The Rise Of Caffeine In Endurance Sport & The Stimulant-Free Alternatives

Caffeine and endurance sport go together like running shoes and matching lycra, but is it really the performance-boosting silver bullet everyone treats it as, and what's the play if it doesn't agree with you? This quick-read unpacks the rise of caffeine as sport's favourite energy boost, the trade-offs worth knowing before race day, and the best stimulant-free alternatives for endurance athletes and hybrid athletes chasing a genuine edge.

Table Of Contents

• Why Caffeine Has Taken Over The Start Line

• The Science Of The Buzz: How Caffeine Improves Performance

• The Trade-Offs: Sleep, Genetics & Side Effects

• Stimulant-Free Options With Real Evidence

• Building A Smart, Personalised Strategy

• Take-home Points
  
  

Why Caffeine Has Taken Over The Start Line

Caffeine has completely taken over the endurance world. From your morning brew to caffeinated gels, chews and pre-workout scoops, it's become the go-to performance supplement for runners, triathletes and HYROX athletes chasing every possible edge on race day. Once banned in competition, caffeine has done a full 180. Today it's one of the most popular, most trusted ergogenic aids in sport, prized for being cheap, legal and genuinely effective.

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About 85% of endurance athletes report habitual caffeine use, though only around 24% use it as a deliberate pre-exercise supplement¹. Urinary caffeine concentrations across Olympic sports have risen significantly since caffeine left the banned substance list in 2004, with endurance disciplines among the heaviest users²˒³. Hybrid performance correlates strongly with aerobic fitness markers, explaining the appeal of caffeine for athletes in this sport⁴.

The Science Of The Buzz: How Caffeine Improves Performance

Caffeine is the OG ergogenic aid, the most popular, most-researched performance booster on the planet, and a staple pre-workout for endurance athletes everywhere. Get the dose and timing right and it can sharpen focus, dull that ‘legs are cooked’ feeling, and help you hold pace when a race gets spicy. The sweet spot is roughly 3-6mg/kg body mass, taken about 60 minutes before you start, with aerobic endurance events seeing the biggest, most consistent performance boost⁵. But more is not more: pushing the dose past this range just piles on side effects, not extra speed.

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Caffeine’s secret weapon is adenosine, the brain chemical that builds up during exercise and makes everything feel harder. By blocking adenosine receptors, caffeine dulls that fatigue signal, lowers perceived effort, and keeps your concentration dialled in when the pace turns up⁶. Moderate doses (4-6mg/kg) reliably beat low doses (1-3mg/kg) for time-to-exhaustion and time-trial performance, and minimal effective doses can be as low as 2mg/kg. Doses above ~9mg/kg mostly add jitters and gut issues, not extra performance⁵˒⁶.

The Trade-Offs: Sleep, Genetics & Side Effects

Caffeine isn't all upside, though. Smash too much too late in the day and you can trade a faster session for a wrecked night's sleep, jittery nerves or an unhappy stomach mid-race. And here's the kicker, not everyone reacts to caffeine the same way. Some athletes can down a coffee before bed and sleep like a baby, while others feel wired for hours after a single cup.

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Even at effective doses, caffeine is linked to disrupted sleep, jitteriness, gut upset and a raised heart rate, with effects lingering for up to 24 hours⁸. Individual response comes down largely to genetics, variants in CYP1A2 and ADORA2A control how fast caffeine clears the body and how sensitive the nervous system is, so identical doses can feel worlds apart between athletes⁷.

Stimulant-Free Options With Real Evidence

Not everyone wants, or can tolerate a stimulant, and that's fine, because caffeine isn't the only ergogenic aid in town. For caffeine-sensitive athletes, evening trainers, or anyone craving a stimulant-free edge, there's a solid line-up of alternatives backed by real evidence, from beetroot juice to buffering supplements built for exactly the kind of stop-start, high-intensity efforts you find in HYROX.

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Dietary nitrate (beetroot juice), at doses of 300-600mg, reliably improves exercise economy and time-trial performance by lowering the oxygen cost of exercise⁹. Beta-alanine (3.2-6.4g/day for 2-4 weeks) raises muscle carnosine by 42-66%, buffering the acid build-up behind fatigue, with the biggest benefit in efforts lasting 60 seconds to 10 minutes¹⁰. Combining beta-alanine with sodium bicarbonate is more effective for enhancing performance than taking either supplement alone¹¹.

