Maltodextrin-Based Carbohydrate Oral Rinsing and Exercise Performance: Systematic Review and Meta-Analysis

Carbohydrate Mouth Rinsing Improves Softball Launch Angle Consistency: A Double-Blind Crossover Study

(1) Background: Carbohydrate mouth rinsing (CMR) stimulates the central nervous system and improves motor control. However, no studies have examined the effects of CMR on softball batting performance. The purpose of this study was to investigate the effect of CMR on softball batting performance. (2) Methods: Fifteen trained female collegiate softball players (age: 20.6 ± 0.9 years; height: 159.5 ± 5.2 cm; body weight: 58.1 ± 6.9 kg) completed two trials in a randomization crossover trail, in which they rinsed their mouths for 20 s with 25 mL of either 6.4% maltodextrin (CMR) or a placebo (PLA). After rinsing, the Posner cueing task and grip force, counter-movement jump (CMJ) and batting tests were performed in sequence. A tanner tee was utilized to hit five sets of five balls at a time, with a minimum 3 min rest between sets. The batting test recorded the average exit velocity, maximum exit velocity and launch angle consistency. The standardized standard deviation (SD) for launch angle represents the standardized variability. (3) Results: The consistency of the launch angle of the CMR trial was significantly greater (p = 0.025; Cohen's d = 0.69) than that of the PLA trial. There were no significant differences in the Posner cueing task, grip strength, vertical jump, or exit velocity. (4) Conclusions: The findings of this study indicate that CMR enhances the launch angle consistency of all-out-effort batting, but does not influence the exit velocity of softball hitting.

Exploring the ergogenic potential of carbohydrate-caffeine combined mouth rinse on exercise and cognitive performance: a systematic review

Carbohydrate (CHO) and caffeine (CAF) mouth rinsing have been independently reported to benefit sport performance. The proposed mechanisms by which mouth rinsing CHO exerts an influence are reported to be different from those for mouth rinsing CAF. However, the potential ergogenic effects of combining CHO and CAF in a single mouth rinse solution, are unclear. This study aimed to review the available evidence of CHO-CAF combined mouth rinse on exercise and cognitive performance in human participants. A systematic literature search was conducted using five databases until April 2024, following the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) recommendations. Among the nine randomized crossover studies included, only one study showed significant improvements in lower-body muscular endurance with CHO-CAF mouth rinse (effect size (ES): 0.48; p < 0.05), while two studies reported non-statistically significant improvements in repeated sprint performance compared to other mouth rinse and placebo conditions (ES: 0.20-0.81; p = 0.07-0.18). However, for other performance measures, including repeated jumps, upper-body strength and endurance, endurance cycling, and intermittent recovery run, most evidence (five studies) did not demonstrate significant ergogenic effects. Notably, of the two studies that examined cognitive performance, both reported significant improvements with CHO-CAF mouth rinse compared with the placebo condition (ES: 0.45-3.45; p < 0.05). Overall, a synergistic influence of CHO-CAF mouth rinse on physical exercise performance is not evident, but preliminary evidence suggests potential benefits on cognitive performance. Future studies are required to address various methodological issues identified in this review, while practitioners and athletes should exercise caution when considering this novel nutritional strategy.

The Effects of Carbohydrate Mouth Rinse on Psychophysiological Responses and Kinematic Profiles in Intermittent and Continuous Small-Sided Games in Adolescent Soccer Players: A Randomized, Double-Blinded, Placebo-Controlled, and Crossover Trial

BACKGROUND

Mouth rinsing (MR) with a carbohydrate solution is one of the most popular methods athletes use to improve their game-based performance due to its acute ergogenic effect.

OBJECTIVES

This study aimed to evaluate the effects of the carbohydrate MR intervention on psychophysiological responses and kinematic profiles during intermittent (INT) and continuous (CON) 4-a-side small-sided soccer games (SSGs).

METHODS

Thirty-two adolescent soccer players (age: 16.5 ± 0.5 years) played six bouts of 4-a-side SSGs with MRINT or MRCON at 3-day intervals in a randomized, double-blinded, placebo-controlled, and crossover study design. Psychophysiological responses and kinematic profiles were continuously recorded during all games. The rating of perceived exertion (RPE), the rating scale of mental effort (RSME), and the physical enjoyment scores (PES) were also determined at the end of each game.

