Caffeine is one of the most well-researched performance supplements in sport. It can help to improve alertness, reduce perceived effort and support endurance performance, but it's important to consider the dosage and timing of your caffeine intake, especially when it comes to endurance events.

The widely used approach is to take caffeine around 30-60 minutes before exercise. That's fine, but during a race lasting several hours, you don't necessarily need to take your entire caffeine dose before the start. Caffeine is also not necessary for every athlete, but can be helpful for some athletes before or during their event (or both).

How much caffeine are we talking about?

Any performance benefits are commonly seen around 3-6mg of caffeine per kilogram of body weight, although lower doses may still be effective for some athletes.[1]

For a 70kg athlete:

Caffeine dose	Approx. amount
2mg/kg	140mg
3mg/kg	210mg
6mg/kg	420mg

Like with most things, a higher dose is not necessarily better. Larger doses are actually more likely to cause side effects such as jitters, gastrointestinal discomfort, anxiety or disrupted sleep.[1] If you are including caffeine as a part of your fuelling strategy, you should find an amount that gives you a useful effect without creating other problems.

Do you need it all before the race?

For shorter events, taking caffeine before the start makes sense because you want the effect available throughout most of the race. For something like a marathon, long-distance triathlon or cycling event, there is more room to be strategic. Some athletes like caffeine before the start, while others prefer to save part of their intake for later in the race when fatigue becomes more noticeable.

A split approach can work well.

A longer race might look something like this (again, just an example, not a rule):

Race stage	Example approach
Before race	Small or moderate caffeine dose if well tolerated
Early race	Mostly non-caffeinated fuelling
Later stages	Introduce caffeinated gel or drink
Throughout	Keep track of total caffeine consumed

Someone who already drinks coffee before an early race might keep that as part of their normal routine, then use a caffeinated gel later. Another athlete might avoid caffeine before the start because it makes them nervous or unsettles their gut. There isn't one perfect timing rule for everyone, but it's worth experimenting in your training sessions to find out what works for you.

Caffeine adds up quickly.

Don't accidentally overdo it. If you're having a coffee before the race and a couple of caffeinated gels throughout, you could be moving towards 320-400mg caffeine pretty quickly. For a 60kg runner, that's more than 5mg/kg, so just like you should count every gram of carbohydrate across your gels and drinks, you should also count every source of caffeine across the day. Coffee, pre-workout, sports drinks, gels and chews all contribute.

Test it in training.

Caffeine response varies considerably between athletes.[1] Some people tolerate it extremely well and it benefits their performance - others find that it affects their gut, makes them feel jittery or impacts how they feel when exercising hard. Your longer, race-specific sessions are where you should test:

• how much caffeine you tolerate
• when you take it
• which form works best
• whether it affects your gut
• how you feel later in the session

Don't introduce a large caffeine dose halfway through an important race if you haven't practised it before.

Caffeine for evening races.

Caffeine can remain in the body for several hours, so taking a large amount later in the day may affect sleep.[1] That becomes especially relevant during multi-day events or heavy training periods, where poor sleep afterwards could compromise recovery. The performance benefit may still be worthwhile depending on the event, but it should be factored into the decision.

Younger athletes.

Adult caffeine recommendations shouldn't necessarily be applied to younger athletes. Research into caffeine as a performance aid is largely based on adults, and Sports Dietitians Australia recommends that adolescent athletes focus on the basics first: adequate carbohydrate intake, hydration, recovery nutrition, sleep and appropriate training.[2] For young athletes, caffeine should not become a replacement for those foundations.

Build caffeine into the race plan.

Again, there isn't one golden point in a race when everyone should take caffeine. For shorter events, a pre-race dose may be enough. During longer endurance races, splitting caffeine intake or saving some for later can be a useful strategy. The important things are to know your total intake, understand your tolerance and practise the timing beforehand. Caffeine should be planned in the same way as your carbohydrates, fluids and sodium, rather than added randomly once fatigue sets in.

References.

1. Guest NS, VanDusseldorp TA, Nelson MT, et al. International society of sports nutrition position stand: caffeine and exercise performance. Journal of the International Society of Sports Nutrition. 2021;18(1):1.
2. Desbrow B, McCormack J, Burke LM, et al. Sports Dietitians Australia position statement: sports nutrition for the adolescent athlete. International Journal of Sport Nutrition and Exercise Metabolism. 2014;24(5):570–584.