02/04/2012 10:07 BST | Updated 30/05/2012 06:12 BST

How Caffeine Can Keep You on the Run

Marathon season is upon us, and first-timers and veteran runners alike will be searching for a performance edge. While the jury is still out on many alleged ergogenic aids, from chromium to creatine, there's one with an ever-increasing pile of evidence in its favour. Caffeine.

How can this ubiquitous drug help the average runner? Let me count the ways! Reduced perception of effort, less reported pain, enhanced glucose uptake during exercise, improved time trial performance and increased time to exhaustion have all been reported in the literature. A study from Loughborough University also found that it improved mental focus and concentration during exhaustive exercise.

But there's more to getting a performance boost than glugging down a pre-race coffee. "A dose of around 3mg of caffeine per kg body weight is needed for endurance exercise, but it's not always easy to equate that to cups of coffee as it depends on size and strength," says sports dietician Ruth McKean. And besides, most of the research showing performance benefits has been done on pure caffeine, not coffee, suggesting you might be better off with energy gels containing caffeine (provided the dose is high enough) or caffeine tablets, rather than a cup of Joe. In fact, one study comparing the performance effects of administering caffeine in its pure form versus in coffee found no improvement in treadmill running performance in the latter scenario. It's thought that other compounds in coffee may hamper the effect of the caffeine.

Caffeinated drinks, including coffee, tea and cola, often get a bad press for having a diuretic effect - potentially leaving you more dehydrated and needing to take a mid-run pitstop. But the American College of Sports Medicine states that there is no evidence to suggest that caffeine consumption prior to exercise either increases urination or dehydration, possibly due to high levels of adrenaline interfering with its usual effect on the kidneys.

Up for a caffeine-charged assault on the 26.2 mile beast? To get the best results, you'll need to 'taper' your customary caffeine intake, according to a study review from the University of Connecticut. McKean recommends cutting down by one caffeinated drink a day to avoid sudden withdrawal symptoms like headaches, until the final three days before your race, over which you should abstain completely. And come race day? Studies show that caffeine peaks in the bloodstream after 30-60 minutes, with levels remaining high for 3-4 hours. "You could either take a caffeine dose about an hour before your race or training run, and 'top up' later in the race (without exceeding the 3mg/kg dose), or you may prefer to take the whole lot in the latter stages of the race when you feel you are hitting a low," says McKean. As with any race day strategy, though, experiment in training to see what works for you - not everyone can tolerate caffeine without ill-effects.

While most of the research on caffeine use in sport has focused on performance, there's some evidence to suggest that caffeine can also be beneficial for recovery. A study published in the Journal of Applied Physiology found that glycogen was replenished more quickly post-exercise when carbohydrate was combined with caffeine. In the study, cyclists who added caffeine to their carbohydrate-based recovery drink had 66% more glycogen in their muscles four hours after finishing an exhaustive session compared to when they consumed carbohydrate alone. So if you see me at the finish line, mine's a latte...