The effect of carbohydrate ingestion on the experience of fatigue during prolonged exercise

Background: Muscle fatigue occurs during prolonged exercise as the body’s energy stocks in the form of muscle glycogen and blood glucose levels within the body become depleted. The sensation of fatigue can become so intense that the person must reduce his or her efforts, or even stop the exercise altogether. Studies have shown that the ingestion of carbohydrate solutions can delay this onset of fatigue. The ingestion of multiple transportable carbohydrates can improve performance and increases exercise capacity more than single transportable carbohydrates. Therefore, the ingestion of multiple transportable carbohydrates may decrease the experience of fatigue during a fixed workload. The purpose of the randomized, double-blind, placebo-controlled study presented in this paper is to explore the effects of the ingestion of multiple transportable carbohydrates such as glucose with fructose, and glucose with sucrose, in decreasing the experience of fatigue as compared to an isoenergetic amount of glucose. Methods: Twelve healthy, trained male athletes cycled 180 minutes at 50% maximum power output while receiving a solution providing either 1.8 g/min of glucose (GLU), 1.2 g/min of glucose + 0.6 g/min of fructose (GLU+FRUC), 0.6 g/min glucose + 1.2 g/min sucrose (GLU+SUC) or water (WAT). The experience of fatigue was assessed with the Borg scale where subjects were asked to rate their perceived exertion every 30 minutes during exercise. Results: The results of this study cannot be published. Conclusion: Although the results cannot be published, some speculations can be made. RPE (ratings of perceived exertion) are expected to differ significantly between the four ingested solutions during the later stages of exercise. The expectation is that the RPE for those subjects ingesting multiple transportable carbohydrates will be lower than those ingesting glucose and water. The same should hold true for the single transportable carbohydrate versus water trials. In summary, when glucose and fructose or glucose and sucrose are ingested simultaneously at high rates during cycling exercise, the experience of fatigue is likely to be reduced in comparison to the ingestion of an isoenergetic amount of glucose