Caffeine - A Deep Dive

Caffeine - A Deep Dive

Coffee is part of cycling culture, but beyond being a midway stop or end destination for any ride, caffeine is a performance enhancer hiding in plain sight.


In this post we are going to break down just exactly what caffeine is, what it does and how you should be using it for maximum effect in training and racing. 


TL;DR Version


Caffeine is an effective training and racing aid, it has many benefits including improving fat burning, increased power output and time to exhaustion. Whilst some contrary evidence exists about its effectiveness in increasing aerobic power output, when all its effects are combined, it is a very effective performance enhancer for getting the most out of training and racing - just don’t overdo it as this can lead to increased tolerance, reduced benefits and side effects.


Caffeine - What is it?


Caffeine is It is the most widely consumed psychoactive drug on the planet. It is a central nervous system stimulant naturally found in seeds, nuts and leaves of many plants, most notably tea leaves and coffee beans. Caffeine has several mechanisms of action, the most prominent of these is its ability to temporarily block Adenosine receptors. Adenosine is an organic compound that is naturally produced in the body. It has a limiting function on the central nervous system and plays a large part in the onset of drowsiness. Reduced adenosine activity leads to an increase in the activity of the neurotransmitters dopamine and glutamate. Dopamine plays an important role in how we feel pleasure, and along with glutamate, are vital to our mental and physical activity. Too little of either of these compounds can leave you feeling sluggish and tired.


Caffeine - How to dose it.


The effective dosage for caffeine can vary from person to person and can be effected by a number of factors including: Existing caffeine usage, time of day and fatigue levels. The information below is an average. When testing caffeine yourself we recommend starting with a low dose and then gradually increasing it until you find what works best for you. Excess caffeine consumption can lead to headaches, nausea, irregular heartbeat, anxiety and insomnia.


Peak absorption time: 30-60 mins [1]

Half life: 3-5 hours [1]

Effective dosage: 2-9mg/kg body weight [2]

Anti Doping status: At the time of publication, caffeine is not prohibited by the World Anti-Doping Agency.



Caffeine in Sport


Caffeine is as close to magic as we can get for performance enhancement. Studies have shown that caffeine supplementation can increase alertness, time to exhaustion and lipid oxidation whilst also reducing recovery time and relative perceived exertion. We are going to summarise these studies for you below.



Aerobic and Anaerobic Power Output


Opinions vary as to whether or not caffeine has any beneficial effect on increasing aerobic power output. Studies show mixed results, some showing increased aerobic power in test subjects whilst others show no effect. No studies we have found show a negative effect, decreasing power output (so it can’t hurt!).



A study conducted by Sasaki et al. [3] reported that in trained distance runners 100g of sucrose combined with approximately 400 mg (6 mg/kg) of caffeine had no additive effect on endurance performance, when compared to consumption of either substrate alone. Supporting this finding, Jacobson et al. [4] found that caffeine (6 mg/kg) combined with carbohydrate (2.6 g/kg), had no significant enhancement on exercise performance or substrate utilisation in trained cyclists.


However, Hulston et al. [5] found that a 6.4% glucose solution in addition to a moderate dose of caffeine (5.3 mg/kg) significantly enhanced time trial performance in trained cyclists. The caffeine-glucose solution improved performance by 9% when compared to placebo and 4.6% in comparison to glucose. However, it was also reported that caffeine consumption had no effect on exogenous carbohydrate oxidation. 


Caffeine has however been shown to have some performance benefit when it comes to anaerobic power output. Anselme et al. [6] found that consumption of 250mg of caffeine increased peak maximal power output by cyclists by 6.7% vs. a placebo. 



Alertness


The combination of caffeine and glucose can improve the efficiency of brain activity. Adan et al. [7] found that the combination of the two substances improves cognitive performance in terms of sustained attention and working memory by increasing the efficiency of the areas of the brain responsible for these two functions. It has been well documented previously that caffeine has a positive effect on alertness but when combined with glucose this effect is increased.


The team found that individuals who consumed caffeine and glucose in combination showed reduced brain activation associated with the task in the bilateral parietal cortex and the left prefrontal cortex - two regions that actively participate in attention and working memory processes. The reduced activity and the fact that no drop in behavioural performance was observed during the task suggests that the brain is more efficient under the combined effect of the two substances, since it needs fewer resources to produce the same level of performance than required by those subjects who were administered the placebo or who took only caffeine or glucose.


An earlier study by the same research team on the effects of caffeine and glucose consumption revealed improvements in attention span and declarative memory without significant alteration of the participants' subjective state. The conclusions suggested that a combination of caffeine and glucose has beneficial effects on attention span, information retention and on the consolidation of verbal memory, none of which were observed when the substances were consumed separately.


Relative Perceived Exertion


A meta analysis of 21 studies conducted by Doherty and Smith [8] revealed moderate to high caffeine doses (4-10 mg/kg) ingested 30-90 min before exercises reduced relative perceived exertion (RPE) obtained during submaximal aerobic exercise versus placebo by 5.6%. In addition, caffeine improved exercise performance by 11.2%.


Analysis of these results revealed that RPE during exercise could account for approximately 29% of the variance in the improvement in exercise performance.


Time To Exhaustion


As mentioned in previous sections discussing power output and relative perceived exertion, there is evidence to suggest that caffeine ingestion can have a positive effect on both factors. Combined together this leads to an increase in time to exhaustion in submaximal exercise.


A study by Denadai et al. [9] involved cyclists performing placebo controlled time to exhaustion tests at 10% above and below their anaerobic threshold. In the sub-threshold test with caffeine, participants' time to exhaustion increased on average by 14.12 min (Caffeine 46.54 +/- 8.05 vs. Placebo 32.42 +/- 14.81). In the above threshold test, no significant improvement was seen in time to exhaustion when compared to placebo.


Lipid Oxidation


Lipid oxidation is the technical term for using stored fat as an energy substrate - this is the key energy source for aerobic respiration. The principle behind fasted training is to adapt your body to use stored fat as a fuel source for progressively higher workload. This has the combined benefits of increasing your threshold power, saving carbohydrate stores for explosive efforts and fuelling on race days much easier - there is an upper limit to how many calories you can digest over time which is often surpassed by how much energy you expend in a race.


The study cited earlier by Sasaki et al.[3] also found that Caffeine use increases the energy derived from stored fat during exercise, whilst reducing the amount of energy derived from carbohydrate for a given power output.



Sources:

  1. http://sleepeducation.org/news/2013/08/01/sleep-and-caffeine
  2. https://www.ncbi.nlm.nih.gov/books/NBK223791/
  3. https://www.thieme-connect.de/products/ejournals/abstract/10.1055/s-2008-1025666
  4. https://onlinelibrary.wiley.com/doi/abs/10.1113/eph8602072
  5. https://journals.lww.com/acsm-msse/Fulltext/2008/12000/Substrate_Metabolism_and_Exercise_Performance_with.12.aspx
  6. https://pubmed.ncbi.nlm.nih.gov/1396643/
  7. https://onlinelibrary.wiley.com/doi/abs/10.1002/hup.1115
  8. https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1600-0838.2005.00445.x
  9. https://pubmed.ncbi.nlm.nih.gov/9698813/

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