Mouth rinse but not ingestion of a carbohydrate solution improves 1-h cycle time trial performance

The effects of caffeine mouth rinsing on selective attention as a function of different caffeine concentrations and perceived taste intensity in recreationally active males at rest: a randomized placebo-controlled cross-over trial

RATIONALE

The effect of caffeine mouth rinsing (CAF-MR) on cognitive performance has not been thoroughly investigated.

OBJECTIVES

To evaluate the effects of different concentrations of CAF-MR on selective attention in relation to perceived taste intensity.

METHODS

A total of 30 healthy and recreationally active male subjects were included in this randomized, double-blind, placebo-controlled crossover trial. Interventions included MR for 20 s at rest with three different caffeine solutions (0.24% [60 mg/25 mL], 0.6% [150 mg/25 mL], and 1.2% [300 mg/25 mL]), MR with 25 mL water (placebo), and no MR (control). Data on Victoria Stroop Test (VST) and the perceived taste intensity were recorded at five sessions.

RESULTS

CAF-MR-300 mg intervention significantly decreased completion time (from 62.93 ± 19.07 to 57.01 ± 16.74 s, p = 0.002 in Part D), while CAF-MR-150 mg intervention significantly decreased number of errors in Part D (7.00 ± 6.21 vs. 5.63 ± 5.76, p = 0.04) and Part C (8.77 ± 8.80 vs. 7.10 ± 7.11, p = 0.02). Perceived difficulty was significantly decreased both after CAF-MR with 150 mg (5.57 ± 1.65 vs. 4.77 ± 1.98, p = 0.006) and 300 mg (5.95 ± 1.77vs. 4.67 ± 1.96, p < 0.001). Perceived taste intensity for 300 mg of caffeine was negatively correlated with completion time (r: ranged, 0.37 to 0.46, p ranged, 0.045 to 0.009) after 300 mg, 150 mg (p ranged, 0.04 to 0.005) and placebo (p ranged 0.044 to 0.03) interventions.

CONCLUSIONS

This study is the first to demonstrate that CAF-MR shows dose-dependent effects on selective attention in healthy recreational males, such as improved speed (for 300 mg caffeine), reduced error rate (for 150 mg caffeine) and decrease in perceived difficulty (for 150 and 300 mg caffeine).

Food for thought: Physiological considerations for nutritional ergogenic efficacy

Top-class athletes have optimized their athletic performance largely through adequate training, nutrition, recovery, and sleep. A key component of sports nutrition is the utilization of nutritional ergogenic aids, which may provide a small but significant increase in athletic performance. Over the last decade, there has been an exponential increase in the consumption of nutritional ergogenic aids, where over 80% of young athletes report using at least one nutritional ergogenic aid for training and/or competition. Accordingly, due to their extensive use, there is a growing need for strong scientific investigations validating or invalidating the efficacy of novel nutritional ergogenic aids. Notably, an overview of the physiological considerations that play key roles in determining ergogenic efficacy is currently lacking. Therefore, in this brief review, we discuss important physiological considerations that contribute to ergogenic efficacy for nutritional ergogenic aids that are orally ingested including (1) the impact of first pass metabolism, (2) rises in systemic concentrations, and (3) interactions with the target tissue. In addition, we explore mouth rinsing as an alternate route of ergogenic efficacy that bypasses the physiological hurdles of first pass metabolism via direct stimulation of the central nervous system. Moreover, we provide real-world examples and discuss several practical factors that can alter the efficacy of nutritional ergogenic aids including human variability, dosing protocols, training status, sex differences, and the placebo effect. Taking these physiological considerations into account will strengthen the quality and impact of the literature regarding the efficacy of potential ergogenic aids for top-class athletes.

Carbohydrate Rinse Fails to Enhance Cycling Performance or Alter Metabolic and Autonomic Recovery in Recreational Cyclists

The purpose of the study was to examine the effects of carbohydrate (CHO) mouth rinsing on autonomic and metabolic recovery as well as cycling performance. Ten male recreational cyclists (age = 30 ± 6 years, VO_2peak = 54.5 ± 8.1 mL·kg^-1·min^-1) completed a randomized, double-blind, placebo-controlled, crossover designed study. A CHO or a placebo (PLA) rinse was administered every 12.5% of a work to completion trial (75%W_max). Heart rate variability (lnRMSSD), the respiratory exchange ratio, and plasma epinephrine, norepinephrine, insulin, glucose, free fatty acids (FFA), and lactate were measured pre- and post-exercise. The CHO rinse did not improve time to completion of the test trial (CHO: 4108 ± 307 s, PLA: 4176 ± 374 s, p = 0.545). Further, the CHO rinse did not impact autonomic recovery, as measured by lnRMSSD (p = 0.787) and epinephrine (p = 0.132). Metabolic biomarkers were also unaffected by the CHO rinse, with no differences observed in responses of FFA (p = 0.064), lactate (p = 0.302), glucose (p = 0.113) or insulin (p = 0.408). Therefore, the CHO mouth rinse does not reduce the acute sympathetic response following strenuous exercise and does not result in improvements in cycling time to completion.

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.

