Caffeine is a naturally occurring alkaloid and central nervous system stimulant. It is widely consumed in coffee, tea, guarana, cocoa, cola and some energy drinks. Caffeine is not itself a prohibited doping substance under current WADA rules, although athletes should always check current rules and product ingredients.
What happens when we drink coffee?
As often happens in nutrition, it depends. Absorption begins relatively quickly, sometimes within around 20 minutes. Blood concentrations can be high at 30–45 minutes and often peak around an hour, although timing varies with the product and food intake. A commonly quoted half-life is 3–5 hours, with substantial individual variation and longer persistence in some circumstances.
How does caffeine work?
Adenosine is involved in sleep pressure. When it acts at its receptors, it can promote sleepiness. Caffeine blocks some of these receptors, reducing the perception of tiredness without removing the underlying need for sleep.
Proposed mechanisms behind its exercise effects include:
- Changes in fat mobilisation have been discussed historically, but glycogen sparing is not considered a reliable explanation for caffeine’s performance benefits.
- Possible effects on muscle excitation and calcium handling, depending on dose and conditions.
- Central nervous system effects that can reduce perceived exertion and fatigue.
So, lots of coffee for a harder workout?
No. The source gives 250 mg/day, approximately three coffees, as a moderate example, but coffee strength varies greatly and no dose is risk-free for everyone. Consider sleep, anxiety, heart symptoms, medication and total intake from all sources.
It is true that caffeine can improve some sporting outcomes, but the effect depends on the athlete, exercise and dose.
A 1998 study by Graham, Hibbert and Sathasivam suggested that coffee might contain compounds affecting caffeine’s ergogenic effect. That single finding does not establish that anhydrous caffeine always outperforms the same dose of caffeine from coffee.
Caffeine can improve some endurance outcomes, but a universal 10–20% delay in fatigue lasting 6 hours is not a reliable promise. Evidence also supports benefits in some short-duration and high-intensity activities, so the source’s blanket exclusion of these is outdated.
Responses to caffeine differ, so a supplementation strategy should be individualised.
Both genetic and environmental factors may contribute.
The CYP1A2 and ADORA2A genes relate to caffeine metabolism and adenosine receptors, respectively. However, genetic categories do not reliably predict every person’s performance or side effects. Caffeine blocks adenosine signalling; increasing the dose does not produce unlimited benefit.
Smoking, hormonal factors, medication, habitual intake, dose, timing and format can all influence response.
Test a suitable plan during training with professional guidance. The original 3–9 mg/kg range includes high doses with greater side-effect risk; lower doses can work. Gum can be absorbed rapidly, but no format is universally best.
Does caffeine dehydrate you?
This linked article discusses hydration. Moderate caffeine intake does not usually cause dehydration in accustomed healthy adults, although it may have a mild diuretic effect at rest. That is different from saying it has no diuretic action at all.
When should it be taken?
Timing depends on the product and individual. Around 1 hour before exercise is commonly studied for capsules or coffee; the original rule of 3 hours for power and 1 hour for endurance is not universal.
Dose depends on the event, person and tolerance. Someone who drinks 3 coffees daily may respond differently from someone who rarely has caffeine, but routine withdrawal is not always needed and can cause headaches or other symptoms.
Studies use a range around 1–6 mg/kg, with benefits often possible toward the lower end. Doses above 9 mg/kg are not recommended as a way to obtain greater benefit and can increase adverse effects. These sporting doses do not override general safety advice or individual contraindications.
Do not test a new caffeine strategy on competition day. Assess response during training, including its effect on sleep and recovery.
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References
- Womack CJ, et al. J Int Soc Sports Nutr. 2012;9(1):7.
- Loy B, et al. Journal of Caffeine Research 2015;5(2):73–81.
- Pickering C, Kiely J. Are the Current Guidelines on Caffeine Use in Sport Optimal for Everyone? Inter-individual Variation in Caffeine Ergogenicity, and a Move Towards Personalised Sports Nutrition. Sports Med. 2017.
