Caffeine and Endurance
Reviewed by Jeffrey Rocco, M.D.

Introduction Caffeine continues to be one of the most studied and consumed ergogenic ingredients. Researchers are constantly re-designing studies to get a clear indication of how caffeine improves performance. Each year new studies are published on the effects of caffeine on endurance activity. Some of the more recent studies will be reviewed in this newsletter.

For years athletes have been using caffeine in various doses to improve their performance. Everyone knows that a strong cup of Java gives you that alertness and sense of extra energy. Drink three cups of leaded Starbucks coffee and you'll feel like you want to run a marathon! So…does the caffeine simply make you want to run that marathon or does the caffeine actually help you finish it faster? Many professional endurance athletes use caffeine to enhance their performance. Prior to 2004, caffeine was banned by the US Olympic Committee, World Anti-Doping Association (WADA) and US Anti-doping association. The level at which caffeine was banned was 12mcg/ml in urine, which requires about 1,200 mg of pure caffeine or 8 cups of strong coffee. However, this decision was reversed in 2004, allowing the use of caffeine in elite level sports. Based on the literature, the dose required to elicit an ergogenic effect is much less than the level banned (3 - 9 mg·kg-1 body mass which is approximately 210-630 mg for a 70 kg athlete). There is some controversy surrounding the lifted ban since caffeine does have some ergogenic properties but it can also be dangerous if abused. Back to running the marathon: caffeine can help you run it faster, but only if done correctly, so let's talk about who can benefit from caffeine and how it can be properly used.

Caffeine stimulates the central nervous system (CNS), increases the release of adrenaline, increases the use of body fat as fuel and spares glycogen. Adrenaline release is accomplished through caffeine's effect on epinephrine and nor-epinephrine. Many athletes seek this CNS excitatory response to increase alertness and to give them the extra 'energy' needed for their workouts. More importantly, caffeine mobilizes free fatty acids (FFA) in the blood. Increased FFA in the blood allows the body to use fat as a fuel source. The use of fat as fuel allows the body to spare glycogen (carbohydrates) for later use in exercise.


Notes to consider:

• Caffeine is often mistakenly classified as a diuretic. Diuresis (elimination of water from the body) can complicate an individual's water balance, which determines how efficient he/she will perform. Diuretics not only dehydrate the body, they can cause bowel movements and gastric distress. However, research performed on trained athletes has NOT FOUND caffeine to cause a diuretic effect. See Diuretic Effects of Caffeine for more details.


• Caffeine has thermogenic properties. This means ingestion of caffeine can raise your heartbeat and core body temperature. Recent research has not shown this to be true (Roti, Miller). Two separate placebo –controlled studies have shown no difference in urinary or plasma electrolytes, thermoregulatory variables or cardiovascular variables, even in warm, humid environments.


• Because our body has the ability to build a tolerance to caffeine, it has been suggested to athletes to abstain from caffeine use days/weeks prior to a race. The theory behind this method is to allow the body to become accustom to not having caffeine and with reintroduction the ergogenic effect will be increased. However, research indicates that the body will respond to the withdrawal from caffeine experienced overnight as much as abstaining from caffeine over prolonged periods of time. The half life (time of clearance) of caffeine in the body is 6 hours. A study by Roti et al. showed improved exercise heat tolerance in a group chronically receiving caffeine compared to placebo.
  

Abstracts supporting use of caffeine with trained athletes:

A study using well-trained cyclists also supports the use of caffeine during competition to improve performance. In this study, 15 cyclists ingested different levels of caffeine in addition to a carbohydrate-electrolyte drink during a time trial. The highest caffeine doses (225 and 320 mg) resulted in a 5% increase in power relative to the control trials without caffeine (308 + 9 and 309 + 10W versus 295 + 9W, respectively). The amount of caffeine ingested during this study were relatively small, and yielded caffeine concentrations in the urine of less than 5 mg/L for the participants.(Kovacs)

