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.

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.

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.

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.

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.

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.

Coffee and Caffeine Ingestion Have Little Effect on Repeated Sprint Cycling in Relatively Untrained Males

The present study investigated the effect of ingesting caffeine-dose-matched anhydrous caffeine or coffee on the performance of repeated sprints. Twelve recreationally active males (mean ± SD age: 22 ± 2 years, height: 1.78 ± 0.07 m, body mass: 81 ± 16 kg) completed eighteen 4 s sprints with 116 s recovery on a cycle ergometer on four separate occasions in a double-blind, randomised, counterbalanced crossover design. Participants ingested either 3 mg·kg⁻¹ of caffeine (CAF), 0.09 g·kg⁻¹ coffee, which provided 3 mg·kg⁻¹ of caffeine (COF), a taste-matched placebo beverage (PLA), or a control condition (CON) 45 min prior to commencing the exercise protocol. Peak and mean power output and rating of perceived exertion (RPE) were recorded for each sprint. There were no significant differences in peak power output (CAF: 949 ± 199 W, COF: 949 ± 174 W, PLA: 971 ± 149 W and CON: 975 ± 170 W; p = 0.872; ηP2 = 0.02) or mean power output (CAF: 873 ± 172 W, COF: 862 ± 44 W, PLA: 887 ± 119 W and CON: 892 ± 143 W; p = 0.819; ηP2 = 0.03) between experimental conditions. Mean RPE was similar for all trials (CAF: 11 ± 2, COF: 11 ± 2, PLA: 11 ± 2 and CON: 11 ± 2; p = 0.927; ηP2 = 0.01). Neither the ingestion of COF or CAF improved repeated sprint cycling performance in relatively untrained males.

Effects of various concentrations of carbohydrate mouth rinse on cycling performance in a fed state

The objective of this study was to identify the effects of mouth rinsing with a 6% and 16% carbohydrate solution (CHO) on time trial performance when compared to a 0% control (PLA) when in a fed state. Twelve recreationally active males underwent three trials by which they had to complete a set workload (600 ± 65 W) in a fed state. Throughout each trial, participants rinsed their mouths with a 25 ml bolus of a 0% PLA, 6% or 16% CHO (maltodextrin) for every 12.5% of work completed. Rating of perceived exertion (RPE) and heart rate were recorded every 12.5% of total work. Performance times and power output improved significantly when using the 6% and 16% CHO versus the PLA trial (6% versus PLA, p = .002 and 16% versus PLA, p = .001). When comparing the performance times of the 6% to 16% CHO, no significance was observed (p = .244). There was no significant difference between heart rate levels or RPE values across the three trials. In conclusion, mouth rinsing with a 6% or 16% CHO solution has a positive effect on a cycling time trial performance undertaken in a fed state.

Mouth Rinsing with Maltodextrin Solutions Fails to Improve Time Trial Endurance Cycling Performance in Recreational Athletes

The carbohydrate (CHO) concentration of a mouth rinsing solution might influence the CHO sensing receptors in the mouth, with consequent activation of brain regions involved in reward, motivation and regulation of motor activity. The purpose of the present study was to examine the effects of maltodextrin mouth rinsing with different concentrations (3%, 6% and 12%) after an overnight fast on a 20 km cycling time trial performance. Nine recreationally active, healthy males (age: 24 ± 2 years; V ˙ O 2 m a x : 47 ± 5 mL·kg(-1)·min(-1)) participated in this study. A double-blind, placebo-controlled randomized study was conducted. Participants mouth-rinsed every 2.5 km for 5 s. Maltodextrin mouth rinse with concentrations of 3%, 6% or 12% did not change time to complete the time trial and power output compared to placebo (p > 0.05). Time trial completion times were 40.2 ± 4.0, 40.1 ± 3.9, 40.1 ± 4.4, and 39.3 ± 4.2 min and power output 205 ± 22, 206 ± 25, 210 ± 24, and 205 ± 23 W for placebo, 3%, 6%, and 12% maltodextrin conditions, respectively. Heart rate, lactate, glucose, and rating of perceived exertion did not differ between trials (p > 0.05). In conclusion, mouth rinsing with different maltodextrin concentrations after an overnight fast did not affect the physiological responses and performance during a 20 km cycling time trial in recreationally active males.

