Caffeine helps athletes to run longer or faster by releasing calcium, researchers in Hamilton have found.
Recreational runners and racers have known for years that downing a cup of java before heading out for a run can give them an extra jolt.
Most assumed that the performance-enhancing drug boosted their running the same way it helps people stay awake.
In Friday's online issue of the journal Applied Physiology, Nutrition and Metabolism, however, Dr. Mark Tarnopolsky of McMaster University Medical Centre found caffeine tricks an athlete's brain into delaying the perception of pain and fatigue.
More importantly, it also prompts muscles into releasing more of the calcium needed to contract and relax.
"The caffeine is allowing a little bit more calcium to be released into that muscle," said Tarnopolsky. "It would make that muscle contraction a little bit stronger, so you can actually either run at the same pace with less input, or run at a faster pace for the same input."
Research from the University of Guelph showed caffeine in high concentrations can actually have the opposite effect, which is one of the reasons it is no longer banned at the Olympics.
"Understanding that very small doses of caffeine enhance performance somewhat, larger doses tend to erode performance," said Dr. Andrew Pipe of Montreal, an adviser to the Canadian Centre for Ethics in Sports.
"And caffeine is a part of the lifestyle and the food ingestion of people around the world," which would also make it difficult to ban.
Regardless of how it works, Canadian running legend Rick Rayman said he plans to keep fuelling his runs with coffee. Rayman has completed 204 marathons and a daily run every day since 1978.
"Definitely, psychologically, to the point that I won't start a marathon or training run even without it."
The Natural Sciences and Engineering Research Council of Canada funded the research and published the findings of the study, called Effect of Caffeine on the Neuromuscular System — Potential as an Ergogenic Aid.