion, the secondary stage is the transport of monosaccharides from the small intestine into the systemic circulation. The passage of these monosaccharides is facilitated by the presence of various transport proteins. The intestinal mucosa has carbohydrate sensors that stimulate the release of two 'incretin' hormones (GIP and GLP-1) whose actions range from the secretion of insulin to appetite regulation. Most of the ingested carbohydrate is taken up by the liver resulting in a transient inhibition of hepatic glucose release in a dose-dependent manner. Nonetheless, the subsequent increased hepatic glucose (and lactate) output can increase exogenous carbohydrate oxidation rates by 40-50%. The recognition and successful distribution of carbohydrate to the brain and skeletal muscles to maintain carbohydrate oxidation as well as prevent hypoglycaemia underpins the mechanisms to improve exercise performance.

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.

Associations between sweet taste function, oral complex carbohydrate sensitivity, liking and consumption of ad libitum sweet and non-sweet carbohydrate milkshakes among female adults

Excess energy intake is recognised as a strong contributing factor to the global rise of being overweight and obese. The aim of this paper was to investigate if oral sensitivity to complex carbohydrate relates to ad libitum consumption of complex carbohydrate foods in a sample group of female adults. Participants' ((n 51 females): age 23·0 (sd 0·6) years (range 20·0-41·0 years); excluding restrained eaters) sensitivity towards maltodextrin (oral complex carbohydrate) and glucose (sweet taste) was assessed by measuring detection threshold (DT) and suprathreshold intensity perception (ST). A crossover design was used to assess consumption of two different iso-energetic preload milkshakes and ad libitum milkshakes - (1) glucose-based milkshake, (2) maltodextrin-based milkshake. Ad libitum intake (primary outcome) and eating rate, liking, hunger, fullness and prospective consumption ratings were measured. Participants who were more sensitive towards complex carbohydrate (maltodextrin DT) consumed significantly more maltodextrin-based milkshake in comparison with less-sensitive participants (P = 0·01) and this was independent of liking. Participants who had higher liking for glucose-based milkshake consumed significantly more glucose-based milkshake in comparison with participants with lower hedonic ratings (P = 0·049). The results provide support regarding the role of the oral system sensitivity (potentially taste) to complex carbohydrate and the prospective to overconsume complex carbohydrate-based milkshake in a single sitting.

Carbohydrate mouth rinse has no effects on behavioral or neuroelectric indices of cognition

Rinsing the mouth with a carbohydrate solution has been suggested as a means to enhance aspects of both physical and cognitive performance. However, evidence in support of these assertions is relatively weak. The purpose of this study was to investigate the effects of a carbohydrate mouth rinse solution on motor speed, inhibition, and sustained attention as indexed by both behavioral and neuroelectric measures. Using a double-blind, placebo-controlled, within-subjects crossover design, 50 college-aged young adults performed a battery of cognitive tasks both before and after rinsing their mouth for 10 s with 20 mL of either a carbohydrate mouth rinse solution or a sensory-matched placebo control solution. A simple tapping task was used as a measure of motor speed, a modified Eriksen flanker task was used to index inhibition, and a rapid visual information processing task was used as a measure of sustained attention. Participants demonstrated longer reaction times in the Flanker task after rinsing their mouths with the carbohydrate mouth rinse, relative to pretest. No differences in reaction time were observed for the placebo control condition. P3 latency in the Flanker task as an index of attentional processing speed was shorter at posttest than at pretest in the placebo control - but not the carbohydrate mouth rinse - condition. These results suggest that despite claims of cognitive enhancement, carbohydrate mouth rinses do not appear to alter motor speed, inhibition, or sustained attention as compared to a placebo control in non-physically-fatigued college-aged adults.

Potato ingestion is as effective as carbohydrate gels to support prolonged cycling performance

Carbohydrate (CHO) ingestion is an established strategy to improve endurance performance. Race fuels should not only sustain performance but also be readily digested and absorbed. Potatoes are a whole-food-based option that fulfills these criteria, yet their impact on performance remains unexamined. We investigated the effects of potato purée ingestion during prolonged cycling on subsequent performance vs. commercial CHO gel or a water-only condition. Twelve cyclists (70.7 ± 7.7 kg, 173 ± 8 cm, 31 ± 9 yr, 22 ± 5.1% body fat; means ± SD) with average peak oxygen consumption (V̇o_2peak) of 60.7 ± 9.0 mL·kg⁻¹·min⁻¹ performed a 2-h cycling challenge (60–85% V̇o_2peak) followed by a time trial (TT; 6 kJ/kg body mass) while consuming potato, gel, or water in a randomized-crossover design. The race fuels were administered with [U-¹³C₆]glucose for an indirect estimate of gastric emptying rate. Blood samples were collected throughout the trials. Blood glucose concentrations were higher (P < 0.001) in potato and gel conditions compared with water condition. Blood lactate concentrations were higher (P = 0.001) after the TT completion in both CHO conditions compared with water condition. TT performance was improved (P = 0.032) in both potato (33.0 ± 4.5 min) and gel (33.0 ± 4.2 min) conditions compared with water condition (39.5 ± 7.9 min). Moreover, no difference was observed in TT performance between CHO conditions (P = 1.00). In conclusion, potato and gel ingestion equally sustained blood glucose concentrations and TT performance. Our results support the effective use of potatoes to support race performance for trained cyclists.

