International Journal of Sport Nutrition and Exercise Metabolism, 2015, 25, 271 -277 http://dx.doi.org/10.1123/ijsnem.2014-0101 © 2015 Human Kinetics, Inc.
Original Research
Acute Consumption of an Energy Drink Does Not Improve Physical Performance of Female Volleyball Players Catalina Fernández-Campos, Ana L. Dengo, and José Moncada-Jiménez To determine the acute effect of an energy drink (ED) on physical performance of professional female volleyball players. 19 females (age= 22.3 ± 4.9 yr.; height= 171.8 ± 9.4 cm; weight= 65.2 ± 10.1 kg) participated in a randomized, crossover, double-blind study to measure grip strength, vertical jump and anaerobic power in 3 different sessions (ED, placebo [PL] or no beverage [CTL]). For each session, participants arrived in a fasted state, consumed a standardized breakfast meal, and 1 hr later completed the 3 baseline performance tests without having ingested the beverage. After completing the premeasurements, the athletes drank 6 ml/kg of body weight of the ED or PL and in the CTL condition no beverage was consumed. Posttest measurements were taken 30 min after the ingestion of liquids. A 3 × 2 repeated-measures ANOVA revealed no significant within-session and measurement time interactions for each performance test. Regardless of the measurement time, right hand grip strength was significantly higher in the ED condition (34.6 ± 0.9 kg) compared with PL (33.4 ± 1.1 kg) and CTL (33.6 ± 1.0 kg) (p < 0.05). Regardless of the beverage ingested, averaged right hand grip strength, taking into account all 3 testing conditions, increased from pre to posttesting (Pre = 33.8 ± 0.9 kg vs. Post = 33.9 ± 1.0 kg; p = 0.029), as did the averaged fatigue index, obtained from the anaerobic power test (Pre = 65.9± 2.2% vs. Post = 68.7± 2.0%; p= 0.049). The acute ingestion of an ED did not improve physical performance of professional Costa Rican female volleyball players. Keywords: ergogenic aids, beverages, Hispanics, strength, power The use of ergogenic aids has become a common practice among athletes around the world. The percentage of elite athletes that use ergogenic aids is as high as 84–94% (Burke & Deakin, 2010; Maughan et al., 2007). Given the increasing demand, the market supply of supplements has grown exponentially and products are offered in many forms for consumption. Drinks are one of the preferred forms because they are easy and fast to consume. Energy drinks (ED) in particular are the most commonly used supplements by British elite athletes (Petróczi et al., 2008) and have been in the market for approximately 27 years in Europe and 17 years in America (Higgins et al., 2010). The use of EDs is increasingly popular among athletic and nonathletic populations, including children (Azagba et al., 2014; Goldman, 2013; Terry-McElrath et al., 2014). Demand for EDs has been stimulated by marketing strategies to capture the willing athlete by using aggressive names, sponsoring sporting events, and endorsing athletes, as well as by mixing key ingredients with Fernández-Campos is with the Dept. of Human Sciences, Ohio State University, Columbus, OH. Dengo is with the graduate school, EARTH University, Limón, Costa Rica. Moncada-Jiménez is with the Human Movement Sciences Research Center (CIMOHU), University of Costa Rica, San José, Costa Rica. Address author correspondence to José Moncada-Jiménez at [email protected].
caffeine. Caffeine itself has been shown to benefit performance in several exercise specific protocols (Doherty & Smith, 2004, 2005), but EDs are also enhanced with other energetic ingredients like guarana and green tea extract. This mixture of energetic components appeal to those athletes looking for extra energy to boost their performance and gain a competitive advantage against their opponent. Nonetheless, regular consumption of these ingredients has been questioned and criticized because an over consumption may lead to undesired effects like insomnia, anxiety, headaches, dehydration, and heart rate disturbances (Iyadurai & Chung, 2007; Seifert et al., 2013; Shah et al., 2014). There have been mixed results from the studies that have focused on the effect of EDs on athletic performance. While some studies that tested performance through endurance (Geiβ et al., 1994; Cureton et al., 2007; Ganio et al., 2010; Ivy et al., 2009) or power (Alamdari et al., 2007) found an improvement in performance with ED, others with similar samples and tests did not (Umaña-Alvarado & Moncada-Jiménez, 2005; Campbell et al., 2010; Forbes et al., 2007). Most protocols that study the effect of EDs on physical performance have focused on endurance sports using a mixed male/female samples like the ones mentioned before. To our knowledge, only one study has focused specifically on the effect on female athletes (Astorino et al., 2012). In this study 15 female soccer players were
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272 Fernández-Campos, Dengo, and Moncada-Jiménez
tested in a sprint-based trial with ED and a placebo and ED did not affect performance or RPE. The effects of ED in sports performance are still contradictory and they vary according to the population tested and the exercise protocols used. Therefore, the aim of this study was to investigate the acute effect of ED on the physical performance of female athletes that participate in a mixed sport (volleyball) that has an important anaerobic component.
