Withdrawal of Caffeine in Athletes

Before we understand how caffeine affects the brain it is important to understand the body’s natural process of inducing wakefulness and lethargy, particularly the effects of adenosine on the body which inhibit the release of most excitary neurotransmitters such as the ones in the Venn diagram which results in decreased arousal and increased drowsiness.

The most illustrative example of this is the body’s circadian cycle whereby melatonin is secreted at night to induce sleep, in this process sleep inertia is brought about via melatonin secretion, increasing the pooling of adenosine in the brain thereby inducing sleep!

Ingest caffeine: When caffeine is ingested in any form, a process called adenosine receptor antagonism is brought around via caffeine molecules binding with these adenosine receptors. The caffeine molecules are able to do this for two reasons; they are able to diffuse across the blood/brain barrier due to their composition of being water and lipid soluble, secondly their cellular make up is very similar to that of adenosine – sharing a double ring structure.

Caffeine molecules compete with adenosine for these receptors which then inflicts stress upon the body causing vasoconstriction. Just like many other stressors places upon the body, the brain responds by releasing catecholamine’s to counter-react this stress and increase alertness.

In 2004, caffeine was removed from the banned substance list from WADA, since then over 75% of athletes use this “wonder drug” to improve performance whilst staying under the threshold.

So how good is it for endurance performance?

Just a few studies I had put into a table but essentially, just like most ergogenic aids the research is equivocal. This is perhaps due to the effects of non-responders vs. responders and caffeine sensitivity for individuals which is often neglected.

Repeated sprint ability:

More studies, more equivocalness. However there are many implications upon research when poor methodologies are employed; using poor sample sizes, untrained individuals, not using baseline plasma/urine analysis and use of fixed doses to name a few.

Whist the research may or may not support the use of caffeine within different areas of the sporting arena, I think it is important to understand that caffeine is a very potent drug with risks of increased tolerance and even in some cases physical dependence.

Tolerance occurs by compensatory changes such as down regulation and desensitisation in the number and sensitivity of central nervous system receptors. Longitudinally these changes compel a person to consume more of a substance to achieve the same affect.

Disregarding the specific mechanism/s behind how caffeine increases performance, it is evident that athletes should be educated on how quickly the body adapts to ingesting a regular dose of caffeine. A process whereby the brain deploys more adenosine receptors, almost trying to force a state of lethargy due to the lack of binding sites for the adenosine molecules. Longitudinally, an ever increasing amount of caffeine is required to block the adenosine molecules from there receptors just to achieve the same affect.

Conclusions for athletes:

Doses should be between 3-9mg per Kg of bodyweight to minimise negative effects associated with increased intake due to increases in tolerance and side effects.

I propose that if caffeine is to be used for benefits during training, it should be cycled to minimise withdrawal affects and also an increased tolerance which would increase the amount required for competition or for an effect. Especially as there is an upper limit for athletes, even though it has been taken off the WADA banned substance list, if you can decrease individual caffeine sensitivity, it would make sense that the stimulating effects of caffeine on the body would increase.

Regarding supplementation within team sport, research has demonstrated that there are large inter-individual differences. I advise that athletes use their training diaries and/or coaches monitor behaviour and use logbooks to observe caffeine ingestion longitudinally. Specifically when looking to peak for competition and using caffeine as an ergogenic aid.

Although evidence is inconsistent with regards to the performance effects of caffeine, it is important to note the methodological implications of certain studies whilst applying an ecologically valid system by a means of monitoring athletes and their individual response to caffeine supplementation.