The solution must be made of real carbohydrates; for example during this study, a mixture of a starch derivative called maltodextrin and water was used.
When sugary beverages are consumed during athletic performance, blood is rerouted from the stomach to the muscles where it is needed. However drinking or eating too much can cause one to cramp up. Using a carbohydrate rinse results in the same effect without the bloating from drinking or the cramping from eating. You are essentially tricking your brain into thinking that you are sending carbohydrates into your body. Once the body senses this, the brain sends a message telling your nerves and muscles it is time to start working harder. The effect is small and probably would not make a difference for the average exerciser; however when competing at higher levels even a small difference can give that athlete a winning edge over the competition.
How did this discovery come about? During the 1990s, most scientists were in agreement that it was beneficial if athlete ate or drank carbohydrates prior to and during athletic events such as marathons. They knew that muscles used during these events utilise stored glycogen and that by consuming additional carbohydrates they could increase the energy levels for these muscles. The effects of these carbohydrates were thought to be beneficial only in races that lasted more than an hour, because muscles do not use glycogen that quickly or in that short amount of time. In other words, in shorter events, the event would be over before your body could metabolize any carbohydrates you consume.
This theory was challenged when a new study showed that carbohydrates did in fact affect athletes during short exercise periods. The study showed that athletes performing exercise sessions that lasted half an hour or more could go faster and longer by consuming a drink containing carbohydrates. In addition, their athletic performance increased a whopping 14%! In contrast, the study showed that there was no effect on some athletes who followed the same guideline. There was speculation that because some of the athletes were hungry, their performance would improve. However, no one believed that the carbohydrates in the drinks could have been metabolized and used by the muscles that quickly. This led to the next question: were additional carbohydrates even needed when exercising for short periods of time?
This led a research team at the University of Birmingham to start conducting additional tests. They gave a group of trained cyclists intravenous solutions of glucose and then told them to ride their bicycles for approximately 24 miles, which would require about one hour. By giving them intravenous solutions of glucose they knew that these athletes would have the sugar they needed to perform. However the glucose had no effect at all. Next they asked the athletes to only rinse their mouths with a solution of maltodextrin and to repeat after one hour of riding. Interestingly, rinsing their mouths with the solution yielded the same results as if they had drank it. This led other scientists to try the same experiment. It was repeated with long-distance runners who were asked to run for 30 minutes in one study and 60 minutes in another. The results were the same: the carbohydrate rinse allowed them to run further, just as with the cyclists. It should be noted that some athletes were given salt-water placebos and these participants had no change in their performance.
To be sure that it was not just the sugar that the body was responding to, neuroscientists studied the brains of rodents and found that it was the carbohydrates that make the difference, and that the artificial sweeteners do not have the same effect. Researchers also conducted tests to see if only ingesting glucose, which tastes sweet, would have the same effect as the carbohydrate maltodextrin. Their results confirmed their previous findings, that carbohydrates stimulated those areas of the brain that tell the muscles to work harder and longer and that artificial sweeteners have no effect.
Is rinsing with a carbohydrate something that all athletes should be doing? While it is acknowledged that rinsing does have an impact on performance, most athletes are probably better off just eating the calories that they need. Unless you're performing at a high level of athletic competition then mouth rinsing for added carbohydrates is not going to be necessary. Those who compete in events such as long-distance marathons and cycling events will benefit best from carbohydrate rinsing.