Method
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Participants
they completed the pretests (see description of physical performance tests below). If they were assigned to ED or PL (double-blind), they were asked to drink the beverage in no more than 10-min (see details under supplementation below). After that, participants waited 30-min before completing the second series of physical tests (posttest). This resting period was chosen based on the previous research (Goldstein et al., 2010b) indicating that once caffeine is consumed, it is rapidly absorbed and it reaches the bloodstream in approximately 15–35-min after the ingestion. Physical Performance Tests. Physical performance
Twenty active female volleyball players from the elite league of Costa Rica were recruited for this study. The best players from the top-four teams in the national ranking were chosen to reach a sample size of 20 participants, a sample size used in similar studies in terms of research design and physical performance tests (Alamdari et al., 2007; Campbell et al., 2010; Carvajal-Sancho & Moncada-Jiménez, 2005; Cureton et al., 2007; Forbes et al., 2007; Ganio et al., 2010; Ivy et al., 2009; UmañaAlvarado & Moncada-Jiménez, 2005; Walsh et al., 2010). Sixteen of the nineteen players who finished the study also played for the National Volleyball Team. One subject withdrew from the study due to an injury unrelated to the protocol. Athletes who participated had a mean age of 22.3 ± 4.9 yrs. and were considered active if they trained at least three times per week for the last year. Participants were instructed to keep their training schedule and diet unaltered during the study, and they all provided written consent for their participation. The study protocol was approved by the Scientific Ethics Committee of the University of Costa Rica. Experimental design. A randomized double-blind,
true experiment was conducted for 3 weeks (one trial per week). One of the following conditions was tested each week: ED, placebo (PL) or control (CTL). Participants arrived to the laboratory in a fasted condition, and approximately at the same time each testing session. Body composition was assessed using DXA-Scan (Lunar Prodigy Advance, General Electric, Madison, WI, USA) and general health questionnaires were administered during the first day of trials. A standardized breakfast (ham and cheese sandwich, orange juice, fresh apple = 336 kcal, 62 g CHO, 11 g protein, 3 g fat) for all trials and all participants was given first each testing day, and then rested in the laboratory for 45 min to allow for digestion. During this period, athletes completed a 24-hr dietary recall of the day before the trials. After the 45 min, they warmed up for 5 min on a regular cycle ergometer and stretched individually for 10-min. When this preparation stage was concluded, participants went through the first series of physical performance tests (pretest) having consumed only the breakfast provided. Participants were randomly assigned to their respective experimental condition, ED or PL, once
was determined by upper body muscle strength through hand grip strength, lower body muscle power and anaerobic power measured in three different tests. Hand grip strength was measured with a hand held dynamometer where the subject had three opportunities with each hand to reach the highest score. Lower body muscle power was measured by vertical jump test that included two types of jump: countermovement (CMJ) and squat jump (SJ). For each type of jump the athletes had three opportunities to reach the highest jump. The duration of each jump was collected through a contact mat (Lafayette Instrument Co., model 54035, Lafayette, IN, USA) and converted to cm through a formula (MacDougall et al., 1990): Distance (cm) = (flight duration [seconds]2 x 1.226) × 100. To determine anaerobic power the Wingate anaerobic test (Inbar et al., 1996) was conducted on a cycle ergometer (Lode Excalibur Sport, Groningen, Netherlands) where peak power (PP), mean power (MP) and fatigue index (FI) were collected from the data provided by the software. Supplementation. ED and PL were similar in texture and taste; however, PL was calorie free (carbonated water and sugar free artificial flavors). Table 1 shows the composition of both drinks. The drinks were always provided in opaque bottles, after the first series of physical performance tests and in a room next to the testing area. The amount of liquid provided was calculated according to the athletes’ weight: 6 ml/kg. In the CTL condition, participants went to the same room where they could rinse their mouth with water. Participants were instructed as not to drink the water. Statistical Analysis. Statistical analysis was performed
with the Statistical Package for the Social Sciences (SPSS) version 20.0 (IBM Corporation, New York, USA). Values are presented as mean and standard deviation (M ± SD). Statistical significance was set a priori at p < .05. A descriptive analysis was calculated for each dependent variable: hand strength (right hand strength [RHS] and left hand strength [LHS]), vertical jump (countermovement jump [CMJ] and squat jump [SJ]), peak power (PP), mean power (MP), and fatigue index (FI). Independent variables included: experimental condition (ED, PL, and CTL) and measurements (pre and post). Mixed factorial ANOVA (3 experimental conditions × 2 measurements) was calculated for each
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Energy Drink Consumption and Physical Performance 273
dependent variable. Bonferroni post hoc analysis was used to follow-up significant F ratios.
Results Twenty athletes began the experiment, and one participant dropped out because of an injury unrelated to the
study. Of the nineteen participants who completed the study, fourteen trained volleyball for more than 12 hr per week, and the other five trained 6 hr per week. The main characteristics of the participants are shown in Table 2. On average, during the physical performance tests the athletes drank 391.4 ± 60.5 ml of ED and PL, according to their body weight. Regarding previous consumption
Table 1 Nutritional Facts and Ingredients in 273 ml of Energy Drink (ED) and Placebo (PL) Beverage Ingredient
Energy Drink
Placebo
125 kcal2
0 kJ (0 kcal)
Total carbohydrate (g)
312
0
Carbohydrates (%)
342
0
Sugar (g)
312
0
Protein (g)
02
0
Fat (g)
02
0
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Energy
Sodium (mg)
1042
41
Potassium (mg)
202
NR
Vitamin C (mg)
87,71
NR
Folic acid (mg)
0,191
NR
Vitamin B6 (mg)
51
NR
Vitamin B12 (mg)
0,0051
NR
Inositol (mg)
96,71
-
Taurine (mg)
9482
-
Caffeine (mg)
764
-
48,8 / 75,83
-
L-carnitine (mg)
2421
-
Ginseng root extract (mg)
242
-
Guarana extract (mg)
Note. Data were collected from the nutritional labels. In the case of the ED, the label changed from the year 2011–2012, reporting different quantities and/or ingredients. Data from both labels were used to complete the table (12011 label; 22012 label; 3Label from 2011 repeated the ingredient and reported two different amounts each time; 4Reported by Mayo & Kravitz (2008), data were not included on the can). Percentage of carbohydrate based on calculations (31g/273ml = 11.3%) differs from the 34% reported. NR: Not reported
Table 2 Characteristics of the Participants Characteristic
Mean ± SD
Min-Max
Age (years)
22.3 ± 4.9
18–35
Weight (kg)
65.2 ± 10.1
50.0–86.0
Height (cm)
171.8 ± 9.4
154.0–185.8
BMI (kg/m2)
22.0 ± 1.8
17.9–26.3
Fat mass DXA (%)
28.6 ± 5.6
17.6–40.0
Muscle mass DXA (kg)
25.6 ± 3.6
19.3–32.8
Muscle mass DXA (%)
39.4 ± 3.0
33.9–45.6
Experience (total years playing)
8.9 ± 4.5
2–20
Years in the elite league
4.9 ± 3.6
1–14
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274 Fernández-Campos, Dengo, and Moncada-Jiménez
of EDs, only two participants (11%) consumed them “frequently” before exercise (approximately twice per month) and four (21%) had never tried them before. During the experiment none of the athletes presented adverse effects after consuming the ED.
siderably differently on the day before the trial tests. In these cases performance results were compared taking into consideration the variation in pretrial dietary intake to confirm that diet did not become a confounding factor. Overall, results followed the same pattern no matter the changes in the diet.
