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

Effects of Different Caffeine Dosages on Maximal Physical Performance and Potential Side Effects in Low-Consumer Female Athletes: Morning vs. Evening Administration

While previous studies have explored a range of factors governing the optimal use of caffeine (CAF) in athletes, limited research has explored how time of day (TOD) affects the ergogenic effects of various CAF dosages on physical performance. This study aimed to increase knowledge about how different recommended CAF doses (3 mg/kg vs. 6 mg/kg) ingested at different TODs affected maximal high-intensity physical performance and the perception of potential side effects in female athletes. In this double-blind, randomized, and counterbalanced study, 15 low CAF consumer athletes (aged 18.3 ± 0.5 y) underwent six trials, including three testing conditions assessed across two TODs: one in the morning (08:00 a.m.) and one in the evening (06:00 p.m.). During each condition, the participants ingested either a placebo, 3 mg/kg CAF (CAF (3 mg)), or 6 mg/kg CAF (CAF (6 mg)) capsules 60 min before each test with an in-between washout period of at least 72 h. In each trial, the participants performed a countermovement jumps test (CMJ), a modified agility t test (MATT), a repeated sprint ability (RSA), a rating of perceived exertion (RPE), and finally, a CAF side effects questionnaire. Our findings indicate the absence of an ergogenic effect on CMJ, MAT, and RSA performance in the evening after administering CAF (3 mg) or CAF (6 mg) compared to a placebo. Likewise, when CAF was ingested in the morning, there was an improvement in these performances with both CAF (3 mg) and CAF (6 mg), with greater improvement observed after CAF (6 mg). Additionally, neither the CAF dosage nor the TOD had a significant effect on the RPE. The occurrence of side effects increased significantly after the evening ingestion of CAF, particularly with a moderate dose of CAF (6 mg). Our findings indicate that the effectiveness of CAF depends on the TOD and CAF dosage. When ingested in the morning, a moderate dose of CAF (6 mg), rather than CAF (3 mg), is more effective in improving short-term physical performance without affecting CAF side effects in female athletes. Nevertheless, when ingested in the evening, neither dose was sufficient to enhance short-term physical performance, and both dosages increased the incidence of CAF side effects, particularly at a moderate dose.

Caffeine Does Not Alter Performance, Perceptual Responses, and Oxidative Stress After Short Sprint Interval Training

Despite the abundance of research investigating the efficacy of caffeine supplementation on exercise performance, the physiological and biochemical responses to caffeine supplementation during intermittent activities are less evident. This study investigated the acute effects of caffeine supplementation on measures of exercise performance, ratings of perceived exertion, and biomarkers of oxidative stress induced by an acute bout of sprint interval training. In a randomized crossover design, 12 healthy males (age: 26 ± 4 years, height: 177.5 ± 6 cm, body mass: 80.7 ± 7.6 kg) ingested 6 mg/kg of caffeine or placebo 60 min prior to performing sprint interval training (12 × 6 s "all-out sprints" interspersed by 60 s of rest). Performance scores and ratings of perceived exertion were assessed after every sprint. Blood samples were collected before supplementation, prior to and following each sprint, and 5 and 60 min after the last sprint. Caffeine had no effect on any performance measures, ratings of perceived exertion, or biomarkers of oxidative stress (p > .05). In conclusion, caffeine supplementation does not improve performance or decrease oxidative stress after an acute bout of sprint interval training.

Optimizing Short-Term Maximal Exercise Performance: The Superior Efficacy of a 6 mg/kg Caffeine Dose over 3 or 9 mg/kg in Young Female Team-Sports Athletes

