The Effects of Energy Drinks on Sport Performance
Conclusions derived from existing research differ on the significant effect of components of energy drinks on performance, despite most concluding significant improvements in performance (Ganio et al, 2010). Branded drinks have been developed on the basis of findings within such research, which has gone on to provide numerous opportunities for further research. Existing research will be critically analysed to come to a conclusion of the effects on performance of energy drinks.
Research as far back as the 1970s (Burke, 1995) has found that caffeine doses at about 5-6mg.kg-1 have an effect on stimulation of numerous bodily functions, including muscles and the central nervous system, during exercise to improve sporting performance (Burke, 1995). As much of the existing literature on caffeine effects is not contemporary; it is questionable as to whether research methods are up to date with modern technology. For example, Engels et al (1999) found positive correlations between caffeine ingestion and augmentation of arterial blood pressure, suggesting that this would lead to an increase in substrates being delivered to working muscles. However these increases were found using auscultation, which is not the most reliable technique. Increases in arterial pressure through caffeine ingestion in Red Bull can have positive effects on both aerobic and anaerobic endurance along with mental performance, such as memory recall and concentration (Alford et al, 2001). It may be noted that the research design was double blinded and consisted of both preliminary and subsequent studies with additional controls, thus increasing the reliability of this study. Adversely, it may be argued that the highly controlled conditions of the reaction time and concentration task (a psychomotor test battery and number cancelling from a pseudo-random list of characters) reduces external validity. Although Alford et al (2001) found improvements to ‘aerobic and anaerobic endurance’, in more recent research, it remains unclear as to whether caffeine produces any effect on anaerobic activities; Astorino et al (2008) discovered that caffeine does not have an effect on muscular strength or short, intense exercises (1RM).
Research by Spriet et al (1992) revealed the use of caffeine in fluids helps reduce the amount of muscle glycogenolysis in the first 15 minutes of exercise, thereby sustaining glucose in the muscles and increasing the oxidation of fat. Costill et al (1978) found similar results but discovered evidence that caffeine increases fat oxidation from the start of exercise by increasing free fatty acids in the plasma; helping to maintain glucose levels to continue high intensity exercise later on. However, caffeine has been found to improve performance not only through changing substrate utilisation but also by increasing Beta endorphins (Ivy et al, 2009). Ivy et al (2009) could have shown different results, in terms of substrate utilisation, compared to other studies because trial time and distance were not set to a specific amount; participants had to complete a session equivalent to an hour at 70% VO2max so all subjects exercised different amounts potentially leading to subjects using different substrates to each other.
Tarnopolsky (2008) concluded that improvement in endurance following caffeine administration is multi-factoral, including improvement in excitation-contraction coupling in skeletal muscle, calcium release from sarcoplasmic reticulum and reductions in pain perception (PP) and perceived effort (RPE). It should be made aware that much of the physiologically assessed research was conducted in lab experiments involving rats, therefore making it difficult to generalise to humans. The reduction in PP and RPE results in an increase in tolerance to noxious afferent signals experienced during fatiguing contractions (providing an ergogenic aid to performance). The opinion of Borg (1982) is that RPE is the greatest indicator of physical strain integrating various signals elicited from peripheral musculoskeletal structures, central nervous system, cardiovascular and respiratory functions. RPE scales are very subjective and will differ between individual participants, especially when considering pre-existing pain threshold and perceived effort differences, which may be innate or trained. A practical application of this assumption is reflected in a study by Cole et al (1996), whereby RPE was measured during 30 minute trials of isokinetic variable resistance cycling, in either caffeine or placebo conditions. Participants cycled at a fixed rating of 9 on the Borg scale and total work performed was significantly higher in the caffeine condition, suggesting that increased performance was resulted by an alteration in the participants’ neural perception of effort.
Rehydration is important in prolonged exercise as the body’s water volume decreases rapidly through its attempts to maintain core body temperature through sweating, therefore leading to dehydration and a decrease in performance (Armstrong et al, 1985). It has been found that although caffeine drinks and water rehydrate performers, carbohydrate electrolyte drinks do so significantly better (P<0.05) (Gonzalez-Alonso et al, 1992).
Compiling this previous literature provides a conclusion that caffeine certainly has a positive effect on muscular endurance and cognitive functioning, including intermittent activity with prolonged duration, such as that experienced in team sports as found by Goldstein et al (2010).
However many energy drinks, including those containing caffeine, can have side effects. Various literature exists highlighting adverse effects of the administration of caffeine. One extreme example is that over consumption of caffeine can result in symptoms of tachycardia leading to hospitalisation (Popke, 2010).