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Physical Performance Table 3 shows the descriptive analysis with the mean and standard deviation collected in each physical performance test for each of the experimental conditions used. According to the inferential statistical analysis through the ANOVA test, there were no significant statistical differences in the performances between the three conditions (CTL, PL, ED). Table 4 shows the results of the ANOVA significant tests for each of the variables considered to evaluate performance. Column A (conditions: ED, PL, CTL) and B (measurements: pre, post), represent the main effects, while column AxB (interaction: drink x time) shows the combined effect of the type of beverage and the measurement, that is to say the interaction between them. As shown in Table 4, there was a significant difference for fatigue index (FI) and right hand strength (RHS); regardless of the experimental condition, both variables increased from pre to post (FI: Pre = 65.9 ± 2.2% vs. Post = 68.7 ± 2.1%; p = .049 and RHS: Pre = 33.8 ± 0.9 kg vs. Post = 33.9 ± 1.0 kg; p = .029). In addition, there was a statistically significant main effect for the RHS variable between the mean of the experimental conditions (CTL = 33.6 ± 1.0 kg; PL = 33.4 ± 1.1 kg; ED = 34.6± 0.9 kg; p = .024), independently of the measurement. Post hoc analysis indicated significant mean differences between PL and ED (p = .025) and between CTL and ED (p = .006) experimental conditions. According to the 24-hr recall that was collected each trial day, athletes maintained, in general, the same pattern of diet the day before the three visits to the laboratory. There were only two cases where the athletes ate con-
Discussion The main purpose of the current study was to examine the acute effect of an ED on the physical performance of female athletes in a mixed sport (aerobic/anaerobic). After conducting the experiment with female volleyball players, no significant statistical difference was found between the interaction of experimental condition (CTL, PL, ED) in comparison with the measurements (pre and post) as can be seen in the “Interaction” column from Table 4. This lack of interaction means that the physical performance was, in general, the same (Table 3) whether the players drank a beverage or not. Contrary to what was found in the current study, others (Geiß et al., 1994) have tested the effects of EDs on 10 male endurance athletes and reported longer cycling times to exhaustion after cycling for 60-min at 70% VO2max on a cycle ergometer under the ED condition compared with two placebo beverages partially lacking the full-set of ingredients of an ED. Other endurance cycling experiments with cyclists have been conducted (Cureton et al., 2007; Ganio et al., 2010; Ivy et al., 2009) with similar results showing more accumulated work with ED. Nonetheless, another endurance study with male runners (Umaña-Alvarado & Moncada-Jiménez, 2005) found no significant differences in mean running times between ED and placebo conditions. However, the results of our study must be compared with those that used similar protocols based on anaerobic power testing. For instance, a mixed male/female sample of active participants was studied (Forbes et al., 2007) and reported no significant effects between ED and placebo
Table 3 Descriptive Statistics for Physical Tests According to Experimental Conditions Control Variable
Pre
Placebo Post
Pre
Energy Drink Post
Pre
Post
Right hand grip strength (kg)
33.2 ± 4.2
34.1 ± 4.4
33.2 ± 4.4
33.7 ± 5.0
34.1 ± 4.4
35.0 ± 4.0
Left hand grip strength (kg)
33.1 ± 5.3
33.2 ± 5.5
32.7 ± 5.3
33.0 ± 5.3
32.9 ± 5.8
33.1 ± 5.8
CM Jump (cm)
41.7 ± 5.1
42.3 ± 5.0
43.9 ± 4.1
41.8 ± 5.5
41.6 ± 3.8
41.9 ± 4.2
SJ (cm)
37.5 ± 5.9
37.9 ± 5.9
37.3 ± 5.3
36.8 ± 4.9
36.1 ± 5.1
37.4 ± 5.2
Peak power (W)
845.2 ± 166.3 848.0 ± 184.7
888.0 ± 200.4 911.2 ± 184.4
859.8 ± 214.6 908.0 ± 211.6
Mean power (W)
492.5 ± 71.1
487.1 ± 89.1
476.0 ± 81.7
497.1 ± 76.9
484.6 ± 70.0
499.9 ± 65.4
Fatigue index (%)
65.3 ± 12.4
67.0 ± 12.3
65.2 ± 10.0
70.8 ± 10.6
67.0 ± 14.1
68.2 ± 11.5
Note. Values are means with standard deviation. CM Jump = counter movement jump; SJ = squat jump.
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Table 4 Results of Statistical Significant Testing of Physical Performance Tests A (Conditions: ED, PL, CTL)
B (Measurements: Time—pre, post)
A x B (Interaction: Drink x Time)
Right hand strength (kg)
0.024
0.029
0.797
Left hand strength (kg)
0.735
0.459
0.957
CM Jump (cm)
0.341
0.538
0.096
SJ (cm)
0.621
0.348
0.332
Peak power (W)
0.331
0.156
0.367
Mean power (W)
0.825
0.071
0.209
Fatigue index (%)
0.740
0.049
0.446
Variable
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Note. CM Jump = counter movement jump; SJ = squat jump; ED = Energy drink; PL = placebo; CTL = control.Text in bold indicates where the results for the particular physical test were significant (p < .05) for each variable.
