Nutrition

Caffeine tolerance: does your pre-workout coffee stop working?

Regular caffeine use builds partial tolerance to some effects, but its performance benefits appear to largely persist.

Caffeine works mainly by blocking adenosine receptors in the brain, which reduces the sense of fatigue and effort and can improve endurance, power and strength performance. When caffeine is taken every day, the body adapts, partly by increasing the number of these receptors. This is why regular coffee drinkers often notice that the alertness and jittery buzz they once felt fades, and why missing the usual dose can bring headaches and tiredness for a day or two.

The interesting part is that tolerance to the performance effects seems smaller than tolerance to the feeling of stimulation. Several studies have found that people who consume caffeine habitually still improve their exercise performance after a dose of around 3 to 6 milligrams per kilogram of body weight, though some research suggests the benefit may shrink slightly with very high daily intake. Because the felt boost is weaker, regular users sometimes keep increasing their dose, which raises the risk of poor sleep, anxiety, a racing heart and stomach upset without adding much performance.

Some athletes reduce caffeine for one to two weeks before an important event to restore sensitivity, but the evidence that this improves performance is mixed, and withdrawal can make training feel worse in the meantime. A more practical approach for most people is to keep daily intake moderate, save larger doses for the sessions that matter most and avoid caffeine in the six to eight hours before bed. Remember that total daily caffeine counts, including coffee, energy drinks, pre-workouts and tea, and that individual sensitivity varies widely.

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