Effect of carbohydrate mouth rinse on muscle strength and muscular endurance: A systematic review with meta-analysis

The present systematic review with meta-analysis summarized studies that investigated the effect of carbohydrate (CHO) mouth rinse on muscle strength and muscular endurance. The search was performed in six databases. Thirteen randomized clinical trials were selected and the standardized mean difference between CHO mouth rinse and placebo for maximal strength and muscular endurance was determined via a random-effects model using Review Manager 5.4 software. Meta-regression was also performed to explore the influence of load, number of sets, number of exercises, fasting time, CHO concentration, and number of mouth rinses on the main outcomes. There was no significant effect of CHO mouth rinse on maximal strength (mean difference= 0.25 kg, 95%CI - 1.81 to 2.32 kg, z = 0.24, p = 0.810). However, there was a significant positive effect of CHO mouth rinse on muscular endurance (mean difference = 1.24 repetitions, 95%CI 0.70 to 1.77 repetitions, z = 4.55, p < 0.001). Meta-regression identified that CHO mouth rinse has greater benefits on muscular endurance when using high workloads, multiple exercises, and a smaller number of mouth rinses (p = 0.001). In conclusion, CHO mouth rinse has no effect on maximal muscle strength but has a positive effect on muscular endurance and seems to optimize when fewer mouth rinses, high workloads and numbers of exercises are used.Supplemental data for this article is available online at https://doi.org/10.1080/10408398.2022.2057417.

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.

Carbohydrate Mouth Rinse Increases High but Not Low Intensity Repetitions to Failure in Resistance-Trained Males

Carbohydrate mouth rinsing (CMR) has been shown to enhance exercise performance. However, the influence of CMR on repetitions to failure with different intensities (40% or 80% of 1 RM) is unknown. Therefore, the purpose of this study was to examine the effects of a 6% CMR solution on muscular endurance assessed at 40% and 80% of 1 RM in resistance-trained males. Sixteen resistance-trained males (age: 25 ± 3 years, height: 182 ± 6 cm, body mass: 86 ± 3 kg, body fat: 16 ± 3%, bench press 1 RM: 106 ± 16 kg, resistance training experience: 5 ± 1 years) completed four conditions in random order. The four conditions consisted of ten seconds of mouth rinsing with 25 mL solutions containing either maltodextrin or placebo (sweetened water) prior to performing a bench press muscular endurance test at either 40% of 1 RM or 80% of 1 RM. Total repetitions, heart rate (HR), ratings of perceived exertion (RPE), glucose (GLU) and felt arousal (FA) were recorded for each condition. There was a significant condition by intensity interaction (p = 0.02). CMR significantly increased total repetitions compared with placebo at the higher intensity (80% of 1 RM; p = 0.04), while there was no effect at the lower intensity (p = 0.20). In addition, HR, RPE, GLU and FA did not differ between conditions or across intensities (p > 0.05). In conclusion, CMR-enhanced muscular endurance performed at higher but not lower intensities.

Carbohydrate Mouth Rinsing Does Not Alter Central or Peripheral Fatigue After High-Intensity and Low-Intensity Exercise in Men

ABSTRACT

Black, CD, Haskins, KR, Bemben, MG, and Larson, RD. Carbohydrate mouth rinsing does not alter central or peripheral fatigue after high-intensity and low-intensity exercise in men. J Strength Cond Res 36(1): 142-148, 2022-Carbohydrate (CHO) mouth rinsing improves performance during endurance exercise. However, its ability to attenuate fatigue during strength-based exercise is less certain. This study sought to determine the effects of a CHO mouth rinse on torque production and voluntary activation (VA%) after high-intensity and low-intensity isometric exercise. Twelve male subjects (22.5 ± 2.3 years; 183.5 ± 6.5 cm; 82.2 ± 13.9 kg) completed 4 testing sessions in a double-blind crossover fashion. Knee extension maximal voluntary isometric strength (MVC) was assessed before(Pre), immediately (iPost-Ex), and 5 minutes (5-min Post Ex) after isometric exercise performed at 80% or 20% of MVC. An 8% CHO solution or placebo (PLA) was rinsed for 20 seconds after exercise. VA% was determined by twitch interpolation. A 2 condition (CHO vs. PLA) × 2 contraction intensity (20 vs. 80%) × 3 time (Pre, iPost Ex, and 5-min Post Ex) completely within subject-repeated measured analysis of variance was performed; statistical significance was set at p ≤ 0.05. Greater reductions in MVC were found at iPost-Ex after exercise at 20% compared with 80% of MVC (-25 ± 14% vs. -11 ± 8%; p < 0.001) as well as for VA% (-17 ± 14% vs. -8 ± 14%; p < 0.004). No differences were observed in the CHO vs. PLA condition (p ≥ 0.34). We were successful in eliciting differing levels of central and peripheral fatigue by exercising at a low and high intensity. Despite significantly larger declines in VA% after exercise at 20% of MVC, CHO mouth rinsing had no effects compared with placebo on any measured variable.

Meta-Analysis of Carbohydrate Solution Intake during Prolonged Exercise in Adults: From the Last 45+ Years' Perspective

Carbohydrate (CHO) supplementation during prolonged exercise postpones fatigue. However, the optimum administration timing, dosage, type of CHO intake, and possible interaction of the ergogenic effect with athletes' cardiorespiratory fitness (CRF) are not clear. Ninety-six studies (from relevant databases based on predefined eligibility criteria) were selected for meta-analysis to investigate the acute effect of ≤20% CHO solutions on prolonged exercise performance. The between-subject standardized mean difference [SMD = ([mean post-value treatment group-mean post-value control group]/pooled variance)] was assessed. Overall, SMD [95% CI] of 0.43 [0.35, 0.51] was significant (p < 0.001). Subgroup analysis showed that SMD was reduced as the subjects' CRF level increased, with a 6-8% CHO solution composed of GL:FRU improving performance (exercise: 1-4 h); administration during the event led to a superior performance compared to administration before the exercise, with a 6-8% single-source CHO solution increasing performance in intermittent and 'stop and start' sports and an ~6% CHO solution appearing beneficial for 45-60 min exercises, but there were no significant differences between subjects' gender and age groups, varied CHO concentrations, doses, or types in the effect measurement. The evidence found was sound enough to support the hypothesis that CHO solutions, when ingested during endurance exercise, have ergogenic action and a possible crossover interaction with the subject's CRF.