in the peak (ED = 701 ± 124 W vs. placebo = 700 ± 132 W) and mean power of a Wingate test (ED = 479 ± 74 W vs. placebo = 471 ± 74 W). These findings were similar to the results reported by others (Campbell et al., 2010) using the same test and type of sample (ED = 786.4 ± 245.9 W and 722 ± 242 W vs. placebo = 777.1 ± 276 W and 716.7 ± 247.6 W). In addition, one study (Astorino et al., 2012), which used an all-female sample of soccer players, found no significant differences in sprint times (ED = 11.3 ± 0.6 s vs. placebo = 11.4 ± 0.6 s). The results of the current study are limited by the lack of valid and reliable options for measuring specific volleyball performance. The tests were chosen based on the available literature, laboratory equipment and former elite volleyball experience from one of the authors; therefore, face validity and practical convenience were the main criteria used for selecting the tests. As jumping is a common movement in volleyball, the inclusion of the SJ and CMJ tests were the most appropriate tests used in the current study. Nonetheless, during volleyball, jumping is preceded by a series of movements, takes place as consecutive jumps and is determined by the net’s position. The Wingate anaerobic test was a risky but reasonable choice because, even as it is performed in a seated position, it tests a short continuous bout of an “all out” effort like those expected during a volleyball match. The hand grip test was included to test the upper body, but upper body in volleyball mostly means the arm’s swing for a spike. Similarly, no validated laboratory test that measures the strength of the shoulder or the speed of the swing was found to obtain a more volleyball-specific performance measure. In general, the design and validation of new tests specific to volleyball like anaerobic drills or technique specific measurements warrants further research. In terms of EDs ingredients, caffeine is the principal energetic component. Several attempts have been made to explain the specific physiological effects of caffeine during exercise, including mechanisms involving: a)
direct competition with adenosine for its receptor sites and a greater release of β-endorphins (Goldstein et al., 2010a), b) a change in the central nervous system altering perceived exertion (Burke, 2007), c) a change in substrate use from glycogen to free fatty acids (Higgins et al., 2010), and d) direct stimuli over muscle contractibility (Burke, 2007; Higgins et al., 2010). Of all the ED components, caffeine is also the ingredient that has been studied the most in the literature (Burke, 2007; Burke & Deakin, 2010; Doherty & Smith, 2004, 2005; Goldstein et al., 2010b). Even though the physiological mechanism of action is not entirely clear, caffeine indeed has a potential to enhance performance in different types of sports and at different exercise intensities. In the current study, however, no performance enhancement was found. According to the total ED volume consumed by the athletes in our study, the approximate amount of caffeine ingested was 2 mg/kg of body weight. Previous studies (Astorino et al., 2012; Campbell et al., 2010; Forbes et al., 2007), used EDs with similar caffeine amounts of 2.1 mg/kg, 2 mg/kg and 1.3 mg/kg, respectively, and did not find any statistically significant effects regarding anaerobic power either. In contrast, others (Forbes et al., 2007; Goldstein et al., 2010a) have reported improvements in upper body strength using 1.3 and 6 mg/kg of body mass, respectively. Commonly used caffeine intake protocols for athletes that involved the ingestion of a low-moderate dose of 3–6 mg/kg approximately are traditionally described in the literature (Burke, 2007; Goldstein et al., 2010a). This might suggest that the amount of caffeine contained in the ED for the current study was not enough to show any significant performance improvements. It should be mentioned that some manufacturers abstain from reporting the real amounts of caffeine present in their product, especially when other caffeine sources are included (e.g., guarana extract). The ED that was used in our study also
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276 Fernández-Campos, Dengo, and Moncada-Jiménez
contained guarana extract; therefore, it is possible that the amount of caffeine ingested by our participants was greater than 2 mg/kg body weight. Table 1 shows that besides macronutrients, the ingredient with the highest concentration in the ED is taurine. There are few studies that have shown that taurine intake is related to an improvement in the physical performance of athletes (Balshaw et al., 2013; Geiβ et al., 1994). Even though some researchers (Geiβ et al., 1994) used an ED for their study, they altered the taurine composition in the three different conditions used. In the case where the male athletes consumed the beverage with taurine (2 g), the endurance time was significantly longer (p = .015) in the cycling to exhaustion test. Others (Balshaw et al., 2013) used a one-time 1000 mg dose of taurine, an amount that is similar to the amount present in EDs, and found that performance in a 3-km time trial improved significantly (1.7%) in comparison with the placebo condition (taurine 646.6 ± 52.8 s vs. placebo 658.5 ± 58.2 s). However, in our study no improvement was found, even when the approximate amount of taurine that was ingested by the athletes (2g) was similar, or even higher, than the amounts reported in previous research. Another important claimed source of energy from EDs is the high amount of carbohydrates, which are frequently combined with vitamins from the B complex to produce energy. For carbohydrates in general, there is evidence to support the benefits for athletes who consume them around exercise bouts; and entities like the American Dietetic Association (Rodriguez et al., 2009) suggest protocols for carbohydrate consumption and exercise. In our study, participants reported to the laboratory under fasting conditions and consumed the same breakfast before starting the trials to minimize the possible confounding effect of premeal composition on the performance results. Nonetheless, in the current study extra amounts of sugars from the ED were not a determinant of performance compared with the CTL and PL conditions, in which no carbohydrates were included. EDs contain other ingredients, but in the absence of any evidence of performance enhancing effects they were not examined. However, regarding the wide variation of ingredients used in EDs it is important to highlight previous research (Alamdari et al., 2007) where the effects of EDs on power in football players was tested using the running basic anaerobic spring test (RAST). The study reported an increase of minimum and mean power of 11.01% and 9.15%, respectively, with ED, but for this particular study the authors compared two different EDs and a placebo and, interestingly, the positive effects were found with only one of EDs. In conclusion, muscle strength, muscle power and anaerobic power were not affected by the consumption of an ED, PL or no beverage at all (CTL). Whether similar findings would be obtained with different populations, varying volumes of EDs, and under testing conditions outside of the laboratory scenario are still areas for further study. Furthermore, studies including EDs should
also focus on the possible additive or synergistic effects among the various ingredients commonly used. Acknowledgments All authors approved the final version of the paper. No funding was received to conduct this study. The authors report no conflict of interest.
