Many people who participate in long distance running, cycling or swimming supplement with carbohydrate beverages. The idea is that over long-periods time, the glucose necessary for fatty acid mobilization becomes used up and the athlete ‘hits the wall’ or ‘bonks out’. With replenishment, they can continue properly mobilizing fatty acids to fuel the activity and not stop from lack of fuel.
A study by Clark, et al 2000 caught our eye when they compared carbohydrate refeeds with placebo. 43 competitive cyclists completed a 40km course on water to establish a baseline. Mean power was 256 +/-46 W for 58 +/- 4min. One week later, they did the same ride. Half were given a drink of 16ml/kg with 7.6g carbohydrate/100ml of water. The water group had a non-caloric sugar flavor added to their water so they could not know if they had received water or the carbohydrate beverage. These 2 groups were further subdivided; some groups were told what they drank (placebo or carbohydrate) while another group was not told.
After the second trial, the informed carbohydrate-informed group had 4.3% more power, the placebo-informed group improved their power by 0.5%, the uninformed group demonstrated -1.1% in mean power!
This indicates that a) the power of a carbohydrate comes from the athletes’ belief in it and b) over the course of ~1 hr cycling courses, the difference is minimal: 4.3%! If one is not a high level athlete, the difference is negligible and would have no real effect for the recreational athlete.
We then turned to reviews and meta-analyses to see if this type of result had been reproduced. Many of the athletes we work with use some of the popular brands of carbohydrate drinks during longer workouts.
The review by Vandenbogaerde and Hopkins, 2011 checked 88 randomized controlled studies. These studies used different concentrations of carbohydrate, with and without protein. The studies showed improvement in time to exhaustion ranging from 6% to -2%. The drink that improved performance the most was a 0.7g/kg/h glucose, 0.2g/kg/h fructose and 0.2g/kg/h protein. Carbohydrate ingestion in excess of 0.25g/kg/h of fructose was found to impair performance severely. Interestingly, most other variables (gender, temperature, how many boluses/hour to consume, etc.) were found to have no effect or a very small positive effect.
This would lead one to believe that if you are not on track to compete at elite levels of endurance racing, getting an extra 6% out of your body might be more trouble than it’s worth. If you will be competing in a course that is >1hr, using some form of carbohydrate reefed during the course may be called for but don’t break your head trying to get concentration, timing, etc. perfect. The changes are negligible.
Considering games like European football, American football and rugby rely on sports drinks, the data would indicate that these drinks would have only a minimal effect on outcomes. If you regularly consume sports drinks, don’t go cold turkey but begin watering them down until you reach a point where you are drinking water. This way, you will not impair performance.