Caffeine

effects on exercise performance
Caffeine is a well researched and popular substance widely used and abused by athletes and just about everybody for its stimulating effects. It is also not regulated by anti-doping agency.
 
Factors like dose, timing and genes affect the benefits of caffeine on endurance and strength performance. Here is what the science says.

Effects of caffeine on exercise performance:

  • Increases aerobic endurance and muscle endurance – medium effect. Aerobic endurance appears to be the form of exercise with the most consistent moderate-to-large benefits.
  • Increases in force and anaerobic power have constantly shown weaker effects.
  • A study from 2021 show that coffee ingested 30 minutes before endurance exercise increased maximal fat oxidation in coffee naive men (drinking less than a cup of coffee a day) by 11-13% (source)
  • According to some studies, caffeine appears to improve physical performance in both trained and untrained individuals.
  • The metastudy analysis by Grgic et.al 2018 indicated a significant increase in upper body, but not lower body strength, with caffeine ingestion. Lower body strength increased more with free weights compared to leg press on machines.
  • Caffeine seems like an effective aid for achieving acute increases in muscle power expressed as vertical jump height.
  • Effects of caffeine are affected by genes, but the reasearch is inconclusive whether your genes makes you benefit from caffeine or not.

What needs more reasearch?

Habituation to caffeine

There’s also some research looking into whether people get habituated to caffeine’s ergogenic effects over the long term. However, the conclusions conflict.
 
In the study by Gonçalves et. al, low, moderate, and high caffeine consumers showed similar absolute and relative improvements in cycling time-trial performance following acute supplementation of 6 mg/kg body mass caffeine. Performance effects of acute caffeine were not influenced by the level of habitual caffeine consumption, suggesting that high habitual caffeine intake does not negate the benefits of acute caffeine supplementation.
 

Research in females and across the cycle

Research in females in sports is lacking across the field. There are only few studies on caffeine and female athletes.
 
The landmark study by Goldstein et al. reported a significant increase in the 1RM bench press in resistance trained females. However, the effect size was very small (SMD = 0.07), thereby limiting the practical significance of the finding.
Another study among female participants was performed by Sabblah et al. The researchers reported an SMD of 0.33 for increases in upper body strength with caffeine ingestion.
 
A study by Wilk et al. shown benefits of caffeine supplementation in trained collage females who habitually drink coffee. They observed strength benefits in 1RM upper body strength and time under tension strength-endurance. Additionally they noted, that lowering caffeine intake to might be necessary to get performance benefit of caffeine.
 
*These studies did not control for the potential variability attributable to metabolic alterations across the menstrual cycle
 
One study shown increase in strength and power performance in trained females during follicular phase when supplemented with 4mg/kg 60 minutes before exercise.

 Caffeine metabolism

There are three main genetic factos involved in metabolism of caffeine. CYP1a2 enzyme that breaks down caffeine, ADORA2A adenoine receptor, and AHR varience. The AHR is the transcription factor protein product  that regulates gene expression of enzymes.

More about genes involved in caffeine metabolism

CYP1A2

  • Rate limiting gene responsible for 95% of the metabolism of caffeine.
  • The rate of this metabolism determines how long caffeine stays in the body and therefore its potential to impact on the body’s systems.
  • The rate of caffeine metabolism can vary 40-fold between, and even within individuals,
  • Women appear to have a lower CYP1A2 enzyme activity compared with men
The SNP is in the noncoding region of theCYP1A2 gene and likely impacts on the levels of expression of theCYP1A2 enzyme by affecting the binding of regulatory proteins to the surrounding gene sequences (source)
 
There are three genotypes of the CYP1A2 SNP (AA,AC, and CC) resulting in differing CYP1A2 enzyme activity.

AA genotype

  • fast rate genotype (1.6 times faster than other genotypes)
  • may be linked to increased coffee consumption

CC and CT genotypes of

  • slow rate genotype /low-responders and no-responders
  • most vulnerable to adverse effects of caffeine
  • T allelles are predisposed to caffeine-induced anxiety
  • Studies show caffeine improved performance in 21/25 exercises in CT/CC genotype.

ADORA2A adenosine receptor

There is a physical limit to how many molecules of adenosine can bind to adenosine receptors.

When caffeine binds to this receptor, adenosine can’t and as a result you don’t feel tired. In sports, it means you feel less fatigued and exercise longer.

Does it mean that there is no benefit in caffeine for performance if you have CT/CC genotype?

Some  studies found caffeine improved performance in 21/25 exercises in CT/CC genotype and a study by Mark Glaisterfrom et al. from 2020 and Grgic et al. 2021 shown benefits of caffeine supplementation independent of genotype.

Caffeine Absorption:

  • Caffeine is absorbed slower when taken with food and the fastest in form of chewing gum.
  • It takes 15-45 minutes for the caffeine metabolites to enter the bloodstream and peaks in about an hour. The rate of digestion depends on the form of caffeine.
  • Carbohydrates combined with caffeine (such as used in sports gels) reduce the effectiveness of caffein (source)
  • Caffeine absorption is inhibited by turmeric, vegetables such as cabbages, cauliflower and broccoli  (increase levels of CYP1A2)
  • Smoke from cigarettes and burnt animal fat increases metabolism rate of caffeine , enhancing its effects, decreasing half-life of caffeine. Polycyclic aromatic hydrocarbons (PAHs) in cigarette smoke can almost double the metabolism rate of caffeine. Smokers are reported to drink almost one cup of coffee more each day than nonsmokers. (source)
  • Low dose is metabolised slower than high dose.
 

