Caffeine is the single most-researched performance-enhancing substance in sports science. It's also the primary reason pre-workout supplements actually work.
Here's what the research says about caffeine — and why the $40 pre-workout scoop is largely a $0.15 caffeine dose surrounded by expensive marketing.
The evidence for caffeine is unusually solid
We're talking about hundreds of RCTs and multiple meta-analyses. The International Society of Sports Nutrition position stand on caffeine (Guest et al., 2021) reviewed the literature and concluded:
Improves endurance performance by ~2–5%
