Acute effects of commercial energy drink consumption on exercise performance and cardiovascular safety: a randomized, double-blind, placebo-controlled, crossover trial

The aim of this study was to examine the acute effects of a non-caloric energy drink (C4E) compared to a traditional sugar-containing energy drink (MED) and non-caloric placebo (PLA) on exercise performance and cardiovascular safety. Thirty healthy, physically active males (25 ± 4 y) completed three experimental visits under semi-fasted conditions (5-10 h) and in randomized order, during which they consumed C4E, MED, or PLA matched for volume, appearance, taste, and mouthfeel. One hour after drink consumption, participants completed a maximal, graded exercise test (GXT) with measurement of pulmonary gases, an isometric leg extension fatigue test (ISOFTG), and had their cardiac electrical activity (ECG), leg blood flow (LBF), and blood pressure (BP) measured throughout the visit. Neither MED nor C4E had an ergogenic effect on maximal oxygen consumption, time to exhaustion, or peak power during the GXT (p > 0.05). Compared to PLA, MED reduced fat oxidation (respiratory exchange ratio (RER) +0.030 ± 0.01; p = 0.026) during the GXT and did not influence ISOFTG performance. Compared to PLA, C4E did not alter RER (p = 0.94) and improved impulse during the ISOFTG (+0.658 ± 0.25 V·s; p = 0.032). Relative to MED, C4E did not significantly improve gas exchange threshold (p = 0.05-0.07). Both MED and C4E increased systolic BP at rest (+7.1 ± 1.2 mmHg; p < 0.001 and + 5.7 ± 1.0 mmHg; p < 0.001, respectively), C4E increased SBP post-GXT (+13.3 ± 3.8 mmHg; p < 0.001), and MED increased SBP during recovery (+3.2 ± 1.1 mmHg; p < 0.001). Neither MED nor C4E influenced ECG measures (p ≥ 0.08) or LBF (p = 0.37) compared to PLA. C4E may be more efficacious for improving performance in resistance-type tasks without altering fat oxidation under semi-fasted conditions during fatiguing exercise bouts, but promotes similar changes in BP and HR to MED.

Effects of Caffeine-Taurine Co-Ingestion on Endurance Cycling Performance in High Temperature and Humidity Environments

BACKGROUND

Taurine (TAU) and caffeine (CAF), as common ergogenic aids, are known to affect exercise performance; however, the effects of their combined supplementation, particularly in high temperature and humidity environments, have not been studied.

HYPOTHESIS

The combination of TAU and CAF will have a greater effect on endurance cycle performance and improve changes in physiological indicators during exercise compared with TAU or CAF supplementation alone and placebo.

STUDY DESIGN

Single-blind crossover randomized controlled study.

LEVEL OF EVIDENCE

Level 1.

METHODS

Twelve university students majoring in physical education volunteered to receive 4 different supplement ingestions: (1) placebo (maltodextrin), (2) TAU, (3) CAF, (4) TAU + CAF. After a 7-day washout period, participants completed a time to exhaustion (TTE) test in the heat (35°C, 65% relative humidity).

RESULTS

All experimental groups improved TTE compared with the placebo group. Peak and mean power of countermovement jump were significantly higher in the CAF group compared with the placebo group before the exhaustion exercise (P = 0.02, d = 1.2 and P = 0.04, d = 1.1, respectively). Blood lactate was significantly lower after the exhaustion test in the TAU group compared with the CAF (P < 0.01, d = 0.8) and TAU + CAF (P < 0.01, d = 0.7) groups. Core temperature in the TAU group was significantly reduced in the placebo group later in the exhaustion test (P < 0.01, d = 1.9).

CONCLUSION

In high temperature and humidity environments, acute TAU, CAF, and combined supplementation all improved TTE and did not affect recovery from lower limb neuromuscular fatigue compared with placebo, with TAU having the best effect. Combined supplementation failed to exhibit superimposed performance.

CLINICAL RELEVANCE

The results provide suggestions for the effects of TAU, CAF, and their combined intake on exercise performance in high temperature and humidity environments.