Caffeine (CAF) is among the most extensively researched dietary supplements worldwide. However, little is known about the relationship between dosage and performance enhancement, particularly in female athletes. This study aimed to explore the effects of three different CAF dosages (3 mg·kg-1, 6 mg·kg-1, and 9 mg·kg-1) on high-intensity exercise and the prevalence of undesirable side effects related to these doses among female team-sports athletes. All participants (n = 16; age: 16.9 ± 0.6 y; height: 1.64 ± 0.1 m; BMI: 21.6 ± 1.5 kg·m-2) were mild CAF consumers. This study had a randomized, crossover, double-blind design in which each athlete performed four experimental sessions after ingesting either a placebo (PLAC), 3 mg·kg-1 CAF (CAF-3), 6 mg·kg-1 CAF (CAF-6), or 9 mg·kg-1 of CAF (CAF-9), with an in-between washout period of at least 72 h. In each experimental session, 60 min after ingesting the capsules, participants underwent a countermovement jumps test (CMJ), modified agility t-test (MATT), repeated sprint ability (RSA) test, and a rating of perceived exertion (RPE) and completed the CAF side effects questionnaire. Our findings revealed that in comparison to the PLAC condition, the MATT, RSAmean, and RSAbest performances were significantly greater only under the CAF-6 and CAF-9 conditions. Although the RPE scores remained unchanged, CMJ performance improved under all CAF conditions. All the performance outcomes were better for the CAF-6 and CAF-9 conditions than for the CAF-3 condition. Notably, no significant difference between the CAF-6 and CAF-9 conditions was observed for any of these parameters despite the highest incidence of side effects being noted for the CAF-9 condition. In summary, our findings highlight the recommendation for a moderate CAF dosage of 6 mg·kg-1 rather than 3 or 9 mg·kg-1 to enhance various aspects of short-term maximal performance in mild-CAF-consumer female team-sports athletes while mitigating the occurrence of adverse CAF side effects.

Acute consumption of a branched chain amino acid and vitamin B-6 containing sports drink does not improve multiple sprint exercise performance, but increases post-exercise blood glucose

Purpose

The aim of this study was to investigate the ergogenicity of BioSteel High Performance Sports Drink (B-HPSD), a commercially available branched chain amino acid (BCAA) and vitamin B-6 (VitB-6) supplement, on multiple sprint exercise (MSE).

Methods

Eleven experienced cyclists completed two MSE trials in counterbalanced order, after ingesting either B-HPSD (2,256 mg of BCAA, 300 mcg of VitB-6) or placebo (PLA). The MSE protocol consisted of five maximal effort 1 km sprints on a cycle ergometer separated by 2 min of active recovery. Power output (PO) was continuously measured throughout the cycling protocol. Heart rate (HR) and ratings of perceived exertion (RPE) were monitored following each sprint. Capillary blood samples were collected and analyzed for lactate and glucose before and 2 min post-trial. Cognitive function was assessed before and 15 min after the exercise protocol.

Results

The PO maintained during each 1 km sprint decreased throughout the protocol (p < 0.05), but the change in PO was similar between conditions. Post-exercise blood glucose was elevated after consuming B-HPSD but not PLA (p < 0.05). Blood lactate (p < 0.05), HR (p < 0.05) and RPE (p < 0.05) increased throughout the trials, however no differences were observed between conditions. Cognitive performance improved after exercise (p < 0.05), but the change was similar between conditions.

Conclusion

These results demonstrate that acute B-HPSD consumption does not have an ergogenic effect on MSE performance. However, ingestion of B-HPSD increased post-exercise blood glucose concentration when compared to PLA.

Effects of Different Doses of Caffeine Supplementation on Collegiate Male Volleyball Players' Specific Performance and Skills: A Randomized, Double-Blind, Placebo-Controlled, Crossover Study

BACKGROUND

The improvement of performance and skill indices of volleyball players can affect their success rate. Therefore, the present study aimed to evaluate the effects of acute caffeine supplementation of varied doses on collegiate volleyball players' specific performance and skills.

METHOD

This research was a randomized, double-blind, crossover design study in which 15 male volleyball players aged 18 to 25 years participated voluntarily. Participants were randomly placed in three different conditions, including 3 mg of caffeine per kilogram of body weight (C3), 6 mg of caffeine per kilogram of body weight (C6), and a placebo (PLA) with a one-week wash-out period between exercise trials. The supplement was taken 60 min before each exercise session. Ball throwing, hand movement speed, agility, Sargent's jump and handgrip, and attacking and serving skill tests were measured and analyzed to check the performance and skill of the volleyball players.