Other side effect of energy drinks is the emergence of Gastro-Intestinal discomfort (G.I.D), including refluxing, nausea, bloating and cramping, which lead to decreased sporting performance (Van Nieuwenhoven, 2005; Sadowska et al, 2009). Energy drinks can also affect performance by their sweet taste and how much they tend to “fill” the stomach (Beckers et al, 2000). When trying to avoid these affects the avoidance of hydrating results in G.I.D anyway due to lower blood plasma volumes, leading to reduced blood flow to the intestines because of high blood viscosity (Beckers & Rehrer, 2000). Therefore it needs to be assessed whether the use of energy drinks as opposed to water produce a net improvement in performance. The appearance of G.I.D usually comes about from longer duration exercise, with Van Nieuwenhoven et al (2003) finding that as many as 67% of marathon runners suffer. G.I.D derived from the use of sports drinks can increase run time by 2.4% whilst the energy element of the drink may only improve performance by 0.3%; therefore leading to a net detrimental affect (Burke et al, 2005). However, this assessment was only a snap shot of a prolonged run as it took data from 200m of a 21.1Km run.
Reliable physiological methods such as catheters have been used to assess the resting values for gastric pH and gastro-oesophageal reflux by revealing no differences in G.I.D for water, energy drink or sports drinks with added caffeine after prolonged cycling trials (Van Nieuwenhoven et al, 2000). However, other studies used questionnaires to analyse their data but this could be problematic due to other variables affecting participants’ decisions, such as tiredness, or illness (Sadowska et al 2009; Van Nieuwenhoven et al, 2005). This could be counteracted by using many subjects to normalise results as done by Van Nieuwenhoven et al (2005), who found that sports drinks, with caffeine or not, gave more incidences of nausea than water but not more severely. However it has been found that G.I.D in prolonged exercise can be reduced by ingesting drinks with two carbohydrate transporters compared to one (Jeukendrup, 2004). For example, the drink Rehydrate carries glucose and fructose and can increase performance by 7.1% on a treadmill VO2max test, regardless of any side effects (Snell, 2010).
On the other hand, a positive side effect of energy drinks, as found by Saunders (2004) is the prevention of muscle damage by adding protein. Creatine Phosphokinase can be reduced by 83% when adding protein to a carbohydrate drink, showing that muscle damage is lowered and recovery will be faster (Saunders, 2004).
Most caffeine containing energy drinks are also supplemented with other compounds such as amino acids to improve performance (Ganio et al, 2010). Many studies, such as those by Saunders et al (2004), Ivy et al (2003) and Niles et al (2001) have examined the use of adding amino acids to a standard carbohydrate-electrolyte drink to assess the comparison of performance. Trials used in the studies were either exercise to exhaustion tests such as by Saunders (2004) or long endurance activities by Madsen et al (1996). Many studies, such as Madsen et al (1996) & Saunders et al (2004), masked the appearance and taste of the beverages to create a double blind design to ensure no favourability between trials. Studies such as one by Niles et al (2001) who did not use a blind design present a reliability issue whether performance is improved due to protein or not. To find results purely on the effects of energy drinks, subjects need to be fasted so their blood glucose levels aren’t altered from food intake (Porte & Woods, 1981). Many studies such as those by Saunders (2004); Ivy et al (2003) & Saunders (2009) did include a fasting period prior to entering the laboratory to overcome this potential influence on results. In contrast, Madsen et al (1996) required the subjects to have a high carbohydrate meal four hours before trials, perhaps showing why there was no significant improvement in performance from carbohydrate or carbohydrate-protein drinks because the subjects already had high carbohydrate levels in their system to avoid glycogen depletion and therefore fatigue.
Differing results occurred in trials regardless of the intensity of exercise. For example many studies, such as Ivy et al (2003), that used exercise to exhaustion in cycle trials or prolonged trials without reaching exhaustion, such as Saunders (2009), found improvements in performance using protein. Conversely, van Essen & Gibala (2006) used a trial that didn’t require complete fatigue to occur and found no significant improvement in cycle performance from added protein. The same inconclusiveness arose from using running as the form of exercise as found by Niles et al (2001) and Betts et al (2005) who achieved different results with the latter finding no significant benefit of adding protein whilst Niles et al (2001) found a 21.2% increase in performance.