Maximal Number of Repetitions at Percentages of the One Repetition Maximum: A Meta-Regression and Moderator Analysis of Sex, Age, Training Status, and Exercise

The maximal number of repetitions that can be completed at various percentages of the one repetition maximum (1RM) [REPS ~ %1RM relationship] is foundational knowledge in resistance exercise programming. The current REPS ~ %1RM relationship is based on few studies and has not incorporated uncertainty into estimations or accounted for between-individuals variation. Therefore, we conducted a meta-regression to estimate the mean and between-individuals standard deviation of the number of repetitions that can be completed at various percentages of 1RM. We also explored if the REPS ~ %1RM relationship is moderated by sex, age, training status, and/or exercise. A total of 952 repetitions-to-failure tests, completed by 7289 individuals in 452 groups from 269 studies, were identified. Study groups were predominantly male (66%), healthy (97%), < 59 years of age (92%), and resistance trained (60%). The bench press (42%) and leg press (14%) were the most commonly studied exercises. The REPS ~ %1RM relationship for mean repetitions and standard deviation of repetitions were best described using natural cubic splines and a linear model, respectively, with mean and standard deviation for repetitions decreasing with increasing %1RM. More repetitions were evident in the leg press than bench press across the loading spectrum, thus separate REPS ~ %1RM tables were developed for these two exercises. Analysis of moderators suggested little influences of sex, age, or training status on the REPS ~ %1RM relationship, thus the general main model REPS ~ %1RM table can be applied to all individuals and to all exercises other than the bench press and leg press. More data are needed to develop REPS ~ %1RM tables for other exercises.

International society of sports nutrition position stand: energy drinks and energy shots

Position Statement: The International Society of Sports Nutrition (ISSN) bases the following position stand on a critical analysis of the literature regarding the effects of energy drink (ED) or energy shot (ES) consumption on acute exercise performance, metabolism, and cognition, along with synergistic exercise-related performance outcomes and training adaptations. The following 13 points constitute the consensus of the Society and have been approved by the Research Committee of the Society: Energy drinks (ED) commonly contain caffeine, taurine, ginseng, guarana, carnitine, choline, B vitamins (vitamins B1, B2, B3, B5, B6, B9, and B12), vitamin C, vitamin A (beta carotene), vitamin D, electrolytes (sodium, potassium, magnesium, and calcium), sugars (nutritive and non-nutritive sweeteners), tyrosine, and L-theanine, with prevalence for each ingredient ranging from 1.3 to 100%. Energy drinks can enhance acute aerobic exercise performance, largely influenced by the amount of caffeine (> 200 mg or >3 mg∙kg bodyweight [BW-1]) in the beverage. Although ED and ES contain several nutrients that are purported to affect mental and/or physical performance, the primary ergogenic nutrients in most ED and ES based on scientific evidence appear to be caffeine and/or the carbohydrate provision. The ergogenic value of caffeine on mental and physical performance has been well-established, but the potential additive benefits of other nutrients contained in ED and ES remains to be determined. Consuming ED and ES 10-60 minutes before exercise can improve mental focus, alertness, anaerobic performance, and/or endurance performance with doses >3 mg∙kg BW-1. Consuming ED and ES containing at least 3 mg∙kg BW-1 caffeine is most likely to benefit maximal lower-body power production. Consuming ED and ES can improve endurance, repeat sprint performance, and sport-specific tasks in the context of team sports. Many ED and ES contain numerous ingredients that either have not been studied or evaluated in combination with other nutrients contained in the ED or ES. For this reason, these products need to be studied to demonstrate efficacy of single- and multi-nutrient formulations for physical and cognitive performance as well as for safety. Limited evidence is available to suggest that consumption of low-calorie ED and ES during training and/or weight loss trials may provide ergogenic benefit and/or promote additional weight control, potentially through enhanced training capacity. However, ingestion of higher calorie ED may promote weight gain if the energy intake from consumption of ED is not carefully considered as part of the total daily energy intake. Individuals should consider the impact of regular coingestion of high glycemic index carbohydrates from ED and ES on metabolic health, blood glucose, and insulin levels. Adolescents (aged 12 through 18) should exercise caution and seek parental guidance when considering the consumption of ED and ES, particularly in excessive amounts (e.g. > 400 mg), as limited evidence is available regarding the safety of these products among this population. Additionally, ED and ES are not recommended for children (aged 2-12), those who are pregnant, trying to become pregnant, or breastfeeding and those who are sensitive to caffeine. Diabetics and individuals with preexisting cardiovascular, metabolic, hepatorenal, and/or neurologic disease who are taking medications that may be affected by high glycemic load foods, caffeine, and/or other stimulants should exercise caution and consult with their physician prior to consuming ED. The decision to consume ED or ES should be based upon the beverage's content of carbohydrate, caffeine, and other nutrients and a thorough understanding of the potential side effects. Indiscriminate use of ED or ES, especially if multiple servings per day are consumed or when consumed with other caffeinated beverages and/or foods, may lead to adverse effects. The purpose of this review is to provide an update to the position stand of the International Society of Sports Nutrition (ISSN) integrating current literature on ED and ES in exercise, sport, and medicine. The effects of consuming these beverages on acute exercise performance, metabolism, markers of clinical health, and cognition are addressed, as well as more chronic effects when evaluating ED/ES use with exercise-related training adaptions.

