Q14 CHO Flashcards
Mechanism
Endurance performance dictated by endogenous carbs (ie glycogen) (hitting the wall)
Fatigue in prolonged exercise is associated with muscle glycogen depletion and blood glucose concentrations
o Blood glucose measured at end or marathon as was found to be low in study
Endurance exercise fatigue is associated with muscle glycogen depletion
o Exogenous carb intake during prolonged exercise may reduce rate of glycogenolysis which spares muscle glycogen
Carbs associated with maintained motor skills and mood state, reduced RPE, fatigue delay, force production and reduced aim decrements
Dose/ Timing
One day of carb loading is just as effective as 3
super compensation effect
24 leading up to event 10g/kg = 550grams low GI
High carb meal 2-3 hours before race
During race consume 60-90grams per hour
Aim for 20 every 20mins
Preferably mix of glucose and fructose for maximal uptake
Positives
Carb supplementation prevents drops in blood glucose levels
Studies have shown that ingestion of multiple transportable carbs increases exogenous carb oxidation
o Different receptors so increased uptake with correct ratio
o Receptors have high affinity for glucose and galactose but not fructose
o May become fully saturated and thus may be limiting factor
Benefits of co-ingestion:
o Reduced RPE
o Improved performance
o Reduced GI discomfort
Negatives
Fat is the predominant macronutrient in lower intensity exercise that would be characteristic of a triathlon
- but depends on how elite (carbs use increases with intensity)
Athletes need to be conscious of carb source choices
o Fructose and galactose oxidized slightly slower oxidation than glucose
o Lower oxidation attributed to intestinal absorption and the need for the liver
Train low, race high theory:
o Low muscle glycogen could enhance training adaptation
o Citrate synthase activity, resting muscle glycogen concentration and exercise time to exhaustion improved when depleted stores
o Low muscle glycogen elevates circulating FFAs and catecholamines