Another recent study supported the use of caffeine both before and during performance. This study involved a cycling time trial which occurred after 2 hours of steady state cycling at 70% of VO2 max. They used several different patterns of caffeine ingestion, including different levels of before and during trial caffeine intake. None of the methods caused an increase of urine caffeine concentrations to exceed 12ug/ml. Their results also demonstrated that ingestion of 1-3 mg/kg of caffeine produced the same level of performance enhancement (~3%) as did the higher levels of caffeine intake (6 mg/kg). (Cox)

Recently published research supporting use of caffeine with trained athletes:

Kovacs et al. (1998) studied well-trained cyclists. The results of this study support the use of caffeine during competition to improve performance. In this study, 15 cyclists ingested different levels of caffeine in addition to a carbohydrate-electrolyte drink during a time trial. The highest caffeine doses (225 and 320 mg) resulted in a 5% increase in power relative to control trials without caffeine (308 + 9 W and 309 + 10W versus 295 + 9W, respectively). The amount of caffeine ingested during this study was relatively small, and yielded caffeine concentrations in the urine of less than 5 mg/L for the participants.

Another recent study by Cox et al. (2002) supported the use of caffeine both before and during cycling performance. This study involved a cycling time trial which occurred after 2 hours of steady state cycling at 70% of VO2max. Several different patterns of caffeine ingestion were utilized, including different levels before and during the trial. None of the methods caused an increase in caffeine concentration in the urine to exceed 12ug/ml. These results also demonstrate that ingestion of 1-3 mg/kg of caffeine produced the same level of performance enhancement (~3%) as did the higher levels of caffeine intake (6 mg/kg).

Yeo et al. (2005) published a recent study that looked at the effects of caffeine ingestion on carbohydrate oxidation. Eight male cyclists exercised for 120 min on three separate occasions. During exercise, cyclists ingested either a 5.8% glucose solution (Glu; 48 g/h), 5.8% glucose solution with caffeine (Glu+Caf, 48 g/h + 5 mg·kg·h-1), or plain water (Wat). Average exogenous CHO oxidation over the 90- to 120-min period was 26% higher (p < 0.05) in Glu+Caf (0.72 +/- 0.04 g/min) compared with Glu (0.57 +/- 0.04 g/min). Total CHO oxidation rates were higher (p < 0.05) in the CHO ingestion trials compared with Wat, but they were highest when Glu+Caf was ingested (1.21 +/- 0.37, 1.84 +/- 0.14, and 2.47 +/- 0.23 g/min for Wat, Glu, and Glu+Caf, respectively; p < 0.05). There was also a trend (P = 0.082) toward an increased endogenous CHO oxidation with Glu+Caf (1.81 +/- 0.22 g/min vs. 1.27 +/- 0.13 g/min for Glu and 1.12 +/- 0.37 g/min for Wat). In conclusion, compared with glucose alone, 5 mg/kg caffeine (approximately 350mg caffeine for a 150lb athlete) co ingested with glucose increases exogenous CHO oxidation, possibly as a result of an enhanced intestinal absorption.

Doherty et al, (2005) recent meta-analysis of the use of caffeine ingestion on rate of perceived exertion (RPE) supports the use of caffeine as an ergogenic aid. Twenty-one studies were reviewed. In comparison to placebo, caffeine reduced RPE during exercise by 5.6% (95% CI). These values were significantly greater (p<0.05) than RPE obtained at the end of exercise (RPE % change, 0.01%; 95%). In addition, caffeine improved exercise performance by 11.2% (95% CI; 4.6 17.8%). Regression analysis revealed that RPE obtained during exercise could account for 29% of the variance in the improvement in exercise performance. These results demonstrate that caffeine reduces RPE during exercise, which may partly explain the subsequent ergogenic effects of caffeine on performance.

