Caffeine Supplementation or Carbohydrate Mouth Rinse Improves Performance

Nutritional Strategies for Optimizing Health, Sports Performance, and Recovery for Female Athletes and Other Physically Active Women: A Systematic Review

CONTEXT

Despite the progress toward gender equality in events like the Olympic Games and other institutionalized competitions, and the rising number of women engaging in physical exercise programs, scientific studies focused on establishing specific nutritional recommendations for female athletes and other physically active women are scarce.

OBJECTIVE

This systematic review aimed to compile the scientific evidence available for addressing the question "What dietary strategies, including dietary and supplementation approaches, can improve sports performance, recovery, and health status in female athletes and other physically active women?"

DATA SOURCES

The Pubmed, Web of Science, and Scopus databases were searched.

DATA EXTRACTION

The review process involved a comprehensive search strategy using keywords connected by Boolean connectors. Data extracted from the selected studies included information on the number of participants and their characteristics related to sport practice, age, and menstrual function.

DATA ANALYSIS

A total of 71 studies were included in this review: 17 focused on the analysis of dietary manipulation, and 54 focused on the effects of dietary supplementation. The total sample size was 1654 participants (32.5% categorized as competitive athletes, 30.7% as highly/moderately trained, and 37.2% as physically active/recreational athletes). The risk of bias was considered moderate, mainly for reasons such as a lack of access to the study protocol, insufficient description of how the hormonal phase during the menstrual cycle was controlled for, inadequate dietary control during the intervention, or a lack of blinding of the researchers.

CONCLUSION

Diets with high carbohydrate (CHO) content enhance performance in activities that induce muscle glycogen depletion. In addition, pre-exercise meals with a high glycemic index or rich in CHOs increase CHO metabolism. Ingestion of 5-6 protein meals interspersed throughout the day, with each intake exceeding 25 g of protein favors anabolism of muscle proteins. Dietary supplements taken to enhance performance, such as caffeine, nitric oxide precursors, β-alanine, and certain sport foods supplements (such as CHOs, proteins, or their combination, and micronutrients in cases of nutritional deficiencies), may positively influence sports performance and/or the health status of female athletes and other physically active women.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD480674.

Effects of Acute Ingestion of Caffeine Capsules on Muscle Strength and Muscle Endurance: A Systematic Review and Meta-Analysis

This study aimed to explore the effects of acute ingestion of caffeine capsules on muscle strength and muscle endurance. We searched the PubMed, Web of Science, Cochrane, Scopus, and EBSCO databases. Data were pooled using the weighted mean difference (WMD) and 95% confidence interval. Fourteen studies fulfilled the inclusion criteria. The acute ingestion of caffeine capsules significantly improved muscle strength (WMD, 7.09, p < 0.00001) and muscle endurance (WMD, 1.37; p < 0.00001), especially in males (muscle strength, WMD, 7.59, p < 0.00001; muscle endurance, WMD, 1.40, p < 0.00001). Subgroup analyses showed that ≥ 6 mg/kg body weight of caffeine (WMD, 6.35, p < 0.00001) and ingesting caffeine 45 min pre-exercise (WMD, 8.61, p < 0.00001) were more effective in improving muscle strength, with the acute ingestion of caffeine capsules having a greater effect on lower body muscle strength (WMD, 10.19, p < 0.00001). In addition, the acute ingestion of caffeine capsules had a greater effect in moderate-intensity muscle endurance tests (WMD, 1.76, p < 0.00001). An acute ingestion of caffeine capsules significantly improved muscle strength and muscle endurance in the upper body and lower body of males.

Load and muscle group size influence the ergogenic effect of acute caffeine intake in muscular strength, power and endurance

INTRODUCTION

Although acute caffeine intake seems to improve muscular strength-power-endurance performance, there is scarce evidence evaluating upper vs lower-body exercises at different loads. Thus, this study aimed to examine the effects of acute caffeine intake on upper and lower-body muscular strength, power and endurance performance at different loads.

METHODS

Twenty resistance-trained athletes (male/female: 10/10; age: 23 ± 4 years; body mass: 70.6 ± 15.1) participated in a double-blind, placebo-controlled, cross-over and randomized study. Participants were provided with either 3 mg/kg of body mass of caffeine or maltodextrin (placebo). Sixty minutes after ingestion, they performed muscular strength and power assessment for bench press and back squat exercise at 25%, 50%, 75% and 90% 1-repetition-maximum (1RM), performing 3, 2, 1 and 1 repetitions respectively, followed by muscular endurance assessment for both exercises at 65% and 85% 1RM performing until task failure. Isometric handgrip, isometric mid-thigh pull and vertical jump tests were also performed.

