Caffeine that deserves its place

Caffeine is the most widely used and researched performance-enhancing substance in sports. Its legal status, availability, and consistent effectiveness across various performance domains make it uniquely valuable for endurance athletes. Especially in ultrarunning — where events can last from ten to thirty hours and mental fatigue is as limiting as physical fatigue — its role extends beyond mere invigoration to genuine race management.

This article discusses the evidence regarding caffeine's effect on ultra-performance and provides practical guidance for its use on race day.

How Caffeine Works

Caffeine's primary mechanism of action is the blockade of adenosine receptors. Adenosine is a neuromodulator that accumulates during prolonged wakefulness and exertion, gradually increasing feelings of fatigue and the perceived effort of physical tasks. Caffeine blocks the receptors to which adenosine binds, masking fatigue signals at the central nervous system level.

The result is a decrease in perceived exertion at the same absolute load, preservation of cognitive function, improvement in mood and motivation, and in some cases, enhanced muscle function.

Secondary mechanisms include increased fat oxidation (marginal at race intensity) and potentially improved muscle contractility at the cellular level.

Performance Effects Relevant to Ultras

Several effects are particularly relevant to ultras. Cognitive function is maintained during prolonged wakefulness, keeping decision-making, route-finding, pace assessment, and risk assessment intact, when fatigue and sleep deprivation would otherwise impair them. Perceived exertion decreases at the same pace — this is not an illusion. It translates into sustainable performance over long durations where the limiting factor is the desire to continue rather than physiological capacity. Alertness during night sections is maintained, which is crucial in events that run overnight, as the circadian trough between two and five AM produces the lowest natural alertness of the entire race. And pain perception is moderately reduced, alleviating the experience of muscle pain and discomfort during prolonged exertion.

Dosage and Timing

The evidence-based dose for performance enhancement is three to six milligrams of caffeine per kilogram of body weight. For a seventy-kilogram runner, this means a lower limit of two hundred ten, a middle range of three hundred fifty, and an upper limit of four hundred twenty milligrams.

For most athletes, two hundred to three hundred milligrams produce significant effects with manageable side effects. Doses over four hundred milligrams increase the risk of stomach issues, anxiety, and disturbed recovery sleep.

Caffeine reaches peak plasma concentration approximately forty-five to sixty minutes after oral ingestion. Time your intake so that the peak coincides with the periods when performance or alertness is most critical — typically the night section and the final quarter of the race.

Strategic Caffeine Use in Ultras

In events under eight hours, a single dose sixty minutes before the final third of the race is usually sufficient.

In eight to sixteen-hour events, two doses — one around the halfway point and one in the final quarter — work well.

In events over sixteen hours that include a night section, three or more doses are timed specifically to cover the night. The first dose at dusk, subsequent doses every three or four hours through the night.

The guiding principle is that caffeine is reserved for where it is needed most. Starting the race with caffeine and continuously consuming it throughout wastes the compound's effectiveness and increases the risk of stomach issues and anxiety in the early hours when neither is needed.

Gastric Considerations

Caffeine stimulates gastric acid secretion and increases intestinal motility. In some athletes, it causes stomach issues, especially in the early hours when the gut is already under stress. Test caffeine-containing products during training before relying on them in a race.

Coffee, in particular, causes a bathroom reaction in many athletes. It is useful two to three hours before the start and problematic in the middle of a race. Caffeine gels and tablets produce more controlled and predictable responses for most runners.

Individual Variation

Caffeine response varies significantly between individuals based on variants of the CYP1A2 gene, which regulates the rate of caffeine metabolism. Fast metabolizers may require higher doses or more frequent dosing. Slow metabolizers should start with smaller doses and allow more time between doses.

Habitual caffeine users need larger doses to achieve the same effect. If you drink coffee daily, your baseline tolerance is elevated, and performance doses must reflect that.

Summary

Caffeine is an ultra-appropriate, evidence-based performance tool. Use it strategically — reserve it for times when cognitive and physical fatigue are greatest, dose three to six milligrams per kilogram, and time intake so that the peak coincides with night sections and the final quarter of the race. Test in training. Keep it separate from your carbohydrate system so that both can be managed independently.

References

Spriet LL. (2014). Exercise and sport performance with low doses of caffeine. Sports Medicine. 44(Suppl 2), S175–S184.

Goldstein ER, Ziegenfuss T, Kalman D, Kreider R, Campbell B, Wilborn C, et al. (2010). International society of sports nutrition position stand: caffeine and performance. Journal of the International Society of Sports Nutrition. 7(1), 5.

McLellan TM, Caldwell JA, Lieberman HR. (2016). A review of caffeine's effects on cognitive, physical and occupational performance. Neuroscience and Biobehavioral Reviews. 71, 294–312.