One pre-workout caffeine dose kept working across 3.5 hours of repeated sprints

Caffeine is the most-studied performance supplement there is, and its status as an ergogenic aid is well established [s2]. What a trial published in Medicine & Science in Sports & Exercise on 1 September adds is narrower and more practical: how long a single pre-exercise dose keeps working when the effort is repeated sprinting spread over several hours [s1].

What the trial did

Twelve healthy young adults, four of them female, completed two randomised, double-blind trials, ingesting either caffeine (5.5 mg per kg of bodyweight) or a placebo [s1]. About 60 minutes after ingestion they began a 3.5-hour protocol of three repeated-sprint sets, each set consisting of five minutes of moderate-intensity cycling followed by six all-out five-second sprints [s1].

The researchers measured more than power output. They drew plasma to track caffeine and noradrenaline, recorded ratings of perceived exertion and leg-muscle pain, and used transcranial Doppler and ultrasound to follow cerebral and carotid blood flow — an attempt to see not just whether caffeine helped, but what it was doing to the body while it did [s1].

The results

Caffeine increased mean sprint power across the repeated-sprint sets compared with placebo, and the effect persisted: modest but consistent, in the range of 0.5% to 2.4%, sustained up to 3.5 hours after ingestion [s1]. Peak power was also enhanced in the second and third sets, with increases of up to 3.7% [s1].

Those performance gains came with a coherent set of physiological changes. Plasma noradrenaline was higher on caffeine, and both perceived exertion and leg-muscle pain were lower — the sprints felt easier [s1]. Caffeine also lowered end-tidal carbon dioxide and reduced middle cerebral artery blood velocity (an index of cerebral blood flow), and it raised heart rate [s1].

How much this tells you

The headline is that a single dose does not fade over a long, intermittent session — a genuinely useful thing to know for sports played in bouts over an afternoon rather than in one continuous effort. The magnitudes, though, are small: differences of a few percent in sprint power, in a controlled cycling protocol. Whether that converts to anything a competitor would notice on the field depends heavily on the sport.

The bigger caveats are in the design. This was 12 participants, only four of them women, so it is underpowered to say anything about sex differences and is a small sample even for its within-subject, crossover structure. Caffeine responses vary between people — partly on genetic and habitual-intake grounds — and a dozen participants cannot capture that spread. The blood-flow measures are mechanistic detail, not health outcomes; a reduction in cerebral blood velocity is a known caffeine effect, not evidence of harm or benefit in itself.

Nothing here is dosing advice. Caffeine is a stimulant with real cardiovascular and sleep effects, and individual tolerance differs; the study used a fixed weight-based dose in a lab, in a young and healthy group, under supervision. What it contributes to the literature is a specific, well-instrumented answer to a specific question: the ergogenic effect of one pre-exercise dose is still measurable hours later, and it travels with lower perceived effort rather than in spite of it [s1].

A little context helps place the size of the effect. The International Society of Sports Nutrition regards caffeine as one of the few supplements with strong, consistent evidence for enhancing performance [s2], so the trial is not testing whether caffeine works but characterising the shape of its effect over time. That distinction matters for how the result should be used: it refines existing knowledge rather than establishing something new. The persistence finding is the genuinely additive part — many athletes take caffeine shortly before a single effort, and this protocol suggests one dose can carry across a multi-hour session of intermittent sprints without a clear fade [s1]. Whether the same holds at other doses, in highly trained athletes, or in women specifically, the study cannot say, and its authors do not claim otherwise.

Sources

• Pre-Exercise Caffeine Enhances Repeated Sprint Performance and Alters Physiological and Perceptual Responses — Medicine & Science in Sports & Exercise, 2026-09-01
• International Society of Sports Nutrition position stand: caffeine and exercise performance — Journal of the International Society of Sports Nutrition, 2021