Effect of caffeine and selected polymorphisms on endurance performance
When you say caffeine, most of us probably think of coffee - but that's not the only source of caffeine. Caffeine can also be found in tea, chocolate, energy drinks and various beverages such as Coca Cola (the seeds of the cola plant are the source of the caffeine in Coca Cola). However, the most well-known source of caffeine is coffee. Statistics from 2016 say that the biggest coffee drinkers in terms of kilograms (of coffee) per person per year are the Finns; one person there consumes an average of 12 kg of coffee per year, which is equivalent to just under four cups of coffee per person per day (worldpopulationreview.com). According to data from the Czech Statistical Office, the Czech Republic's per capita consumption of coffee beans was 2.4 kg per year (data from 2021), so we are still many cups short of the numbers of our northern colleagues.
Coffee, or rather caffeine, is also very popular among the athlete population. Some simply enjoy it, some believe that caffeine can improve their athletic performance. The effect of caffeine on athletic performance has been investigated in a number of studies, and we have a large number of summaries and meta-analyses available, and if we were to summarize as much data as possible, we would conclude that caffeine can indeed positively affect athletic performance (speed, strength, endurance, cognitive). Current recommendations for promoting athletic performance list 3-6 mg/kg body weight as the optimal dose of caffeine (Grgic et al, 2020; Sicova et al., 2021).
Although the performance-enhancing (so-called ergogenic) effect is supported by a large body of scientific evidence, there is still a degree of variability in the physiological response of the body to caffeine intake. This degree of variability may be explained in part by how quickly a given individual breaks down caffeine. In particular, a variant in one gene responsible for the production of the main liver enzyme that metabolises caffeine (95% of which is responsible for caffeine breakdown) has attracted the attention of many research teams. This gene is called CYP1A2, which is responsible for the production of the enzyme of the same name. The activity of this enzyme may influence whether or not caffeine enhances performance in individuals (and in some cases, it may even impair performance). This gene may have three variants: AA, AC, CC. Depending on the variant in this gene, individuals can be divided into fast caffeine metabolizers (AA), and slow caffeine metabolizers (AC, CC), with CC individuals metabolizing caffeine more slowly than AC individuals (Sicova et al., 2021). The effect of variants of the aforementioned gene on athletic performance after caffeine administration has been investigated in several studies, with conflicting results so far (Algrain et al., 2016; Guest et al., 2018; Puente et al., 2018). The discrepancy between studies may be due, for example, to an insufficiently large sample size of the individuals who participated in the testing. Further, as in many areas of research, we have a disparity in the representation of women and men in research, and therefore we cannot generalize the results of studies across the population with confidence. Therefore, our faculty research team has decided to conduct research in this area with the following objectives:
- To investigate the effect of different doses of caffeine on performance in a "time trial" test (a 10 km "time trial" - the goal is to cover a given distance as quickly as possible).
- To determine whether caffeine will have a different effect on performance in selected tests across the gene variants studied
- Verify critical performance using a 3-minute "all out" test
The research will take a total of 4 weeks. During the first week you will undergo initial measurements/testing (body composition, critical power, aerobic capacity, exercise time trial). During the following 3 weeks you will undergo a 10 km time trial once a week under one of the conditions (placebo / 2 mg/kg caffeine / 4 mg/kg caffeine).
To this end, we are looking for healthy women and men meeting the following criteria to participate in our research:
- Age 18-35 years
- No health limitations
- No contraindications to performing the test on a cycle trainer
- No contraindications to caffeine intake
- No cardiovascular disease
- Hypertension
- Not pregnant or lactating women
- Have not had liver disease in the last two months
- Not using pharmaceuticals that could affect liver function
- Free of disease 14 days before the start of the study
- Agree not to use caffeine for the whole duration of the study (4 weeks)
For your participation in the research, you will receive 1000 CZK and results of all the tests.
If you are interested in participating, please, contact dominik.puda@mail.muni.cz