Can I Have My Coffee and Drink It? A Systematic Review and Meta-analysis to Determine Whether Habitual Caffeine Consumption Affects the Ergogenic Effect of Caffeine

OBJECTIVE

The aim was to quantify the proportion of the literature on caffeine supplementation that reports habitual caffeine consumption, and determine the influence of habitual consumption on the acute exercise response to caffeine supplementation, using a systematic review and meta-analytic approach.

METHODS

Three databases were searched, and articles screened according to inclusion/exclusion criteria. Three-level meta-analyses and meta-regression models were used to investigate the influence of habitual caffeine consumption on caffeine's overall ergogenic effect and within different exercise types (endurance, power, strength), in men and women, and in trained and untrained individuals. Sub-analyses were performed according to the following: acute relative dose (< 3, 3-6, > 6 mg/kg body mass [BM]); whether the acute caffeine dose provided was lower or higher than the mean daily caffeine dose; and the caffeine withdrawal period prior to the intervention (< 24, 24-48, > 48 h).

RESULTS

Sixty caffeine studies included sufficient information on habitual consumption to be included in the meta-analysis. A positive overall effect of caffeine was shown in comparison to placebo (standard mean difference [SMD] = 0.25, 95% confidence interval [CI] 0.20-0.30; p < 0.001) with no influence of relative habitual caffeine consumption (p = 0.59). Subgroup analyses showed a significant ergogenic effect when the caffeine dose was < 3 mg/kg BM (SMD = 0.26, 95% CI 0.12-0.40; p = 0.003) and 3-6 mg/kg BM (SMD = 0.26, 95% CI 0.21-0.32; p < 0.0001), but not > 6 mg/kg BM (SMD = 0.11, 95% CI - 0.07 to 0.30; p = 0.23); when the dose was both higher (SMD = 0.26, 95% CI 0.20-0.31; p < 0.001) and lower (SMD = 0.21, 95% CI 0.06-0.36; p = 0.006) than the habitual caffeine dose; and when withdrawal was < 24 h, 24-48 h, and > 48 h. Caffeine was effective for endurance, power, and strength exercise, with no influence (all p ≥ 0.23) of relative habitual caffeine consumption within exercise types. Habitual caffeine consumption did not modify the ergogenic effect of caffeine in male, female, trained or untrained individuals.

CONCLUSION

Habitual caffeine consumption does not appear to influence the acute ergogenic effect of caffeine.

Paraxanthine Supplementation Increases Muscle Mass, Strength, and Endurance in Mice

Paraxanthine is a natural dietary ingredient and the main metabolite of caffeine in humans. Compared to caffeine, paraxanthine exhibits lower toxicity, lesser anxiogenic properties, stronger locomotor activating effects, greater wake promoting properties, and stronger dopaminergic effects. The purpose of this study was to evaluate the potential beneficial effects of paraxanthine supplementation on muscle mass, strength, and endurance performance in comparison to the control and other ingredients commonly used by athletes: L-theanine, alpha-GPC, and taurine. Male Swiss Albino mice from five groups (n = 8 per group) were orally administered paraxanthine (20.5 mg/kg/day, human equivalence dose (HED) 100 mg), L-theanine (10.28 mg/kg/day, HED 50 mg), alpha-GPC (41.09 mg/kg/day, HED 200 mg), taurine (102.75 mg/kg/day, HED 500 mg), or control (carboxy methyl cellulose) for 4 weeks. Exercise performance was evaluated using forelimb grip strength and treadmill endurance exercise. All animals were subject to treadmill training for 60 min 5 days per week. Blood draws were utilized to analyze lipid profile, liver health, renal function, and nitric oxide levels. Paraxanthine significantly increased forelimb grip strength by 17% (p < 0.001), treadmill exercise performance by 39% (p < 0.001), gastrocnemius and soleus muscle mass by 14% and 41% respectively (both p < 0.001), and nitric oxide levels by 100% compared to control (p < 0.001), while reducing triglyceride (p < 0.001), total cholesterol (p < 0.001), LDL (p < 0.05), and increasing HDL (p < 0.001) compared to control, and compared to L-theanine, alpha-GPC, and taurine. Results from this initial investigation indicate that, when compared to the control, L-theanine, alpha-GPC, and taurine, paraxanthine is an effective ingredient for various aspects of sports performance and may enhance cardiovascular health.

