Caffeine in Fitness and Exercise

Does caffeine have beneficial effects on exercise, and if so what are they? Will it have any detrimental effects on performance? What sports would it be beneficial in?

Caffeine is the most highly consumed stimulant throughout the world, with over 500 million cups of coffee consumed everyday. It is found naturally in coffee beans, tea leaves and cocoa, and is contained in numerous soft drinks, confectionary items, tea and coffee.

Caffeine is a behaviourally active substance that belongs to a group of lipid-soluble purines, the chemical name being 1,3,7-trimethylxanthine. It is absorbed rapidly from the intestinal tract with the peak plasma concentration being reached within an hour. The blood caffeine concentrations have a half life of about 3-6 hours meaning that it clears from the body relatively quickly. It is the aim of this investigation to determine the particular effect caffeine has on specific aspects of sports performance.

The optimum dosage an athlete should take will depend on their reasoning for taking the drug, however there is evidence to show that there is no relationship between the dosage consumed and the response gained.

In a study by Pasman WJ et al. it was found that endurance performance, specifically time to fatigue, was increased in all the athletes that were administered caffeine when compared to the placebo. However it was also found that there was no dose-response relationship. The subjects were administered 5,9 or 13 mg of caffeine per kilogram body mass 1 hour before cycling at 80% of maximal power in a VO2 max test. All trials showed a 24% improvement when compared with the non-caffeine consuming placebos. More notably there was no additional benefit when caffeine quantities were consumed above 5 mg per kilogram body mass.

Benefits of Caffeine in Training

Caffeine can have benefits for strength training. It was found in a study by T.A.Astorino et al that although caffeine did not noticeably improve their subjects 1 repetition maximum (1RM) (leg press and barbell bench press), when training at 60% improvements were noticed. Although when working at 60% of the 1RM the weight lifted did not change, muscular endurance was shown to increase by 11-12% with the use of caffeine when compared to placebo. Although this does not directly show that caffeine does not increase the 1 repetition maximum, it does show that the subject can train for longer, and this will indirectly be beneficial in progressing the 1RM because it means the muscles will have to become used to more work, therefore grow to meet the demands placed on them. From this we can see that ingesting caffeine can benefit strength training for sports that require larger muscle masses such as Rugby (union and league), Lacrosse or American Football. Consuming a highly caffeinated energy drinks prior to gym training should increase the benefits gained from strength training.

Caffeine has also been shown to have positive effects on endurance sports. It was found in a study by Costill et al. that ingesting caffeine stimulated Free Fatty Acid (FFA) mobilisation, retarded depletion of muscle glycogen, and therefore enhanced endurance exercise performance. Prior to this, research on animals and humans suggested that elevating plasma FFA spared muscle glycogen and therefore extended exercise capacity. It has been found that the FFA concentration rises after an injection of heparin (this substance stimulated FFA mobilisation and subsequent oxidation). Like Heparin, caffeine also mobilises Free Fatty Acids. Costill investigated caffeine's effect on muscle glycogen levels, the metabolic mixture in exercise, and the endurance performance in athletes. In this study, Costill chose 9 trained, male and female athletes, exercising on a cycle ergometer at 80% of their maximal oxygen uptake (VO2max) until exhaustion. Blood samples where taken before and during the experiment to determine Plasma lactate, FFA and glucose. It was found that the subjects where able to exercise 20% longer, having 1 hour prior to the test consumed 330mg caffeine, when compared to an original test, taken 3 days earlier, where a placebo was used. Free Fatty Acids where found not to differ significantly between conditions, but the caffeinated drink used was seen to significantly increase plasma glycerol levels. With caffeine, fat oxidation is significantly higher for the duration of the experiment, with 118g oxidised compared to 57g without caffeine. Costill’s study demonstrated that the ingestion of caffeine before exercise increased the rate of lipolysis during sustained exercise. This is significant because an increased rate of lipolysis could spare liver and muscle glycogen in the early stages of endurance exercise for later use. These benefits would be ideal for marathon runners where they are exercising between 2-3 hours. Having glycogen stores used later would be very beneficial. It is also important to note that having ingested caffeine, the subjects perceived the exercise to be easier, possibly demonstrating a psychological effect.