NEW & NOTEWORTHY The ingestion of concentrated carbohydrate gels during prolonged exercise has been shown to promote carbohydrate availability and improve exercise performance. Our study aim was to expand and diversify race fueling menus for athletes by providing an evidence-based whole-food alternative to the routine ingestion of gels during training and competition. Our work shows that russet potato ingestion during prolonged cycling is as effective as carbohydrate gels to support exercise performance in trained athletes.

Impact of Carbohydrate Ingestion on Cognitive Flexibility and Cerebral Oxygenation during High-Intensity Intermittent Exercise: A Comparison between Maple Products and Usual Carbohydrate Solutions

BACKGROUND

The aim of this study was to compare the effects of carbohydrate (CHO) drinks (6% per volume) sweetened with maple (syrup or sap) to a commercial sports drink, glucose, and a control solution (water) on cognitive flexibility during high-intensity intermittent exercise.

METHODS

Eighty-five active men completed six 3-min bouts at 95% of their maximal aerobic power on a stationary bike, with 3 min of passive rest between efforts. Subjects were randomly allocated to an ingestion condition. Following each exercise bout, subjects ingested 166 mL of the experimental solution, drinking a total of 1 L of the same solution throughout the experimentation. Cognitive flexibility was measured using reaction time and accuracy on the Stroop task. The cognitive task was performed a total of 10 times, including 15 and 30 min post-exercise. Glycemia and cerebral oxygenation were also measured at each time point. Statistical analyses were performed using a two-way ANOVA (Condition × Time) with repeated measures.

RESULTS

The ingestion of maple products and the commercial sports drink led to a lesser increase in glycemia than glucose ingestion. CHO ingestion, when compared to water, induced a slight reduction in reaction times on the cognitive task, especially in the switching trials. CHO ingestion had no impact on cerebral oxygenation.

CONCLUSIONS

This study shows that CHO ingestion, regardless of its type, tends to improve cognitive performance throughout exercise, especially during difficult cognitive tasks.

Effect of Carbohydrate Mouth Rinse on Training Load Volume in Resistance Exercises

Bastos-Silva, VJ, Prestes, J, and Geraldes, AAR. Effect of carbohydrate mouth rinse on training load volume in resistance exercises. J Strength Cond Res 33(6): 1654-1658, 2019-The aim of this study was to investigate the effect of carbohydrate (CHO) mouth rinse on training load volume (TLV-number of repetitions × load lifted [kg]) on 2 resistance exercises: leg press (LP) and bench press (BP). Twelve recreational resistance trained males were recruited. Subjects were assessed for 1 repetition maximum (1RM) and muscular endurance (ME) in LP and BP. Muscular endurance was determined by the maximum number of repetitions performed to volitional fatigue, with a load equal to 80% of 1RM. Exercises were performed on separate days (72 hours apart) under 3 experimental conditions: control (CONT), CHO (25 ml with 6.4% of maltodextrin), and placebo (juice without CHO [PLA]). Carbohydrate and PLA were used immediately before each exercise. There was no significant difference between conditions for the number of repetitions (CHO = 13.5 ± 4.8; PLA = 11.5 ± 4.4; CONT = 12.4 ± 4.4, p = 0.68) nor TLV (CHO = 2006.7 ± 825.2 kg; PLA = 1712.5 ± 772.9 kg; CONT = 1817.1 ± 672.6 kg, p = 0.99) in LP. However, CHO increased both repetitions (CHO = 8.2 ± 1.6; PLA = 7.1 ± 2.4; CONT = 6.8 ± 1.8, p = 0.002) and TLV (CHO = 557.1 ± 155.4 kg; PLA = 495.9 ± 206.1 kg; CONT = 476.1 ± 175.3 kg, p = 0.035) compared with CON in BP. Thus, a CHO mouth rinse increases BP performance in trained men, suggesting an interesting strategy to be used by experienced resistance training practitioners.

Impact of a Carbohydrate Mouth Rinse on Quadriceps Muscle Function and Corticomotor Excitability

PURPOSE

The purpose of this investigation is to determine the effects of different forms of a CHO MR on quadriceps muscle performance and corticospinal motor excitability.

