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...