Energy Drinks and Sports Performance, Cardiovascular Risk, and Genetic Associations; Future Prospects

The consumption of energy drinks (e.g., containing caffeine and taurine) has increased over the last decade among adolescents and athletes to enhance their cognitive level and improve intellectual and athletic performance. Numerous studies have shown that drinking moderate doses of such drinks produces beneficial effects, as they considerably boost the sporting performance of elite athletes in various sports, including both endurance and explosive events. However, apart from their ergogenic effects, the regular consumption of energy drinks also increases blood pressure and consequently incites problems such as hypertension, tachycardia, and nervousness, all of which can lead to cardiovascular disorders. A potential positive correlation between genetics and the moderate consumption of energy drinks and athletic performance has recently been reported; notwithstanding, a better understanding of the genetic variants involved in metabolism is a key area for future research to optimize the dose of energy drink consumed and obtain the maximal ergogenic effect in elite sports. The aim of this literature review, therefore, is to present the results of recent studies, classifying them according to the differences in the associations between energy drinks and: (i) Athletic performance; (ii) cardiovascular risk factors while practicing sports; and (iii) genetic associations and future prospects between the consumption of energy drinks and performance.

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.

Natural Odor Inhalers (AromaStick®) Outperform Red Bull® for Enhancing Cognitive Vigilance: Results From a Four-Armed, Randomized Controlled Study

Two recent publications demonstrated that specifically designed essential odor inhalers can enhance performance through (a) better selective attention and scanning speed and (b) physiological changes of increased heart rate variability and blood oxygenation. In this study, we compared two natural odor inhalers with a popular energy drink (Red Bull®) with regard to their ability to improve vigilance on a computerized attention test. We employed a four-armed, randomized controlled experimental design and used a modified version of the CompACT-Vi test module to investigate whether deep inhalations of essential oil scents improved vigilance. Both inhalers markedly improved the number of correctly identified targets and participants' reaction time when compared to a control condition and consumption of Red Bull® (0.9 < d < 1.3). Additionally, the number of correctly solved mathematical sums during the second half of the vigilance test was substantially higher (d = 1.3) with the use of inhalers than for the control and Red Bull participants. Inhaler use was also associated with relatively increased heart rate variability (d = 1.0) as a mechanism of adapting to the experimental demands. Thus, short and deep inhalations of essential oil scents delivered directly to the nose improved vigilance, while a popular energy drink failed to show an effect beyond that of a control group receiving no stimulant.

The Influence of Caffeine Supplementation on Resistance Exercise: A Review

This paper aims to critically evaluate and thoroughly discuss the evidence on the topic of caffeine supplementation when performing resistance exercise, as well as provide practical guidelines for the ingestion of caffeine prior to resistance exercise. Based on the current evidence, it seems that caffeine increases both maximal strength and muscular endurance. Furthermore, power appears to be enhanced with caffeine supplementation, although this effect might, to a certain extent, be caffeine dose- and external load-dependent. A reduction in rating of perceived exertion (RPE) might contribute to the performance-enhancing effects of caffeine supplementation as some studies have observed decreases in RPE coupled with increases in performance following caffeine ingestion. However, the same does not seem to be the case for pain perception as there is evidence showing acute increases in resistance exercise performance without any significant effects of caffeine ingestion on pain perception. Some studies have reported that caffeine ingestion did not affect exercise-induced muscle damage, but that it might reduce perceived resistance exercise-induced delayed-onset muscle soreness; however, this needs to be explored further. There is some evidence that caffeine ingestion, compared with a placebo, may lead to greater increases in the production of testosterone and cortisol following resistance exercise. However, given that the acute changes in hormone levels seem to be weakly correlated with hallmark adaptations to resistance exercise, such as hypertrophy and increased muscular strength, these findings are likely of questionable practical significance. Although not without contrasting findings, the available evidence suggests that caffeine ingestion can lead to acute increases in blood pressure (primarily systolic), and thus caution is needed regarding caffeine supplementation among individuals with high blood pressure. In the vast majority of studies, caffeine was administered in capsule or powder forms, and therefore the effects of alternative forms of caffeine, such as chewing gums or mouth rinses, on resistance exercise performance remain unclear. The emerging evidence suggests that coffee might be at least equally ergogenic as caffeine alone when the caffeine dose is matched. Doses in the range of 3-9 mg·kg^-1 seem to be adequate for eliciting an ergogenic effect when administered 60 min pre-exercise. In general, caffeine seems to be safe when taken in the recommended doses. However, at doses as high as 9 mg·kg^-1 or higher, side effects such as insomnia might be more pronounced. It remains unclear whether habituation reduces the ergogenic benefits of caffeine on resistance exercise as no evidence exists for this type of exercise. Caution is needed when extrapolating these conclusions to females as the vast majority of studies involved only male participants.