RESULTS

The MRCON induced higher psychophysiological responses such as RPE, internal training load (ITL), and RSME (p ≤ 0.05, d values ranging from 0.50 to 1.04 [small to moderate effect]). Conversely, the MRINT induced higher PES (p ≤ 0.05, d values = 1.44 [large effect]) compared to MRCON. Although the MR intervention led to similar improvements in the performance of 4-a-side MRINT and MRCON, there was no significant difference between the groups.

CONCLUSIONS

Our results suggest that the MR intervention can be used as an effective ergogenic supplement for acute game performance enhancement, regardless of the game's structure.

[Effects of D-tagatose, Stevia and Sucrose on pH and oral bacterial activity in dentistry students. A randomized controlled trial]

Introduction

Background: stevia and D-tagatose have shown a reduction in total calorie and carbohydrate intake as a substitute for sucrose, demonstrating a stabilizing effect on pH and bacterial proliferation. Objective: to evaluate the effect of D-tagatose, stevia and sucrose on salivary pH and bacterial activity in odontology students. Methodology: a controlled study of parallel and randomized groups with a single blind, whose sample considered three groups subjected to a mouthwash of D-tagatose (n = 10), stevia (n = 10) and sucrose (n = 10). These solutions were administered over 1 minute in a single 6.4 % concentrated dose. Data collection and analysis considered the recording of salivary pH 5 min before exposure to the sweetener, immediately after expulsion of the mouthwash and 15 min later, 30 min, 45 min and 48 hours. The counting of the final number of colony-forming units per mL (CFU/mL) was counted using the salivary samples obtained immediately after exposure of the sweetener together with the sample obtained 30 minutes later, with the cultures performed on agar plates. Results: D-tagatose, stevia and sucrose presented significant differences in total CFU/mL at 30 minutes (p < 0.001), while salivary pH showed significant differences at 48 hours after administration (p < 0.001). Conclusion: D-tagatose, stevia and sucrose present significant differences in total CFU/mL and salivary pH, these findings being a possible indication of a partial inhibitory effect on bacterial metabolism.

No Effects of Carbohydrate Ingestion on Muscle Metabolism or Performance During Short-Duration High-Intensity Intermittent Exercise

Carbohydrates are critical for high-intensity exercise performance. However, the effects of carbohydrate supplementation on muscle metabolism and performance during short-duration high-intensity intermittent exercise remain inadequately explored. Our aim was to address this aspect in a randomized, counterbalanced, double-blinded crossover design. Eleven moderately-to-well-trained males performed high-intensity intermittent cycling receiving carbohydrate (CHO, ~55 g/h) or placebo (PLA) fluid supplementation. Three exercise periods (EX1-EX3) were completed comprising 10 × 45 s at ~105% Wmax interspersed with 135 s rest between bouts and ~20 min between periods. Repeated sprint ability (5 × 6 s sprints with 24 s recovery) was assessed at baseline and after each period. Thigh muscle biopsies were obtained at baseline and before and after EX3 to determine whole-muscle and fiber-type-specific glycogen depletion. No differences were found in muscle glycogen degradation at the whole-muscle (p = 0.683) or fiber-type-specific level (p = 0.763-0.854) with similar post-exercise whole-muscle glycogen concentrations (146 ± 20 and 122 ± 15 mmol·kg-1 dw in CHO and PLA, respectively). Repeated sprint ability declined by ~9% after EX3 with no between-condition differences (p = 0.971) and no overall differences in ratings of perceived exertion (p = 0.550). This was despite distinctions in blood glucose concentrations throughout exercise, reaching post-exercise levels of 5.3 ± 0.2 and 4.1 ± 0.2 mmol·L-1 (p < 0.001) in CHO and PLA, respectively, accompanied by fivefold higher plasma insulin levels in CHO (p < 0.001). In conclusion, we observed no effects of carbohydrate ingestion on net muscle glycogen breakdown or sprint performance during short-duration high-intensity intermittent exercise despite elevated blood glucose and insulin levels. These results therefore question the efficacy of carbohydrate supplementation strategies in high-intensity intermittent sports.

Exercise-Induced Central Fatigue: Biomarkers and Non-Medicinal Interventions

Fatigue, commonly experienced in daily life, is a feeling of extreme tiredness, shortage or lack of energy, exhaustion, and difficulty in performing voluntary tasks. Central fatigue, defined as a progressive failure to voluntarily activate the muscle, is typically linked to moderate- or light-intensity exercise. However, in some instances, high-intensity exercise can also trigger the onset of central fatigue. Exercise-induced central fatigue often precedes the decline in physical performance in well-trained athletes. This leads to a reduction in nerve impulses, decreased neuronal excitability, and an imbalance in brain homeostasis, all of which can adversely impact an athlete's performance and the longevity of their sports career. Therefore, implementing strategies to delay the onset of exercise-induced central fatigue is vital for enhancing athletic performance and safeguarding athletes from the debilitating effects of fatigue. In this review, we discuss the structural basis, measurement methods, and biomarkers of exercise-induced central fatigue. Furthermore, we propose non-pharmacological interventions to mitigate its effects, which can potentially foster improvements in athletes' performances in a healthful and sustainable manner.

