Carbohydrate training and precompetition diets (lecture eight) Flashcards
What is the crossover concept?
The point of intensity where CHO becomes the primary fuel source and FATS become less and less.
Maximal intensity= virtually CHO only.
Where is glycogen stored?
Muscle - used for fuel in intense exercise.
Liver- maintains blood glucose to supply the organs, mainly the brain.
How much glycogen in the muscles?
300-400grams
approximately when at 60% vo2max does glyocogen deplete?
90mins has gone from 100%-35%
Where abouts does the liver maintain blood glucose?
4-6mmol/L
How is blood glucose determined?
Exogenous intake
and endogenous production
What is a muscle punch biopsy useful for?
Determine accurately the glycogen content of muscles.
Why is lactate useful?
Muscles use it as A CHO fuel source
Liver makes glucose from it.
Other organs use it as a fuel source
What is the process of glycogen breakdown in the liver called?
Glycogenolysis
How much glycogen is stored in the liver?
80-100g
what is the process of glucose production called and where does it occur?
Gluconeogenesis and in the liver.
If glucose production does not match uptake what results?
hypoglycemia
What transporters does the muscles use to uptake glucose?
GLUT4
When is CHO loading done?
Days before the event to top up muscle glycogen and on the day to top up liver gylcogen
What can CHO loading result in?
CHO supercompensation
How is supercompensation achieved?
week before event. Start decreasing the exercise levels from ~90mins and start increasing CHO intake. up to 70% (average diet CHO 50%)
what are the disadvantages of supercompensation?
Tend to become hypoglyceamic during the low CHO period..
• GI problems
• Hard to train through the low-CHO period
• Poor recovery (due to low CHO)
• Hard to retrain from training before competition and is not an optimal
peaking strategy
• Irritability.
what are the benefits of CHO loading?
Benefits of CHO loading
• Increases time to exhaustion by about 20%
• Improves time trial performance by 2-3%
• Improves skill in team sports that require repeated high-intensity efforts
(e.g. soccer & rugby)
What are the limitations of CHO loading?
Limitations of CHO loading
• Exercise seems to need to be at least 90 min for benefit to accrue.
• For short high-intensity exercise it does not seem to have a benefit.
What is the benefit of a high CHO diet?
Over a weeks training your muscle glycogen levels remain highish. While in a moderate diet they deplete.
What is GI?
Glycemic index is: The elevation in blood glucose from 50g intake.
i.e low GI slow releasing
What is better low of high GI foods?
Low GI foods as high GI foods can lead to lower blood glucose levels
what type of GI foods should an athlete consume?
Slow GI foods, except during exercise where high GI foods may be of benefit.
What are the serious implications of high GI foods?
Cause large insulin release which inhibits lipolysis and causes rapid glucose uptake into the liver, this can leave no glucose supply to the muscles.