METHODS

Ten subjects (5 females, 5 males; 25±1 years; 1.71±0.03 m 73±5 kg) completed 4 trials. A different MR condition was applied during each trial (Placebo (PLA), 6.4% glucose (GLU), 6.4% maltose (MAL), 6.4% maltodextrin (MDX)). Maximal voluntary contraction (MVIC) of the right quadriceps and motor-evoked potential (MEP) of the right rectus femoris was determined pre (10 min), immediately after, and post (10 min) MR. MEP was precipitated by transcranial magnetic stimulation (TMS) during muscle contraction (50% of MVIC). MR was held in the mouth for 20 s and treatments were applied using a Latin square design. The relative change in MEP from pre-measures was different across treatments (p=0.025) but was not different across time (p=0.357).

RESULTS

Relative change in MEP was greater for all CHO conditions immediately after (GLU=2.58±5.33%; MAL=3.92±3.90%; MDX=18.28±5.57%) and 10 min after (GLU=14.09±13.96%; MAL=8.64±8.67%; MDX=31.54±12.77%) MR compared to PLA (Immediately after=-2.19±4.25%, 10 min=-13.41±7.46%). The relative change in MVC was greater for CHO conditions immediately (GLU=3.98±2.49%; MAL=5.89±2.29.90%; MDX=7.66±1.93%) and 10 min after (GLU=7.22±2.77%; MAL=10.26±4.22%; MDX=10.18±1.50%) MR compared to PLA (Immediately after=-3.24±1.50%, 10 min=-6.46±2.22%).

CONCLUSIONS

CHO MR increased corticospinal motor excitability and quadriceps muscle performance immediately and 10 min after application; however, the form of CHO used did not influence this response.

The ergogenic potency of carbohydrate mouth rinse on endurance running performance of dehydrated athletes

PURPOSE

To examine the effect of carbohydrate (CHO) mouth rinsing on endurance running responses and performance in dehydrated individuals.

METHODS

In a double blind, randomised crossover design, 12 well-trained male runners completed 4 running time to exhaustion (TTE) trials at a speed equivalent to 70% of VO_2peak in a thermoneutral condition. Throughout each run, participants mouth rinsed and expectorated every 15 min either 25 mL of 6% CHO or a placebo (PLA) solution for 10 s. The four TTEs consisted of two trials in the euhydrated (EU-CHO and EU-PLA) and two trials in the dehydrated (DY-CHO and DY-PLA) state. Prior to each TTE run, participants were dehydrated via exercise and allowed a passive rest period during which they were fed and either rehydrated equivalent to their body mass deficit (i.e., EU trials) or ingested only 50 mL of water (DY trials).

RESULTS

CHO mouth rinsing significantly improved TTE performance in the DY compared to the EU trials (78.2 ± 4.3 vs. 76.9 ± 3.8 min, P = 0.02). The arousal level of the runners was significantly higher in the DY compared to the EU trials (P = 0.02). There was no significant difference among trials in heart rate, plasma glucose and lactate, and psychological measures.

CONCLUSIONS

CHO mouth rinsing enhanced running performance significantly more when participants were dehydrated vs. euhydrated due to the greater sensitivity of oral receptors related to thirst and central mediated activation. These results show that level of dehydration alters the effect of brain perception with presence of CHO.

The sweet taste signalling pathways in the oral cavity and the gastrointestinal tract affect human appetite and food intake: a review

Sweet taste is associated with food reward and energy source in the form of carbohydrate. Excessive sweet consumption is blamed for the prevalence of obesity. However, evidence for the potential of sweet taste to influence food intake and bodyweight regulation in humans remains unclear. The purpose of this review was to examine the physiological responses relevant to sweet taste mechanisms and the impact on appetite control. The literature was examined for studies that assessed the effects of non-nutritive sweeteners and natural sugars on hormonal secretions and neural activations via oral and gastrointestinal pathways. The findings indicated that a network of sweet taste signalling pathways in the oral cavity and the gut seem to mediate hormonal responses and some metabolism differences in neural circus that orchestrating the hunger-satiety cycle. Individual variations of sweet taste perception which is modulated by hormonal and genetic factors have been associated with dietary nutrient and sugar consumption.

The effect of carbohydrate mouth rinse on performance, biochemical and psychophysiological variables during a cycling time trial: a crossover randomized trial

BACKGROUND

The hypothesis of the central effect of carbohydrate mouth rinse (CMR) on performance improvement in a fed state has not been established, and its psychophysiological responses have not yet been described. The aim of this study was to evaluate the effect of CMR in athletes fed state on performance, biochemical and psychophysiological responses compared to ad libitum water intake.

METHODS

Eleven trained male cyclists completed a randomized, crossover trial, which consisted of a 30 km cycle ergometer at self-selected intensity and in a fed state. Subjects were under random influence of the following interventions: CMR with a 6% unflavored maltodextrin solution; mouth rinsing with a placebo solution (PMR); drinking "ad libitum" (DAL). The time for completion of the test (min), heart rate (bpm) and power (watts), rating of perceived exertion (RPE), affective response, blood glucose (mg/dL) and lactate (mmol/DL), were evaluated before, during and immediately after the test, while insulin (uIL/mL), cortisol (μg/dL) and creatine kinase (U/L) levels were measured before, immediately after the test and 30 min after the test.

