nonky Posted February 20, 2017 Posted February 20, 2017 Cadence Marathon I'm going to give this a try next. Everyone says it's excellent.
jcza Posted February 21, 2017 Posted February 21, 2017 Dankie Troep... Seems like you need to go racing a bit... Still got 2 x CarboFuel and 1 x Marathon at home. No order from me at this time,
DJTerblanche Posted February 21, 2017 Posted February 21, 2017 With regards to fluid intake: Dilute (low osmolality) fluid results in higher gastric emptying rates but with increasing carbohydrate concentrations the carb delivery initially increases in rate progressively until it peaks with concentrations of about 8% (8g/100ml solution). Above that concentration the gastric emptying rate slows down too much and the carb delivery decreases again. Which is why most commercial drinks are approximately 8% (40g CHO per 500mls) when mixed correctly. Maltodextrin is composed of chains of dextrose. These all compete for absorption across sodium dependant glucose uptake transporter 1 (S-GLUT1). As a result the peak absorption rate is about 60g/hr. Adding Fructose results in up to100g/hr total carbohydrate absorption. This is because fructose has it's own transports (GLUT-5). Hi "The Doctor", great posts, I am just trying to understand the reason for drinking 8% concentrated drinks of 500ml per hour. If one can absorb +- 60g glucose per hour and +-30g fructose per hour, you have to drink a solution of 18% CHO concentration. I cannot find any research which indicate that one needs to mix solids with fluids in order to achieve the 90 CHO p/hour absorption rate. Gastric empty rate does slow down with CHO concentration, but according to the abstract at http://journals.sagepub.com/doi/abs/10.1177/0148607195019005403, "The delivery of carbohydrate-energy per minute from the stomach to the small intestine was the same for all drinks". I have added 100g maltodextrin per 750ml water bottle, on several occasions, drinking two bottles in 3h without experiencing any gastric discomfort. Do you think this solution would not empty fast enough to be absorbed by the stomach/gut?
The Doctor Posted February 27, 2017 Posted February 27, 2017 Hi "The Doctor", great posts, I am just trying to understand the reason for drinking 8% concentrated drinks of 500ml per hour. If one can absorb +- 60g glucose per hour and +-30g fructose per hour, you have to drink a solution of 18% CHO concentration. I cannot find any research which indicate that one needs to mix solids with fluids in order to achieve the 90 CHO p/hour absorption rate. Gastric empty rate does slow down with CHO concentration, but according to the abstract at http://journals.sagepub.com/doi/abs/10.1177/0148607195019005403, "The delivery of carbohydrate-energy per minute from the stomach to the small intestine was the same for all drinks". I have added 100g maltodextrin per 750ml water bottle, on several occasions, drinking two bottles in 3h without experiencing any gastric discomfort. Do you think this solution would not empty fast enough to be absorbed by the stomach/gut? There are really 2 parts to this question that needs answering. 1) Why are you drinking 100g / hr of maltodextrin? Maltodextrin is composed entirely of glucose and max absorption rates in well trained athletes are in the realms of 60g/hr. You are therefore consuming an extra 40g which is just pooling in your GIT and will increase the osmolality, delay fluid absorption and may also cause GI distress (although you don't seem to have any). If you want to consume > 60g/hr you will need to add fructose. 2) Gastric emptying is determined by a complex interaction of fluid osmolality, temperature, composition, volume and other factors. This review will give you a really good overview: http://www.pubpdf.com/pub/24715561/Optimal-composition-of-fluid-replacement-beverages Figure 11 is pertinent, as is the discussion on page 600. To interpret figure 11 look at the % absorbed in 60min. For an 8% solution it is 40% of volume vs 60% of a 4% solution. 40% of 500ml 8% solution = 16g CHO delivered50% of 500ml 6% solution = 15g CHO delivered60% of 500ml 4% solution = 12g CHO delivered Although higher CHO concentrations delay gastric emptying, the higher CHO load results in a peak delivery at approximately 8%. Although there are multiple factors that vary this as per the review. 3) Lastly - 500ml x 8% = 40g/hr. Add a gel with 30g and a bar (45g) every 2 hours. You don't need to drink all of the carbs. Solids and gels are absorbed at good rates too.
'Dale Posted February 27, 2017 Posted February 27, 2017 Having had fuel tank issues over many seasons, especially after 4 hrs, this is such a valuable thread. Thanx for the input, The Doc'
The Doctor Posted March 5, 2017 Posted March 5, 2017 Having had fuel tank issues over many seasons, especially after 4 hrs, this is such a valuable thread. Thanx for the input, The Doc' Happy to assist.
Geronimo Posted March 5, 2017 Posted March 5, 2017 This man knows his stuff ^ He certainly does. Keep on walking... This man knows his stuff ^
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