Carbohydrate intake during exercise can enhance endurance exercise performance. The recommendation is to consume 30-60 g/h carbohydrate for events lasting 1 – 2.5 h and for events over 2.5 h up to 90 g/h. If more than 60g/h is ingested it is important to realise that the type of carbohydrate that is ingested is critically important. With these large amounts, a combination of carbohydrates, for example glucose and fructose, needs to be ingested.
It is recommended to start the exercise with a good volume in the stomach (but without causing gastrointestinal problems), as it is known that the volume in the stomach is one of the main factors that will determine the speed of gastric emptying. A larger volume will empty faster than a smaller volume. But because everything ends up in the stomach, released to the intestine and the intestine then regulates the supply of carbohydrates, it was thought that the timing was not that important. The recommendation of a large volume in the stomach, is not ideal for runners. Runners cant usually drink large volumes during races as the fluids would be slushing around in their stomach and intestines. Runners usually take a few sips of a carbohydrate solution as they rush past the feed stations.
It is likely that the larger volume will stimulate gastric emptying and makes more carbohydrate available for intestinal absorption. Therefore, the strategy that many runners use (small sips at all feed stations) may not be the preferred method. It may be better to make sure there is more fluid in the stomach. In a study there was no difference in gastro-intestinal problems and this is also what is observed in earlier studies. Runners may be able to tolerate much more than they think they can. When 90-100g of carbohydrate intake per hourwas given to runners who were running at high intensity during 10 mile (16km) runs there were seen minimal gastro-intestinal problems even though researchers and the runners themselves were expecting a lot of GI issues with that high intake of carbohydrate! There is certainly a case to be made to take in more carbohydrate and practice this regularly in training to make sure no gastro-intestinal problems will develop and the gut adapts to this practice.
Image & Source : Asker Jeukendrup, mysportscience : https://www.mysportscience.com/post/2020/05/01/what-is-better-frequent-sips-or-larger-amounts-of-drinks-during-running