Does Caffeine Boost Endurance?
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Photo by Chevanon Photography
A new twist in the old debate about caffeine's performance-enhancing powers suggests it helps maintain oxygen levels in the blood
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 support around the same time. Caffeine blocks receptors that detect the presence of adenosine, a molecule associated with fatigue as it builds up in the brain. In this picture, caffeine acts in the brain to make any given physical exertion feel easier, which helps explain why it’s effective for all-out bursts of strength as well as prolonged endurance, and why it has cognitive effects like enhanced attention and vigilance. This is the theory that has seemed most plausible to me.
So which is it? The new study, a small one published in Medicine & Science in Sports & Exercise by a team from six Brazilian universities working with David Bishop of Australia’s Victoria University, suggests that it might be both—and that there might be an additional factor related to oxygen levels in your blood.
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