The Effect of Caffeine on Exercise

turn-on-1709210_640Caffeine was on the International Olympic Committee (IOC) doping list until 2003 although this substance is ingested daily by many people including athletes for hundreds of years. It is probably the most widely used performance-enhancing substance in the world. It is well known that caffeine is widely used by athletes during endurance events because of its known properties to reduce fatigue. Likewise, athletes involved in sprints and power events use caffeine to improve their reaction time and maximal power input.

If you are a fan of coffee, you might be interested in the fact that the coffee beans used -arabica and robusta- have a different organic chemical composition and this has a huge influence on the taste and composition of final drink. People prefer arabica beans because they contain almost 60% more lipids and almost twice the concentration of sugar than robusta beans. Robusta beans, on the other hand, contain more caffeine compared to arabica, but caffeine carries a bitter taste which makes an unpleasant taste. The ways in which beans are roasted and the drink is prepared (espresso, brewed coffee, filter) have their influence on the taste and composition of the beverage as well.

Caffeine Effect

Some time ago it was believed that caffeine, due to its stimulation of the central nervous system, mobilizes the free fatty acids from adipose tissues and enhances the fatty acids uptake and fat oxidation. It was thought that utilization of the muscle glycogen by this mechanism is spared. But later studies showed this theory is not completely valid for the exercising athlete. In many studies, after ingestion of caffeine, the free fatty acid concentration in blood did increase, but this did not lead to an increase in fat oxidation or did it affect the rate of muscle glycogen utilization. But, despite the studies’ observation, in most of the studies caffeine did improve performance. There is evidence suggesting that caffeine acts as a central nervous system stimulant. The data suggest that caffeine helps to promote exercise performance by increasing release of exercise-induced β-endorphin (neurotransmitter substances created by the pituitary gland). An increase in β-endorphin is well known to enhance exercise performance through its ability to decrease pain perception and promote euphoria. Other data suggest that caffeine affects the local processing of nervous stimulation by the muscles. During a process of repeated muscle contractions, caffeine helps in reducing the loss of potassium from muscle cells and increase the calcium concentration in the muscle. It is believed this mechanism may influence endurance performance positively.

Caffeine and Exercise Performance

There is consistent evidence supporting the performance enhancing effects of caffeine in the endurance events, especially in very long lasting events. The studies have shown that caffeine consumed 1 h prior to exercise can improve endurance exercise performance. There are reports that caffeine has a positive effect on 1500 m swimming, 1 hour of cycling, 1500 m running, etc. Also, a number of studies have reported a positive effect of caffeine events like middle distance and speed endurance events with duration between 1 to 10 minutes. In short-term high-intensity performance events, it is generally believed caffeine can improve the mechanisms that stimulate central nervous system and neuromuscular function, although results of these studies are not consistent as results of the endurance studies.

Timing of Caffeine Intake and Performance

Caffeine absorption by the body is pretty fast and it can be measured 15 minutes after ingestion. Maximum levels of caffeine in blood are measured 1 hour after intake. On the other hand, it takes 4-6 hours for caffeine blood level to start to decrease notably. Based on this, it is suggested to take caffeine 1 to 1,5 hours before training/event to enhance the performance. In a long lasting events like a marathon, it can be beneficial to consume rehydration drink that contains caffeine during the event.

Caffeine – Doping???

Caffeine was on the prohibited substances list until 2003, with athletes being limited to a urine level below 12 micrograms per millilitre. This equals to around 5-8 cups of coffee consumed within 1-1.5 hours of competition. And now in 2017, caffeine could be added to World Anti-Doping Agency’s prohibited substance list again. It is currently on WADA’s waiting list of prohibited substances.

Some scientists believe that doping level of 12 mg/l is controversial because it has been observed that some athletes excrete caffeine 3-4 times faster than others, despite a similar caffeine intake. Also, some studies have shown that man and women differ in their responses to caffeine and that these differences may be mediated by changes in circulating steroid hormones. It is also known that urinary caffeine excretion amounts are only 1-3% of the total amount of caffeine ingested. In the urinary test, only one caffeine metabolite is measured – trimethylxanthine. But caffeine is metabolized in the liver to other compounds as well, and they are not measured in the test, although they have a stimulating effect.

Caffeine and Fluid Balance

Who ever drinks coffee is familiar with fact that coffee has a diuretic effect. Accordingly, it has often been suggested that coffee intake might lead to dehydration and reduce sports performance. But the studies have shown that not only is moderate caffeine beneficial for endurance performance, they also concluded that it does not contribute to body dehydration. Also, the recent studies and literature reviews on the caffeine intake during regular life activities showed that moderate caffeine consumption does not lead to dehydration. According to Mayo Clinic, up to 400 milligrams of caffeine a day is considered as safe. This is the amount of caffeine in four cups of brewed coffee, 10 cans of cola or two “energy” drinks. So if you drink coffee or beverages that contain caffeine on regular basis, you needn’t worry about dehydration as long as you are consuming adequate fluid amounts in general.

Caffeine and Side Effects

Drinking coffee in a larger amount (>4 mg/kg body weight) may lead to some side effects. Mostly, caffeine irritates the stomach and the intestine, which can lead to gastric acid reflux and diarrhea. You should think of cutting back your coffee intake if you’re experiencing side effects such as: migraine headache, nervousness, insomnia, fast heartbeat, muscle tremors, etc.

And at the end, a little confession of mine:

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