Caffeine Supplementation for Powerlifting Competitions: An Evidence-Based Approach

In this paper, we review the effects of caffeine on muscle strength and provide suggestions for caffeine supplementation in powerlifting competitions. The currently available studies indicate that caffeine ingestion may enhance strength in two powerlifting competition events, the squat and the bench press. For the deadlift, the same might be expected even though studies directly using this event are lacking. Optimal doses of caffeine are likely in the range from 2 to 6 mg·kg⁻¹, and are highly individual. When using caffeine-containing capsules, 60 minutes pre-exercise seems to be a good timing of caffeine consumption. For other sources such as caffeinated chewing gum, a shorter period (5 to 10 min) from consumption to the start of the exercise seems to be effective. For shorter duration powerlifting competitions (e.g., 2 hours), one pre-competition dose of caffeine could be sufficient for acute performance-enhancing effects that might be maintained across all three events. For longer duration competitions (with longer rest periods between one repetition maximum attempts), there might be a benefit to repeated dosing with caffeine; for example, ingesting smaller doses of caffeine before each attempt or event. During training, powerlifters may consider ingesting caffeine only before the training sessions with the highest intensity. This approach might eliminate the attenuation of caffeine’s effects associated with chronic caffeine ingestion and would help in maximizing performance benefits from acute caffeine ingestion at the competition. Nonetheless, withdrawal from caffeine (e.g., no caffeine intake seven days before competition) does not seem necessary and may have some indirect negative effects.

The Effects of an Energy Drink on Psychomotor Vigilance in Trained Individuals

The psychomotor vigilance test (PVT) measures one's behavioral alertness. It is a visual test that involves measuring the speed at which a person reacts to visual stimuli over a fixed time frame (e.g., 5 min). The purpose of this study was to assess the effects of an energy drink on psychomotor vigilance as well as a simple measure of muscular endurance (i.e., push-ups). A total of 20 exercise-trained men (n = 11) and women (n = 9) (mean ± SD: age 32 ± 7 years; height 169 ± 10 cm; weight; 74.5 ± 14.5 kg; percent body fat 20.3 ± 6.2%; years of training 14 ± 9; daily caffeine intake 463 ± 510 mg) volunteered for this randomized, double-blind, placebo-controlled, crossover trial. In a randomized counterbalanced order, they consumed either the energy drink (ED) (product: BANG^®, Weston Florida) or a similar tasting placebo drink (PL). In the second visit after a 1-week washout period, they consumed the alternate drink. A full 30 min post-consumption, they performed the following tests in this order: a 5-min psychomotor vigilance test, three sets of push-ups, followed once more by a 5-min psychomotor vigilance test. Reaction time was recorded. For the psychomotor vigilance test, lapses, false starts and efficiency score are also assessed. There were no differences between groups for the number of push-ups that were performed or the number of false starts during the psychomotor vigilance test. However, the ED treatment resulted in a significantly lower (i.e., faster) psychomotor vigilance mean reaction time compared to the PL (p = 0.0220) (ED 473.8 ± 42.0 milliseconds, PL 482.4 ± 54.0 milliseconds). There was a trend for the ED to lower the number of lapses (i.e., reaction time > 500 milliseconds) (p = 0.0608). The acute consumption of a commercially available ED produced a significant improvement in psychomotor vigilance in exercise-trained men and women.

