

Combining Caffeine and Beet Juice

Are two ergogenic aids better than one?

Caffeine is the most reliable (legal) performance-enhancing drug out there; beet juice is the most hyped ergogenic aid of the past few years. What happens if you combine them? That's what an Australian study, due to be published in the journal Applied Physiology, Nutrition, and Metabolism, aimed to find out. They recruited 24 competitive cyclists, and put them through a methodical series of time trials (on a virtual-reality set-up simulating the London Olympic time-trial courses, which took 50-60 minutes to complete) with all possible combinations with or without caffeine and/or beet juice, in a double-blinded design.

The results were pretty straightforward: caffeine helped by 3-4% with or without beet juice, while beet juice didn't help with or without caffeine. Here's the power output for the four cases:

The caffeine results aren't a surprise. (They used caffeine gum, with a total dose of 3 mg per kg of bodyweight, starting 40 minutes before the time trial.) The beet juice results (two beet shots the evening before, two more shots 130 minutes before the time trial) were a bit more surprising, but not totally out of line with recent findings that beet juice may be less effective in very well trained athletes, for reasons that aren't yet clear.

The thing I found most interesting about this study is the lengths they went to in order to make sure the cyclists were doing everything as they normally would in a competition. The usual tendency in sports performance studies is to eliminate anything that could possibly be considered a confounding variable -- so in many cases, you have subjects who have fasted overnight, haven't had breakfast or done any of their usual pre-competition routine, and aren't allowed to eat or drink during the test. Only recently have scientists become aware of how much this may skew results -- particularly in studies of things like carbohydrate loading and in-competition feeding. For example, carb loading in the days before a marathon makes a huge difference to performance if you then try to run without taking in any carbohydrates (which is how the initial studies were set up); the effect may be considerably less pronounced if you're allowed to replenish your carbs during the race, as runners do in the real world.

Anyway, here's what the subjects did carb-wise before and during these time trials:

- 15 minutes before time trial: gel containing 28 grams of carb;

- at the start of the time trial: place gel blast in cheek and leave it there until it dissolves, at which time it's replaced with another gel blast; the goal is to have a constant stimulus of carbohydrate in the mouth to produce the boost seen in mouth-rinse studies;

- at 15K and (on the men's course) 30K of time trial: a bottle of carb-electrolyte sports drink, consume as much as possible within one minute; this was based on the real-world characteristics of the time trial courses in London, in terms of where it would be practical to drink.

Very interesting stuff -- and given the affiliation of some of the researchers (i.e. Australian Institute of Sport), I wouldn't be surprised if that was the actual nutrition protocol used by Australian cyclists at the London Olympics.



Advertisement - Continue Reading Below