Sunday, July 25, 2010

Sports Drink? What Sports Drink? by: John Hobbs, MEd.

It seems that there are as many combinations for sports drink preferences as there are wheel and bike frame combinations.  Athletes range their choices from science driven recommendations to one incident I remember where a bonking friend downed a ham-steak mid ride claiming bonking was all in his head.  Needless to say, I pulled all the way home.  My interests are aroused whenever I see an article looking at macro-nutrients during activity and looking at performance.  The research article by Breen, Tipton, and Jeukundrup entitled “No effect of carbohydrate-protein on cycling performance and indices of recovery” was no different and looked at a variety of markers coming from a single study.  A large product line already exists for carbohydrate sports drinks as the benefit of is well accepted in science and in sport.  Carbohydrate and protein “recovery” mixtures also have a market place foothold, although these do not have the depth or the history of empirical data.  Ratios of the two nutrients as well as the types need further studies before an ideal recommendation can be made.  So taking this one step farther, researchers are looking at the effects of these supplements when ingested during exercise.  As the researcher of the article state, there is already some data showing conflicting results.  This could be from differences in methodology, looser or tighter controls, differences in the types of measurements made, or just differences in the findings that have not been figured out yet.
            The methods used by Breen, Tipton, and Jeukundrup appear to mimic a real world application very closely while maintaining laboratory controls.  Twelve cyclists were utilized, a respectable number of volunteers when compared to similar studies, with each athlete being subjects under both conditions.  All of the athletes underwent two hours of cycling at a work rate based on measurements from each cyclist before completing a time trial based on the predicted amount of work completed in an hour TT.  Most athletes don’t warm up for two hours before an event.  The purpose of this exercise time was likely to deplete the athletes without driving them to fatigue before the end of the lab session, a difficult task to do since science has yet to determine exact causes of fatigue and all of their roles.   The athletes were supplied either a carbohydrate or carbohydrate and protein mixture, depending on the trial they were completing, while riding.  Then the hour long time trial based, on the amount of energy used, was completed.
            Several forms of data were extracted from this one group.  First, the power outputs measured at various points of the time trial were not significantly different nor were the times to completion.  So a direct measurement of performance indicated no benefit of the protein addition.  Additionally, an isometric strength test post exercise failed to show any difference on recovery from either drink.  To look at muscle damage, the researchers used levels reported soreness and levels of an enzyme called creatine kinase in the blood.  The idea behind using this enzyme is fairly simple.  It is normally located inside the muscles.  If there is muscle damage, the enzyme is released out of the damage section in to the blood.  A similar test is used to check for a heart attack.  This also revealed no benefit of either drink.
            One point to be discussed is the supplement ratios.  The drinks had 65grams/hour of carbohydrate with the mixed drink having an additional 19grams/hour of protein.  This equates to 260 and 336 calories per hour, respectively.  With a study design like this, a couple of questions would have been raised depending on the results.  If a difference would have been seen, the question would have remained if the was the cause of the increase, or was it just the fact that there were more calories in the mixed drink.  In this case where no difference was seen, we can have questions at the deeper level.  Did the 260 calories maximize the benefit that can be seen in sports drinks due to absorption, hormones, or other causes?  Or would a calorically equivalent beverage have proved to be more or less beneficial?  Additionally, would a control trial with no caloric intake have had similar results indicating that carbohydrate substrate was not the limiter in the testing protocol?  With these questions, however, we have to see the practicality of these studies utilizing this many treatment groups.  The more conditions there are, the more time required, higher drop-out rate, increased cost, and facilities for the study.  The researchers hit on some of these points during their discussion.  However, it has to be remembered that the research in this field is still relatively young with varying results.  A slight modification on the conditions may cause a difference.  The athletes in this study rode for three hours.  What happens during 100+ mile races where the pace is fluctuating over climbs and chasing breaks?  Changes in hormones occur depending on the intensity and duration.  One aspect not touched on is the fact that no difference was seen between the two groups meaning that the protein treatment was not shown to hurt performance either.  So, if you prefer to drink your “recovery drink” that has some protein in it during the race because you like the taste, left the bottle of sports drink in your car by accident, or any other reason, these data indicate it can’t hurt. With all these questions, it can be asked “what good was all this then?”  The article provides several data points to further elaborate on with future research and at least have a larger basis for recommendations to athletes.

Breen, L., Tipton, K., Jeukendrup, A. (2010).  No effect of carbohydrate-protein on cycling performance and indices of fatigue.  Medicine and Science in Sports and Exercise, 42 (46), 1140-1148.