Effective Caffeine Dosage:

  • The effective dose depends on several factors, such as genetic mutations (people who react differently to caffeine), sport, the source of caffeine,,the dose of caffeine, and attenuation to caffeine.
  • 3-6mg / kg has proven to be the best choice, with a lower dose still having an effect and a higher one can already cause feelings of anxiety, insomnia and digestive problems.
  • Ingestion of doses above 6mg / kg may lead to negative effects such as gastro-intestinal issues, anxiety, shakiness, insomnia.
  • The use of caffeine in conjunction with endurance  exercise in the heat and at altitude is well supported when dosages  range from 3 to 6 mg/kg and 4–6 mg/kg
  • “The International Olympic Committee mandates an allowable limit of 12 μg of caffeine per ml of urine. A caffeine dose in the range of 9 to 13 mg/kg approximately one hour prior to performance will reach the maximum allowable urinary concentration for competition.” AceFitness.org
In the case of sports drinks and caffeine supplements, you know the caffeine content. It is the most reliable way to use it.
In the case of beverages such as coffee and tea, the caffeine content varies depending on several factors (variety, harvest, processing, batch …).
caffeine content in beverages

Source: https://www.issf-sports.org/news.ashx?newsid=3065

 
On average, espresso contains 80mg of caffeine.
  • Nespresso capsules (5g) Espresso Capsules: 55-65 milligrams
  • Nespresso capsules (5g) Lungo Capsules: 77-89 milligrams
  • McCafe Espresso (single shot): 71 milligrams
  • McCafe Espresso (double shot): 142 milligrams
  • McCafe Latte (all flavors; 16 ounces): 142 milligrams
  • McCafe Mocha (all flavors; 16 ounces): 167 milligrams

Source

Caffeine Tolerance:

By daily consumption of caffeine the body gets used to it and builds tolerance. If you want to use caffeine to enhance performance, you should exclude caffeine drinks 20 days in advance, but some people need less time. If you don’t, you will need a higher dose and the effect will not be as pronounced.
 
In one of the previous posts I mentioned preworkouts, specifically coffee, and why you need to be careful about when and how you use it.
 
Adverse effects on sleep or feelings of  anxiety following caffeine ingestion may be attributed to genetic  variation associated with caffeine metabolism, and physical and  psychological response. Other factors such as habitual caffeine intake  also may play a role in between-individual response variation.

Caffeine in combination with lack of sleep:

We often use caffeine for stimulation when we are tired. I definitely do not recommend practicing this because while caffeine wakes you up a bit,  it can also lead to an increased risk of injury among other negative effects mentioned in the post about coffee.
 
Insufficient sleep in combination with caffeine leads us to make bad decisions faster, in game, during a race, but also in our private life.
 

In this study on athletes, they observed the performance of athletes with reduced sleep duration (4.5 hours). They compared the results in three conditions:

  • caffeine 5mg / kg
  • 20 minutes of sleep
  • placebo followed by 20 minutes of sleep / caffeine followed by 20 minutes of sleep

Subsequently, approx. they did 6 sprints for half an hour.

And how did it turn out?

  • It has been confirmed that sleep has improved sprint performance.
  • It was confirmed that caffeine did not have a positive effect on sprint performance. Even with mild lack of sleep.
  • It has been shown that caffeine in combination with a np has had a greater benefit for performance than sleep or caffeine alone.

However, this strategy should not be part of the usual training protocol, as caffeine also increases muscle damage caused by exercise. You better sleep well.

 

Caffeine Tolerance:

By daily consumption of caffeine the body gets used to it and builds tolerance. If you want to use caffeine to enhance performance, you should exclude caffeine drinks 20 days in advance, but some people need less time. If you don’t, you will need a higher dose and the effect will not be as pronounced.
 
In one of the previous posts I mentioned preworkouts, specifically coffee, and why you need to be careful about when and how you use it.
 
Adverse effects on sleep or feelings of  anxiety following caffeine ingestion may be attributed to genetic  variation associated with caffeine metabolism, and physical and  psychological response. Other factors such as habitual caffeine intake  also may play a role in between-individual response variation.

Caffeine in combination with lack of sleep:

We often use caffeine for stimulation when we are tired. I definitely do not recommend practicing this because while caffeine wakes you up a bit,  it can also lead to an increased risk of injury among other negative effects mentioned in the post about coffee.
 
Insufficient sleep in combination with caffeine leads us to make bad decisions faster, in game, during a race, but also in our private life.
 

In this study on athletes, they observed the performance of athletes with reduced sleep duration (4.5 hours). They compared the results in three conditions:

  • caffeine 5mg / kg
  • 20 minutes of sleep
  • placebo followed by 20 minutes of sleep / caffeine followed by 20 minutes of sleep

Subsequently, approx. they did 6 sprints for half an hour.

And how did it turn out?

  • It has been confirmed that sleep has improved sprint performance.
  • It was confirmed that caffeine did not have a positive effect on sprint performance. Even with mild lack of sleep.
  • It has been shown that caffeine in combination with a np has had a greater benefit for performance than sleep or caffeine alone.

However, this strategy should not be part of the usual training protocol, as caffeine also increases muscle damage caused by exercise. You better sleep well.