The effect of carbohydrate mouth rinse on a 30-minute arm cranking performance

The aim of this study was to examine the effect of carbohydrate mouth rinse on 30-min arm cranking performance. Twelve healthy, active males (age 21.6, standard deviation (SD)=3.1 years; mass 76.2, SD=12.2 kg) volunteered in a single-blind, randomised crossover design. Firstly they completed an incremental exercise test to exhaustion (VO2max test) on an arm crank (50W for 2 min, increasing by 10W every min). During visit 2 and 3 they arm cranked for maximal distance over 30 min at a resistance equivalent to 50% of their peak power, mouth rinsing for 5 s with either 25 ml of a tasteless 6.4% maltodextrin solution (CHO) or 25 ml of water (placebo) every 6 min. A letter cancellation test was performed pre and post exercise to measure cognitive function. The result showed that cognitive function was not significantly different between trials (P=0.874). There was no significant difference in distance arm cranked between trials (P=0.164) even though 9 out of 12 participants had improved performance on the CHO trial. In conclusion, further research is needed to determine the ergogenic effect of CHO mouth rinsing on upper body exercise performance.

Half-time strategies to enhance second-half performance in team-sports players: a review and recommendations

A number of intermittent team sports require that two consecutive periods of play (lasting for ~30-45 min) are separated by a 10-20 min half-time break. The half-time practices employed by team-sports players generally include returning to the changing rooms, temporarily relaxing from the cognitive and physical demands of the first half, rehydration and re-fuelling strategies, addressing injury or equipment concerns, and receiving tactical instruction and coach feedback. However, the typically passive nature of these actions has been associated with physiological changes that impair performance during the second half. Both physical and cognitive performances have been found to decline in the initial stages of subsequent exercise that follows half-time. An increased risk of injury has also been observed during this period. Therefore, half-time provides sports scientists and strength and conditioning coaches with an opportunity to optimise second-half performance. An overview of strategies thought to benefit team-sports athletes is presented; specifically, the efficacy of heat maintenance strategies (including passive and active methods), post-activation potentiation, hormonal priming, and modified hydro-nutritional practices are discussed. A theoretical model of applying these strategies in a manner that compliments current practice is also offered.

The acute effects of green tea and carbohydrate coingestion on systemic inflammation and oxidative stress during sprint cycling

Green tea (Camellia sinensis) has anti-oxidative and anti-inflammatory effects, which may be beneficial to athletes performing high-intensity exercise. This study investigated the effects of carbohydrate and green tea coingestion on sprint cycling performance and associated oxidative stress and immunoendocrine responses to exercise. In a crossover design, 9 well-trained male cyclists completed 3 sets of 8 repetitions of 100-m uphill sprint cycling while ingesting green tea and carbohydrate (TEA) (22 mg/kg body mass catechins, 6 mg/kg body mass caffeine, 230 mg/kg glucose, and 110 mg/kg fructose) or carbohydrate only (CHO) (230 mg/kg body mass glucose and 110 mg/kg body mass fructose) during each 10-min recovery period between sets. Blood samples were collected before exercise, 10 min after exercise, and 14 h after exercise. There was no effect of acute TEA ingestion on cycling sprint performance (p = 0.29), although TEA maintained postexercise testosterone and lymphocyte concentrations, which decreased significantly in the CHO group (p < 0.001). While there was a trend for lower postexercise neutrophil count with TEA (p = 0.05), there were no significant differences between TEA and CHO for circulating cytokines (p > 0.20), markers of oxidative stress and antioxidant capacity (p > 0.17), adiponectin concentration (p = 0.60), or muscle damage markers (p > 0.64). While acute green tea ingestion prevents the postexercise decrease in testosterone and lymphocytes, it does not appear to benefit cycling sprint performance or reduce markers of oxidation and inflammation when compared with carbohydrate alone.

