Caffeine & Exercise: Does It Really Help?
For many of us, the day doesn’t start until we’ve had that first cup of coffee. But beyond the morning ritual, caffeine is one of the most researched and widely used performance enhancers in sport and fitness. The question is - does it actually help, and if so, how?
How caffeine boosts performance
Research consistently shows that caffeine can improve endurance, strength, and high-intensity exercise performance. A large meta-analysis covering 21 trials found caffeine supplementation increased muscular strength and power, particularly in upper body exercises.
The key mechanism is neurological. Caffeine blocks adenosine receptors in the brain - the chemicals that make us feel drowsy. This reduces perceived exertion, meaning your workout feels easier at the same effort. It also enhances alertness and motor unit recruitment, which explains its positive impact on both endurance and strength.
In endurance sport, studies show caffeine improves time to exhaustion and overall output by sparing glycogen and encouraging greater reliance on fat as a fuel source. That’s why marathoners, cyclists, and even footballers often rely on it pre-competition.
Potential downsides
While caffeine has clear benefits, it isn’t without drawbacks. Overconsumption can cause:
Anxiety or jitteriness
Digestive upset
Insomnia (especially if taken later in the day)
Increased heart rate and blood pressure
Some athletes also find that the diuretic effect (though mild) can contribute to dehydration in long events if fluid intake isn’t carefully managed.
The “non-responders”
Interestingly, not everyone benefits from caffeine. Genetics play a role: variations in the CYP1A2 gene determine how quickly someone metabolises caffeine. Fast metabolisers tend to get the full performance boost, while slow metabolisers may feel little effect - or even worse, experience heightened anxiety and reduced performance.
Habitual use also matters. If you’re a heavy coffee drinker, the body may adapt, blunting the “kick” you get from supplemental caffeine.
Alternatives if caffeine isn’t for you
If you’re sensitive to caffeine or fall into the non-responder category, don’t worry - you’re not missing the only performance aid available. Other options include:
Beetroot juice (nitrate supplementation): Enhances blood flow and endurance capacity.
Creatine: Proven to improve power, strength, and recovery.
Adaptogens (like Rhodiola Rosea): Early evidence suggests benefits for perceived exertion and fatigue.
Simply optimising sleep, hydration, and nutrition - the most underrated performance enhancers of all.
Takeaway
Caffeine is one of the most effective, legal, and affordable performance enhancers we have evidence for. It works by making exercise feel easier, improving alertness, and allowing you to sustain higher output for longer. But it’s not universal - your genetics, tolerance, and sensitivity all influence whether caffeine is a friend or foe.
For many, a moderate dose (around 3-6 mg per kg of bodyweight, taken 30-60 minutes before exercise) is the sweet spot. For others, skipping it and focusing on alternative strategies may be the smarter play.
References: Grgic et al., Sports Medicine (2018); Spriet, Applied Physiology, Nutrition, and Metabolism (2014); Guest et al., Sports Medicine (2018).