The only main difference between studies is that with the investigations where protein improved performance it was added to the drink in place of the carbohydrate, whereas with failing improvement studies; the protein was added to the carbohydrate. For example, Niles et al (2001) had their carbohydrate-protein drink contain 112g of dextrose and maltodextrin and 40.7g of protein and the carbohydrate drink contained 152.7g of dextrose and maltodextrin. This means both drinks had the same mass of supplement. However, for the carbohydrate drink in the study by Betts et al (2005) there was 1.2g.Kg-1.h-1 for study A and 0.8g.Kg-1.h-1 for study B. These substances contained 6.2% glucose and 3.1% fructose. However, the carbohydrate-protein drink added 1.5% glutamine, therefore increasing the amount of supplement in the drink. This could explain the results of some studies in not increasing performance as the carbohydrate-protein drink still contained a lot of carbohydrate. This suggests that protein will help increase performance more than solely carbohydrate but only in large amounts or if carbohydrate is lacking.
In conclusion, combinations of carbohydrate-electrolyte with caffeine and carbohydrate-electrolyte with amino acids drinks are both beneficial, with most studies finding a significant positive effect on performance, due to the increased psychological focus and physiological substrate utilisation (Ganio et al, 2010). Further research can be conducted to determine whether it is amino acids or caffeine that causes most of this positive effect. As technology becomes increasingly advanced, there will be more accurate and easier ways to research this topic. However, as the existing research is expansive and vast, it is unclear as to whether further conclusions have been made that were not analysed in this review.
References
Alford, C., Cox, H., & Wescott, R. (2001). The effects of Red Bull Energy Drink on
human performance and mood. Amino Acids, 21(2), 139-150.
Armstrong, L.E., Costill, D.L., & Fink, W.J. (1985). Influence of diuretic-induced
dehydration on competitive running performance. Medicine and Science in Sport and Exercise, 17(4), 456-461.
Astorino, T.A., Rohmann, R.L., & Firth, K. (2008). Effect of caffeine ingestion on
one-repetition maximum muscular strength. European Journal of Applied Physiology, 102(2), 127-132.
Beckers E.J., & Rehrer, N.J. (2000). Gastric emptying of liquids and the effects of
exercise. International Journal of Sports Medicine, 4(1), 51-60.
Betts, J.A., Stevenson, E., Williams, C., Sheppard, C., Grey, E., & Griffin, J. (2005).
Recovery of endurance running capacity: effect of carbohydrate-protein mixtures. International Journal of Sports Nutrition and Exercise Metabolism, 15(6), 590-609.
Borg, G.A.V. (1982). Psychophysical bases of perceived exertion. Medicine and
Science in Sports and Exercise, 14(5), 377-381.
Burke, L. (1995). The Complete Guide to Food for Sports Performance, p127. Allen
& Unwin.
Burke, L.M., & Read, R.S. (1993). Dietary supplements in sport. International
Journal of Sports Medicine, 15(1), 43-65.
Burke, L.M., Wood, C., Pyne, D.B., Telford, D.R., & Saunders, P.U. (2005). Effect of
carbohydrate intake on half marathon performance of well trained runners. International Journal of Sports Nutrition and Exercise Metabolism, 15(6), 573-589.
Cole, K.J., Costill, D.L., Starling, R.D., Goodpaster, B.H., Trappe, S.W. & Fink, W.J.
(1996). Effect of caffeine ingestion on perception of effort and subsequent work production. International Journal of Sport Nutrition, 6(1), 14-23.
Costill, D.L., Dalsky, G.P., & Fink, W.J. (1978). Effects of caffeine ingestion on
metabolism and exercise performance. Medicine and Science in Sport and Exercise, 10(3), 155-158.
Engels, H.J., Wirth, J.C., Celik, S., & Dorsey, J.L. (1999). Influence of caffeine on
metabolic and cardiovascular functions during sustained light intensity cycling and at rest. International Journal of Sport Nutrition, 9(4), 361-370.
Ganio, M.S., Klau, J.F., Lee, E.C., Yeargin, S.W., McDermott, B.P., Buyckx, M.,
Maresh, C.M., & Armstrong, L.E. (2010). Effect of various carbohydrate-electrolyte fluids on cycling performance and maximal voluntary contraction. International Journal of Sport Nutrition and Exercise Metabolism, 20(2), 104-114.
Goldstein, E.R., Ziegenfuss, T., Kalman, D., Kreider, R., Campbell, B., Wilborn, C.,
Taylor, L., Willoughby, D., Stout, J., Graves, B.S., Wildman, R., Ivy, J.L., Spano, M., Smith, A.E., & Antonio, J. (2010). International society of sports nutrition position stand: caffeine and performance. Journal of the International Society of Sports Nutrition, 7, 15.