In a 2004 study, Doherty et al. investigated the effects of caffeine ingestion on a 'preloaded' protocol that involved cycling for 2 min at a constant rate of 100% maximal power output immediately followed by a 1-min 'all-out' effort. Eleven male cyclists completed a ramp test to measure maximal power output. On two other occasions, the participants ingested caffeine (5 mg·kg) or placebo. Ratings of perceived exertion (RPE; 6-20 Borg scale) were lower in the caffeine trial by approximately 1 RPE point at 30, 60 and 120 s during the constant rate phase of the preloaded test (p <0.05). The mean power output during the all-out effort was increased following caffeine ingestion compared with placebo (794+/-164 vs. 750+/-163 W; p=0.05). Blood lactate concentration 4, 5 and 6 min after exercise was also significantly higher by approximately 1 mmol. in the caffeine trial (p <0.05). These results suggest that high-intensity cycling performance can be increased following moderate caffeine ingestion and that this improvement may be related to a reduction in RPE and an elevation in blood lactate concentration.

McClellan and Bell (2004) looked at the ergogenic role of ingesting coffee (COF) prior to the subsequent ingestion of anhydrous caffeine (CAF). Thirteen subjects performed 6 rides to exhaustion at 80 % VO2max 1.5 h after ingesting combinations of COF, decaffeinated coffee (DECOF), CAF, or placebo. Time to exhaustion was significantly greater for all trials with CAF compared to placebo. In conclusion, the prior consumption of COF did not alter the ergogenic effect of the subsequent ingestion of anhydrous CAF.

Brinbaum et al. (2004) observed the physiological effects of caffeine on cross-country runners during submaximal exercise. Ten college-age subjects (5 women; 5 men) volunteered to participate in this study. After completing a VO2max test, each subject completed 2 30-minute runs at 70% VO2max on the treadmill, 1 after ingesting caffeine and the other after ingesting a placebo. Tidal volume (TV), alveolar ventilation (VA), and rating of perceived exertion (RPE) were significantly different (p < 0.05) between treatment and control groups. The results suggest that the ingestion of caffeine at 7 mg·kg of body weight prior to submaximal running might provide a modest ergogenic effect via improved respiratory efficiency and psychological lift.

It was previously thought that caffeine's ergogenic effect was limited to endurance events lasting greater than 2 hours. Based on the latest clinical research, evidence now suggests that individual's participating in short bouts of exercise may also benefit from the use of caffeine. The mechanism of action appears to be quite different and varied depending on the length of activity. There are very few controlled studies looking at the effects of caffeine on edurance events lasting longer than 2 hours.

For low to moderate intensity activities
Caffeine has been shown to stimulate the use of stored fat (free fatty acids). This in-turn spares carbohydrates and allows athletes to exercise longer.

For high Intensity activities
Caffeine improves the athlete's rate of perceived exertion and oxidation of ingested carbohydrates as well as allowing for higher lactate levels to be reached. These physiological changes allow the athlete to push a little harder and may elicit improved performance.

The use of caffeine is ubiquitous, there do appear to be significant performance benefits. Caffeine is not a banned substance, however a survey of 140 competitors at the 2005 Ironman Triathlon World Championships revealed only 72% of the athletes were aware of this. 89% of athletes indicated they planned on using caffeine either before or during competition. Levels of plasma caffeine taken immediately post race indicated that athletes typically finish with quantities of caffeine that have been shown to improve endurance performance (i.e., approximately 20 micromol/L or a dose of > or = 3 mg/kg body weight). (Desbrow)

Recommendations:
Using caffeine as an ergogenic aid should be done with caution. Caffeine's stimulatory effect on the central nervous system can pose harm to individuals at risk. One suggested protocol is to limit your caffeine intake for 3-4 days leading up to an event. On the day of your event consume caffeine as suggested below. If you choose to use caffeine as an ergogenic aid surrounding activity, consume 3 - 9 mg·kg body weight (that's 210mg to 630mg for a 150 lb athlete). This can be a large amount of caffeine for some athletes, be sure to experiment by gradually increasing the amount of caffeine you ingest. Excess caffeine can cause anxiety, irritability, delirium and hallucinations. Be aware of the possible side effects (mentioned above). Athletes should assess how their bodies respond to caffeine to determine if the use if beneficial for them. WADA's removal of caffeine from its banned substance list does raise some concerns. If abused, caffeine can be detrimental and dangerous. Caffeine's actions on the CNS, excitory response can cause serious damage if abused. We strongly urge all athletes wanting to use caffeine to do so under caution.