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MacDougall, J.D., Wenger, H.A., & Green, H.J. (1990). Physiological testing of the high-performance athlete (2nd ed.). Champaign, IL: Human Kinetics. Maughan, R.J., Depiesse, F., & Geyer, H. (2007). The use of dietary supplements by athletes. Journal of Sports Sciences, 25, S103–S113. PubMed doi:10.1080/02640410701607395 Petróczi, A., Naughton, D.P., Pearce, G., Bailey, R., Bloodworth, A., & McNamee, M. (2008). Nutritional supplement use by elite young UK athletes: fallacies of advice regarding efficacy. Journal of the International Society of Sports Nutrition, 5, 22. PubMed doi:10.1186/1550-2783-5-22 Rodriguez, N.R., DiMarco, N.M., & Langley, S. (2009). Position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and athletic performance. Journal of the American Dietetic Association, 109(3), 509–527. PubMed doi:10.1016/j.jada.2009.01.005 Seifert, S.M., Seifert, S.A., Schaechter, J.L., Bronstein, A.C., Benson, B.E., Hershorin, E.R., . . . Lipshultz, S.E. (2013). An analysis of energy-drink toxicity in the National Poison Data System. Clinical Toxicology (Philadelphia, PA), 51(7), 566–574. PubMed doi:10.3109/15563650.2 013.820310 Shah, S.A., Lacey, C.S., Bergendahl, T., Kolasa, M., & Riddock, I.C. (2014). QTc interval prolongation with high dose energy drink consumption in a healthy volunteer. International Journal of Cardiology. PubMed Terry-McElrath, Y. M., O’Malley P, M., & Johnston, L. D. (2014). Energy drinks, soft drinks, and substance use among United States secondary school students. Journal of Addiction Medicine, 8(1), 6–13. PubMed doi:10.1097/01. ADM.0000435322.07020.53 Umaña-Alvarado, M., & Moncada-Jiménez, J. (2005). Consumption of an ‘Energy Drink’ does not improve aerobic performance in male athletes. Intl J Appl Sport Sci, 17(2), 26–34. Walsh, A.L., Gonzalez, A.M., Ratamess, N.A., Kang, J., & Hoffman, J.R. (2010). Improved time to exhaustion following ingestion of the energy drink Amino Impact. Journal of the International Society of Sports Nutrition, 7, 14. PubMed doi:10.1186/1550-2783-7-14
IJSNEM Vol. 25, No. 3, 2015
Original Research
Acute Consumption of an Energy Drink Does Not Improve Physical Performance of Female Volleyball Players Catalina Fernández-Campos, Ana L. Dengo, and José Moncada-Jiménez To determine the acute effect of an energy drink (ED) on physical performance of professional female volleyball players. 19 females (age= 22.3 ± 4.9 yr.; height= 171.8 ± 9.4 cm; weight= 65.2 ± 10.1 kg) participated in a randomized, crossover, double-blind study to measure grip strength, vertical jump and anaerobic power in 3 different sessions (ED, placebo [PL] or no beverage [CTL]). For each session, participants arrived in a fasted state, consumed a standardized breakfast meal, and 1 hr later completed the 3 baseline performance tests without having ingested the beverage. After completing the premeasurements, the athletes drank 6 ml/kg of body weight of the ED or PL and in the CTL condition no beverage was consumed. Posttest measurements were taken 30 min after the ingestion of liquids. A 3 × 2 repeated-measures ANOVA revealed no significant within-session and measurement time interactions for each performance test. Regardless of the measurement time, right hand grip strength was significantly higher in the ED condition (34.6 ± 0.9 kg) compared with PL (33.4 ± 1.1 kg) and CTL (33.6 ± 1.0 kg) (p < 0.05). Regardless of the beverage ingested, averaged right hand grip strength, taking into account all 3 testing conditions, increased from pre to posttesting (Pre = 33.8 ± 0.9 kg vs. Post = 33.9 ± 1.0 kg; p = 0.029), as did the averaged fatigue index, obtained from the anaerobic power test (Pre = 65.9± 2.2% vs. Post = 68.7± 2.0%; p= 0.049). The acute ingestion of an ED did not improve physical performance of professional Costa Rican female volleyball players. Keywords: ergogenic aids, beverages, Hispanics, strength, power The use of ergogenic aids has become a common practice among athletes around the world. The percentage of elite athletes that use ergogenic aids is as high as 84–94% (Burke & Deakin, 2010; Maughan et al., 2007). Given the increasing demand, the market supply of supplements has grown exponentially and products are offered in many forms for consumption. Drinks are one of the preferred forms because they are easy and fast to consume. Energy drinks (ED) in particular are the most commonly used supplements by British elite athletes (Petróczi et al., 2008) and have been in the market for approximately 27 years in Europe and 17 years in America (Higgins et al., 2010). The use of EDs is increasingly popular among athletic and nonathletic populations, including children (Azagba et al., 2014; Goldman, 2013; Terry-McElrath et al., 2014). Demand for EDs has been stimulated by marketing strategies to capture the willing athlete by using aggressive names, sponsoring sporting events, and endorsing athletes, as well as by mixing key ingredients with Fernández-Campos is with the Dept. of Human Sciences, Ohio State University, Columbus, OH. Dengo is with the graduate school, EARTH University, Limón, Costa Rica. Moncada-Jiménez is with the Human Movement Sciences Research Center (CIMOHU), University of Costa Rica, San José, Costa Rica. Address author correspondence to José Moncada-Jiménez at [email protected].
caffeine. Caffeine itself has been shown to benefit performance in several exercise specific protocols (Doherty & Smith, 2004, 2005), but EDs are also enhanced with other energetic ingredients like guarana and green tea extract. This mixture of energetic components appeal to those athletes looking for extra energy to boost their performance and gain a competitive advantage against their opponent. Nonetheless, regular consumption of these ingredients has been questioned and criticized because an over consumption may lead to undesired effects like insomnia, anxiety, headaches, dehydration, and heart rate disturbances (Iyadurai & Chung, 2007; Seifert et al., 2013; Shah et al., 2014). There have been mixed results from the studies that have focused on the effect of EDs on athletic performance. While some studies that tested performance through endurance (Geiβ et al., 1994; Cureton et al., 2007; Ganio et al., 2010; Ivy et al., 2009) or power (Alamdari et al., 2007) found an improvement in performance with ED, others with similar samples and tests did not (Umaña-Alvarado & Moncada-Jiménez, 2005; Campbell et al., 2010; Forbes et al., 2007). Most protocols that study the effect of EDs on physical performance have focused on endurance sports using a mixed male/female samples like the ones mentioned before. To our knowledge, only one study has focused specifically on the effect on female athletes (Astorino et al., 2012). In this study 15 female soccer players were
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272 Fernández-Campos, Dengo, and Moncada-Jiménez
tested in a sprint-based trial with ED and a placebo and ED did not affect performance or RPE. The effects of ED in sports performance are still contradictory and they vary according to the population tested and the exercise protocols used. Therefore, the aim of this study was to investigate the acute effect of ED on the physical performance of female athletes that participate in a mixed sport (volleyball) that has an important anaerobic component.
