Caffeine Makes the Bar Move Faster

Opener

Caffeine is the one ingredient almost every pre-workout has in common, and the one most lifters already take before training. The useful question isn't whether it works. It's what it actually improves, how much, and for whom.

A 2025 meta-analysis from Xiao, Ding and colleagues pulled together the placebo-controlled studies that measured bar speed and power output during lifting. The answer is fairly clear: caffeine makes the bar move faster at every load tested. It does more for speed than for your max, and it does less the more caffeine you already use every day.

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1. What this review is asking

Earlier meta-analyses found caffeine gives only a trivial bump to a one-rep max, with effect sizes around 0.17 to 0.20. But most training isn't max singles. Most of it is submaximal sets where the goal is to move a heavy load with intent.

So this review asked a narrower question: during lifts with a fixed number of reps, does caffeine change mean bar velocity and mean power output? And does the effect depend on sex, dose, daily caffeine habit, muscle group or load?