RESULTS

This study showed a significant increase in agility test in C6 compared with the PLA condition (p = 0.02). Additionally, there was a significant improvement in Sargent's jump in C6 compared with PLA (p = 0.00) and C6 compared with the C3 condition (p = 0.00). Also, attacking skill significantly increased in C3 compared with PLA (p = 0.00) and C6 compared with the PLA condition (p = 0.00). In addition, there was a significant increase in serving skill for C6 compared with PLA (p = 0.00) and C3 (p = 0.00). However, there were no significant differences in hand movement speed (p = 0.06), left handgrip (p = 0.85), right handgrip (p = 0.47), or medicine ball throwing (p = 0.22) between the three conditions.

CONCLUSIONS

In conclusion, the findings of the current study suggested that a higher dose of caffeine compared with a lower dose may be more effective in movements requiring lower-body explosive power and the ability to change direction. Also, according to the findings, it seems that caffeine can lead to the improvement of complex skills, such as serving and attacking in volleyball.

Fueling the Female Athlete: Auditing Her Representation in Studies of Acute Carbohydrate Intake for Exercise

PURPOSE

The aim of this audit was to assess the representation of female athletes within the literature that has led to current guidelines for carbohydrate (CHO) intake in the acute periods surrounding exercise and the quality of this research.

METHODS

We conducted a standardized audit of research assessing CHO loading protocols, CHO mouth rinse, and CHO intake before, during, and after exercise.

RESULTS

A total of 937 studies were identified in this audit. There were a total of 11,202 participants across these studies, with only ~11% being women. Most studies involved male-only cohorts (~79%), with a mere 38 studies (~4%) involving female-only cohorts and 14 studies (~2%) including a methodological design for comparison of sex-based responses. The frequent use of incorrect terminology surrounding menstrual status and the failure of most studies (~69%) to provide sufficient information on the menstrual status of participants suggests incomplete understanding and concern for female-specific considerations among researchers. Of the 197 studies that included women, only 13 (~7%) provided evidence of acceptable methodological control of ovarian hormones, and no study met all best-practice recommendations. Of these 13 studies, only half also provided sufficient information regarding the athletic caliber of participants. The topics that received such scrutiny were CHO loading protocols and CHO intake during exercise.

CONCLUSIONS

The literature that underpins the current guidelines for CHO intake in the acute periods around exercise is lacking in high-quality research that can contribute knowledge specific to the female athlete and sex-based differences. New research that considers ovarian hormones and sex-based differences is needed to ensure that the recommendations for acute CHO fueling provided to female athletes are evidence based.

Risk or benefit? Side effects of caffeine supplementation in sport: a systematic review

PURPOSE

The aim of this study was to systematically review evidence on the prevalence and magnitude of side effects associated with caffeine supplementation in athletes.

METHODS

Systematic searches through the PubMed, VHL, Scopus, and Web of Science databases were conducted according to the PRISMA guidelines. Peer-reviewed articles written in English that reported the prevalence/percentage or magnitude/effect size of side effects after caffeine supplementation in athletes in a sports context were included. Studies were grouped by the dose of caffeine administered as follows: low =  ≤ 3.0 mg/kg; moderate = from 3.1 to 6.0 mg/kg; high =  ≥ 6.1 mg/kg. The magnitude of the side effects was calculated with effect sizes.

RESULTS

The search retrieved 25 studies that met the inclusion/exclusion criteria with a pooled sample of 421 participants. The supplementation with caffeine produced a higher prevalence or magnitude of all side effects under investigation when compared to placebo/control situations. The prevalence (magnitude) was between 6 and 34% (ES between 0.13 and 1.11) for low doses of caffeine, between 0 and 34% (ES between -0.13 and 1.20) for moderate doses of caffeine, and between 8 and 83% (ES between 0.04 and 1.52) with high doses of caffeine. The presence of tachycardia/heart palpitations and the negative effects on sleep onset had the highest prevalence and magnitude, in athletes using supplementation with caffeine.

CONCLUSION

In summary, caffeine supplementation in the doses habitually used to enhance physical performance produces several side effects, both after exercise and at least 24 h after the ingestion. However, the prevalence and magnitude of side effects with high doses of caffeine were habitually higher than with low doses of caffeine. From a practical perspective, using ~3.0 mg/kg of caffeine may be the dose of choice to obtain the ergogenic benefits of caffeine with the lowest prevalence and magnitude of side effects.