Single and Serial Carbohydrate Mouth Rinsing Do Not Improve Yo-Yo Intermittent Recovery Test Performance in Soccer Players

Carbohydrate (CHO) mouth rinsing seems to improve performance in exercises lasting 30-60 min. However, its effects on intermittent exercise are unclear. It is also unknown whether serial CHO mouth rinses can promote additional ergogenic effects when compared with a single mouth rinse. The aim of this study was to evaluate the effect of single and serial CHO mouth rinses on Yo-Yo Intermittent Recovery Test Level 1 (Yo-Yo IR1) performance in soccer players. In a randomized, crossover, double-blind, placebo-controlled design, 12 male (18.9 ± 0.5 years) soccer players performed eight serial mouth rinses under three different conditions: placebo solution only (noncaloric juice), seven placebo mouth rinses plus a single CHO mouth rinse (8% maltodextrin), or eight CHO mouth rinses (8-CHO). Following the final mouth rinse, individuals performed the Yo-Yo IR1 test to evaluate the maximal aerobic endurance performance measured via total distance covered. There were no differences in Yo-Yo IR1 performance between sessions (p = .32; single CHO mouth rinse (8% maltodextrin): 1,198 ± 289 m, eight CHO mouth rinses: 1,256 ± 253 m, placebo: 1,086 ± 284 m). In conclusion, single and serial CHO mouth rinsing did not improve performance during the Yo-Yo IR1 for soccer players. These data suggest that CHO mouth rinsing is not an effective ergogenic strategy for intermittent exercise performance irrespective of the number of rinses.

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.

Menthol Mouth Rinsing Is More Than Just a Mouth Wash-Swilling of Menthol to Improve Physiological Performance

Interventions that solely act on the central nervous system (CNS) are gaining considerable interest, particularly products consumed through the oral cavity. The oropharyngeal cavity contains a wide array of receptors that respond to sweet, bitter, and cold tastants, all of which have been shown to improve physiological performance. Of late, the ergogenic benefits of carbohydrate (CHO) and caffeine (CAF) mouth rinsings (MRs) have been widely studied; however, less is known about menthol (MEN). That the physiological state and environmental conditions impact the response each product has is increasingly recognized. While the effects of CHO and CAF MRs have been thoroughly studied in both hot and thermoneutral conditions, less is known about MEN as it has only been studied in hot environments. As such, this review summarizes the current knowledge regarding the MEN MR and exercise modality, frequency of the mouth rinse, and mouth rinse duration and compares two different types of study designs: time trials vs. time to exhaustion (TTE).

Different Doses of Carbohydrate Mouth Rinse Have No Effect on Exercise Performance in Resistance Trained Women

Carbohydrate (CHO) mouth rinse has been shown to enhance aerobic endurance performance. However, the effects of CHO mouth rinse on muscular strength and endurance are mixed and may be dependent on dosage of CHO. The primary purpose was to examine the effects of different dosages of CHO rinse on strength (bench press 1 repetition maximum [1-RM]) and muscular endurance (40% of 1-RM repetitions to failure) in female athletes. Sixteen resistance-trained females (age: 20 ± 1 years; height: 167 ± 3 cm; body mass: 67 ± 4 kg; BMI: 17 ± 2 kg/m²; resistance training experience: 2 ± 1 years) completed four conditions in random order. The four conditions consisted of a mouth rinse with 25 mL solutions containing either 6% of CHO (Low dose of CHO: LCHO), 12% CHO (Moderate dose of CHO: MCHO), 18% CHO (High dose of CHO: HCHO) or water (Placebo: PLA) for 10 s prior to a bench press strength and muscular endurance test. Maximal strength (1-RM), muscular endurance (reps and total volume), heart rate (HR), ratings of perceived exertion (RPE) and glucose (GLU) were recorded each condition. There were no significant differences in strength (p = 0.95) or muscular endurance (total repetitions: p = 0.06; total volume: p = 0.20) between conditions. Similarly, HR (p = 0.69), RPE (p = 0.09) and GLU (p = 0.92) did not differ between conditions. In conclusion, various doses of CHO mouth rinse (6%, 12% and 18%) have no effect on upper body muscular strength or muscular endurance in female athletes.

Acute caffeine mouth rinsing does not improve 10-km running performance in CYP1A2 C-allele carriers

PURPOSE

This study assessed whether caffeine mouth rinsing affects 10-km run performance and vertical jump in recreational runners.

METHODS

A double-blind, placebo-controlled, crossover study was conducted. Ten well-trained volunteers performed two trials, following caffeine or placebo mouth rinse, separated by seven days. Immediately before the 10-km run, a 10-second mouth rinse with either 300 mg of caffeine (1.2%) or microcrystalline cellulose (placebo) diluted in 25 mL of water was performed. Pre- and post-exercise, participants performed a vertical jump test. A Garmin Forerunner® GPS, was used to measure 10-km running time and an 11-point Borg scale was used post-exercise to measure ratings of perceived exertion. Blood samples were also collected during the visit in the laboratory in the afternoon period to classify individuals according to their CYP1A2 genotype. Vertical jump performance was evaluated using a force plate.

