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Compared to, say, ice baths, it doesn’t take a lot of convincing for people to embrace caffeine as an essential performance aid. After all, there’s plenty of favorable research, and 90 percent of people already guzzle it daily. Rebranding your morning brew as a pre-race supplement isn’t a big lift. But caffeine’s ubiquity sometimes obscures the big gaps in what we know about it—including, as a new study from researchers in Brazil highlights, the very basic question of how it works.
The first time I wrote about caffeine as a performance-booster was way back in 2008. Back then, most people thought that caffeine was simply a stimulant, or that it enhanced fat-burning to give muscles more energy. But the evidence didn’t back up either theory, a leading researcher named Terry Graham explained. Instead, Graham thought the magic happened in the muscle fibers themselves. “If I were to place electrodes on your muscle and start to stimulate it so that your muscle is contracting and your brain’s not involved,” he told me, “I can still see an effect.”
Another theory was also gaining…