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.

Can caffeine supplementation reverse the impact of time of day on cognitive and short-term high intensity performances in young female handball players?

ABBREVIATIONS

CAF: Caffeine PLC: Placebo SRT: Simple Reaction Time AT: Attention Test SJ: Squat Jump IAT: Illinois Agility Test OT: Oral Temperature QUEST: Questionnaire RPE: Rating of Perceived Exertion PD: Peak Distance TD: Total Distance.

Does Acute Caffeine Supplementation Improve Physical Performance in Female Team-Sport Athletes? Evidence from a Systematic Review and Meta-Analysis

Introduction: Recent original research and meta-analyses suggest that acute caffeine supplementation improves exercise performance in team-sport athletes (TSA). Nonetheless, most of the studies testing the effects of caffeine on TSA included samples of male athletes, and there is no meta-analysis of the performance-enhancing effects of caffeine on female TSA. The aim of the present study was to synthesize the existing literature regarding the effect of caffeine supplementation on physical performance in adult female TSA. Methods: A search was performed in Pubmed/Medline, SPORTDiscus and Scopus. The search was performed from the inception of indexing until 1 September 2021. Crossover randomized controlled trials (RCT) assessing the effects of oral caffeine intake on several aspects of performance in female TSA were selected. The methodological quality and risk of bias were assessed for individual studies using the Physiotherapy Evidence Database scale (PEDro) and the RoB 2 tool. A random-effects meta-analysis of standardized mean differences (SMD) was performed for several performance variables. Results: The search retrieved 18 articles that fulfilled the inclusion/exclusion criteria. Overall, most of the studies were of excellent quality with a low risk of bias. The meta-analysis results showed that caffeine increased performance in specific team-sport skills (SMD: 0.384, 95% confidence interval (CI): 0.077–0.691), countermovement jump (SMD: 0.208, CI: 0.079–0.337), total body impacts (SMD: 0.488; 95% CI: 0.050, 0.927) and handgrip strength (SMD: 0.395, CI: 0.126–0.665). No effects were found on the ratings of perceived exertion, squat jumps, agility, repeated sprint ability or agility tests performed after fatigue. Conclusions: The results of the meta-analysis revealed that acute caffeine intake was effective in increasing some aspects of team-sports performance in women athletes. Hence, caffeine could be considered as a supplementation strategy for female athletes competing in team sports.

Acute performance responses to repeated treadmill sprints in hypoxia with varying inspired oxygen fractions, exercise-to-recovery ratios and recovery modalities

PURPOSE

For optimizing the quality of repeated-sprint training in hypoxia, the differences in the acute performance responses to a single session of repeated-sprint exercise with various (i) inspired oxygen fractions; (ii) exercise-to-recovery (E:R) ratios and (iii) recovery modalities were examined.

METHODS

Ten male participants performed three sets, 5 × 5-s all-out treadmill sprints, E:R ratio of 1:5, passive recovery, in seven trials randomly. In four of the seven trials, hypoxic levels were set corresponding to sea level (SL_1:5P), 1500 (1.5K_1:5P), 2500 (2.5K_1:5P), and 3500 m (3.5K_1:5P), respectively. In a further two trials, the hypoxic level of 3.5K_1:5P was maintained, while the E:R ratio was reduced to 1:4 (3.5K_1:4P) and 1:3 (3.5K_1:3P), respectively. In the last trial, the passive recovery mode of 3.5K_1:5P was changed to active (3.5K_1:5A).

RESULTS

In comparison to SL_1:5P, the averaged peak velocity (P-Vel), mean velocity (M-Vel), and velocity decrement score (Sdec) of the sprints, and the cumulative HR-based training impulse (cTRIMP) in 1.5K_1:5P and 2.5K_1:5P were well maintained. Minor decrement in the M-Vel was found in 3.5K_1:5P. Conversely, lowered E:R ratio in 3.5K_1:4P and 3.5K_1:3P significantly reduced the P-Vel (≥ -2.3%, Cohen's d ≥ 0.43) and M-Vel (≥ -2.4%, ≥ 0.49), and in 3.5K_1:3P altered the Sdec (107%, ≥ 0.96), and cTRIMP (-16%, 1.39), when compared to 3.5K_1:5P. Furthermore, mild reductions in M-Vel (-2.6%, 0.5) was observed in 3.5K_1:5A using the active recovery mode. Other variables did not change.

