Not every supplement deserves a place in your routine, but these four have the research to back them up. Here's what they do, how to use them, and what the science says. Caffeine, Protein Powder, Creatine & Electrolytes Caffeine The world's most widely used psychoactive compound. Caffeine works by blocking adenosine, which is your brain's natural fatigue signal. By occupying adenosine receptors, caffeine keeps you feeling alert and focused. But that's not all: it also increas