Administration of Caffeine in Alternate Forms

There has been recent interest in the ergogenic effects of caffeine delivered in low doses (~ 200 mg or ~ 3 mg/kg body mass) and administered in forms other than capsules, coffee and sports drinks, including chewing gum, bars, gels, mouth rinses, energy drinks and aerosols. Caffeinated chewing gum is absorbed quicker through the buccal mucosa compared with capsule delivery and absorption in the gut, although total caffeine absorption over time is not different. Rapid absorption may be important in many sporting situations. Caffeinated chewing gum improved endurance cycling performance, and there is limited evidence that repeated sprint cycling and power production may also be improved. Mouth rinsing with caffeine may stimulate nerves with direct links to the brain, in addition to caffeine absorption in the mouth. However, caffeine mouth rinsing has not been shown to have significant effects on cognitive performance. Delivering caffeine with mouth rinsing improved short-duration, high-intensity, repeated sprinting in normal and depleted glycogen states, while the majority of the literature indicates no ergogenic effect on aerobic exercise performance, and resistance exercise has not been adequately studied. Studies with caffeinated energy drinks have generally not examined the individual effects of caffeine on performance, making conclusions about this form of caffeine delivery impossible. Caffeinated aerosol mouth and nasal sprays may stimulate nerves with direct brain connections and enter the blood via mucosal and pulmonary absorption, although little support exists for caffeine delivered in this manner. Overall, more research is needed examining alternate forms of caffeine delivery including direct measures of brain activation and entry of caffeine into the blood, as well as more studies examining trained athletes and female subjects.

Effect of Energy Drink Consumption on Power and Velocity of Selected Sport Performance Activities

Jacobson, BH, Hester, GM, Palmer, TB, Williams, K, Pope, ZK, Sellers, JH, Conchola, EC, Woolsey, C, and Estrada, C. Effect of energy drink consumption on power and velocity of selected sport performance activities. J Strength Cond Res 32(6): 1613-1618, 2018-Energy drinks (ED) comprise a multibillion dollar market focused on younger, active, and competitive individuals. Marketing includes claims of improved alertness and performance. The purpose of this study was to assess power (W) and velocity (m·s) of a simulated, isolated forehand stroke (FHS), and a countermovement vertical jump (CVJ) before and after ingestion of a commercially available energy shot (ES) or a placebo (PL). Healthy college-aged men and women (N = 36) volunteers were randomly placed in the ES or PL. Before and 30 minutes after ingesting either the ES or PL, participants performed 3 FHSs and CVJs. Power and velocity of each performance was measured using a linear velocity transducer and the highest value for each measure was used for subsequent analysis. The ES group demonstrated a significant (p = 0.05) increase in velocity and W for the FHS, but not for the CVJ. All measures remained unchanged in the PL group for both, the FHS and CVJ. Females demonstrated a significant increase in velocity over males in FHS, but not in CVJ. It was concluded that while the dose of stimulants in the ES was adequate to improve performance of smaller muscle groups, it may not have been sufficient to affect the larger muscle groups of the lower legs which contribute to the CVJ. While the ES used in the present study contained a caffeine dosage within the NCAA limit and did improve performance for the upper body, it must be noted that there are health risks associated with ED consumption.

Are the Current Guidelines on Caffeine Use in Sport Optimal for Everyone? Inter-individual Variation in Caffeine Ergogenicity, and a Move Towards Personalised Sports Nutrition

Caffeine use is widespread in sport, with a strong evidence base demonstrating its ergogenic effect. Based on existing research, current guidelines recommend ingestion of 3-9 mg/kg approximately 60 min prior to exercise. However, the magnitude of performance enhancement following caffeine ingestion differs substantially between individuals, with the spectrum of responses ranging between highly ergogenic to ergolytic. These extensive inter-individual response distinctions are mediated by variation in individual genotype, environmental factors, and the legacy of prior experiences partially mediated via epigenetic mechanisms. Here, we briefly review the drivers of this inter-individual variation in caffeine response, focusing on the impact of common polymorphisms within two genes, CYP1A2 and ADORA2A. Contemporary evidence suggests current standardised guidelines are optimal for only a sub-set of the athlete population. Clearer understanding of the factors underpinning inter-individual variation potentially facilitates a more nuanced, and individually and context-specific customisation of caffeine ingestion guidelines, specific to an individual's biology, history, and competitive situation. Finally, we identify current knowledge deficits in this area, along with future associated research questions.

Acute effects of caffeine-containing energy drinks on physical performance: a systematic review and meta-analysis

PURPOSE

Caffeine-containing energy drinks (EDs) are currently used as ergogenic aids to improve physical performance in a wide variety of sport disciplines. However, the outcomes of previous investigations on this topic are inconclusive due to methodological differences, especially, in the dosage of the active ingredients and the test used to assess performance.