CONCLUSION

The findings suggest that a 3.5K_1:5P marginally maintained sea-level training loads, and as a result, could maximally optimize the training stress of hypoxia.

International society of sports nutrition position stand: caffeine and exercise performance

Following critical evaluation of the available literature to date, The International Society of Sports Nutrition (ISSN) position regarding caffeine intake is as follows: 1. Supplementation with caffeine has been shown to acutely enhance various aspects of exercise performance in many but not all studies. Small to moderate benefits of caffeine use include, but are not limited to: muscular endurance, movement velocity and muscular strength, sprinting, jumping, and throwing performance, as well as a wide range of aerobic and anaerobic sport-specific actions. 2. Aerobic endurance appears to be the form of exercise with the most consistent moderate-to-large benefits from caffeine use, although the magnitude of its effects differs between individuals. 3. Caffeine has consistently been shown to improve exercise performance when consumed in doses of 3-6 mg/kg body mass. Minimal effective doses of caffeine currently remain unclear but they may be as low as 2 mg/kg body mass. Very high doses of caffeine (e.g. 9 mg/kg) are associated with a high incidence of side-effects and do not seem to be required to elicit an ergogenic effect. 4. The most commonly used timing of caffeine supplementation is 60 min pre-exercise. Optimal timing of caffeine ingestion likely depends on the source of caffeine. For example, as compared to caffeine capsules, caffeine chewing gums may require a shorter waiting time from consumption to the start of the exercise session. 5. Caffeine appears to improve physical performance in both trained and untrained individuals. 6. Inter-individual differences in sport and exercise performance as well as adverse effects on sleep or feelings of anxiety following caffeine ingestion may be attributed to genetic variation associated with caffeine metabolism, and physical and psychological response. Other factors such as habitual caffeine intake also may play a role in between-individual response variation. 7. Caffeine has been shown to be ergogenic for cognitive function, including attention and vigilance, in most individuals. 8. Caffeine may improve cognitive and physical performance in some individuals under conditions of sleep deprivation. 9. The use of caffeine in conjunction with endurance exercise in the heat and at altitude is well supported when dosages range from 3 to 6 mg/kg and 4-6 mg/kg, respectively. 10. Alternative sources of caffeine such as caffeinated chewing gum, mouth rinses, energy gels and chews have been shown to improve performance, primarily in aerobic exercise. 11. Energy drinks and pre-workout supplements containing caffeine have been demonstrated to enhance both anaerobic and aerobic performance.

Effects of Various Doses of Caffeine Ingestion on Intermittent Exercise Performance and Cognition

To date, no study has examined the effects of caffeine on prolonged intermittent exercise performance that imitates certain team-sports, and the suitable concentration of caffeine for improved intermittent exercise performance remains elusive. The purpose of the present cross-over, double-blind preliminary study was to investigate effects of low, moderate, and high doses of caffeine ingestion on intermittent exercise performance and cognition. Ten males performed a familiarization session and four experimental trials. Participants ingested capsules of placebo or caffeine (3, 6, or 9 mg/kg) at 1 h before exercise, rested quietly, and then performed cycling for 2 × 30 min. The cycling protocol consisted of maximal power pedaling for 5 s (mass × 0.075 kp) every minute, separated by unloaded pedaling for 25 s and rest for 30 s. At pre-ingestion of capsules, 1 h post-ingestion, and post-exercise, participants completed the Stroop task. The mean power-output (MPO), peak power-output (PPO), and response time (RT) in the Stroop task were measured. Only 3 mg/kg of caffeine had positive effects on the mean PPO and MPO; 3 mg/kg caffeine decreased RTs significantly in the incongruent and congruent conditions. These results indicate that the ingestion of low-dose caffeine had greater positive effects on the participants' physical strength during prolonged intermittent exercise and cognition than moderate- or high-dose caffeine.

