By Dr. Nicholas Shannon | Sports Chiropractor, Melbourne CBD
Whether you are a competitive runner lining up at the start of the Melbourne Marathon, a weekend cyclist heading out along Beach Road, or an office professional in the Melbourne CBD trying to squeeze in a lunchtime workout, there is a good chance caffeine has crossed your mind before exercise. That morning flat white, a pre-workout supplement, or a caffeine gel mid-race — we reach for these almost instinctively. But what does the research actually tell us about caffeine and aerobic performance? Is it genuinely helpful, or is it more marketing than medicine?
As a sports chiropractor in Melbourne’s CBD, Dr. Nicholas Shannon works with a broad spectrum of patients — from elite athletes to office workers looking to improve their health — and questions about caffeine supplementation come up regularly. So let us take a deep dive into the evidence.
How Does Caffeine Actually Work?
Before examining what the science says about performance, it helps to understand the mechanism. Caffeine (1,3,7-trimethylxanthine) primarily works by blocking adenosine receptors in the brain. Adenosine is a chemical that accumulates during wakefulness and promotes fatigue and drowsiness. By blocking these receptors, caffeine reduces the perception of effort and fatigue, effectively allowing you to work harder for longer without feeling like you are working harder.
Beyond the central nervous system, caffeine also has peripheral effects on muscle contractility and metabolism — particularly at doses above 3 mg per kg of body weight. This dual mechanism is part of what makes it such a consistently effective ergogenic aid.
Does Caffeine Enhance Tolerance to High-Intensity Exercise?
A particularly promising area of recent research explores caffeine’s role in high-intensity exercise tolerance — and the findings are striking. In a small-scale but well-designed study, participants who consumed 5 mg of caffeine per kg of body weight were able to sustain high-intensity exercise for approximately 30% longer than those who received a placebo. Perhaps even more noteworthy, the caffeine group burned around 40% more calories during the session.
These are not trivial numbers. The researchers concluded that caffeine may be beneficial in enabling people to maintain peak exercise cardiorespiratory and muscular functions for a longer duration, while achieving greater energy expenditure. This opens real possibilities for combining high-intensity exercise and caffeine in training programs designed to maximise exercise-induced health benefits and athletic performance.
For office workers in Melbourne who struggle to find time to exercise and want to make every session count, this is meaningful: a caffeine-assisted high-intensity session could deliver significantly more physiological bang for your buck.
What the Broader Research Tells Us
This finding is not an isolated one. The weight of evidence from the past five to seven years strongly supports caffeine as a genuine ergogenic aid for aerobic performance, particularly when used strategically.
The ISSN Position Stand (2021)
The International Society of Sports Nutrition (ISSN) published a landmark position stand in 2021 concluding that caffeine supplementation enhances various aspects of exercise performance. Crucially, aerobic endurance was identified as the form of exercise showing the most consistent moderate-to-large performance benefits from caffeine use. The optimal dose range identified was 3–6 mg per kg of body weight, taken 30–90 minutes before exercise. Very high doses of 9 mg/kg were associated with a high rate of side effects without additional benefit, and therefore are not recommended.
Caffeine and Endurance Running (2023)
A comprehensive systematic review and meta-analysis published in Nutrients in 2023 by Wang, Qiu, Gao, and Del Coso specifically examined caffeine’s effects on endurance running performance — an area that had been under-researched compared to cycling studies. The analysis found that caffeine intake showed a meaningful ergogenic effect in increasing time to exhaustion in running trials, as well as improving performance in running time trials. Pre-exercise caffeine supplementation in the range of 3–9 mg per kg body mass produced a medium ergogenic effect on time to exhaustion and a small but meaningful effect on time trial performance. The authors concluded that caffeine may have genuine utility as an ergogenic aid for endurance running events.
For Melbourne’s active population — whether training for Run Melbourne, the Great Ocean Road Running Festival, or simply trying to improve their 5 km personal best — this is directly relevant and actionable information.
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Caffeine and Cycling Performance (2021)
A 2021 study published in Scientific Reports examined caffeine’s effects on cycling time-trial performance and cardiac autonomic response. Fourteen recreationally trained male cyclists ingested 6 mg per kg of caffeine prior to a simulated 16 km time trial. The caffeine group demonstrated meaningful improvements in completion time and power output compared to placebo, alongside a notable cardioprotective response at the end of the time trial — greater parasympathetic modulation (vagal tone), suggesting a more favourable post-exercise cardiac state.