Effects of caffeine and maltodextrin mouth rinsing on P300, brain imaging, and cognitive performance

Caffeine (CAF) and maltodextrin (MALT) mouth rinses (MR) improve exercise performance. The current experiment aims to determine the effect of CAF and MALT MR on cognitive performance and brain activity. Ten healthy male subjects (age 27 ± 3 yr) completed three experimental trials. Each trial included four Stroop tasks: two familiarization tasks, and one task before and one task after an MR period. The reaction time (in milliseconds) and accuracy (percent) of simple, congruent, and incongruent stimuli were assessed. Electroencephalography was applied throughout the experiment to record brain activity. The amplitudes and latencies of the P300 were determined during the Stroop tasks before and after the MR period. Subjects received MR with CAF (0.3 g/25 ml), MALT (1.6 g/25 ml), or placebo (PLAC) in a randomized, double-blind, crossover design. During MR, the brain imaging technique standardized low-resolution brain electromagnetic tomography was applied. Magnitude-based inferences showed that CAF MR is likely trivial (63.5%) and likely beneficial (36.4%) compared with PLAC MR, and compared with MALT MR likely beneficial to reaction time on incongruent stimuli (61.6%). Additionally, both the orbitofrontal and dorsolateral prefrontal cortex were activated only during CAF MR, potentially explaining the likely beneficial effect on reaction times. MALT MR increased brain activity only within the orbitofrontal cortex. However, this brain activation did not alter the reaction time. Furthermore, no significant differences in the accuracy of stimuli responses were observed between conditions. In conclusion, only CAF MR exerted a likely beneficial effect on reaction time due to the subsequent activation of both the orbitofrontal and dorsolateral prefrontal cortexes.

The efficacy of acute nutritional interventions on soccer skill performance

BACKGROUND

The use of nutritional ergogenic aids in team sports such as soccer is now commonplace. Aligned with the primary aim of soccer, which is to score more goals than the opposition within the allotted time, the quality of performance of technical actions (i.e., skills) executed during soccer-specific exercise is likely to determine success. However, when seeking to maintain soccer skill performance, information about the efficacy of nutritional interventions is lacking and factors which might modulate the efficacy of such strategies are unclear.

OBJECTIVE

This review aimed (i) to systematically evaluate the current research that examines the efficacy of nutritional interventions on soccer skills, and (ii) to provide a qualitative commentary on factors that have the potential to modulate the efficacy of such strategies.

DATA SOURCES

Relevant databases (PubMed and SPORTDiscus) were searched up to and including 1 July, 2013 for studies that investigated the efficacy of acute nutritional interventions on soccer skill performances.

STUDY SELECTION

Overall, 279 records were retrieved. Articles were sequentially excluded from the review based on specific criteria, being: (A) articles that did not report outcomes directly relating to skilled performances in soccer, (B) articles that examined the influence of interventions that were not nutritional in origin and/or were nutritional in origin but provided >3 hours before skill testing commenced, (C) articles that were review papers, and (D) post-acceptance withdrawal of articles methods from database.

STUDY APPRAISAL AND SYNTHESIS METHODS

Articles were independently assessed for the quality of the methods employed based upon the Physiotherapy Evidence Database (PEDro) scale. Records achieving a minimum PEDro score of 5 out of 10 were included in this review. Qualitative appraisal of 13 articles was performed after the application of exclusion criteria and quality assurance processes. The majority (n = 8) of articles examined the influence of carbohydrates on technical performance whereas fewer studies investigated the influence of caffeine ingestion (n = 2) and fluid provision (n = 3).

RESULTS

Findings were reported for a total of 171 participants and all but one of the included articles used cross-over study designs. Most participants (94 %) were male, highly trained (reported maximal aerobic capacity range 50-59 ml·kg(-1)·min(-1)) and exercised in temperate environments (reported temperature range 13-25 °C). Six of the eight studies reported that carbohydrates, consumed in the form of a 6-8 % solution of glucose, sucrose or maltodextrin at rates of 30-60 g·h(-1), enhanced at least one aspect of skilled performance over the duration of exercise (75-90 min). Although some evidence exists to support the consumption of caffeine (6 mg·kg(-1) body mass [BM]) and prescribed fluid to preserve skills performed during soccer-specific exercise, findings from the small number of included studies were inconsistent.

LIMITATIONS

The outcome measures and methods used to quantify skilled performance were not consistent across studies; consequently, it was not possible to perform meta-analyses to produce pooled effect sizes in this review.