Ingestion of Carbohydrate Prior to and during Maximal, Sprint Interval Cycling Has No Ergogenic Effect: A Randomized, Double-Blind, Placebo Controlled, Crossover Study

Carbohydrate (CHO) ingestion may improve intermittent sprint performance in repeated sprint efforts ≤15 s. Yet, evidence for its efficacy on sprint interval durations ~30 s is lacking. The purpose of this study was to investigate the effects of CHO ingestion on maximal sprint interval exercise. Fifteen (n = 15) recreational athletes (13/2 males/females, age 22 ± 2 years; height 176 ± 11 cm; mass 76.8 ± 11.3 kg) volunteered for this randomised, double-blind, placebo-controlled, crossover design. Participants completed two experimental trials (performed 10-days apart) involving the ingestion of an 8% CHO solution or a flavour and appearance-matched placebo (PLA) solution (5 mL/kg/bw), immediately before exercise, and preceding the second interval of four × 30 s bouts of repeated maximal sprint efforts (separated by 3.5 min of passive recovery). Peak and mean power (W) output progressively decreased during the repeated sprints (main effect of time, p < 0.0001), but there were no differences between CHO and PLA during any of the sprints (p > 0.05 for condition main effect and condition × time interaction). Physiological responses (blood lactate, heart rate, oxygen consumption, respiratory exchange ratio and RPE) were also unaltered by CHO ingestion. In conclusion, CHO ingestion does not enhance performance or modulate physiological responses during intermittent maximal, sprint cycling.

Nutrition for Female Soccer Players-Recommendations

Soccer is one of the most popular sports in the world. As its number of players is increasing, the number of female players is also on the rise. However, there are limited data about how the diets of female soccer players should be designed. Thus, the aim of our work is to deliver concise nutritional recommendations for women practicing this sport. Based on a literature review, we emphasize that individual adjustment of the energy value of the diet is the key factor for the physical performance of female soccer players. Appropriate macronutrient intake makes it possible to achieve the proper energy value of the diet (5-10 g/kg body mass/day carbohydrates; 1.2-1.7 g/kg body mass/day proteins; <30% fats from energy). The micronutrients should be consumed in amounts corresponding to individual values recommended in national standards. Soccer players should pay special attention to the proper consumption of such micronutrients, as well as vitamins such as iron, calcium, and vitamin D. The right amount of fluid intake, consistent with the player's needs, is crucial in maximizing exercise performance. The diet of a female practicing soccer is usually characterized with low energy values, which increases the risk of various health consequences related to low energy availability. Monitoring the diets of female soccer players is, therefore, necessary.

The effect of 30-m repeated sprint exercise on muscle damage indicators, serum insulin-like growth factor-Iand cortisol

Study aim: The purpose of this study was to examine the effects of arepeated sprint exercise protocol on muscle damage indicators, serum IGF-Iand cortisol levels.

Material and methods: Nine trained male subjects (age 23.3 ± 3.6 years) completed arepeated sprint protocol consisting of two sets of 10 × 30-m maximal sprints with 30 s of active recovery between sprints and 5 min of passive recovery between sets. The isometric strength and flexibility were measured before, immediately after and 24 hours after exercise. 30-m maximal sprint time was measured before and 24 hours after exercise. Blood samples were taken before, immediately after and 24 hours after exercise.

Results: Isometric strength and flexibility were significantly decreased after exercise and 24 hours after exercise (p < 0.05). 30-m sprint time was significantly increased 24 hours after exercise (p < 0.05). Asignificant increase in serum lactate dehydrogenase, IGF-Iand cortisol were found after exercise (p < 0.05). Serum creatine kinase increased significantly immediately after and 24 hours after exercise compared to pre-exercise values (p < 0.05).

Conclusion: Our data show that due to increased serum IGF-Ilevel, repeated sprint exercise may have anabolic effects as well as traumatic effects on the muscles.