RESULTS

Time for completion of the 30 km trial did not differ significantly among CMR, PMR and DAL interventions (means = 54.5 ± 2.9, 54.7 ± 2.9 and 54.5 ± 2.5 min, respectively; p = 0.82). RPE and affective response were higher in DAL intervention (p < 0.01). Glucose, insulin, cortisol and creatine kinase responses showed no significant difference among interventions.

CONCLUSIONS

In a fed state, CMR has not caused metabolic changes, and it has not improved physical performance compared to ad libitum water intake, but demonstrated a possible central effect. ReBec registration number: RBR-4vpwkg. Available in http://www.ensaiosclinicos.gov.br/rg/?q=RBR-4vpwkg.

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.

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 (TT_4km) performance. After a preliminary session, cyclists (n = 9) performed a TT_4km after a CHO or placebo (PLA) mouth rinse. Mean power output, time, and ratings of perceived exertion (RPE) were recorded throughout the TT_4km. Twitch interpolation responses (%VA; voluntary activation and ∆Tw; delta peak twitch torque) were compared pre and post TT_4km 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 RPE_SLOPE with only one CHO mouth rinse were not translated into improved TT_4km 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.

Impact of carbohydrate mouth rinsing on time to exhaustion during Ramadan: A randomized controlled trial in Jordanian men

Mouth rinsing using a carbohydrate (CHO) solution has been suggested to improve physical performance in fasting participants. This study examined the effects of CHO mouth rinsing during Ramadan fasting on running time to exhaustion and on peak treadmill speed (V_peak). In a counterbalanced crossover design, 18 sub-elite male runners (Age: 21 ± 2 years, Weight: 68.1 ± 5.7 kg, VO_2max: 55.4 ± 4.8 ml/kg/min) who observed Ramadan completed a familiarization trial and three experimental trials. The three trials included rinsing and expectorating a 25 mL bolus of either a 7.5% sucrose solution (CHO), a flavour and taste matched placebo solution (PLA) for 10 s, or no rinse (CON). The treatments were performed prior to an incremental treadmill test to exhaustion. Three-day dietary and exercise records were obtained on two occasions and analysed. Anthropometric characteristics were obtained and recorded for all participants. A main effect for mouth rinse on peak velocity (V_peak) (CHO: 17.6 ± 1.5 km/h; PLA: 17.1 ± 1.4 km/h; CON: 16.7 ± 1.2 km/h; P < .001, η_p² = 0.49) and time to exhaustion (CHO: 1282.0 ± 121.3 s; PLA: 1258.1 ± 113.4 s; CON: 1228.7 ± 98.5 s; P = .002, η_p² = 0.41) was detected, with CHO significantly higher than PLA (P < .05) and CON (P < .05). Oxygen consumption, heart rate, respiratory exchange ratio, and rating of perceived exertion were not significantly different between treatments or trials (P > .05). Energy availability from dietary analysis, body weight, and fat-free mass did not change during the last two weeks of Ramadan (P > .05). This study concludes that carbohydrate mouth rinsing improves running time to exhaustion and peak treadmill speed under Ramadan fasting conditions.

Effects of carbohydrate mouth rinse and caffeine on high-intensity interval running in a fed state

The current study aims to identify if mouth rinsing with a 6% carbohydrate mouth-rinse (CMR) solution and mouth rinsing and ingestion of caffeine (CMR+CAFF) can affect exercise performance during steady-state (SS) running and high-intensity intervals (HIIT) in comparison with a 0% control solution (PLA) when in a fed state. Eight recreationally trained males completed 3 trials (CMR, CMR+CAFF, and PLA) of 45 min SS running and an HIIT protocol (90% peak treadmill velocity) until fatigue in a double blinded, repeated-measures study. Participants ingested a capsule of either CAFF or PLA before and after SS. Participants received a 25-mL bolus of carbohydrate solution (CMR and CMR+CAFF trials) or taste-matched PLA (PLA trial) prior to HIIT protocol and after every second effort. Heart rate and lactate responses were recorded throughout the SS and HIIT protocol. CMR+CAFF was significantly different when compared with PLA (p = 0.001; Cohens d = 1.34) and CMR (p = 0.031; Cohens d = 0.87) in relation to distance covered before fatigue. Although there was no significant difference between CMR and PLA, there was a small benefit for CMR (p = 0.218; Cohens d = 0.46). Results indicate that CMR and ingestion of CAFF leads to improvements in performance during interval sessions while participants were in a fed state. These findings indicate that the regular use of CMR can decrease the risk of gastrointestinal distress reported by athletes, which can be applicable to athletes in a real-world setting.