Psychological Effects of Caffeine

The Psychological effects of caffeine must also be noted. Sökmen and Bülent-Armstrong have shown that there is no difference in exercise performance when taking lower doses as opposed to higher doses. In fact there are benefits in taking caffeine at lower doses before intense training. It was found that it can be taken gradually at low doses to avoid tolerance over a 3-4 day period prior to intense training as this helps to sustain exercise intensity without affecting sensitivity to the drug, which may increase the subjects tolerance. It also improves cognitive aspects of performance, such as concentration, if an athlete has not slept well the night before, helping the athlete to focus more on their performance.

The ability of caffeine to improve concentration was also found in a military study by Gillingham et al, examining the effect of caffeine on target detection and rifle marksmanship during simulated combat operations. Caffeine ingestion was seen to improve engagement speeds during vigilance exercises after 2.5 hour loaded run and then 2.5 hour shooting exercises. This shows evidence that caffeine can help to maintain alertness in stressful situations, like that which an athlete may face such as the biathlon (cross-country skiing and shooting). The evidence shows caffeine ingestion improves the speed of target recognition after strenuous exercise, and this is very beneficial for biathletes or those in similar sports as it can improve performance.

Drawbacks of Taking Caffeine when Training

Other studies suggest, however, that caffeine may also have a negative effect on training. Graham T.E et al. tested the suggested adverse effect that caffeine-induced diuresis leads to fluid and electrolyte loss and a decrease in plasma volume. In a comparative study between caffeine and coffee intake, the subjects urine was tested an hour after intake and after exercise. Graham et al found no difference in urine output between either caffeine or coffee. Quantitative measurements of body mass loss, sweat rates, plasma volume and electrolytes did not find and significant change. The reason for this is that while caffeine is a mild diuretic it takes several hours for changes in rennin to occur. The presumable reason for this is that exercise takes place within a shorter period than the time required for caffeine to noticeably act as a diuretic, and overrides the potential for fluid loss. This demonstrates that the concern over athletes becoming dehydrated after consuming caffeine is unfounded. Wemple et al. gave evidence that caffeine intake results in mild diureses, however if exercise had taken place there was no diuretic effect. It is also to note in either case, the diureses did not provide measurable effects on plasma volume, rate of sweat perfusion or urine osmolarity.

Caffeine Addiction

There is evidence of a physical dependence on caffeine. Strain et al. discovered substance dependency in caffeine, where dependence is characterised by tolerance, withdrawl symptoms, taking the substance in larger doses and persistent desires for caffeine. Withdrawl symptoms include headaches, mood changes, drowsiness and fatigue. Dependency can develop within 3 days of regular consumption. Symptoms develop between 12-24 hours, peaking 24-48 hours and lasting around 7 days. The dependency is generally mild with some subjects not presenting a dependency. Strain et al. found that the syndrome is similar to substance dependency syndromes for other psychoactive drugs. A few individuals also presented with caffeine-induced anxiety attacks. Although evidence for caffeine dependency exists, the effects are generally very mild. An athlete’s performance should not demonstrate any noticeable adverse affect.

In conclusion, it has been shown that caffeine does have a definite effect on exercise performance, although it benefits different exercises, sports and types of training in different ways. We can see the most noticeable effect gained in endurance training. The least effect would be during one repetition maximum tests although it does provide benefits in strength training.

The negative effects, both psychological and physiological although present are minimal when compared to the potential gains. Caffeine, when taken in lower doses should benefit athletic performance in most sports.

References

Pages 576-580
Exercise Physiology. Energy, Nutrition and Human Performance (Sixth Edition)
McArdle, Katch & Katch
Published by Lippincott Williams & Wilkins

Costill DL, et al.
Effects of caffeine ingestion on metabolism and exercise performance.
Medicine, Science and Sports Exercise 1978;10:155

Caffeine and Exercise; Metabolism, Endurance Performance
Terry E. Graham
Sports Med 2001; 31(11):785-807

Effects of caffeine ingestion on one-repetition maximum muscular strength.
Todd A. Astorino, Riana L. Rohmann and Kelli Firth,
Eur J Applied Physiology (2008) 102:127-132
Springer-Verlag 2007

Caffeine Use in Sports: Considerations for the Athlete
Sökmen, Bülent – Armstrong