Effect of caffeinated gum on a battery of rugby-specific tests in trained university-standard male rugby union players

Background

Caffeine has been shown to enhance strength, power and endurance, characteristics that underpin performance in rugby. Caffeinated gum has attracted interest as a novel vehicle for delivering caffeine, because absorption of caffeine from gum is quick. Rapid absorption of caffeine may be useful during rugby matches when there is limited time for supplementation such as at half-time or when substitutes enter play. The purpose of this study was to determine whether a low dose of caffeine in gum improves performance in a battery of rugby-specific tests.

Methods

In a double-blind, randomized, placebo-controlled, crossover design, 17 male university-standard rugby players (mass: 85.6 ± 6.3 kg; height: 179.4 ± 6.2 cm; age: 20.4 ± 1.2 years) chewed caffeinated gum (200 mg caffeine) or a placebo gum on two occasions separated by a week. After a standardized warm-up, gum was chewed for 5 min. Subsequently, participants performed three countermovement jumps, followed by an Illinois agility test, 6 × 30 m repeated sprints, and the Yo-Yo IR-2 test; each test was separated by short rest periods.

Results

Caffeinated gum enhanced countermovement jump by 3.6% (caffeine: 43.7 ± 7.6 cm vs. placebo: 42.2 ± 6.2 cm; d = 0.22, 95% CI [0.006, 0.432]; p = 0.044). There was a greater resistance to fatigue during the 6 × 30 m repeated sprint test (fatigue index caffeine: 102.2 ± 0.9% vs. placebo: 103.3 ± 1.2%; d = 1.03, 95% CI [0.430, 1.613]; p = 0.001), and performance on the Yo-Yo IR2 was improved by 14.5% (caffeine: 426 ± 105 m, placebo: 372 ± 91 m; d = 0.55, 95% CI [0.130, 0.957]; p = 0.010). Caffeine gum had no significant effect on the Illinois agility test (caffeine 16.22 ± 1.08 s vs. placebo 15.88 ± 1.09 s; d = − 0.31, 95% CI [− 0.855, 0.240]; p = 0.271).

Conclusions

In university-standard rugby players, a low dose of caffeine (200 mg) supplied in chewing gum enhanced performance on the Yo-Yo IR-2 test and the countermovement jump test and reduced fatigue index during repeated sprints. These improvements in a battery of rugby-specific tests may transfer to enhanced performance in rugby matches.

Isolated ingestion of caffeine and sodium bicarbonate on repeated sprint performance: A systematic review and meta-analysis

OBJECTIVES

This study is a systematic review and meta-analysis aimed at investigating the isolated effects of caffeine and sodium bicarbonate (NaHCO₃) ingestion on repeated sprint ability (RSA).

METHODS

Following a search through PubMed and Scopus, 13 studies (7 with caffeine and 6 with NaHCO₃) were found to meet inclusion criteria. Random-effects of standardized mean difference (SMD) for total work and best sprint performance was examined. Study quality was assessed using QualSyst.

RESULTS

The meta-analysis indicated that caffeine ingestion did not improve the total work done (weighted average effect size Hedges's g = -0.01, 95%CI: -0.32 to 0.31, p = 0.97), best sprint (weighted average effect size Hedges's g = -0.02, 95% CI: -0.32 to 0.27; p = 0.87) or last sprint performance (weighed average effect size Hedge's g = -0.27, 95%CI: -0.68 to 0.14; p = 0.20), when compared with a placebo condition. Similarly, NaHCO₃ ingestion did not improve the total work done (weighted average effect size Hedges's g = 0.43, 95% CI: -0.11 to 0.97, p = 0.12), best sprint (weighted average effect size Hedges's g = 0.02, 95% CI -0.30 to 0.34; p = 0.90) or last sprint performance (weighted average effect size Hedge's g = 0.20, 95%CI: -0.13 to 0.52, p = 0.14), compared with a placebo condition. Quality assessment of selected articles was classified as strong.

CONCLUSION

This meta-analysis provides evidence that repeated sprint ability is not affected by acute ingestion of caffeine or NaHCO₃.

Can caffeine supplementation reverse the effect of time of day on repeated-sprint exercise performance?

