Itinerary · 7Beginner10 min read

Caffeine and pre-workouts

The most versatile ergogenic aid there is: dose per kilo, when to take it, why it does nothing for some people, and what is really inside a pre-workout.

Caffeine is the one supplement that improves almost everything: endurance, strength, power, reaction time and — probably what counts most — how hard the effort feels. It is also cheap, legal and already in the coffee you drink.

What the evidence saysHigh-quality evidence

It improves performance in virtually every modality studied

Grgic’s umbrella review pooled 21 published meta-analyses and found consistent favourable effects on aerobic endurance, muscular power, strength and speed. The ISSN position stand puts the useful range at 3-6 mg/kg of body weight and notes that above 9 mg/kg there is no further benefit, only more adverse effects.

[2] Grgic J (2020)[1] Guest NS (2021)

How much and when

Dose: 3-6 mg per kg of body weight
Timing: 45-60 minutes before
Half-life: 3-6 hours
Safe daily ceiling: 400 mg in healthy adults

Start at the bottom

Try 3 mg/kg first. The benefit curve flattens early and the side-effect curve — palpitations, anxiety, GI upset, broken sleep — does not. Plenty of people perform the same on 200 mg as on 400 and sleep considerably better.

In long efforts there is a second window: small, repeated doses during the race, on the order of 1-2 mg/kg in the second half, work well and are better tolerated than one large hit. That is why many gels contain caffeine (how to space them).

Why it does more for some people than others

What the evidence saysModerate evidence

The response varies by genetics, and not a little

Caffeine is metabolised mainly by the CYP1A2 enzyme. Guest’s study in athletes found that carriers of the fast-metaboliser genotype (AA) clearly improved their 10 km trial with caffeine, while slow metabolisers did not improve or even got worse. It is a finding that needs more replication, but it explains a common experience well: that it works for your training partner and just makes you jittery.

[3] Guest N (2018)[1] Guest NS (2021)

You do not need genotyping. Two or three trials in similar sessions tell you the same thing for free.
Never debut it on race day. Not the dose, not the brand, not the format.
Tolerance exists, but the effect does not vanish. Studies in habitual consumers still see benefit; what fades is the feeling of stimulation.
Withdrawing it for a few days before a race is common practice with little support: abstinence brings headaches and worse mood, and the effect it restores is small.

Formats: coffee, capsule, gel, gum

Format	Typical dose	Advantage	Downside
Coffee	60-140 mg per cup	Cheap and already in your routine	The real dose varies enormously between coffees
Capsule / tablet	100-200 mg	Exact, reproducible dose	Easy to overshoot once you add the day’s coffee
Caffeinated gel	25-100 mg	Combines carbohydrate and caffeine mid-race	Less fine control of the dose
Gum	50-100 mg	Buccal absorption: peak in 10-15 min	Expensive per dose
Pre-workout	150-350 mg	All-in-one	Caffeine is usually the only thing on the list that works

What is inside a pre-workout

A typical pre-workout carries eight to fifteen ingredients. It is worth knowing which do something and which are there to fill the label.

Caffeine: Works
Beta-alanine: Works, over the long run
Citrulline: Small, inconsistent effect
Creatine: Works, but not here
Taurine, tyrosine, extracts: Scarce evidence
B vitamins: None without a deficiency

Pre-workouts are the most adulterated category

This is where undeclared stimulants and amphetamine analogues withdrawn from the market have repeatedly turned up. If you buy one, make it a large brand with a full breakdown; if you compete, make it batch-tested (why).

The most efficient pre-workout

200-300 mg of caffeine in a capsule, your creatine daily and separate, and beta-alanine on its own if you compete in 1-10 minute efforts. It costs a fraction, you control every dose, and you are not paying for eight under-dosed ingredients.

Takeaways

3-6 mg/kg, 45-60 minutes before. Start at 3 and go up only if needed.
A 400 mg daily ceiling for healthy adults, coffee included.
Individual response varies a lot: test it in training, never in a race.
In a pre-workout, what works is the caffeine; the rest is usually under-dosed.
Watch your sleep: a mid-afternoon dose can cost more than it returns.

Sources for this chapter

[1]Guest NS, VanDusseldorp TA, Nelson MT, et al. (2021). International society of sports nutrition position stand: caffeine and exercise performance. Journal of the International Society of Sports Nutrition. position stand
[2]Grgic J, Grgic I, Pickering C, Schoenfeld BJ, Bishop DJ, Pedisic Z (2020). Wake up and smell the coffee: caffeine supplementation and exercise performance—an umbrella review of 21 published meta-analyses. British Journal of Sports Medicine. review
[3]Guest N, Corey P, Vescovi J, El-Sohemy A (2018). Caffeine, CYP1A2 Genotype, and Endurance Performance in Athletes. Medicine & Science in Sports & Exercise. trial
[4]EFSA Panel on Dietetic Products, Nutrition and Allergies (2015). Scientific Opinion on the safety of caffeine. EFSA Journal. official guideline
[5]Trexler ET, Smith-Ryan AE, Stout JR, et al. (2015). International society of sports nutrition position stand: Beta-Alanine. Journal of the International Society of Sports Nutrition. position stand
[6]Gonzalez AM, Trexler ET (2020). Effects of Citrulline Supplementation on Exercise Performance in Humans: A Review of the Current Literature. Journal of Strength and Conditioning Research. review
[7]Australian Institute of Sport (2025). AIS Sports Supplement Framework: clasificación ABCD de suplementos. Australian Institute of Sport. official guideline

Creatine

For running