METHODS

We performed a systematic review and meta-analysis of published studies to evaluate the effects of acute ED intake on physical performance. The search for references was conducted in the databases PubMed, ISI Web of Knowledge and SPORTDiscus until December 2015.

RESULTS

Thirty-four studies published between 1998 and 2015 were included in the analysis. Using a random-effects model, effect sizes (ES) were calculated as the standardized mean difference. Overall, ED ingestion improved physical performance in muscle strength and endurance (ES = 0.49; p < 0.001), endurance exercise tests (ES = 0.53; p < 0.001), jumping (ES = 0.29; p = 0.01) and sport-specific actions (ES = 0.51; p < 0.001), but not in sprinting (ES = 0.14; p = 0.06). The meta-regression demonstrated a significant association between taurine dosage (mg) and performance (slope = 0.0001; p = 0.04), but not between caffeine dosage (mg) and performance (slope = 0.0009; p = 0.21).

CONCLUSION

ED ingestion improved performance in muscle strength and endurance, endurance exercise tests, jumping and sport-specific actions. However, the improvement in performance was associated with taurine dosage.

Caffeine improves muscular performance in elite Brazilian Jiu-jitsu athletes

Scientific information about the effects of caffeine intake on combat sport performance is scarce and controversial. The aim of this study was to investigate the effectiveness of caffeine to improve Brazilian Jiu-jitsu (BJJ)-specific muscular performance. Fourteen male and elite BJJ athletes (29.2 ± 3.3 years; 71.3 ± 9.1 kg) participated in a randomized double-blind, placebo-controlled and crossover experiment. In two different sessions, BJJ athletes ingested 3 mg kg(-1) of caffeine or a placebo. After 60 min, they performed a handgrip maximal force test, a countermovement jump, a maximal static lift test and bench-press tests consisting of one-repetition maximum, power-load, and repetitions to failure. In comparison to the placebo, the ingestion of the caffeine increased: hand grip force in both hands (50.9 ± 2.9 vs. 53.3 ± 3.1 kg; respectively p < .05), countermovement jump height (40.6 ± 2.6 vs. 41.7 ± 3.1 cm; p = .02), and time recorded in the maximal static lift test (54.4 ± 13.4 vs. 59.2 ± 11.9 s; p < .01).The caffeine also increased the one-repetition maximum (90.5 ± 7.7 vs. 93.3 ± 7.5 kg; p = .02), maximal power obtained during the power-load test (750.5 ± 154.7 vs. 826.9 ± 163.7 W; p < .01) and mean power during the bench-press exercise test to failure (280.2 ± 52.5 vs. 312.2 ± 78.3 W; p = .04). In conclusion, the pre-exercise ingestion of 3 mg kg(-1) of caffeine increased dynamic and isometric muscular force, power, and endurance strength in elite BJJ athletes. Thus, caffeine might be an effective ergogenic aid to improve physical performance in BJJ.

Acute effects of caffeine on strength and muscle activation of the elbow flexors

The purpose of this study was to examine the effects of caffeine on strength and muscle activation of the elbow flexors. Thirteen recreationally active male volunteers (mean ± SD, age: 21.38 ± 1.26 years) came to the laboratory 4 times. Visit 1 served as a familiarization visit. During visits 2 through 4, subjects ingested a randomly assigned drink, with or without caffeine (0, 5, or 10 mg·kg of body mass), and performed 3 maximal isometric muscle actions of the elbow flexors 60 minutes after ingestion. Maximal strength and rate of torque development (RTD) were recorded. Electromyographic (EMG) and mechanomyographic (MMG) amplitude and frequency, and electromechanical delay (EMD), and phonomechanical delay (PMD) were measured from the biceps brachii. The results indicated that the ingestion of 0 (placebo), 5, or 10 mg·kg of body mass of caffeine did not significantly influence (p > 0.05) peak torque, RTD, normalized EMG amplitude or frequency, normalized MMG amplitude, or EMD and PMD. Normalized MMG frequency was significantly lower (p ≤ 0.05) following ingestion of 5 mg·kg of body mass of caffeine compared with the placebo trial. This was most likely an isolated finding because MMG frequency was the only variable to have a significant difference across all trials. The results suggested that ingestion of either 5 or 10 mg·kg of body mass of caffeine does not provide an ergogenic effect for the elbow flexors during isometric muscle actions.