RESULTS

Nine runners (90%) were CC homozygotes and one (10%) was an AC heterozygote for CYP1A2. There was no difference in 10-km time-trial performance (Placebo: 47.07 ± 5.18 vs. CAF: 47.45 ± 6.34 min, p = 0.89), ratings of perceived exertion (Placebo: 17 ± 1 vs. CAF: 16 ± 2, p = 0.34) or vertical jump power (Placebo, Pre: 4.5 ± 0.6 W•kg-1 and Post: 4.5 ± 0.7 W•kg-1; CAF: Pre: 4.4 ± 0.7 W•kg-1 and Post: 4.4 ± 0.8 W•kg-1, d = 0.21, p = 0.66) between trials.

CONCLUSION

Acute caffeine mouth rinsing (1.2%) did not improve 10-km performance and showed similar null effects on vertical jump performance in CYP1A2 C-allele carriers.

Perceptual and Physiological Responses to Carbohydrate and Menthol Mouth-Swilling Solutions: A Repeated Measures Cross-Over Preliminary Trial

Carbohydrate and menthol mouth-swilling have been used to enhance exercise performance in the heat. However, these strategies differ in mechanism and subjective experience. Participants (n = 12) sat for 60 min in hot conditions (35 °C; 15 ± 2%) following a 15 min control period, during which the participants undertook three 15 min testing blocks. A randomised swill (carbohydrate; menthol; water) was administered per testing block (one swill every three minutes within each block). Heart rate, tympanic temperature, thermal comfort, thermal sensation and thirst were recorded every three minutes. Data were analysed by ANOVA, with carbohydrate intake controlled for via ANCOVA. Small elevations in heart rate were observed after carbohydrate (ES: 0.22 ± 90% CI: −0.09–0.52) and water swilling (0.26; −0.04–0.54). Menthol showed small improvements in thermal comfort relative to carbohydrate (−0.33; −0.63–0.03) and water (−0.40; from −0.70 to −0.10), and induced moderate reductions in thermal sensation (−0.71; from −1.01 to −0.40 and −0.66; from −0.97 to −0.35, respectively). Menthol reduced thirst by a small to moderate extent. These effects persisted when controlling for dietary carbohydrate intake. Carbohydrate and water may elevate heart rate, whereas menthol elicits small improvements in thermal comfort, moderately improves thermal sensation and may mitigate thirst; these effects persist when dietary carbohydrate intake is controlled for.

Carbohydrate mouth rinse improves resistance exercise capacity in the glycogen-lowered state

The effect of carbohydrate mouth rinse (CHO MR) on resistance exercise performance is equivocal and may be moderated by carbohydrate availability. This study determined the effect of CHO MR on low-load resistance exercise capacity completed in a fed but glycogen-lowered state. Twelve resistance-trained men (age: 22 ± 4 years; height: 1.79 ± 0.05 m; mass: 78.7 ± 7.8 kg; bench press one-repetition maximum (1RM): 87 ± 21 kg; squat 1RM: 123 ± 19 kg) completed two fed-state resistance exercise bouts consisting of six sets of bench press and six sets of squat to failure at 40% 1RM. Each bout was preceded by glycogen-depleting cycling the evening before, with feeding controlled to create acute energy deficit and maintain low muscle glycogen. During resistance exercise, participants rinsed with either a 6% CHO MR solution or a taste-matched placebo (PLA) between sets. Total volume workload was greater with CHO MR (9354 ± 2051 vs. 8525 ± 1911 kg, p = 0.010). Total number of repetitions of squat were greater with CHO MR (107 ± 26 vs. 92 ± 16, p = 0.017); the number of repetitions of bench press were not significantly different (CHO MR: 120 ± 24 vs. PLA: 115 ± 22, p = 0.146). This was independent of differences in feeling or arousal. CHO MR may be an effective ergogenic aid for athletes completing resistance exercise when in energy deficit and with low carbohydrate availability. Novelty: CHO MR can increase low-load resistance exercise capacity undertaken in a glycogen-lowered but fed state. This effect was driven by a greater number of repetitions-to-failure in the squat - using muscles lowered in glycogen content with exhaustive cycling on the evening prior to resistance exercise - but not bench press.

Effects of Carbohydrate Mouth Rinse on Cycling Time Trial Performance: A Systematic Review and Meta-Analysis

BACKGROUND

Despite the growing number of studies reporting carbohydrate mouth rinse effects on endurance performance, no systematic and meta-analysis review has been conducted to elucidate the level of evidence of carbohydrate mouth rinse effects on cycling trial performance such as time-, work-, and distance-based trials.

OBJECTIVES

The objective of this study were to establish the effect of a carbohydrate mouth rinse on cycling performance outcomes such as mean power output and time to complete a trial, together with the risk of bias in the cycling-carbohydrate mouth rinse literature.

METHODS

We systematically reviewed randomized placebo-controlled trials that assessed carbohydrate mouth rinse effects on mean power output and time to complete the trial. A random-effects meta-analysis assessed the standardized mean difference between carbohydrate and placebo mouth rinses.

RESULTS

Thirteen studies (16 trials) were qualitatively (systematic review) and quantitatively (meta-analysis) analyzed with regard to mean power output (n = 175) and time to complete the trial (n = 151). Overall, the reviewed studies showed a low risk of bias and homogeneous results for mean power output (I² = 0%) and time to complete the trial (I² = 0%). When compared with placebo, the carbohydrate mouth rinse improved mean power output (standardized mean difference = 0.25; 95% confidence interval 0.04-0.46; p = 0.02), but not the time to complete the trial (standardized mean difference = - 0.13; 95% confidence interval - 0.36 to 0.10; p = 0.25).