The Effect of a Carbohydrate Mouth Rinse on Upper-Body Muscular Strength and Endurance

Dunkin, JE and Phillips, SM. The effect of a carbohydrate mouth rinse on upper-body muscular strength and endurance. J Strength Cond Res 31(7): 1948-1953, 2017-Carbohydrate (CHO) mouth rinsing rapidly increases corticomotor output and maximal muscle force production, which could enhance muscular strength and endurance during resistance exercise. However, previous research has found no effect of CHO rinsing on muscular strength or endurance. The current study altered the CHO rinse composition and frequency and the muscular endurance test to further investigate the effects of a CHO mouth rinse on upper-body muscular strength and endurance. Twelve recreationally resistance-trained men (mean ± SD age 22 ± 1 year, height 179.2 ± 1.8 cm, body mass 80.9 ± 6.1 kg) completed a bench press protocol (1 repetition maximum [RM] test followed by repetitions to failure at 40% of 1RM) on 3 occasions. Subjects rinsed 25 ml of an 18% CHO solution or a placebo for 10 seconds before 1RM and repetitions to failure and completed a no-rinse control condition. Felt arousal (FA) was measured before and after each rinse, heart rate (HR) was measured before and after both exercise protocols, and rating of perceived exertion (RPE) was recorded after repetitions to failure. Rinsing did not influence 1RM (p = 0.680, (Equation is included in full-text article.)= 0.03), repetitions to failure (p = 0.677, (Equation is included in full-text article.)= 0.04), or exercise volume (load × reps; p = 0.600, (Equation is included in full-text article.)= 0.05). There were no significant treatment effects on heart rate (p = 0.677, (Equation is included in full-text article.)= 0.04), FA (p = 0.674, (Equation is included in full-text article.)= 0.04) or rating of perceived exertion (p = 0.604, (Equation is included in full-text article.)= 0.05). A CHO mouth rinse does not improve upper-body muscular strength or endurance.

Neural basis of exertional fatigue in the heat: A review of magnetic resonance imaging methods

The central nervous system, specifically the brain, is implicated in the development of exertional fatigue under a hot environment. Diverse neuroimaging techniques have been used to visualize the brain activity during or after exercise. Notably, the use of magnetic resonance imaging (MRI) has become prevalent due to its excellent spatial resolution and versatility. This review evaluates the significance and limitations of various brain MRI techniques in exercise studies-brain volumetric analysis, functional MRI, functional connectivity MRI, and arterial spin labeling. The review aims to provide a summary on the neural basis of exertional fatigue and proposes future directions for brain MRI studies. A systematic literature search was performed where a total of thirty-seven brain MRI studies associated with exercise, fatigue, or related physiological factors were reviewed. The findings suggest that with moderate dehydration, there is a decrease in total brain volume accompanied with expansion of ventricular volume. With exercise fatigue, there is increased activation of sensorimotor and cognitive brain areas, increased thalamo-insular activation and decreased interhemispheric connectivity in motor cortex. Under passive hyperthermia, there are regional changes in cerebral perfusion, a reduction in local connectivity in functional brain networks and an impairment to executive function. Current literature suggests that the brain structure and function are influenced by exercise, fatigue, and related physiological perturbations. However, there is still a dearth of knowledge and it is hoped that through understanding of MRI advantages and limitations, future studies will shed light on the central origin of exertional fatigue in the heat.

Efficacy of Carbohydrate Ingestion on CrossFit Exercise Performance

The efficacy of carbohydrate (CHO) ingestion during high-intensity strength and conditioning type exercise has yield mixed results. However, little is known about shorter duration high-intensity exercise such as CrossFit. The purpose of this study was to investigate the performance impact of CHO ingestion during high-intensity exercise sessions lasting approximately 30 min. Eight healthy males participated in a total of four trials; two familiarizations, a CHO trial, and a similarly flavored, non-caloric placebo (PLA) trial. CrossFit's "Fight Gone Bad Five" (FGBF) workout of the day was the exercise model which incorporated five rounds of maximal repetition exercises, wall throw, box jump, sumo deadlift high pull, push press, and rowing, followed by one minute of rest. Total repetitions and calories expended were summated from each round to quantify total work (FGBF score). No difference was found for the total work between CHO (321 ± 51) or PLA (314 ± 52) trials (p = 0.38). There were also no main effects (p > 0.05) for treatment comparing exercise performance across rounds. Based on the findings of this study, it does not appear that ingestion of CHO during short duration, high-intensity CrossFit exercise will provide a beneficial performance effect.

