Alex Hutchinson draws on the latest research to answer your fitness and workout questions in this biweekly column on the science of sport.
Will drinking coffee help or hinder my workout?
Until 2004, caffeine was a banned substance for elite athletes, who could test positive if they drank as few as three cups of strong coffee. That, one would assume, means it's a performance enhancer.
Then, frustrated with trying to regulate such a commonly used substance, the World Anti-Doping Agency removed caffeine from its restricted list - and the strangest thing happened. After the ban was lifted, caffeine levels in WADA urine tests decreased in most sports. If it wasn't worth banning, athletes apparently figured, it wasn't worth taking.
They were wrong.
"I don't think there's any doubt that caffeine is a very powerful ergogenic [performance-enhancing]aid," says University of Guelph professor Terry Graham, one of the world's leading researchers on the topic.
After decades of studies, it is well established that caffeine helps sprint performance and endurance in activities for up to two hours. There is also increasingly solid evidence that it helps resistance exercise such as weightlifting.
The usual counterargument is that caffeine's diuretic effect can leave you dehydrated, ultimately hurting performance. But recent research has thoroughly dispelled that notion, Dr. Graham says.
How caffeine works is still a matter of some debate. A number of popular, commonly repeated theories, such as the idea that caffeine helps the body burn fat for energy, have been ruled out by researchers.
It's certainly true that caffeine is a stimulant, and it may also carry a placebo effect for some athletes - but that's not the whole story either.
"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, I can still see an effect," Dr. Graham says. The current theory is that caffeine directly affects how muscle fibres contract at a fundamental level, making each fibre contract more strongly when it receives a signal from the nervous system.
Caffeine, however, is not
the same thing as coffee. The only rigorous study directly comparing the effects of caffeine (in pill form) and coffee was performed in Dr. Graham's lab. To their surprise, his team found that only pure caffeine produced a performance boost, even when the level of caffeine in the bloodstream from coffee was identical.
Other studies have found a performance-enhancing effect from coffee, so Dr. Graham is cautious about overstating his results. What is clear is that the effects of coffee, with its complex mix of bioactive ingredients, are far harder to nail down than the unambiguous effects of pure caffeine.
Still, coffee remains a popular choice among athletes. A British study published in June found that 38.1 per cent of track and field athletes drank coffee for the specific purpose of enhancing performance, while 28.6 per cent took caffeine pills.
For recreational athletes, who are typically focused on beating their own best performances rather than beating specific competitors, the value of a caffeine-fuelled personal best is more questionable, suggests Dr. Graham - who, despite his research, has never used caffeine in the many marathons he has run over the past 20 years.
Current estimates suggest that between 82 and 92 per cent of North American adults consume coffee on a regular basis. It may be addictive and expensive, but at least it's not hurting them at the gym.
Alex Hutchinson is a former member of Canada's long-distance running team, and has a PhD in physics.
Caffeinated workout tips
Caffeine is absorbed quickly and lasts for hours, which means that the timing of a pre-workout boost isn't crucial. Most studies administer caffeine an hour before exercise.
A recent Australian study found that five milligrams of caffeine for every kilogram of body weight improved five-kilometre running time by about 1 per cent (for example, 300 milligrams for someone who weighs 60 kilograms, or 130 pounds). Health Canada recommends no more than 400 milligrams a day for adults, the equivalent of about three cups of coffee.
Surprisingly, the same performance boost from caffeine is seen in regular coffee drinkers and in complete abstainers. We do habituate to some of caffeine's effects, such as elevated pulse and blood pressure, but apparently not to its performance-enhancing effects. So there's no need to swear off coffee for a week before a big competition.