Performance effects and metabolic consequences of caffeine and caffeinated energy drink consumption on glucose disposal

This review documents two opposing effects of caffeine and caffeine-containing energy drinks, i.e., their positive effects on athletic performance and their negative impacts on glucose tolerance in the sedentary state. Analysis of studies examining caffeine administration prior to performance-based exercise showed caffeine improved completion time by 3.6%. Similar analyses following consumption of caffeine-containing energy drinks yielded positive, but more varied, benefits, which were likely due to the diverse nature of the studies performed, the highly variable composition of the beverages consumed, and the range of caffeine doses administered. Conversely, analyses of studies administering caffeine prior to either an oral glucose tolerance test or insulin clamp showed a decline in whole-body glucose disposal of ~30%. The consequences of this resistance are unknown, but there may be implications for the development of a number of chronic diseases. Both caffeine-induced performance enhancement and insulin resistance converge with the primary actions of caffeine on skeletal muscle.

Performance outcomes and unwanted side effects associated with energy drinks

Energy drinks are increasingly popular among athletes and others. Advertising for these products typically features images conjuring great muscle power and endurance; however, the scientific literature provides sparse evidence for an ergogenic role of energy drinks. Although the composition of energy drinks varies, most contain caffeine; carbohydrates, amino acids, herbs, and vitamins are other typical ingredients. This report analyzes the effects of energy drink ingredients on prolonged submaximal (endurance) exercise as well as on short-term strength and power (neuromuscular performance). It also analyzes the effects of energy drink ingredients on the fluid and electrolyte deficit during prolonged exercise. In several studies, energy drinks have been found to improve endurance performance, although the effects could be attributable to the caffeine and/or carbohydrate content. In contrast, fewer studies find an ergogenic effect of energy drinks on muscle strength and power. The existing data suggest that the caffeine dose given in studies of energy drinks is insufficient to enhance neuromuscular performance. Finally, it is unclear if energy drinks are the optimal vehicle to deliver caffeine when high doses are needed to improve neuromuscular performance.

Legitimacy of concerns about caffeine and energy drink consumption

Whether caffeine and energy drink consumption presents a critical emerging health problem is not currently known. Available evidence suggests that energy drink consumption represents a change in the ways in which individuals in the United States consume caffeine but that the amount of caffeine consumed daily has not appreciably increased. In the present review, the question of whether Americans are sleep deprived (a potential reason for using caffeine) is briefly explored. Reported rates of daily caffeine consumption (based on beverage formulation) and data obtained from both civilian and military populations in the United States are examined, the efficacy of ingredients other than caffeine in energy drinks is discussed, and the safety and side effects of caffeine are addressed, including whether evidence supports the contention that excessive caffeine/energy drink consumption induces risky behavior. The available evidence suggests that the main legitimate concern regarding caffeine and energy drink use is the potential negative impact on sleep but that, otherwise, there is no cause for concern regarding caffeine use in the general population.

Taurine and skeletal muscle function

PURPOSE OF REVIEW

To discuss the recent work examining the importance of taurine in skeletal muscle and outline the discrepancy that exists between research findings in rodent vs. human skeletal muscle.

RECENT FINDINGS

There is clear evidence that a normal taurine level is important for the normal functioning of skeletal muscle. Taurine is believed to be involved in many cellular functions, but in skeletal muscle its main roles are to facilitate Ca2+ dependent excitation-contraction processes, contribute to the regulation of cellular volume, and aid in antioxidant defense from stress responses. Most research has studied the importance of taurine in rodent skeletal muscle by downregulating and upregulating the muscle taurine content and examining the effects on the functioning of skeletal muscle at rest and during the stress of contractions (exercise). One successful research approach is to supplement the diet with taurine, which leads to increases in muscle taurine content and contractile function in rodents. However, this approach does not work in human skeletal muscle as the processes involved in the transport of taurine into the muscle are resistant to large and prolonged increases in plasma taurine following oral taurine supplementation. At present, attempts to influence muscle function with taurine supplementation can only occur through interactions outside the muscle cell in humans.

SUMMARY

Future research should target the mechanisms responsible for the transport of taurine into human skeletal muscle and determine why the muscle defends the normal taurine content in the face of elevated plasma taurine levels, as opposed to the results in rodent muscle. This may lead to more fruitful usage of taurine as a skeletal muscle enhancing nutrient in athletic and clinical populations.