Method
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Participants
they completed the pretests (see description of physical performance tests below). If they were assigned to ED or PL (double-blind), they were asked to drink the beverage in no more than 10-min (see details under supplementation below). After that, participants waited 30-min before completing the second series of physical tests (posttest). This resting period was chosen based on the previous research (Goldstein et al., 2010b) indicating that once caffeine is consumed, it is rapidly absorbed and it reaches the bloodstream in approximately 15–35-min after the ingestion. Physical Performance Tests. Physical performance
Twenty active female volleyball players from the elite league of Costa Rica were recruited for this study. The best players from the top-four teams in the national ranking were chosen to reach a sample size of 20 participants, a sample size used in similar studies in terms of research design and physical performance tests (Alamdari et al., 2007; Campbell et al., 2010; Carvajal-Sancho & Moncada-Jiménez, 2005; Cureton et al., 2007; Forbes et al., 2007; Ganio et al., 2010; Ivy et al., 2009; UmañaAlvarado & Moncada-Jiménez, 2005; Walsh et al., 2010). Sixteen of the nineteen players who finished the study also played for the National Volleyball Team. One subject withdrew from the study due to an injury unrelated to the protocol. Athletes who participated had a mean age of 22.3 ± 4.9 yrs. and were considered active if they trained at least three times per week for the last year. Participants were instructed to keep their training schedule and diet unaltered during the study, and they all provided written consent for their participation. The study protocol was approved by the Scientific Ethics Committee of the University of Costa Rica. Experimental design. A randomized double-blind,
true experiment was conducted for 3 weeks (one trial per week). One of the following conditions was tested each week: ED, placebo (PL) or control (CTL). Participants arrived to the laboratory in a fasted condition, and approximately at the same time each testing session. Body composition was assessed using DXA-Scan (Lunar Prodigy Advance, General Electric, Madison, WI, USA) and general health questionnaires were administered during the first day of trials. A standardized breakfast (ham and cheese sandwich, orange juice, fresh apple = 336 kcal, 62 g CHO, 11 g protein, 3 g fat) for all trials and all participants was given first each testing day, and then rested in the laboratory for 45 min to allow for digestion. During this period, athletes completed a 24-hr dietary recall of the day before the trials. After the 45 min, they warmed up for 5 min on a regular cycle ergometer and stretched individually for 10-min. When this preparation stage was concluded, participants went through the first series of physical performance tests (pretest) having consumed only the breakfast provided. Participants were randomly assigned to their respective experimental condition, ED or PL, once
was determined by upper body muscle strength through hand grip strength, lower body muscle power and anaerobic power measured in three different tests. Hand grip strength was measured with a hand held dynamometer where the subject had three opportunities with each hand to reach the highest score. Lower body muscle power was measured by vertical jump test that included two types of jump: countermovement (CMJ) and squat jump (SJ). For each type of jump the athletes had three opportunities to reach the highest jump. The duration of each jump was collected through a contact mat (Lafayette Instrument Co., model 54035, Lafayette, IN, USA) and converted to cm through a formula (MacDougall et al., 1990): Distance (cm) = (flight duration [seconds]2 x 1.226) × 100. To determine anaerobic power the Wingate anaerobic test (Inbar et al., 1996) was conducted on a cycle ergometer (Lode Excalibur Sport, Groningen, Netherlands) where peak power (PP), mean power (MP) and fatigue index (FI) were collected from the data provided by the software. Supplementation. ED and PL were similar in texture and taste; however, PL was calorie free (carbonated water and sugar free artificial flavors). Table 1 shows the composition of both drinks. The drinks were always provided in opaque bottles, after the first series of physical performance tests and in a room next to the testing area. The amount of liquid provided was calculated according to the athletes’ weight: 6 ml/kg. In the CTL condition, participants went to the same room where they could rinse their mouth with water. Participants were instructed as not to drink the water. Statistical Analysis. Statistical analysis was performed
with the Statistical Package for the Social Sciences (SPSS) version 20.0 (IBM Corporation, New York, USA). Values are presented as mean and standard deviation (M ± SD). Statistical significance was set a priori at p < .05. A descriptive analysis was calculated for each dependent variable: hand strength (right hand strength [RHS] and left hand strength [LHS]), vertical jump (countermovement jump [CMJ] and squat jump [SJ]), peak power (PP), mean power (MP), and fatigue index (FI). Independent variables included: experimental condition (ED, PL, and CTL) and measurements (pre and post). Mixed factorial ANOVA (3 experimental conditions × 2 measurements) was calculated for each
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Energy Drink Consumption and Physical Performance 273
dependent variable. Bonferroni post hoc analysis was used to follow-up significant F ratios.
Results Twenty athletes began the experiment, and one participant dropped out because of an injury unrelated to the
study. Of the nineteen participants who completed the study, fourteen trained volleyball for more than 12 hr per week, and the other five trained 6 hr per week. The main characteristics of the participants are shown in Table 2. On average, during the physical performance tests the athletes drank 391.4 ± 60.5 ml of ED and PL, according to their body weight. Regarding previous consumption
Table 1 Nutritional Facts and Ingredients in 273 ml of Energy Drink (ED) and Placebo (PL) Beverage Ingredient
Energy Drink
Placebo
125 kcal2
0 kJ (0 kcal)
Total carbohydrate (g)
312
0
Carbohydrates (%)
342
0
Sugar (g)
312
0
Protein (g)
02
0
Fat (g)
02
0
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Energy
Sodium (mg)
1042
41
Potassium (mg)
202
NR
Vitamin C (mg)
87,71
NR
Folic acid (mg)
0,191
NR
Vitamin B6 (mg)
51
NR
Vitamin B12 (mg)
0,0051
NR
Inositol (mg)
96,71
-
Taurine (mg)
9482
-
Caffeine (mg)
764
-
48,8 / 75,83
-
L-carnitine (mg)
2421
-
Ginseng root extract (mg)
242
-
Guarana extract (mg)
Note. Data were collected from the nutritional labels. In the case of the ED, the label changed from the year 2011–2012, reporting different quantities and/or ingredients. Data from both labels were used to complete the table (12011 label; 22012 label; 3Label from 2011 repeated the ingredient and reported two different amounts each time; 4Reported by Mayo & Kravitz (2008), data were not included on the can). Percentage of carbohydrate based on calculations (31g/273ml = 11.3%) differs from the 34% reported. NR: Not reported
Table 2 Characteristics of the Participants Characteristic
Mean ± SD
Min-Max
Age (years)
22.3 ± 4.9
18–35
Weight (kg)
65.2 ± 10.1
50.0–86.0
Height (cm)
171.8 ± 9.4
154.0–185.8
BMI (kg/m2)
22.0 ± 1.8
17.9–26.3
Fat mass DXA (%)
28.6 ± 5.6
17.6–40.0
Muscle mass DXA (kg)
25.6 ± 3.6
19.3–32.8
Muscle mass DXA (%)
39.4 ± 3.0
33.9–45.6
Experience (total years playing)
8.9 ± 4.5
2–20
Years in the elite league
4.9 ± 3.6
1–14
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274 Fernández-Campos, Dengo, and Moncada-Jiménez
of EDs, only two participants (11%) consumed them “frequently” before exercise (approximately twice per month) and four (21%) had never tried them before. During the experiment none of the athletes presented adverse effects after consuming the ED.