CONCLUSIONS

The findings from this systematic review suggest that nutritional interventions, which provide carbohydrate, caffeine and fluid, have potential to preserve skills performed under conditions that induce soccer-specific fatigue. The weight of current evidence supports the consumption of carbohydrate, but is less conclusive with respect to caffeine and fluid provision. It is likely that the efficacy of a nutritional intervention will be modulated by factors including the dose consumed, the mode of administration, individual responsiveness to the intervention and interactions with other physiological changes occurring during soccer-specific exercise. Consequently, these factors should be considered when using carbohydrates, caffeine and fluid provision to maintain skilled performances in soccer. Future research should seek to optimise the nutritional strategies employed to maintain technical performance throughout match-play.

Exercise and sport performance with low doses of caffeine

Caffeine is a popular work-enhancing supplement that has been actively researched since the 1970s. The majority of research has examined the effects of moderate to high caffeine doses (5-13 mg/kg body mass) on exercise and sport. These caffeine doses have profound effects on the responses to exercise at the whole-body level and are associated with variable results and some undesirable side effects. Low doses of caffeine (<3 mg/kg body mass, ~200 mg) are also ergogenic in some exercise and sport situations, although this has been less well studied. Lower caffeine doses (1) do not alter the peripheral whole-body responses to exercise; (2) improve vigilance, alertness, and mood and cognitive processes during and after exercise; and (3) are associated with few, if any, side effects. Therefore, the ergogenic effect of low caffeine doses appears to result from alterations in the central nervous system. However, several aspects of consuming low doses of caffeine remain unresolved and suffer from a paucity of research, including the potential effects on high-intensity sprint and burst activities. The responses to low doses of caffeine are also variable and athletes need to determine whether the ingestion of ~200 mg of caffeine before and/or during training and competitions is ergogenic on an individual basis.

The Governor has a sweet tooth - mouth sensing of nutrients to enhance sports performance

The oral-pharyngeal cavity and the gastrointestinal tract are richly endowed with receptors that respond to taste, temperature and to a wide range of specific nutrient and non-nutritive food components. Ingestion of carbohydrate-containing drinks has been shown to enhance endurance exercise performance, and these responses have been attributed to post-absorptive effects. It is increasingly recognised, though, that the response to ingested carbohydrate begins in the mouth via specific carbohydrate receptors and continues in the gut via the release of a range of hormones that influence substrate metabolism. Cold drinks can also enhance performance, especially in conditions of thermal stress, and part of the mechanism underlying this effect may be the response to cold fluids in the mouth. There is also some, albeit not entirely consistent, evidence for effects of caffeine, quinine, menthol and acetic acid on performance or other relevant effects. This review summarises current knowledge of responses to mouth sensing of temperature, carbohydrate and other food components, with the goal of assisting athletes to implement practical strategies that make best use of its effects. It also examines the evidence that oral intake of other nutrients or characteristics associated with food/fluid intake during exercise can enhance performance via communication between the mouth/gut and the brain.

Effects of carbohydrate combined with caffeine on repeated sprint cycling and agility performance in female athletes

Background

Caffeine (CAF) has been shown to improve performance during early phase of repeated sprint exercise; however some studies show that CAF also increases the magnitude of physical stress represented by augmented blood lactate, glucose, and cortisol concentrations during latter phase of repeated sprint exercise. No studies have investigated the efficacy of combined carbohydrate (CHO) and CAF consumption during repeated sprint exercise (RSE) in female athletes. Thus, the purpose of this study was to investigate the effects of CAF with CHO supplementation on RSE and agility.

Methods

Eleven female athletes completed four experimental trials performed 7 d apart in a double-blind, randomized, and counter-balanced crossover design. Treatments included CAF + PLA (placebo), CAF + CHO, PLA + CHO, and PLA + PLA. Participants ingested capsules containing 6 mg · kg⁻¹ of CAF or PLA 60-min prior to RSE, and 0.8 g · kg⁻¹ of CHO solution or PLA immediately before the RSE, which consisted of ten sets of 5 × 4-s sprints on the cycle ergometer with 20-s active recovery. The agility T-test (AT-test) was performed before and after the RSE. Blood samples were acquired to assess glucose, lactate, testosterone, and cortisol.

Results

During Set 6 of RSE, peak power and mean power were significantly higher in PLA + CHO than those in CAF + PLA and PLA + PLA, respectively (p < .05). Total work was significantly increased by 4.8% and 5.9% with PLA + CHO than those of CAF + CHO and CAF + PLA during Set 3. PLA + CHO also increased total work more than CAF + PLA and PLA + PLA did during Set 6 (p < .05). No significant differences in AT-test performance either before or after the RSE were occurred among treatments (p > .05). Blood lactate and glucose concentrations were significantly higher under CAF + CHO, CAF + PLA, and PLA + CHO versus PLA + PLA (p < .05), but no differences in testosterone or cortisol levels were found (p > .05).