CONCLUSION

The present systematic and meta-analytic review supports the notion that a carbohydrate mouth rinse has the potential to increase mean power output in cycling trials, despite showing no superiority over placebo in improving time to complete the trials.

Effects of Carbohydrate Mouth Rinsing on Salivary Lysozyme, Mood States and Running Performance Among Recreational Runners

Introduction

Carbohydrate (CHO) mouth rinsing can enhance sports performance through a central action mediated by receptors in the mouth. This study examined the effect of a CHO mouth rinse on salivary lysozyme concentrations, mood states and running performances.

Methods

Ten males recreational runners were randomised to three running trials with a 1 week recovery period between the trials. Each trial involved running at 75% maximum heart rate (HRmax) for 1 h, followed by a 15 min time trial. The participants used a CHO mouth rinse, placebo (PLA) solution or control (CON, no solution) every 15 min during the exercise. Heart rate (HR), rating of perceived exertion (RPE) and mood states were recorded pre-, during and post-exercise. Saliva samples were collected pre-, post- and 1 h post-exercise.

Results

There was no significant interaction and time effect (P > 0.05) on the salivary lysozyme concentration and running performance, but it was significant (P < 0.05) for HR and RPE (increase in all trials). However, there was no significant difference (P > 0.05) in salivary lysozyme concentrations, running performances, HR values or RPE between the trials. Mood states were not significantly different (P > 0.05) between the trials, but one of the mood sub-scales showed a significant (P < 0.001) time effect (increase fatigue in all trials).

Conclusion

CHO mouth rinsing did not affect physiological parameters, salivary lysozyme concentrations, mood states or running performance among recreational runners.

Effect of glucose and sodium chloride mouth rinses on neuromuscular fatigue: a preliminary study

Carbohydrate (CHO) mouth rinse has been shown to improve endurance performance and maintain the central drive of contracting muscles. Salt (NaCl) mouth rinse solution, often used in dentistry to desensitise the oral cavity to pain, could also activate cortical areas of the brain. Hence, the objective of this preliminary study was to investigate whether CHO (glucose) and NaCl mouth rinses could attenuate the reduction in maximum voluntary contraction (MVC) and sustained MVC (sMVC) following an endurance exercise (30-minute cycling at 70% VO₂max). Ten subjects (male, age: 22 ± 1 years, weight: 65.3 ± 12.4 kg, height: 164.5 ± 7.5 cm, VO₂max: 48.3 ± 6.1 mL kg^-1 min^-1) completed three trials of 30-minute cycling exercise. In a randomised cross-over study, in each trial, the participants rinsed using either water, 6% glucose, or 6% NaCl solution for 5 s immediately prior to and every 10 min during the cycling exercise. The MVC and sMVC were measured pre and post cycling. Analysis of variance showed significant interaction and time effects for MVC, while for sMVC there was a significant interaction with time and group effects. Both MVC and sMVC were higher post cycling in the glucose and NaCl groups compared to the water group, which suggests that activation of glucose and NaCl oral receptors could better preserve post-exercise force production. This is the first study to show that NaCl mouth rinse can produce a comparable effect on glucose. Hence, mouth rinses may be able to activate other distinct pathways that could attenuate fatigue.

No Improvement in Running Time to Exhaustion at 100% VO2max in Recreationally Active Male Runners With a Preexercise Single-Carbohydrate Mouth Rinse

BACKGROUND

Carbohydrate (CHO) mouth rinse has been used as an ergogenic strategy due to its central effect; however, the effects of this intervention during short-duration high-intensity exercises are not fully understood.

PURPOSE

To investigate the effect of CHO mouth rinse on time to exhaustion in a short-duration high-intensity exercise performed on a treadmill.

METHODS

A randomized double-blind, placebo-controlled, crossover study was conducted with 10 (24.1 [4.3] y) recreationally active male runners. The protocol consisted of a warm-up at 65% of VO2max for 5 min followed by 3 min passive rest. At the end of this rest period, the individuals performed their mouth rinse either with CHO (maltodextrin, 6%) or with placebo (industrialized noncaloric juice with the same taste). Immediately after mouth rinse, the subjects ran at velocity equivalent to 100% of individual VO2max until voluntary exhaustion. The perceived effort was obtained through a Borg scale. Blood lactate was quantified before and after the protocol, and heart rate was evaluated during the protocol.

RESULTS

No difference was found (P = .90) in time to exhaustion between placebo (193.9 [46.5] s) and CHO mouth rinse (195.1 [51.8] s). Blood lactate, heart rate, and perception of effort increased in both groups, but with no differences (all variables, P > .05) between groups.

CONCLUSION

The findings showed that a preexercise single-CHO mouth rinse was ineffective to improve running time to exhaustion at velocity equivalent to 100% VO2max on a treadmill in recreationally active male runners.

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.

Mouth Rinsing Cabohydrates Serially Does Not Improve Repeated Sprint Time

Sensing carbohydrates via the oral cavity benefits performance outcomes during brief high intensity bouts of exercise. However, the extent to which carbohydrates need to be present in the oral cavity to influence sprint performance is less understood. The purpose of this study was to determine if serial increases in carbohydrate rinse time across sprint sets attenuates increases in sprint time compared to no serial increases in carbohydrate rinse time across sprint sets. Fifteen sprint trained participants completed three repeated anaerobic sprint tests (RAST), 3 sets of 6 x 35-m sprints, under two different carbohydrate mouth rinsing (CMR) conditions; (1) rinsing for only 5 seconds (s), and (2) rinsing for 5 s, 10 s and 15 s (serial rinse). Prior to a RAST, participants provided perceived recovery status (PRS) and perceived feeling of arousal (FAS). Upon completion of each individual sprint, participants gave a rating of perceived exertion (RPE). A lactate sample was taken upon completion of each individual sprint set and after all 3 RASTs a session rating of perceived exertion (S-RPE) was measured. There were no significant differences in peak (p = 0.18) and average sprint time (p = 0.41). There were no significant differences in perceptual measures: RPE, PRS, FAS, S-RPE or for blood lactate concentration between CMR conditions. Overall, serial rinsing resulted in changes that were most likely trivial, but showed a 50% chance in perceiving a sprint session as less difficult. Rinsing carbohydrates in a serial manner between repeated sprint sets produces trivial changes of sprint speed and perceptual measures from sprint performance.