siderably differently on the day before the trial tests. In these cases performance results were compared taking into consideration the variation in pretrial dietary intake to confirm that diet did not become a confounding factor. Overall, results followed the same pattern no matter the changes in the diet.
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Physical Performance Table 3 shows the descriptive analysis with the mean and standard deviation collected in each physical performance test for each of the experimental conditions used. According to the inferential statistical analysis through the ANOVA test, there were no significant statistical differences in the performances between the three conditions (CTL, PL, ED). Table 4 shows the results of the ANOVA significant tests for each of the variables considered to evaluate performance. Column A (conditions: ED, PL, CTL) and B (measurements: pre, post), represent the main effects, while column AxB (interaction: drink x time) shows the combined effect of the type of beverage and the measurement, that is to say the interaction between them. As shown in Table 4, there was a significant difference for fatigue index (FI) and right hand strength (RHS); regardless of the experimental condition, both variables increased from pre to post (FI: Pre = 65.9 ± 2.2% vs. Post = 68.7 ± 2.1%; p = .049 and RHS: Pre = 33.8 ± 0.9 kg vs. Post = 33.9 ± 1.0 kg; p = .029). In addition, there was a statistically significant main effect for the RHS variable between the mean of the experimental conditions (CTL = 33.6 ± 1.0 kg; PL = 33.4 ± 1.1 kg; ED = 34.6± 0.9 kg; p = .024), independently of the measurement. Post hoc analysis indicated significant mean differences between PL and ED (p = .025) and between CTL and ED (p = .006) experimental conditions. According to the 24-hr recall that was collected each trial day, athletes maintained, in general, the same pattern of diet the day before the three visits to the laboratory. There were only two cases where the athletes ate con-
Discussion The main purpose of the current study was to examine the acute effect of an ED on the physical performance of female athletes in a mixed sport (aerobic/anaerobic). After conducting the experiment with female volleyball players, no significant statistical difference was found between the interaction of experimental condition (CTL, PL, ED) in comparison with the measurements (pre and post) as can be seen in the “Interaction” column from Table 4. This lack of interaction means that the physical performance was, in general, the same (Table 3) whether the players drank a beverage or not. Contrary to what was found in the current study, others (Geiß et al., 1994) have tested the effects of EDs on 10 male endurance athletes and reported longer cycling times to exhaustion after cycling for 60-min at 70% VO2max on a cycle ergometer under the ED condition compared with two placebo beverages partially lacking the full-set of ingredients of an ED. Other endurance cycling experiments with cyclists have been conducted (Cureton et al., 2007; Ganio et al., 2010; Ivy et al., 2009) with similar results showing more accumulated work with ED. Nonetheless, another endurance study with male runners (Umaña-Alvarado & Moncada-Jiménez, 2005) found no significant differences in mean running times between ED and placebo conditions. However, the results of our study must be compared with those that used similar protocols based on anaerobic power testing. For instance, a mixed male/female sample of active participants was studied (Forbes et al., 2007) and reported no significant effects between ED and placebo
Table 3 Descriptive Statistics for Physical Tests According to Experimental Conditions Control Variable
Pre
Placebo Post
Pre
Energy Drink Post
Pre
Post
Right hand grip strength (kg)
33.2 ± 4.2
34.1 ± 4.4
33.2 ± 4.4
33.7 ± 5.0
34.1 ± 4.4
35.0 ± 4.0
Left hand grip strength (kg)
33.1 ± 5.3
33.2 ± 5.5
32.7 ± 5.3
33.0 ± 5.3
32.9 ± 5.8
33.1 ± 5.8
CM Jump (cm)
41.7 ± 5.1
42.3 ± 5.0
43.9 ± 4.1
41.8 ± 5.5
41.6 ± 3.8
41.9 ± 4.2
SJ (cm)
37.5 ± 5.9
37.9 ± 5.9
37.3 ± 5.3
36.8 ± 4.9
36.1 ± 5.1
37.4 ± 5.2
Peak power (W)
845.2 ± 166.3 848.0 ± 184.7
888.0 ± 200.4 911.2 ± 184.4
859.8 ± 214.6 908.0 ± 211.6
Mean power (W)
492.5 ± 71.1
487.1 ± 89.1
476.0 ± 81.7
497.1 ± 76.9
484.6 ± 70.0
499.9 ± 65.4
Fatigue index (%)
65.3 ± 12.4
67.0 ± 12.3
65.2 ± 10.0
70.8 ± 10.6
67.0 ± 14.1
68.2 ± 11.5
Note. Values are means with standard deviation. CM Jump = counter movement jump; SJ = squat jump.
