All in the mind?

During long distance events, glycogen is the primary source of energy to the body. These stores of glycogen are of course, limited. This means that, as the stores of glycogen become depleted, a loss of performance is experienced.

I have recently been reading about the "Central Governed" theory. This theory suggests that fatigue is "Centrally" controlled by the brain, rather than the traditional view of being controlled "Peripherally" by the muscles.

This raises the question, is it a lack of glycogen in the muscles which causes an athlete's work rate to drop? Or is it the brain monitoring glycogen levels, and as they decrease, using nerve signals to reduce the work rate to make it more sustainable?

A recent study carried out at Ghent University claimed to test this "Central Governed" theory.

"Riders completed two separate time trials, riding for 1 hour in each. In the first time trail, riders rinsed out their mouths at regular intervals with a sports drink containing carbohydrates and electrolytes. They did not swallow the sports drink, the simply rinsed for 5 seconds before spitting the drink out. in the second time trial, the riders repeated this but used a "Placebo" which was sweetened drink with no actual carbohydrate content. The drinks were taste tested beforehand to ensure that riders could not tell the difference between either drink."

The results gained from this test showed "swilling with the carbohydrate drink increased power output by 3.7%, which equated to a 2.37 minute improvement compared to swilling with the placebo drink. In addition to power output being higher, lactate levels and heart rate were also higher."

It is also noted that the rider's perceived level of exertion did not change between the two time trials.

The researches of this experiment suggested that the differences between the time trials could be put down to the fact that carbohydrates were detected in the mouth, "which fooled the brain into thinking the rider had taken fuel on board". This would allow the brain to remove limitations on the muscles.

There is however, one problem with this conclusion. It is stated that the detection of carbohydrate in the mouth was the cause of improved performance, and that this must be the case as no carbohydrate was ingested. However, this conclusion makes no consideration for the fact that glucose is able to pass through membranes, and can therefore be absorbed into the bloodstream from the mouth. This would mean that in the 5 second period the athlete is swilling the sports drink, glucose is being absorbed which will provide energy to the working muscles. It is not possible though, to say how much glucose would be provided to the muscles as a result of this.

With this taken into consideration, it is clear that the experiment is not completely valid. However, as a concept it may have some validity. If we refer back to the piece i wrote about Caffeine as a supplement, it showed that it was the ability to change an athlete's perception of fatigue , rather than have a physiological effect is key to the way it works.

Rather than this experiment proving the "Central Governed" theory to be true or false, i feel it can provide a base to further experiments concerning this theory. I also believe it could be used as an opportunity to look further into this use of sports drinks, as some athletes suffer from bloating when drinking during exercise.




Ben Brown