Caffeine at 3-6mg/kg roughly 60 minutes pre-race has well-established, triathlon-specific ergogenic evidence regardless of habitual intake, but late or close-to-bedtime dosing carries a real, separately quantified sleep-disruption cost
Interpretation
The ISSN's position stand establishes caffeine's aerobic-endurance benefit as the most consistent of its effects, at 3-6mg/kg roughly 60 minutes pre-exercise, working in habitual and non-habitual users alike. Potgieter et al.'s field trial in 26 triathletes found 6mg/kg produced a 3.7% faster swim split and 1.3% faster overall Olympic-distance time — direct multi-discipline race evidence, not just single-sport lab data. Gardiner et al.'s meta-analysis of 24 studies quantifies the opposing cost: a coffee-strength dose needs roughly 8.8 hours before bed to avoid disrupting subsequent sleep, and a pre-workout-strength dose needs around 13.2 hours.
Practical implication
Recommend 3-6mg/kg caffeine roughly an hour before race start as well-supported, triathlon-specific advice. Separately, caution against caffeine use close to a pre-race bedtime or late in a long race if sleep that night matters (e.g. a multi-day event) — the sleep cost is just as well quantified as the performance benefit.
Sources
3 sources, independently verified.
Aerobic endurance is the most consistent, moderate-to-large benefit caffeine produces; the position stand recommends 3-6mg/kg (a possible minimum effective dose around 2mg/kg), typically 60 minutes pre-exercise, with roughly 9mg/kg carrying a high side-effect rate for no added benefit. Benefits apply in both habitual and non-habitual caffeine users — individual response varies with genetics, but prior habitual intake doesn't reliably blunt the acute effect.
The most directly relevant trial for this article: 6mg/kg of microencapsulated caffeine, taken 60 minutes before an Olympic-distance race, produced a 3.7% faster swim split and a 1.3% faster total race time, without a change in perceived exertion. One of a small number of caffeine trials run in an actual multi-discipline race setting with mixed-sex participants, rather than a single-sport lab test.
Caffeine measurably disrupts subsequent sleep: total sleep time fell by 45 minutes on average, sleep efficiency dropped 7%, and sleep latency rose 9 minutes. A typical coffee-strength dose (107mg) needs roughly 8.8 hours before bed to avoid disruption, and a pre-workout-strength dose (217.5mg) needs around 13.2 hours — a real, quantified cost against late-race or late-day caffeine dosing that the race-day article weighs against the performance benefit.