Will caffeine really boost my PB? When to have that all-important caffeine-hit to improve your performance

Will caffeine really boost my PB? When to have that all-important caffeine-hit to improve your performance

Is caffeine really an effective sport enhancer? James Witts takes a look at the benefits of this common stimulant.

Published: April 20, 2025 at 4:34 am

If you're planning on tackling a tough endurance sport such as a triathlon or marathon, then you're likely looking into ways you can improve your performance. Caffeine has been shown to have an affect on sports performance – but how effective is it?

Why is caffeine used for improving exercise performance?

Over 2.5-billion cups of coffee are drunk every day but did you know that caffeine is arguably the most proven ergogenic aid around; in other words, it can help you exercise harder for greater gains.

One of the key reasons why is that it reduces your perception of effort and pain, meaning that stiff moorland climb is that bit easier. It also boosts something called ‘behavioural activation’, which is your determination to work harder.

That’s not all. Studies have shown caffeine cranks up strength, endurance, speed and agility, plus raises how quickly and efficiently you burn fat for fuel. Your mind benefits, too, as caffeine’s linked to better cognitive function, especially memory.

Caffeine works its magic by acting rapidly on the central nervous system, shifting a selection of physiological levers that are conducive to improved performance. These include super-charging the cardiovascular system by elevating heart rate and blood pressure; firing up the endocrine (hormonal) system to accelerate the breakdown of glycogen into glucose for energy purposes; stimulating the release of calcium for more muscular force; and titillating the central nervous system for the pain relief mentioned.

How much caffeine is needed to enjoy a performance advantage?

“The recommended caffeine dose for performance is 3-6mg per kg of bodyweight,” says sport scientist, top athlete and founder of Precision Fuel & Hydration Andy Blow. “So, for a 70kg athlete that’s 200-400mg. This isn’t a set figure, though, and should be determined by how accustomed a person is to caffeine and its effects. For instance, a non-caffeine consumer should start low and build it up over time, allowing the body to become used to it.

“Studies have shown that ingesting doses greater than 9mg/kg doesn’t boost performance any more than a moderate 3-6mg/kg dose, while for some individuals even a low dose of 1-3 mg/kg can be all that’s required to tap into caffeine’s ergogenic effects. In general, erring on the side of caution with your caffeine intake – both before and during exercise – is sensible.” That’s because caffeine has its downsides as well.

What if you take too much caffeine?

Too much caffeine can result in jitteriness, headaches and regular trips to the bathroom. In an extreme case of when caffeine use went wrong, researchers at the University of Northumbria made a dangerous error when they delivered 30g of caffeine to participants instead of 0.3g – a dose 100 times greater. Two sport-science graduates were admitted to intensive care for dialysis and the university was fined £400,000.

Does instant or fresh coffee make a difference?

Caffeine levels of every cuppa vary but, broadly speaking, fresh coffee contains around 80-120mg caffeine. That’s significantly more than instant – around 60-80mg – and is down to caffeine being lost from the coffee beans during the instant-coffee production process.

Are caffeinated sports nutrition products actually worth it or is the caffeine content too low?

Many endurance athletes reach for the Coca Cola during the latter stages of a race. But, perhaps surprisingly, there’s only 33mg caffeine in a 330ml can. Red Bull, on the other hand, contains 80mg caffeine per 250ml can. That’s still an insufficient caffeine hit to tap into those physiological boosters. However, athletes tend to use caffeine judiciously with a pre-mediated training plan.

How long does caffeine stay in the body and when should I take it?

“Studies show that 99% of caffeine is absorbed within the first 45-60 minutes after ingestion and effects start to be noticeable around 20-30 minutes,” says Blow. “With a half-life of around five hours (depending on individual variations in metabolism), high concentrations of caffeine can stay in the system for several hours. When taken during the hour before exercise, the ergogenic effect can comfortably last the duration of a 5km, 10km or even a marathon for some individuals.”

“An example plan for a 70kg athlete competing in an Ironman would be a pre-race double-shot of coffee (around 120mg caffeine),” Blow adds. “During the course of the race, which lasts over 10 hours, they’d top up with two caffeinated gels (200mg), a caffeinated energy drink (140mg) and Coca Cola at aid stations (50mg). That’d deliver around 390mg caffeine.”

This is for a committed athlete who’s well versed in caffeine intake. Note that most health organisations advise consuming no more than 400mg of caffeine per day, nor single doses above 200mg.

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