Carbohydrate ingestion during exercise has been shown to improve exercise performance in events lasting 60 min or longer by maintaining high plasma glucose levels and high CHO oxidation rates. From numerous studies, it appears that most of the soluble carbohydrates are oxidized at similar rates (i.e. glucose, maltose, sucrose, glucose polymers and dispersable starch). The exceptions are fructose, galactose and insoluble starch, which are oxidized at slightly slower rates. Interestingly, however, is the finding from one particular study that when 50 g of fructose and 50 g of glucose were ingested together, during exercise, the cumulative amount of CHO oxidized was 21% greater compared with the ingestion of 100 g of glucose (409).
The amount of CHO ingested is important for its contribution to energy expenditure and sparing of liver glycogen. However, the oxidation of exogenous CHO does not exceed 1.0-1.1 g/min, even when much greater quantities are ingested. This observation suggests that the maximum CHO intake during exercise should not exceed 60 g/h. Nowadays, CHO electrolyte drinks and energy bars, which are promoted to give rapid provision of CHO and fluid, are the most common food supplements in endurance sports. Untrained individuals may benefit as much from the CHO fluid supply as trained athletes.
Optimally, athletes should ingest a CHO electrolyte drink throughout exercise. It has recently been shown that ingestion of CHO throughout exercise improves performance more than when an identical amount of CHO is consumed late in the exercise period.
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