Conclusions

Findings indicate that CAF + PLA or CAF + CHO ingestion did not improve repeated sprint performance with short rest intervals or agility. However, CHO ingested immediately prior to exercise provided a small but significant benefit on RSE performance in female athletes.

The effect of caffeine mouth rinse on self-paced cycling performance

The aim of the study was to determine whether caffeine mouth rinse would improve 30 min self-paced cycling trial. Twelve healthy active males (age 20.5±0.7 years, mass 87.4±18.3 kg) volunteered for the study. They attended the laboratory on 3 separate occasions performing a 30 min self-paced cycling trial. On one occasion water was given as a mouth rinse for 5 s (PLA), on another occasion a 6.4% maltodextrin (CHO) solution was given for 5 s and finally a caffeine solution (containing 32 mg of caffeine dissolved in 125 ml water; CAF) was given for 5 s. Distance cycled, heart rate, ratings of perceived exertion, cadence, speed and power output were recorded throughout all trials. Distance cycled during the CAF mouth rinse trial (16.2±2.8 km) was significantly greater compared to PLA trial (14.9±2.6 km). There was no difference between CHO and CAF trials (P=0.89). Cadence, power and velocity were significantly greater during the CAF trial compared to both PLA and CHO (P<0.05). There were no differences between trials for heart rate and perceived exertion (P>0.05). Caffeine mouth rinse improves 30 min cycling performance by allowing the participant to increase cadence, power and velocity without a concurrent increase in perceived exertion and heart rate.

Effect of carbohydrate mouth rinsing on multiple sprint performance

Background

Research suggests that carbohydrate mouth rinsing (CMR) improves endurance performance; yet, little is known regarding the effect of CMR on multiple sprint efforts. As many sports involve multiple sprinting efforts, followed by periods of recovery, the aim of our current study was to investigate the influence of CMR on multiple sprint performance.

Methods

We recruited eight active males (Age; 22 ± 1 y; 75.0 ± 8.8 kg; estimated VO2_max 52.0 ± 3.0 ml/kg/min) to participate in a randomly assigned, double-blind, counterbalanced study administering a CMR (6.4% Maltodextrin) or similarly flavoured placebo solution. Primary outcomes for our study included: (a) time for three repeated sprint ability tests (RSA) and (b) the Loughborough Intermittent Shuttle Test (LIST). Time was expressed in seconds (sec). Secondary outcomes included ratings of perceived exertion (RPE) and blood glucose concentration. Tertiary outcomes included two psychological assessments designed to determine perceived activation (i.e., arousal) and pleasure-displeasure after each section of the LIST. We analysed our data using a two-way analysis of variance (ANOVA) for repeated measures, a Bonferroni adjusted post hoc t-test to determine significant differences in treatment, and a liberal 90% confidence interval between treatment conditions. Effect sizes were calculated between trials and interpreted as ≤ 0.2 trivial, > 0.2 small, > 0.6 moderate, > 1.2 large, > 2 very large and > 4 extremely large. Data are means ± SD. Overall statistical significance was set as P < 0.05; yet, modified accordingly when Bonferroni adjustments were made.

Results

Overall, we observed no significant difference in average (3.46 ± 0.2 vs. 3.44 ± 0.17; P = 0.11) or fastest time (3.38 ± 0.2 vs. 3.37 ± 0.2; P = 0.39) in the RSA test for the placebo vs. CMR conditions, respectively. Similar findings were also noted for the placebo vs. CMR, respectively, during the LIST test (3.52 ± 0.2 vs. 3.54 ± 0.2 sec; P = 0.63). Despite a significantly higher within group RPE during the 3rd and 4th sections of the LIST (< 0.05), no between group differences were otherwise noted. No differences were noted for blood glucose concentrations throughout the testing protocol. Lastly, from a psychological perspective, we observed no differences in pleasure-displeasure or perceived activation.

Conclusions

The results of our current study suggest that CMR does not improve exercise performance, RPE or perceived pleasure-displeasure during high intensity activity requiring repeated, intermittent, sprint efforts.