Typical Caffeine amounts:
Soda: 35 - 90mg caffeine
Cup of Coffee: 50 - 150mg caffeine
Cup of tea: 10 - 80mg caffeine
Guarana: active ingredient is caffeine (8% to 15%)
Green tea herb: active ingredient is caffeine (0% to 15%)
I.E. 100mg of Green Tea extract provides between 0mg and 15mg total caffeine content.

References:
Costill DL, Dalsky GP, Fink WJ. Effects of caffeine ingestion on metabolism and exercise performance. Med Sci Sports Exercise. 1978; 10: 155-158

Cox GR, Desbrow B, Montgomery PG, Anderson ME, Bruce CR, Macrides TA, Martin DT, Moquin A, Roberts A, Hawley JA, Burke LM. Effect of different protocols of caffeine intake on metabolism and endurance performance. J Appl Physiol. 2002; 93(3):990-9.

Desbrow B, Leveritt M. Awareness and use of caffeine by athletes competing at the 2005 World Ironman Triathlon Championships. Int j Sport Nutr Exerc Metab. 2006 Oct;16(5):545-58.

Essig D, Costill DL, Van Handel RJ. Effects of caffeine ingestion on utilization of muscle glygogen and lipid during leg ergometer cycling. International Journal of Sports Med. 1980; 1:86-9

Fisher SM, McMurray RG, Berry M, et al. Influence of caffeine on exercise performance in habitual caffeine users. International Journal of Sports Med 1986;7:276-280

Greer F, Friars D, Graham TE; Comparison of caffeine and theophylline ingestion: exercise metabolism and endurance.J Appl Physiol 2000 Nov;89(5):1837-44 Department of Human Biology and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada N1G 2W1.

Ivy JL, Costill DL, Fink WJ, et al. Influence of caffeine and carbohydrate feedings on endurance performance Med Science Sports and Exercise. 1979; 11;6-1

Kovacs EMR, Stegen JHCH, Brouns F. Effect of caffeinated drinks on substrate metabolism, caffeine excretion, and performance. J Appl Physiol 1998; 85: 709-715.

Millard-Stafford ML, Cureston KJ, Wingo JE, Trilk J, Warren GL, Buyckx M. Hydration during warm, humid conditions: effect of a caffeinated sports drink. Int J Sport Nutr Exerc Metab. 2007 Apr;17(2):163-77.

Roti MW, Casa DJ, Pumerantz AC, Watson G, Judelson DA, Dias JC, Ruffin K, Armstrong LE. Thermoregulatory responses to exercise in the heat: chronic caffeine intake has no effect. Aviat Space Environ Med. 2006 Feb;77(2):124-9.

World Anti-Doping Association http://www.wada-ama.org

Caffeine Drug Info: http://www.nlm.nih.gov/medlineplus/druginfo/uspdi/202105.html

Yeo SE, Jentjens RL, Wallis GA, Jeukendrup AE. Caffeine increases exogenous carbohydrate oxidation during exercise. J Appl Physiol. 2005 Sep;99(3):844-50. Epub 2005 Apr 14.

M. Doherty, P. M. Effects of caffeine ingestion on rating of perceived exertion during and after exercise: a meta-analysis. Smith Scandinavian Journal of Medicine & Science in Sports. Volume 15 Issue 2 Page 69 - April 2005

Doherty M, Smith P, Hughes M, Davison R. Caffeine lowers perceptual response and increases power output during high-intensity cycling. J Sports Sci. 2004 Jul;22(7):637-43. Department of Sport, Exercise and Biomedical Sciences, University of Luton, Luton LU1 3JU.

McLellan TM, Bell DG. The impact of prior coffee consumption on the subsequent ergogenic effect of anhydrous caffeine. Int J Sport Nutr Exerc Metab. 2004 Dec;14(6):698-708.

Birnbaum LJ, Herbst JD. Physiologic effects of caffeine on cross-country runners. J Strength Cond Res. 2004 Aug;18(3):463-5.