Building A Smart, Personalised Strategy

So, caffeine or no caffeine? The honest answer is: it depends. The smartest athletes treat supplementation like any other part of training, personalised, practised and never left to chance on race day. A well-rehearsed caffeine dose can be a genuine weapon for the long aerobic grind, while stimulant-free options can cover the gaps caffeine leaves behind.

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A practical approach: use a practised caffeine dose (3-6mg/kg, ~60 min pre-event) for aerobic efforts, taper intake beforehand to preserve sensitivity, and layer in nitrate or beta-alanine/sodium bicarbonate for high-intensity stations. Because hybrid and endurance sports require both aerobic endurance and the ability to sustain repeated high-intensity efforts, combining nitrate loading (3-6 days pre-event), a practised caffeine dose before competition, and beta-alanine loaded over several weeks may better support performance than relying on stimulants alone⁴˒⁹˒¹⁰˒¹¹.

Takehome Points

• Caffeine is genuinely ergogenic at 3-6mg/kg, taken around 60 min pre-exercise, more isn’t better.

• While effective for performance, caffeine can cause side effects such as poor sleep, gastrointestinal upset and palpitations.

• Dietary nitrate, beta-alanine and sodium bicarbonate are solid stimulant-free options, well suited to sports with mixed energy system demands.

• Combining strategies (nitrate + caffeine or beta-alanine + bicarbonate) can outperform any single approach.

Ash Miller
Dietitian and Nutritionist (Masters)
Bachelor of Physical and Health Education
Instagram: @ashthomo_nutrition

References

1. Kreutzer A, Graybeal AJ, Moss K, Braun-Trocchio R, Shah M. Caffeine supplementation strategies among endurance athletes. Front Sports Act Living. 2022;4:821750.
2. Aguilar-Navarro M, Muñoz G, Salinero JJ, Muñoz-Guerra J, Fernández-Álvarez M, Plata MDM, et al. Urine caffeine concentration in doping control samples from 2004 to 2015. Nutrients. 2019;11(2):286.
3. Van Thuyne W, Delbeke FT. Distribution of caffeine levels in urine in different sports in relation to doping control before and after the removal of caffeine from the WADA doping list. Int J Sports Med. 2006;27(9):745–50.
4. Brandt T, Ebel C, Lebahn C, Schmidt A. Acute physiological responses and performance determinants in Hyrox© – a new running-focused high intensity functional fitness trend. Front Physiol. 2025;16:1519240.
5. Guest NS, VanDusseldorp TA, Nelson MT, Grgic J, Schoenfeld BJ, Jenkins NDM, et al. International society of sports nutrition position stand: caffeine and exercise performance. J Int Soc Sports Nutr. 2021;18(1):1.
6. Wang Z, Qiu B, Gao J, Del Coso J. Effects of caffeine intake on endurance running performance and time to exhaustion: a systematic review and meta-analysis. Nutrients. 2023;15(1):148.
7. 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. 2018;48(1):7–16.
8. Souza JG, Del Coso J, Fonseca FS, Silva BVC, Souza DB, Gianoni RLS, et al. Risk or benefit? Side effects of caffeine supplementation in sport: a systematic review. Eur J Nutr. 2022;61(8):3823–34.
9. Poon ETC, Iu JCK, Sum WMK, Wong PS, Lo KKH, Ali A, et al. Dietary nitrate supplementation and exercise performance: an umbrella review of 20 published systematic reviews with meta-analyses. Sports Med. 2025;55:1213–31.
10. Hobson RM, Saunders B, Ball G, Harris RC, Sale C. Effects of β-alanine supplementation on exercise performance: a meta-analysis. Amino Acids. 2012;43(1):25–37.
11. Curran-Bowen T, da Silva AG, Barreto G, Buckley J, Saunders B. Sodium bicarbonate and beta-alanine supplementation: is combining both better than either alone? A systematic review and meta-analysis. Biol Sport. 2024;41(3):79–87.

Disclaimer:

The content in this blog is for general information only and is not a substitute for professional medical advice, diagnosis, or treatment. Always speak with your doctor or allied health team before changing your diet, exercise, or taking supplements, especially if you have a health condition or take medication. Please use this information as a guide only. Aid Station doesn't take responsibility for individual outcomes.