Does caffeine actually make you train better?

This is unusually well supported. The International Society of Sports Nutrition (ISSN) states in its position stand that caffeine acutely improves several parts of performance: muscular endurance, movement velocity and strength, sprinting, jumping and throwing, along with a range of aerobic and anaerobic sport-specific actions. Aerobic endurance is the form where the benefit is most consistent, with moderate-to-large effects.

The dose that repeatedly works is 3–6 mg per kilo of body weight. The minimum effective dose is unclear but may be as low as 2 mg/kg, while very high doses (around 9 mg/kg) add side effects without adding performance. The most common timing is roughly 60 minutes before the session. Both trained and untrained people respond to it.

The reviews point the same way. In an umbrella review, Grgic and colleagues went through eleven published reviews that together held 21 meta-analyses. Caffeine was ergogenic for aerobic endurance, muscle strength, muscle endurance, power, jumping and movement speed, and the quality of evidence was rated as moderate overall. In a separate meta-analysis of strength and power, the same group found a small but statistically significant improvement in both.

There are caveats. Most studies were done on young men, so the transfer to other groups rests on thinner ground. The response also varies between individuals, partly tied to genetic differences in how caffeine is metabolised, and habitual caffeine intake may matter. So the effect is real and well documented, but it is a margin on top of training, not a shortcut past it.

Unusually, the error here isn't that the effect gets exaggerated but that it gets dressed up. Caffeine is cheap, old and unexciting, so the supplement industry rarely sells it plainly. Instead it arrives packaged in pre-workout powders with twenty-odd ingredients and a dose well beyond the effective range, which shifts the credit from the caffeine to the brand and justifies the price. The same logic drives the dose arms race: more feels stronger, even though the research says the high doses mostly add side effects. In the other direction sits the skepticism that it's just placebo or jitters. That survives because the effect is a margin, not an explosion, and a margin is easy to dismiss when you don't measure it.

If you want to use caffeine, the recipe is simple: 3–6 mg per kilo of body weight about an hour before training. For an average-sized person that's roughly a couple of cups of coffee. More is not better; the high doses mostly bring a racing heart and disrupted sleep with no extra performance. If you're sensitive or unused to it, start at the low end and try it on an ordinary session first. If you train in the evening, weigh the benefit against your sleep, which it affects more than people expect. You don't need an expensive pre-workout powder for this.