Caffeine vs. a Sleepy Morning: Experiment Produces an Unexpected Result

It may seem that a strong cup of coffee or a dose of caffeine before an early workout could quickly shake off sleepiness and improve reaction time. However, an experiment involving young men found that, at least at a dose of 300 mg, caffeine in the morning did not significantly improve either brain performance or movement speed.

The results of the study were published in the journal Nutrients. The study involved 51 healthy, physically active men aged 18 to 30 who typically consumed less than 150 mg of caffeine per day. Participants arrived at the laboratory early in the morning and, on different days, received either 300 mg of caffeine, a placebo, or no tablets at all.

About an hour after taking the substance, the volunteers completed a series of tests. The researchers assessed memory, attention, the ability to suppress automatic responses, and reactive agility — the ability to respond quickly to changing visual signals and move in the appropriate direction.

However, no significant differences were found among the three conditions. Caffeine did not improve performance on tests of attention, memory, or information-processing speed. Measures of reactive agility also remained unchanged: participants did not respond to signals more quickly or perform movements more efficiently.

Caffeine also failed to improve participants’ subjective sense of morning alertness. Regardless of whether they received caffeine, a placebo, or nothing, the participants reported similar levels of sleepiness, fatigue, energy, mood, hunger, and satiety.

The researchers also found no notable effect of caffeine on body temperature. After the warm-up, average skin temperature decreased, which the researchers attributed to heat loss during physical activity rather than to the effects of caffeine.

The authors point out several limitations of the study. Only 27 participants completed the reactive-agility test, and all participants were young men who habitually consumed relatively little caffeine.

In addition, the tests were conducted while participants were fasting. Therefore, the findings may not necessarily apply to athletes who eat breakfast before an early-morning workout or competition.