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Caffeine and Energy Expenditure During Self-Paced Exercise (2022)
One study particularly relevant to office workers and recreational exercisers is a 2022 trial published on PubMed examining caffeine’s effect on energy expenditure during one hour of self-paced cycling. Participants who consumed 3 mg/kg of caffeine naturally selected a higher exercise intensity, completed significantly more total work, and burned more total calories compared to the placebo group — without being instructed to exercise harder. This is a fascinating finding: caffeine may organically push people to exercise at a higher intensity without any conscious effort to do so, which over time could meaningfully influence body composition and fitness outcomes.
Repeated Sprint Performance (2025)
A 2025 systematic review and meta-analysis found that acute caffeine ingestion significantly enhanced repeated sprint peak power output in both male and female athletes. This is particularly relevant to team sport athletes and those engaged in high-intensity interval training (HIIT) — a population Dr. Shannon regularly works with at the Shannon Clinic Melbourne CBD.
Does Everyone Respond the Same Way?
The short answer is no, and this is an important nuance. Inter-individual variation in response to caffeine is well documented and is influenced significantly by genetics. The CYP1A2 gene governs how quickly your liver metabolises caffeine. Those with the “fast metaboliser” variant (AA genotype) tend to experience greater performance benefits, while slow metabolisers may experience less benefit and a higher rate of side effects like anxiety, elevated heart rate, and disrupted sleep.
The ADORA2A gene, which codes for adenosine receptors, also plays a role in determining both the ergogenic response and individual sensitivity to caffeine’s anxiogenic effects.
This is why habitual caffeine intake also matters. Regular caffeine consumers may develop partial tolerance to its ergogenic effects over time, meaning the performance boost can be attenuated in heavy users. Periodic caffeine reduction prior to competition or an important training block is sometimes used strategically by athletes to restore sensitivity.
What About the Timing and Form of Caffeine?
The research consistently points to caffeine consumed 30–60 minutes before exercise as optimal for most people, given that plasma caffeine levels peak within this window. The most studied forms — anhydrous caffeine capsules, regular coffee, flat coke, caffeinated gels, and chewing gum — all appear effective, with caffeinated coffee providing an additional benefit from its antioxidant content.
Mouth rinsing with caffeine has shown some benefit for short, high-intensity efforts and in cases when athletes are training with low carbohydrate energy availability, though evidence for aerobic endurance via this method is less convincing.
Practical Takeaways for Athletes and Active People in Melbourne
Whether you are training for a triathlon, attending lunchtime group fitness classes near the Melbourne CBD, or simply trying to maximise a 45-minute morning workout before heading into the office, here is what the current evidence supports:
- A dose of 3–6 mg of caffeine per kg of body weight consumed 30–60 minutes before exercise is well supported for aerobic performance gains.
- For a person weighing 75 kg, that equates to roughly 225–450 mg — approximately 2–4 shots of espresso, depending on the brew.
- Caffeine appears to be most beneficial for aerobic endurance performance (~2-7% performance gains), but also meaningfully supports high-intensity and repeated sprint efforts.
- Individual genetic variation means responses differ — pay attention to your own body, particularly regarding sleep and anxiety.
- Avoid high doses (>6mg/kg or above), which increase side effects without proportional benefit this includes a 4 fold increase risk of atrialar fibrillation.
- If you are a habitual coffee drinker, you may benefit from a period of reduced intake before a particularly important training block or competition to restore caffeine sensitivity.
A Note on Sleep
One critical caveat that Melbourne sports chiropractor Dr. Shannon always raises with patients: caffeine consumed late in the day can significantly impair sleep quality, and sleep is one of the most powerful recovery and performance tools available. Given caffeine’s half-life of 5–6 hours, afternoon training sessions fuelled by caffeine could still be disrupting your sleep at 11 pm. Poor sleep will more than offset any performance gains from caffeine. Timing matters enormously.
The Bottom Line
The evidence base for caffeine as an ergogenic aid for aerobic performance is among the most robust in sports nutrition. When used correctly — at the right dose, at the right time, and with consideration for individual variation — caffeine can genuinely help athletes and active individuals train harder, run longer, and burn more calories. For those who are time-poor but want to maximise their health outcomes from exercise, this is a tool worth understanding.
As always, performance is multi-factorial. Caffeine is one piece of a larger puzzle that includes training load, sleep, nutrition, mobility, and musculoskeletal health. If you are experiencing any pain, injury, or movement limitation that is holding back your training, book an appointment with Dr. Nicholas Shannon at Shannon Clinic — Melbourne’s CBD sports chiropractic clinic, centrally located on Collins Street in the Manchester Unity Building, opposite Melbourne Town Hall.
Shannon Clinic – Melbourne Chiropractic and Sports Care Collins Street, Melbourne CBD 3000 www.shannonclinic.com.au