Carbohydrate Mouth Rinse Decreases Time to Complete a Simulated Cycling Time Trial

Rinsing carbohydrate solutions in the mouth can produce positive effects on the central nervous system via mouth/tongue receptors, ultimately increasing cycling performance. However, previous investigations on this topic have used complex carbohydrate solutions and time trials on a cyclergometer to complete a set amount of work. The purpose of the present study was to examine the effects of carbohydrate mouth rinsing on physical performance by using a commercially available drink during a cycling time trial with varying slopes. In a double-blind, placebo-controlled and randomized manner, 16 well-trained cyclists (37.6 ± 3.5 years; 76.9 ± 7.9 kg) performed two simulated cycling time trial (25.3 km) with their own bikes on a 3D virtual trainer. In one occasion, participants mouth-rinsed a 6.4% carbohydrate mixed solution for 5 s each 12.5% of total completion of the trial; in other occasion participants rinsed with a taste-matched placebo with 0.0% of carbohydrate. During the trials, participants were instructed to perform as fast as possible at a self-chosen pace while time, cycling power output and ratings of perceived exertion were obtained during the trials. When compared to the placebo, carbohydrate mouth rinse decreased the time employed to complete the distance (2,960 ± 412 vs. 2,888 ± 396 s; P = 0.04, respectively), while it increased overall cycling power (222 ± 51 vs. 231 ± 46 w, P = 0.04) and cycling power during the climbing sections (238 ± 46 vs. 248 ± 47 w, P = 0.03). Carbohydrate mouth rinse also increased the rating of perceived exertion at the end of the trial (18.3 ± 1.7 vs. 18.9 ± 1.1 arbitrary units, P = 0.04). In summary, mouth rinsing with a commercially available carbohydrate drink might be considered as an effective strategy to increase physical performance during cycling time trials. However, due to the performance downsides of breaking the aero-position or interrupting the breathing pattern for rising during a time trial, carbohydrate mouth rinse protocols might be more suitable for high-intensity training sessions, particularly those sessions intentionally performed with low carbohydrate intake.

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

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

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.

The Effects of Carbohydrates, in Isolation and Combined with Caffeine, on Cognitive Performance and Mood-Current Evidence and Future Directions

This review examines the effects of carbohydrates, delivered individually and in combination with caffeine, on a range of cognitive domains and subjective mood. There is evidence for beneficial effects of glucose at a dose of 25 g on episodic memory, but exploration of dose effects has not been systematic and the effects on other cognitive domains is not known. Factors contributing to the differential sensitivity to glucose facilitation include age, task difficulty/demand, task domain, and glucoregulatory control. There is modest evidence to suggest modulating glycemic response may impact cognitive function. The evidence presented in this review identifies dose ranges of glucose and caffeine which improve cognition, but fails to find convincing consistent synergistic effects of combining caffeine and glucose. Whilst combining glucose and caffeine has been shown to facilitate cognitive performance and mood compared to placebo or glucose alone, the relative contribution of caffeine and glucose to the observed effects is difficult to ascertain, due to the paucity of studies that have appropriately compared the effects of these ingredients combined and in isolation. This review identifies a number of methodological challenges which need to be considered in the design of future hypothesis driven research in this area.

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.

Carbohydrate Mouth Rinsing Does Not Prevent the Decline in Maximal Strength After Fatiguing Exercise

Black, CD, Schubert, DJ, Szczyglowski, MK, and Wren, JD. Carbohydrate mouth rinsing does not prevent the decline in maximal strength after fatiguing exercise. J Strength Cond Res 32(9): 2466-2473, 2018-Carbohydrate (CHO) rinsing has been shown to attenuate the decline of maximal voluntary contractions (MVCs) after fatiguing exercise-perhaps through a central mechanism. This study sought to determine the effect of a CHO rinse on MVC, voluntary activation, and contractile properties after fatiguing exercise. Thirteen adults participated in a double-blind, cross-over study. Maximal voluntary contraction of the dominant knee extensors was assessed, and voluntary activation (%VA) was determined using twitch interpolation. Participants then held 50% of MVC until volitional fatigue followed by a 20-second rinse with a solution of 8% maltodextrin (CHO) or placebo (PLA). Maximal voluntary contraction and %VA were reassessed immediately and 5 minutes after exercise. Maximal voluntary contraction did not differ between the CHO and PLA conditions initially (230 ± 90 vs. 232 ± 90 N·m; p = 0.69). Maximal voluntary contraction declined after exercise (p ≤ 0.01), but no differences were found between the CHO and PLA conditions (p ≥ 0.59). %VA did not differ between conditions (91.9 ± 2.9% vs. 91.5 ± 3.8%; p ≥ 0.11) nor did it change after exercise (p = 0.57). Twitch torque, rate of torque development, and rate of torque relaxation were reduced after exercise (p ≤ 0.05) but were unaffected by CHO rinsing (p > 0.05). Unlike a previous study, a CHO rinse did not preserve MVC after fatiguing exercise. This was likely due to a lack of central fatigue induced by the exercise protocol (as %VA was unaffected) as the CHO rinse is thought to work through a central mechanism.