Gonzalez-Alonso, J., Heaps, C.L., & Coyle, E.F. (1992). Rehydration after exercise
with common beverages and water. International Journal of Sports Medicine, 13, 399-406.
Ivy, J.L., Jammer, L., Ding, Z., Wang, B., Bernard, J.R., Liao, Y., & Hwang, J.
(2009). Improved cycling time-trial performance after ingestion of a caffeine energy drink. International Journal of Sport Nutrition and Exercise Metabolism, 19(1), 61-78.
Ivy, J.L., Res, P.T., Sprague, R.C., & Widzer, M.O. (2003). Effect of carbohydrate-
protein supplement on endurance performance during exercise of varying intensity. International Journal of Sports Nutrition and Exercise Metabolism, 13, 382-395.
Jeukendrup, A.E. (2004). Carbohydrate intake during exercise and performance.
International Journal of Applied and Basic Nutritional Sciences, 20(7), 669-677.
Jentjens, R.L.P.G., Achten, J.U.U.L., & Jeukendrup, A.E. (2004). High oxidation
rates from combines carbohydrates ingested during exercise. Medicine and Science in Sport and Exercise, 36(9), 1551-1558.
Khanna, G.L., & Manna, I. (2005). Supplementary effect of carbohydrate-electrolyte
drink on performance, lactate removal and cardiovascular response of athletes. Journal of Indian Medical Research, 121, 665-669.
Madsen, K., MacLean, D.A., Kiens, B., & Christensen, D. (1996). Effects of glucose,
glucose plus branched-chain amino acids, or placebo on bike performance over 100 km. Journal of Applied Physiology, 81(6), 2644-2650.
Niles, E.S., Lachowetz, T., Garfi, J., Sullivan, W., Smith, J.C., Leyh, B.P., &
Headley, S.A. (2001). Carbohydrate-Protein drink improves time to exhaustion after recovery from endurance exercise. Journal of Exercise Physiology, 4(1), 45-52.
Popke, M. (2010). Buzz Kill. Athletic Business, 34(10), 68-70.
Porte, D., Woods, S.C. (1981). Regulation of food intake and body weight by insulin.
Diabetologia, 20(3), 274-280.
Sadowska, K., Bajerska, J., & Jeszka, J. (2009). The effect of two carbohydrate-
electrolyte drinks on gastrointestinal complaints and physical performance in rowers. International Journal of Sports Medicine, 13(3), 171-176.
Saunders, M. (2009). Does coingestion of carbohydrate and amino acids improve
recovery from endurance exercise? The Physician and Sports Medicine, 37(4), 157-159.
Saunders, M.J., Kane,M.D., & Todd,M.K. (2004). Effects of a carbohydrate-protein
beverage on cycling endurance and muscle damage. Medicine and Science in Sport and Exercise, 36(7), 1233-1238.
Saunders, M.J., Moore, R.W., Kies, A.K., Luden, N.D., & Pratt, C.A. (2009).
Carbohydrate and protein hydrolysate coingestions improvement of late-exercise time-trial performance. International Journal of Sports Nutrition and Exercise Metabolism, 19(4), 337-339.
Snell, P.G., Ward, R., Kandaswami, C., & Stohs, S.J. (2010). Comparison effects of
selected non caffeinated rehydration drinks on short time performance following moderate dehydration. Journal of the International Society of Sports Nutrition, 7(1), 28.
Spriet, L.L., MacLean, D.A., Dyck, D.J., Hultman, G., Cederblad, G., & Graham,
T.E. (1992). Caffeine ingestion and muscle metabolism during prolonged exercise in humans. American Journal of Physiology, Endocrinology and Metabolism, 262(6), E891-E898.
Tarnopolsky, M.A. (2008). Effect of caffeine on the neuromuscular system – potential
as an ergogenic aid. Applied Physiology Nutrition and Metabolism, 33(6), 1284-1289.
Van Essen, M., & Gibala, M.J. (2006). Failure of protein to improve time trial
performance when added to a sports drink. Medicine and Science in Sport and Exercise, 38(8), 1476-1483.
Van Nieuwenhoven, M.A., Brouns, F., & Kovacs, E.M. (2005). The effect of two
sports drinks and water on GI complaints and performance during an 18-km run. International Journal of Sports Medicine, 26(4), 281-285.
Van Nieuwenhoven, M.A., Brummer, R.J.M., & Brouns, F. (2000). Gastrointestinal
function during exercise: comparison of water, sports drink and sports drink with caffeine. Journal of Applied Physiology, 89(3), 1079-1085.
No comments:
Post a Comment