RESULTS

In muscular strength and power, compared to placebo, caffeine improved mean velocity (P = 0.045; _pη² = 0.101), mean power (P = 0.049; _pη² = 0.189) and rate of force development (RFD, P = 0.032; _pη² = 0.216), particularly in back squat exercise at 75% and 90% 1RM where mean velocity increased by 5-7% (P = 0.48-0.038; g = 0.348-1.413), mean power by 6-8% (P = 0.050-0.032; g = 0.547-0.818) and RFD by 17-97% (P = 0.042-0.046; g = 1.436-1.196). No differences were found in bench press exercise. In muscular endurance, caffeine improved the number of repetitions in all exercises and loads (P = 0.003; _pη² = 0.206), but only in back squat exercise at 85% 1RM, caffeine increased mean and peak velocity (8-9%, P = 0.006-0.004; g = 2.029-2.075), mean and peak power (10-13%, P = 0.006-0.003; g = 0.888-1.151) and force peak (3%, P = 0.009; g = 0.247).

CONCLUSIONS

Acute caffeine intake (3 mg/kg) improved muscular strength, power and endurance performance, revealing a more pronounced effect at high-loads (≥ 75% 1RM) and in lower-body (back squat) than in upper-body exercise (bench press) according to muscle group size.

Synergy of carbohydrate and caffeine ingestion on physical performance and metabolic responses to exercise: A systematic review with meta-analysis

Carbohydrates (CHO) and caffeine (CAF) are two ergogenic aids commonly used among athletes to enhance performance. However, there is some controversy as to whether the concurrent intake of both supplements might result in an additive and synergistic improvement in exercise performance. The aim of this systematic review and meta-analysis was to determine the effect of adding CAF to a protocol of CHO ingestion, compared with the intake of each ergogenic aid alone and with placebo, on exercise performance and metabolic responses in healthy young physically active adults. This study was conducted according to PRISMA 2020 guidelines. The PubMed, Web of Science, Medline Complete, CINAHL, SPORTDiscus and CENTRAL databases were searched including randomized controlled trials (RCT) that were at least single blind. The risk of bias assessment was performed using the Cochrane Risk-of-Bias tool 2. Meta-analysis were performed on performance variables and rating of perceived exertion (RPE) using the random-effects model. Thirteen RCT with 128 participants (117 men and 11 women) were included in this study. The ingestion of CAF and CHO reduced sprint time during repeated sprint protocols in comparison with CHO isolated ingestion (SMD: -0.45; 95% CI: -0.85, -0.05) while there was a tendency for a reduction in the time employed during time trials (SMD: -0.36; 95% CI: -0.77, 0.05). The RPE tended to be lower with CAF and CHO compared with CHO isolated ingestion during steady-state exercise (SMD: -0.43; 95% CI: -0.91, 0.05) with no differences between conditions in performance trials (SMD: -0.05, 95% CI: -0.39, 0.29). Although most of the studies showed higher values of blood glucose when CHO was co-ingested with CAF compared with PLA, only two studies observed higher values with CHO and CAF co-ingestion with respect to the isolated intake of CHO. One study observed greater fat oxidation and lower glycogen use when CAF was added to CHO. In terms of cortisol levels, one study showed an increase in cortisol levels when CAF was co-ingested with CHO compared with PLA. In summary, concurrent CHO and CAF intake may produce an additive ergogenic effect respect of the isolated ingestion of CHO. This additive effect was present when CHO was provided by a 6-9% of CHO solution (maltodextrin/dextrin + fructose) and CAF is administered in a dose of 4-6.5 mg/kg.

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.

Effects of carbohydrate and caffeine mouth rinsing on strength, muscular endurance and cognitive performance

Background

Carbohydrate (CHO) and caffeine (CAF) mouth rinsing have been shown to enhance endurance and sprint performance. However, the effects of CHO and CAF mouth rinsing on muscular and cognitive performance in comparison between male and female athletes are less well-established. The aim of this study was to examine the effect of CHO and CAF rinsing on squat and bench press 1 repetition maximum (1-RM) strength, 3 sets of 40% of 1-RM muscular endurance and cognitive performance in both male and female athletes.