Evidence supporting oral sensitivity to complex carbohydrates independent of sweet taste sensitivity in humans

Compared to simple sugars, complex carbohydrates have been assumed invisible to taste. However, two recent studies proposed that there may be a perceivable taste quality elicited by complex carbohydrates independent of sweet taste. There is precedent with behavioural studies demonstrating that rats are very attracted to complex carbohydrates, and that complex carbohydrates are preferred to simple sugars at low concentrations. This suggests that rats may have independent taste sensors for simple sugars and complex carbohydrates. The aim of this paper is to investigate oral sensitivities of two different classes of complex carbohydrates (a soluble digestible and a soluble non-digestible complex carbohydrate), and to compare these to other caloric and non-nutritive sweeteners in addition to the prototypical tastes using two commonly used psychophysical measures. There were strong correlations between the detection thresholds and mean intensity ratings for complex carbohydrates (maltodextrin, oligofructose) (r = 0.94, P < 0.001). There were no significant correlations between the detection thresholds of the complex carbohydrates (maltodextrin, oligofructose) and the sweeteners (glucose, fructose, sucralose, Rebaudioside A, erythritol) (all P > 0.05). However, moderate correlations were observed between perceived intensities of complex carbohydrates and sweeteners (r = 0.48–0.61, P < 0.05). These data provide evidence that complex carbohydrates can be sensed in the oral cavity over a range of concentrations independent of sweet taste sensitivity at low concentrations, but with partial overlap with sweet taste intensity at higher concentrations.

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.

Carbohydrate mouth rinse improves cycling performance carried out until the volitional exhaustion

BACKGROUND

Carbohydrates (CHO) are among the most investigated nutritional ergogenic aids, and may be consumed in different forms, e.g., mouth rinse with carbohydrate solution (MRCS). In this sense, the aim of this study was to evaluate the impact of MRCS on the performance of physically active individuals undergoing a physical exercise session carried out until the volitional exhaustion.

METHODS

This is a counter-balanced randomized study, with a double-blind design. The sample consisted of twenty-one physically active healthy men with a mean (±SD) of age of 22.4 (±2.7) years old, 76.7 (±6.0) cm of height,12.1% (±3.7) of body fat mass, and 23.9 (±2.4) kg/m2 of body mass index. After familiarizing the participants with the protocol (cycle ergometer, with oral mouth rinse procedure) and assessing the maximal lactate steady state the cycling exercise was performed until the volitional exhaustion in the following conditions: without mouth rinse (CONTROL), PLACEBO and MRCS.

RESULTS

Time to reach exhaustion was statistically different (P<0.0001) between conditions (control: 43.0±27.5 minutes; placebo: 57.4±30.6 minutes; MRCS: 70.9±30.3 minutes).

CONCLUSIONS

The administration of MRCS was shown to be effective in improving cycling performance, increasing the time to exhaustion until the volitional exhaustion. Thus, the use of methodology proposed by the present study may help coaches and practitioners improve the performance of physically active young adults.

Resource forecasting: Differential effects of glucose taste and ingestion on delay discounting and self-control

We tested a novel hypothesis that glucose taste acts as a signal for resource acquisition, motivating preference for immediate rewards while actual glucose ingestion prompts resource conservation, promoting future-orientated self-regulation. In Study 1, participants were engaged in a delay-discounting task and a grip-control task before and after a beverage intervention (glucose drink, water drink, or glucose mouth-rinse). Glucose ingestion decreased delay discounting, making larger-and-later rewards more attractive. In contrast, glucose rinse increased delay discounting. Water ingestion had none of the effects. In the grip-control task, only glucose ingestion improved the performance. Study 2 using fMRI revealed that glucose rinse and glucose ingestion resulted in distinct brain activational patterns. Compared to glucose rinse, glucose ingestion deactivated a few brain regions (e.g., the anterior cingulate gyrus and inferior frontal gyrus) that are previously shown to be more active when making more difficult intertemporal choices, suggesting that glucose ingestion eases the process of making intertemporal choice. In sum, our behavioral and neuroimaging findings together suggest a dual signaling role of glucose sensation and ingestion in regulating delay discounting and self-control.

Quantifying the Effect of Carbohydrate Mouth Rinsing on Exercise Performance

The purpose of this study was to review the existing literature investigating carbohydrate mouth rinsing as an ergogenic aid using the effect sizes (ES) and percentage change in performance of the respective studies as outcome measures. A trivial-small average overall ES was present for the 25 studies included in the review (0.18, 95% confidence interval [CI] = 0.10-0.27). Effect sizes for the subgroups were ≥25 minutes (0.25, 95% CI = 0.14-0.36), ≤180 seconds (0.06, 95% CI = -0.03 to 0.15), resistance exercise (-0.09, 95% CI = -0.20 to 0.03) but the ES is still small. A subanalysis of ∼1-h cycling time trial performance resulted in an overall ES of 0.20 (95% CI = 0.02-0.38), and ES for performance time and power output of 0.31 (95% CI = -0.02 to 0.64) and 0.19 (95% CI = -0.09 to 0.46), respectively. Although ES were small, the average percentage change in performance in ∼1-hour trials was 2.48%, which may have implications for elite performers as this is greater than the 1.30% smallest worthwhile change recommended in the past research.