New Insights into Enhancing Maximal Exercise Performance Through the Use of a Bitter Tastant

It is generally acknowledged that for an orally administered ergogenic aid to enhance exercise performance it must first be absorbed by the gastrointestinal tract before exerting its effects. Recently, however, it has been reported that some ergogenic aids can affect exercise performance without prior absorption by the gastrointestinal tract. This is best illustrated by studies that have shown that rinsing the mouth with a carbohydrate (CHO) solution, without swallowing it, significantly improves exercise performance. The ergogenic effects of CHO mouth rinsing in these studies have been attributed to the activation of the brain by afferent taste signals, but the specific mechanisms by which this brain activation translates to enhanced exercise performance have not yet been elucidated. Given the benefits of CHO mouth rinsing for exercise performance, this raises the issue of whether other types of tastants, such as bitter-tasting solutions, may also improve exercise performance. Recently, we performed a series of studies investigating whether the bitter tastant quinine can improve maximal sprint performance in competitive male cyclists, and, if so, to examine some of the possible mechanisms whereby this effect may occur. These studies have shown that mouth rinsing and ingesting a bitter-tasting quinine solution can significantly improve the performance of a maximal cycling sprint. There is also evidence that the ergogenic effect of quinine is mediated, at least in part, by an increase in autonomic nervous system activation and/or corticomotor excitability. The purpose of this article is to discuss the results and implications of these recent studies and to suggest avenues for further research, which may add to the understanding of the way the brain integrates signals from the oral cavity with motor behaviour, as well as uncover novel strategies to improve exercise performance.

Cognitive Performance Enhancement Induced by Caffeine, Carbohydrate and Guarana Mouth Rinsing during Submaximal Exercise

The aim of this study was to investigate the influence of serial mouth rinsing (MR) with nutritional supplements on cognitive performance (i.e., cognitive control and time perception) during a 40-min submaximal exercise. Twenty-four participants completed 4 counterbalanced experimental sessions, during which they performed MR with either placebo (PL), carbohydrate (CHO: 1.6 g/25 mL), guarana complex (GUAc: 0.4 g/25 mL) or caffeine (CAF: 67 mg/25 mL) before and twice during exercise. The present study provided some important new insights regarding the specific changes in cognitive performance induced by nutritional supplements. The main results were: (1) CHO, CAF and GUA MR likely led participants to improve temporal performance; (2) CAF MR likely improved cognitive control; and (3) CHO MR led to a likely decrease in subjective perception of effort at the end of the exercise compared to PL, GUA and CAF. Moreover, results have shown that performing 40-min submaximal exercise enhances information processing in terms of both speed and accuracy, improves temporal performance and does not alter cognitive control. The present study opens up new perspectives regarding the use of MR to optimize cognitive performance during physical exercise.

Carbohydrate mouth rinse improves morning high-intensity exercise performance

Oral carbohydrate (CHO) rinsing has been demonstrated to provide beneficial effects on exercise performance of durations of up to one hour. The aim of the present study was to investigate the effects of CHO mouth rinsing on morning high-intensity exercise performance. Following institutional ethical approval and familiarisation, 12 healthy males (mean ± SD age: 23 ± 3 years, height: 175.5 ± 7.4 cm, body mass: 75.4 ± 7.5 kg) participated in this study. Countermovement jump (CMJ) height, isometric mid-thigh pull peak force, 10 m sprint time and bench press and back squat repetitions to failure were assessed following CHO and placebo (PLA) rinsing or a control condition (CON). All testing took place at 07:30 following an 11 hour overnight fast. Performance of CMJ height (CHO: 39 ± 7 cm; PLA: 38 ± 7 cm; CON: 36 ± 6 cm; P = .003, [Formula: see text] = 0.40), 10 m sprint time (CHO: 1.78 ± 0.07 s; PLA: 1.81 ± 0.07 s; CON: 1.85 ± 0.05 s; P = .001, [Formula: see text] = 0.47), the number of bench press (CHO: 25 ± 3; PLA: 24 ± 4; CON: 22 ± 4; P < .001, [Formula: see text] = 0.55) and squat (CHO: 31 ± 4; PLA: 29 ± 5; CON: 26 ± 6; P < .001, [Formula: see text] = 0.70) repetitions and mean felt arousal (CHO: 5 ± 1; PLA: 4 ± 0; CON: 4 ± 0; P = .009, [Formula: see text] = 0.25) improved following CHO rinsing. However, isometric mid-thigh pull peak force was unchanged (CHO: 2262 ± 288 N; PLA: 2236 ± 354 N; CON: 2212 ± 321 N; P = .368, [Formula: see text] = 0.08). These results suggest that oral CHO rinsing solution significantly improved the morning performance of CMJ height, 10 m sprint times, bench press and squat repetitions to failure and felt arousal, although peak force during an isometric mid-thigh pull, rating of perceived exertion and heart rate were unaffected.

Effect of mouth rinsing and ingestion of carbohydrate solutions on mood and perceptual responses during exercise

Background

The aim of this study was to investigate whether mouth rinsing or ingesting carbohydrate (CHO) solutions impact on perceptual responses during exercise.