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Energy Drink Consumption and Physical Performance 275
Table 4 Results of Statistical Significant Testing of Physical Performance Tests A (Conditions: ED, PL, CTL)
B (Measurements: Time—pre, post)
A x B (Interaction: Drink x Time)
Right hand strength (kg)
0.024
0.029
0.797
Left hand strength (kg)
0.735
0.459
0.957
CM Jump (cm)
0.341
0.538
0.096
SJ (cm)
0.621
0.348
0.332
Peak power (W)
0.331
0.156
0.367
Mean power (W)
0.825
0.071
0.209
Fatigue index (%)
0.740
0.049
0.446
Variable
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Note. CM Jump = counter movement jump; SJ = squat jump; ED = Energy drink; PL = placebo; CTL = control.Text in bold indicates where the results for the particular physical test were significant (p < .05) for each variable.
in the peak (ED = 701 ± 124 W vs. placebo = 700 ± 132 W) and mean power of a Wingate test (ED = 479 ± 74 W vs. placebo = 471 ± 74 W). These findings were similar to the results reported by others (Campbell et al., 2010) using the same test and type of sample (ED = 786.4 ± 245.9 W and 722 ± 242 W vs. placebo = 777.1 ± 276 W and 716.7 ± 247.6 W). In addition, one study (Astorino et al., 2012), which used an all-female sample of soccer players, found no significant differences in sprint times (ED = 11.3 ± 0.6 s vs. placebo = 11.4 ± 0.6 s). The results of the current study are limited by the lack of valid and reliable options for measuring specific volleyball performance. The tests were chosen based on the available literature, laboratory equipment and former elite volleyball experience from one of the authors; therefore, face validity and practical convenience were the main criteria used for selecting the tests. As jumping is a common movement in volleyball, the inclusion of the SJ and CMJ tests were the most appropriate tests used in the current study. Nonetheless, during volleyball, jumping is preceded by a series of movements, takes place as consecutive jumps and is determined by the net’s position. The Wingate anaerobic test was a risky but reasonable choice because, even as it is performed in a seated position, it tests a short continuous bout of an “all out” effort like those expected during a volleyball match. The hand grip test was included to test the upper body, but upper body in volleyball mostly means the arm’s swing for a spike. Similarly, no validated laboratory test that measures the strength of the shoulder or the speed of the swing was found to obtain a more volleyball-specific performance measure. In general, the design and validation of new tests specific to volleyball like anaerobic drills or technique specific measurements warrants further research. In terms of EDs ingredients, caffeine is the principal energetic component. Several attempts have been made to explain the specific physiological effects of caffeine during exercise, including mechanisms involving: a)
direct competition with adenosine for its receptor sites and a greater release of β-endorphins (Goldstein et al., 2010a), b) a change in the central nervous system altering perceived exertion (Burke, 2007), c) a change in substrate use from glycogen to free fatty acids (Higgins et al., 2010), and d) direct stimuli over muscle contractibility (Burke, 2007; Higgins et al., 2010). Of all the ED components, caffeine is also the ingredient that has been studied the most in the literature (Burke, 2007; Burke & Deakin, 2010; Doherty & Smith, 2004, 2005; Goldstein et al., 2010b). Even though the physiological mechanism of action is not entirely clear, caffeine indeed has a potential to enhance performance in different types of sports and at different exercise intensities. In the current study, however, no performance enhancement was found. According to the total ED volume consumed by the athletes in our study, the approximate amount of caffeine ingested was 2 mg/kg of body weight. Previous studies (Astorino et al., 2012; Campbell et al., 2010; Forbes et al., 2007), used EDs with similar caffeine amounts of 2.1 mg/kg, 2 mg/kg and 1.3 mg/kg, respectively, and did not find any statistically significant effects regarding anaerobic power either. In contrast, others (Forbes et al., 2007; Goldstein et al., 2010a) have reported improvements in upper body strength using 1.3 and 6 mg/kg of body mass, respectively. Commonly used caffeine intake protocols for athletes that involved the ingestion of a low-moderate dose of 3–6 mg/kg approximately are traditionally described in the literature (Burke, 2007; Goldstein et al., 2010a). This might suggest that the amount of caffeine contained in the ED for the current study was not enough to show any significant performance improvements. It should be mentioned that some manufacturers abstain from reporting the real amounts of caffeine present in their product, especially when other caffeine sources are included (e.g., guarana extract). The ED that was used in our study also
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276 Fernández-Campos, Dengo, and Moncada-Jiménez
contained guarana extract; therefore, it is possible that the amount of caffeine ingested by our participants was greater than 2 mg/kg body weight. Table 1 shows that besides macronutrients, the ingredient with the highest concentration in the ED is taurine. There are few studies that have shown that taurine intake is related to an improvement in the physical performance of athletes (Balshaw et al., 2013; Geiβ et al., 1994). Even though some researchers (Geiβ et al., 1994) used an ED for their study, they altered the taurine composition in the three different conditions used. In the case where the male athletes consumed the beverage with taurine (2 g), the endurance time was significantly longer (p = .015) in the cycling to exhaustion test. Others (Balshaw et al., 2013) used a one-time 1000 mg dose of taurine, an amount that is similar to the amount present in EDs, and found that performance in a 3-km time trial improved significantly (1.7%) in comparison with the placebo condition (taurine 646.6 ± 52.8 s vs. placebo 658.5 ± 58.2 s). However, in our study no improvement was found, even when the approximate amount of taurine that was ingested by the athletes (2g) was similar, or even higher, than the amounts reported in previous research. Another important claimed source of energy from EDs is the high amount of carbohydrates, which are frequently combined with vitamins from the B complex to produce energy. For carbohydrates in general, there is evidence to support the benefits for athletes who consume them around exercise bouts; and entities like the American Dietetic Association (Rodriguez et al., 2009) suggest protocols for carbohydrate consumption and exercise. In our study, participants reported to the laboratory under fasting conditions and consumed the same breakfast before starting the trials to minimize the possible confounding effect of premeal composition on the performance results. Nonetheless, in the current study extra amounts of sugars from the ED were not a determinant of performance compared with the CTL and PL conditions, in which no carbohydrates were included. EDs contain other ingredients, but in the absence of any evidence of performance enhancing effects they were not examined. However, regarding the wide variation of ingredients used in EDs it is important to highlight previous research (Alamdari et al., 2007) where the effects of EDs on power in football players was tested using the running basic anaerobic spring test (RAST). The study reported an increase of minimum and mean power of 11.01% and 9.15%, respectively, with ED, but for this particular study the authors compared two different EDs and a placebo and, interestingly, the positive effects were found with only one of EDs. In conclusion, muscle strength, muscle power and anaerobic power were not affected by the consumption of an ED, PL or no beverage at all (CTL). Whether similar findings would be obtained with different populations, varying volumes of EDs, and under testing conditions outside of the laboratory scenario are still areas for further study. Furthermore, studies including EDs should
also focus on the possible additive or synergistic effects among the various ingredients commonly used. Acknowledgments All authors approved the final version of the paper. No funding was received to conduct this study. The authors report no conflict of interest.
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