The aim of this study was to evaluate if caffeine can reduce the negative influence of diurnal variations on repeated-sprint performance, in addition to investigating if caffeine in the afternoon would potentiate performance compared with the morning. Thirteen physically active men took part in this randomized, double-blind, placebo-controlled and crossover study. All participants underwent a repeated-sprint ability test (10 × 6 s cycle sprints, with 30 s of rest) at 60 min after ingestion of either 5 mg·kg^-1 or placebo under 4 different conditions: morning with caffeine ingestion, morning with placebo ingestion, afternoon with caffeine ingestion, and afternoon with placebo ingestion. Total work, peak power (PP) and anaerobic power reserve (APR) were assessed. Oxygen uptake, heart rate, lactate concentration, and rating of perceived exertion were also measured during the repeated-sprint test. Total work (+8%, d = 0.2, small), PP (+6%, d = 0.2), and APR (+9%, d = 0.2) were significantly higher in the afternoon when compared with morning. However, physiological responses were not different between caffeine and placebo conditions. Repeated-sprint (10 × 6 s cycle sprint) performance was influenced by time of day, with lower performance in the morning compared with the afternoon. However, caffeine supplementation did not prevent the reduction in performance in the morning or improve performance in the afternoon.

A Low Dose Caffeine and Carbohydrate Supplement does not Improve Athletic Performance during Volleyball Competition

Dietary supplements are widely used to enhance sport performance and the combination of carbohydrate and caffeine (CHO+CAF) has yielded particularly high performance gains. Though the effects of a CHO+CAF supplement have been studied in a laboratory environment, little research exists on the effects of supplementation during competition. Therefore, the purpose of this study was to determine the effects of a CHO+CAF supplement on athletic performance in competition. Eight female collegiate volleyball players completed three testing sessions under three different conditions separated by approximately one week each: CHO+CAF supplement, placebo (PBO), and control (CTL) using a randomized, cross-over design. Blood glucose (BG) was assessed prior to supplementation and immediately after set three. The supplement and PBO were administered prior to play and between sets two and three. Following three sets of play, three performance tests were completed: vertical jump (VJ), agility (AGL), and repeated 30-m sprint ability (RSA). While CHO+CAF supplementation significantly increased BG, the performance tests were not different (p>.05) among the testing conditions. These findings suggest that the amount of the supplement used in this study is not beneficial to VJ, AGL, and RSA in female volleyball players. As these performance tests were largely anaerobic and non-glycolytic in nature, the ergogenicity of the supplement may have been underutilized. Additionally, coaches and athletes should not only be aware of what ingredients are in the supplements they choose, but the amount of those ingredients as they may modify the efficacy of the supplement to impact performance.

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.

Substrate Utilization and Cycling Performance Following Palatinose™ Ingestion: A Randomized, Double-Blind, Controlled Trial

(1) Objective: To compare the effects of isomaltulose (Palatinose™, PSE) vs. maltodextrin (MDX) ingestion on substrate utilization during endurance exercise and subsequent time trial performance; (2) Methods: 20 male athletes performed two experimental trials with ingestion of either 75 g PSE or MDX 45 min before the start of exercise. The exercise protocol consisted of 90 min cycling (60% VO₂max) followed by a time trial; (3) Results: Time trial finishing time (−2.7%, 90% CI: ±3.0%, 89% likely beneficial; p = 0.147) and power output during the final 5 min (+4.6%, 90% CI: ±4.0%, 93% likely beneficial; p = 0.053) were improved with PSE compared with MDX. The blood glucose profile differed between trials (p = 0.013) with PSE resulting in lower glycemia during rest (95%–99% likelihood) and higher blood glucose concentrations during exercise (63%–86% likelihood). In comparison to MDX, fat oxidation was higher (88%–99% likelihood; p = 0.005) and carbohydrate oxidation was lower following PSE intake (85%–96% likelihood; p = 0.002). (4) Conclusion: PSE maintained a more stable blood glucose profile and higher fat oxidation during exercise which resulted in improved cycling performance compared with MDX. These results could be explained by the slower availability and the low-glycemic properties of Palatinose™ allowing a greater reliance on fat oxidation and sparing of glycogen during the initial endurance exercise.

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.