Methods

Nine moderately trained male cyclists underwent a 90-min glycogen-reducing exercise, and consumed a low CHO meal, prior to completing an overnight fast. A 1-h cycle time trial was performed the following morning. Four trials, each separated by 7 days, were conducted in a randomized, counterbalanced study design: 15% CHO mouth rinse (CHOR), 7.5% CHO ingestion (CHOI), placebo mouth rinse (PLAR) and placebo ingestion (PLAI). Solution volumes (1.5 ml · kg⁻¹ ingestion trials and 0.33 ml · kg⁻¹ rinsing trials) were provided after every 12.5% of completed exercise. Perceptual scales were used to assess affective valence (feeling scale, FS), arousal (felt arousal scale, FAS), exertion (ratings of perceived exertion, RPE) and mood (profile of mood states, POMS) before, during and immediately after exercise.

Results

There was no difference in RPE (CHOI, 14.0 ± 1.9; CHOR, 14.2 ± 1.7; PLAI, 14.6 ± 1.8; PLAR, 14.6 ± 2.0; P = 0.35), FS (CHOI, 0.0 ± 1.7; CHOR, −0.2 ± 1.5; PLAI, −0.8 ± 1.4; PLAR, −0.8 ± 1.6; P = 0.15), or FAS (CHOI, 3.6 ± 1.1; CHOR, 3.5 ± 1.0; PLAI, 3.4 ± 1.4; PLAR, 3.3 ± 1.3; P = 0.725) scores between trials. While overall POMS score did not appear to differ between trials, the ‘vigour’ subscale indicated that CHOI may facilitate the maintenance of ‘vigour’ scores over time, in comparison to the steady decline witnessed in other trials (P = 0.04). There was no difference in time trial performance between trials (CHOI, 65.3 ± 4.8 min; CHOR, 68.4 ± 3.9 min; PLAI, 68.7 ± 5.3 min; PLAR, 68.3 ± 5.2 min; P = 0.21) but power output was higher in CHOI (231.0 ± 33.2 W) relative to other trials (221–223.6 W; P < 0.01).

Conclusions

In a CHO-reduced state, mouth rinsing with a CHO solution did not impact on perceptual responses during high-intensity exercise in trained cyclists and triathletes. On the other hand CHO ingestion improved perceived ratings of vigour and increased power output during exercise.

Running Performance With Nutritive and Nonnutritive Sweetened Mouth Rinses

Using mouth rinse (MR) with carbohydrate during exercise has been shown to act as an ergogenic aid.

PURPOSE

To investigate if nutritive or nonnutritive sweetened MR affects exercise performance and to assess the influence of sweetness intensity on endurance performance during a time trial (TT).

METHODS

This randomized, single-blinded study had 4 treatment conditions. Sixteen subjects (9 men, 7 women) completed a 12.8-km TT 4 different times. During each TT, subjects mouth-rinsed and expectorated a different solution at time 0 and every 12.5% of the TT. The 4 MR solutions were sucrose (S) (sweet taste and provides energy of 4 kcal/g), a lower-intensity sucralose (S1:1) (artificial sweetener that provides no energy but tastes sweet), a higher-intensity sucralose (S100:1), and water as control (C). Completion times for each TT, heart rate (HR), and ratings of perceived exertion (RPE) were also recorded.

RESULTS

Completion time for S was faster than for C (1:03:47 ± 00:02:17 vs 1:06:56 ± 00:02:18, respectively; P < .001) and showed a trend to be faster vs S100:1 (1:03:47 ± 00:02:17 vs 1:05:38 ± 00:02:12, respectively; P = .07). No other TT differences were found. Average HR showed a trend to be higher for S vs C (P = .08). The only difference in average or maximum RPE was for higher maximum RPE in C vs S1:1 (P = .02).

CONCLUSION

A sweet-tasting MR did improve endurance performance compared with water in a significant manner (mean 4.5% improvement; 3+ min.); however, the presence of energy in the sweet MR appeared necessary since the artificial sweeteners did not improve performance more than water alone.

Electro-physiological changes in the brain induced by caffeine or glucose nasal spray

OBJECTIVE

A direct link between the mouth cavity and the brain for glucose (GLUC) and caffeine (CAF) has been established. The aim of this study is to determine whether a direct link for both substrates also exist between the nasal cavity and the brain.

METHODS

Ten healthy male subjects (age 22 ± 1 years) performed three experimental trials, separated by at least 2 days. Each trial included a 20-s nasal spray (NAS) period in which solutions placebo (PLAC), GLUC, or CAF were provided in a double-blind, randomized order. During each trial, four cognitive Stroop tasks were performed: two familiarization trials and one pre- and one post-NAS trial. Reaction times and accuracy for different stimuli (neutral, NEUTR; congruent, CON; incongruent INCON) were determined. Electroencephalography was continuously measured throughout the trials. During the Stroop tasks pre- and post-NAS, the P300 was assessed and during NAS, source localization was performed using standardized low-resolution brain electromagnetic tomography (sLORETA).