Methods

Thirteen male and fourteen female resistance-trained participants completed four testing sessions following the rinsing of 25 ml of i) 6% of CHO (1.5 g); ii) 2% CAF (500 mg), iii) combined CHO and CAF (CHOCAF) solutions or iv) water (PLA) for 10 s. Heart rate (HR), felt arousal (FA), ratings of perceived exertion (RPE) and glucose (GLU) were recorded throughout the test protocol.

Results

There were no significant differences in squat and bench press 1-RM, HR, RPE and GLU (p > 0.05) for males and females, respectively. FA was significantly increased with CAF (p = 0.04, p = 0.01) and CHOCAF (p = 0.03, p = 0.01) condition in both males and females, respectively. Squat endurance performance in the first set was significantly increased with CHOCAF condition compared to PLA in both males (p = 0.01) and females (p = 0.02). Bench press endurance was similar for all conditions in both genders (p > 0.05). Cognitive performance was significantly increased with CHOCAF compared to PLA in males (p = 0.03) and females (p = 0.02).

Conclusion

Combined CHO and CAF mouth rinsing significantly improved lower body muscular endurance and cognitive performance in both males and females.

Effects of Caffeine on Resistance Exercise: A Review of Recent Research

In the last few years, a plethora of studies have explored the effects of caffeine on resistance exercise, demonstrating that this field of research is growing fast. This review evaluates and summarizes the most recent findings. Given that toxic doses of caffeine are needed to increase skeletal muscle contractility, the binding of caffeine to adenosine receptors is likely the primary mechanism for caffeine's ergogenic effects on resistance exercise. There is convincing evidence that caffeine ingestion is ergogenic for (i) one-repetition maximum, isometric, and isokinetic strength; and (ii) muscular endurance, velocity, and power in different resistance exercises, loads, and set protocols. Furthermore, there is some evidence that caffeine supplementation also may enhance adaptations to resistance training, such as gains in strength and power. Caffeine ingestion is ergogenic for resistance exercise performance in females, and the magnitude of these effects seems to be similar to that observed in men. Habitual caffeine intake and polymorphisms within CYP1A2 and ADORA2A do not seem to modulate caffeine's ergogenic effects on resistance exercise. Consuming lower doses of caffeine (e.g., 2-3 mg/kg) appears to be comparably ergogenic to consuming high doses of caffeine (e.g., 6 mg/kg). Minimal effective doses of caffeine seem to be around 1.5 mg/kg. Alternate caffeine sources such as caffeinated chewing gum, gel, and coffee are also ergogenic for resistance exercise performance. With caffeine capsules, the optimal timing of ingestion seems to be 30-60 min before exercise. Caffeinated chewing gums and gels may enhance resistance exercise performance even when consumed 10 min before exercise. It appears that caffeine improves performance in resistance exercise primarily due to its physiological effects. Nevertheless, a small portion of the ergogenic effect of caffeine seems to be placebo-driven.

Ergogenic Effects of Acute Caffeine Intake on Muscular Endurance and Muscular Strength in Women: A Meta-Analysis

This meta-analysis aimed to explore the effects of caffeine ingestion on muscular endurance and muscular strength in women. Five databases were searched to find relevant studies. A random-effects meta-analysis of standardized mean differences (SMD) was performed for data analysis. Subgroup meta-analyses explored the effects of caffeine on upper-body and lower-body muscular endurance and muscular strength. Eight crossover placebo-controlled studies were included in the review. In the main meta-analysis that considered data from all included studies, there was a significant ergogenic effect of caffeine on muscular endurance (SMD = 0.25; p = 0.027) and muscular strength (SMD = 0.18; p < 0.001). In a subgroup analysis that considered only upper-body exercises, there was a significant ergogenic effect of caffeine on muscular endurance (SMD = 0.20; p = 0.007) and muscular strength (SMD = 0.17; p < 0.001). In a subgroup analysis that considered only lower-body exercises, there was no significant difference between caffeine and placebo for muscular endurance (SMD = 0.43; p = 0.092) or muscular strength (SMD = 0.16; p = 0.109). The main finding of this meta-analysis is that caffeine ingestion has a significant ergogenic effect on muscular endurance and muscular strength in women. The effects reported in this analysis are similar to those previously observed in men and suggest that women may use caffeine supplementation as an ergogenic aid for muscular performance. Future research is needed to explore the effects of caffeine on lower-body muscular endurance and muscular strength in this population.