Carbohydrate Oral Rinsing, Cycling Performance and Individual Complex Carbohydrate Taste Sensitivity

The aim of this pilot study was to determine the effect of individual complex carbohydrate taste sensitivity on cycling performance with complex carbohydrate oral rinsing. Ten male participants completed five cycling time trials in a fasted state with a seven-day washout period between each trial. Participants completed a fixed amount of work (738.45 ± 150.74 kJ) as fast as possible on a cycle ergometer while rinsing with an oral rinse for 10 s every 12.5% of the trial. An oral rinse (maltodextrin, oligofructose, glucose, sucralose or water control) was given per visit in a randomised, crossover, blinded design. Afterwards, participants had their taste assessed with three stimuli, complex carbohydrate (maltodextrin), sweet (glucose) and sour (citric acid), using taste assessment protocol to determine individual taste sensitivity status. Participants were subsequently grouped according to their complex carbohydrate taste sensitivity and complex carbohydrate taste intensity. There were no significant effects of the oral rinses on cycling performance time (p = 0.173). Participants who did not have improvements in exercise performance with the maltodextrin rinse experienced a stronger taste intensity with complex carbohydrate stimuli at baseline (p = 0.047) and overall (p = 0.047) than those who did have improvements in performance. Overall, a carbohydrate oral rinse was ineffective in significantly improving cycling performance in comparison with a water control. However, when participants were grouped according to complex carbohydrate taste intensity, differences in exercise performance suggest that individual sensitivity status to complex carbohydrates could impact the efficacy of a carbohydrate-based oral rinse.

Central effects of mouth rinses on endurance and strength performance

Rinsing the mouth with a carbohydrate (CHO) solution has been shown to enhance exercise performance while reducing neuromuscular fatigue. This effect is thought to be mediated through the stimulation of oral receptors, which activate brain areas associated with reward, motivation, and motor control. Consequently, corticomotor responsiveness is increased, leading to sustained levels of neuromuscular activity prior to fatigue. In the context of endurance performance, the evidence regarding the central involvement of mouth rinse (MR) in performance improvement is not conclusive. Peripheral mechanisms should not be disregarded, particularly considering factors such as low exercise volume, the participant's fasting state, and the frequency of rinsing. These factors may influence central activations. On the other hand, for strength-related activities, changes in motor evoked potential (MEP) and electromyography (EMG) have been observed, indicating increased corticospinal responsiveness and neuromuscular drive during isometric and isokinetic contractions in both fresh and fatigued muscles. However, it is important to note that in many studies, MEP data were not normalised, making it difficult to exclude peripheral contributions. Voluntary activation (VA), another central measure, often exhibits a lack of changes, mainly due to its high variability, particularly in fatigued muscles. Based on the evidence, MR can attenuate neuromuscular fatigue and improve endurance and strength performance via similar underlying mechanisms. However, the evidence supporting central contribution is weak due to the lack of neurophysiological measures, inaccurate data treatment (normalisation), limited generalisation between exercise modes, methodological biases (ignoring peripheral contribution), and high measurement variability.Trial registration: PROSPERO ID: CRD42021261714.

Exercise metabolism and adaptation in skeletal muscle

Viewing metabolism through the lens of exercise biology has proven an accessible and practical strategy to gain new insights into local and systemic metabolic regulation. Recent methodological developments have advanced understanding of the central role of skeletal muscle in many exercise-associated health benefits and have uncovered the molecular underpinnings driving adaptive responses to training regimens. In this Review, we provide a contemporary view of the metabolic flexibility and functional plasticity of skeletal muscle in response to exercise. First, we provide background on the macrostructure and ultrastructure of skeletal muscle fibres, highlighting the current understanding of sarcomeric networks and mitochondrial subpopulations. Next, we discuss acute exercise skeletal muscle metabolism and the signalling, transcriptional and epigenetic regulation of adaptations to exercise training. We address knowledge gaps throughout and propose future directions for the field. This Review contextualizes recent research of skeletal muscle exercise metabolism, framing further advances and translation into practice.

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.