RESULTS AND DISCUSSION

NAS activated the anterior cingulate cortex (ACC). CAF-NAS also increased θ and β activity in frontal cortices. Furthermore, GLUC-NAS increased the β activity within the insula. GLUC-NAS also increased the P300 amplitude with INCON (P = 0.046) and reduced P300 amplitude at F3-F4 and P300 latency at CP1-CP2-Cz with NEUTR (P = 0.001 and P = 0.016, respectively). The existence of nasal bitter and sweet taste receptors possibly induce these brain responses.

CONCLUSION

Greater cognitive efficiency was observed with GLUC-NAS. CAF-NAS activated cingulate, insular, and sensorymotor cortices, whereas GLUC-NAS activated sensory, cingulate, and insular cortices. However, no effect on the Stroop task was found.

Dose-response effects of water supplementation on cognitive performance and mood in children and adults

Water supplementation has been found to facilitate visual attention and short-term memory, but the dose required to improve performance is not yet known. We assessed the dose response effect of water on thirst, mood and cognitive performance in both adults and children. Participants were offered either no water, 25 ml or 300 ml water to drink. Study 1 assessed 96 adults and in Study 2, data are presented from 60 children aged 7-9 years. In both studies, performance was assessed at baseline and 20 min after drinking (or no drink); on thirst and mood scales, letter cancellation and a digit span test. For both children and adults, a large drink (300 ml) was necessary to reduce thirst, while a small drink (25 ml) was sufficient to improve visual attention (letter cancellation). In adults, a large drink improved digit span, but there was no such effect in children. In children, but not adults, a small drink resulted in increased thirst ratings. Both children and adults show dose-response effects of drinking on visual attention. Visual attention is enhanced by small amounts of fluid and appears not to be contingent on thirst reduction. Memory performance may be related to thirst, but differently for children and adults. These contrasting dose-response characteristics could imply cognitive enhancement by different mechanisms for these two domains.

Effect of Carbohydrate Intake on Maximal Power Output and Cognitive Performances

The present study aimed to assess the beneficial effect of acute carbohydrate (7% CHO) intake on muscular and cognitive performances. Seventeen high levels athletes in explosive sports (fencing and squash) participated in a randomized, double-blind study consisting in series of 6 sprints (5s) with a passive recovery (25s) followed by 15 min submaximal cycling after either maltodextrine and fructose (CHO) or placebo (Pl) intake. Cognitive performances were assessed before and after sprint exercise using a simple reaction time (SRT) task at rest, a visual scanning task (VS) and a Go/Nogo task (GNG) during a submaximal cycling exercise. Results showed a beneficial effect of exercise on VS task on both conditions (Pl: −283 ms; CHO: −423 ms) and on SRT only during CHO condition (−26 ms). In the CHO condition, SRT was faster after exercise whereas no effect of exercise was observed in the Pl condition. According to a qualitative statistical method, a most likely and likely positive effect of CHO was respectively observed on peak power (+4%) and tiredness (−23%) when compared to Pl. Furthermore, a very likely positive effect of CHO was observed on SRT (−8%) and a likely positive effect on visual scanning (−6%) and Go/Nogo tasks (−4%) without any change in accuracy. In conclusion acute ingestion of 250 mL of CHO, 60 min and 30 min before exercise, improve peak power output, decrease muscular tiredness and speed up information processing and visual detection without changing accuracy.

Effects of carbohydrate intake on time to exhaustion and anaerobic contribution during supramaximal exercise

ABSTRACT Objective: This study evaluated the effect of carbohydrate intake on time to exhaustion and anaerobic contribution during supramaximal exercise on a cycle ergometer. Methods: The sample comprised ten participants with a mean age of 23.9±2.5 years, mean body mass of 75.1±12.3 kg, mean height of 170.0±1.0 cm, and mean body fat of 11.3±5.2%. The participants underwent an incremental test to determine maximal oxygen uptake and maximum power output, and two supramaximal tests with a constant load of 110% of the maximum power output to exhaustion. Thirty minutes before the supramaximal tests the participants consumed carbohydrates (2 g.kg-1) or placebo. Results: The times to exhaustion of carbohydrate and placebo did not differ (carbohydrate: 170.7±44.6s; placebo: 156.1±26.7s, p=0.17; effect size=0.39). Similarly, the anaerobic contributions of the two treatments did not differ (carbohydrate: 3.0±0.9 L; placebo: 2.7±1.1 L, p=0.23; effect size=0.29). Conclusion: Carbohydrate intake was not capable of increasing time to exhaustion and anaerobic contribution in physically active men cycling at 110% of maximum power output.