Carbohydrate mouth rinse does not affect performance during a 60-min running race in women

This study examined the effect of carbohydrate mouth rinsing on endurance running performance in women. Fifteen female recreational endurance runners, who used no oral contraceptives, ran two races of 1-h duration on an indoor track (216-m length) at 18:00 h after an 8-h fast with a 7-days interval between races, corresponding to the 3^rd-10th day of each premenopausal runner's menstrual cycle, or any day for the postmenopausal runners. In a double-blind random order, participants rinsed their mouth with 25 ml of either a 6.4% carbohydrate (RCHO) or a placebo solution (RP). No fluid was ingested during exercise. Serum 17β-Εstradiol (P = 0.59) and Progesterone (P = 0.35) did not differ between treatments. There was no difference in 1-hour running performance (RCHO: 10,621.88 ± 205.98 m vs. RP: 10,454.00 ± 206.64 m; t = 1.784, P = 0.096). Furthermore, the mean percentage effect (±99%CI) of RCHO relative to RP, 1.67% (-1.1% to 4.4%), and Cohen's effect size (d = 0.21) support a trivial outcome of RCHO for total distance covered. In conclusion, carbohydrate mouth rinsing did not improve 60-min track running performance in female recreational runners competing in a low ovarian hormone condition, after an 8-h fast and when no fluid was ingested during exercise.

Effect of carbohydrate mouth rinse on exercise performance in horses

The mechanism related to the practice of oral carbohydrate (CHO) supplementation prior to intense exercise of a short duration (<30 min) for athletic horses remains unclear. Several studies in human athletes showed that the central nervous system played an important role in the enhancement of athletic performance due to CHO contact with undefined receptors in the oropharyngeal mucosa. This study aims to investigate the influence of CHO mouth rinse on the exercise performance of horses. In this double blind, randomised, placebo-controlled study, seven Mangalarga Marchador horses underwent a standardised exercise test (SET) in a field. The following protocols involving a single mouthwash (1 litre) had been used: a mouth rinse of 6.4% maltodextrin-water solution (CHO test), and a mouth rinse of only water solution (placebo test). The mean plasma lactate concentration immediately after SET (lactate peak) was higher in the CHO test (24.33±3.72 mmol/l) than in the placebo test (18.19±4.01 mmol/l), (P<0.001). No difference was observed in the mean time-to-exhaustion, mean and maximum heart rate, plasma glucose concentration and serum creatinine-kinase activity. Several studies described that there were improvements in the time-trial performance of cyclists and runners after a mouth rinse of CHO solution, whereas some did not. Carbohydrate mouth rinse had no influence on exercise performance in this study. Further investigations are required, as the significance of an increased plasma lactate concentration due to a CHO mouth rinse has yet to be elucidated.

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.

No Dose-Response Effect of Carbohydrate Mouth Rinse Concentration on 5-km Running Performance in Recreational Athletes

Clarke, ND, Thomas, JR, Kagka, M, Ramsbottom, R, and Delextrat, A. No dose-response effect of carbohydrate mouth rinse concentration on 5-km running performance in recreational athletes. J Strength Cond Res 31(3): 715-720, 2017-Oral carbohydrate rinsing has been demonstrated to provide beneficial effects on exercise performance of durations of up to 1 hour, albeit predominately in a laboratory setting. The aim of the present study was to investigate the effects of different concentrations of carbohydrate solution mouth rinse on 5-km running performance. Fifteen healthy men (n = 9; mean ± SD age; 42 ± 10 years; height, 177.6 ± 6.1 cm; body mass, 73.9 ± 8.9 kg) and women (n = 6; mean ± SD age, 43 ± 9 years; height, 166.5 ± 4.1 cm; body mass, 65.7 ± 6.8 kg) performed a 5-km running time trial on a track on 4 separate occasions. Immediately before starting the time trial and then after each 1 km, subjects rinsed 25 ml of 0, 3, 6, or 12% maltodextrin for 10 seconds. Mouth rinsing with 0, 3, 6, or 12% maltodextrin did not have a significant effect on the time to complete the time trial (0%, 26:34 ± 4:07 minutes:seconds; 3%, 27:17 ± 4:33 minutes:seconds; 6%, 27:05 ± 3:52 minutes:seconds; 12%, 26:47 ± 4.31 minutes:seconds; p = 0.071; (Equation is included in full-text article.)= 0.15), heart rate (p = 0.095; (Equation is included in full-text article.)= 0.16), rating of perceived exertion (p = 0.195; (Equation is included in full-text article.)= 0.11), blood glucose (p = 0.920; (Equation is included in full-text article.)= 0.01), and blood lactate concentration (p = 0.831; (Equation is included in full-text article.)= 0.02), with only nonsignificant trivial to small differences between concentrations. Results of this study suggest that carbohydrate mouth rinsing provides no ergogenic advantage over an acaloric placebo (0%) and that there is no dose-response relationship between carbohydrate solution concentration and 5-km track running performance.

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.

Glucose Increases Risky Behavior and Attitudes in People Low in Self-Control

Abstract. People low in self-control have a strong proclivity toward risk-taking. Risk-taking behavior provides an opportunity to obtain some form of reward. Glucose, on the other hand, seems to facilitate reward and goal-directed behavior. In a pilot study executed in the laboratory, we investigated whether consuming a glucose drink would increase risky behavior and attitudes in people low in self-control. Our findings revealed that a dose of glucose compared to placebo increased risk-taking on a behavioral and cognitive level in participants low in self-control but not in participants high in self-control. The findings may shed some light on the psychological underpinnings of glucose: By showing glucose’s association with high-risk behavior, they support the assumption of glucose driving a goal-directed motivation.