Carbohydrates And Exercise Flashcards
How many grams of carbs are stored in muscle, the liver, and blood
Muscle: 300-400 g
Liver: 75-100 g
Blood: 5-25 g
How many mmol/kg does carbohydrate loading increase muscle glycogen stores?
210-230 mmol/kg
What percentage of fuel does muscle glycogen and blood glucose account for in both moderate and high intensity exercise?
Moderate (65% of VO2 max): 50%
High intensity (85% of VO2 max): 66%
What are daily carbohydrate intake guidelines for trained athletes
Very light training (low intensity or skill based): 3-5 g/kg
Moderate intensity (60 min/d): 5-7 g/kg
Moderate to high intensity endurance exercise (1-3 hr/d): 6-10 g/kg
Moderate to high intensity exercise (4-5 hr/d): 8-12 g/kg
Formula for glycemic load
GL = GI (expressed as a decimal) x carbohydrate content (grams)
What can a high GI modified starch do if consumed post exercise?
Enhance muscle glycogen storage
What can a low GI modified starch do if consumed pre exercise?
Sustain blood glucose levels during prolonged endurance exercise
What can carbohydrate loading do for performance
Postpone fatigue
Extend duration of steady state exercise by about 20%
Improve endurance performance by about 2-3%
Modern way of doing glycogen supercompensation
Taper training for 3 days AND consume a high carbohydrate diet of 10 g/kg/d
OR
Rest for 36-48 hours AND consume 10-12 g/kg/d (new loading guideline)
When is carbohydrate loading not going to work?
When exercise is less than 90 minutes
It may harm performance by causing stiffness and weight gain
Benefits of consuming carbs
Restore liver glycogen
Increase muscle glycogen
Prevents hunger
Provides glucose for central nervous system
Morning carbohydrate fueling recommendations
1-4 g/kg to be consumed 1-4 hours prior to exercise
What nutrients should be limited before exercise?
Protein, fat, and fiber
Rank from most to least effective:
Carbs consumed prior to exercise
Carbs consumed during exercise
Both
Both
Carbs consumed during exercise
Carbs consumed before exercise
What are liquid meals good for?
Reducing nausea
Making weight due to low stool residue
Convenience for multiple or very long competitions
Preventive strategies for experiencing hypoglycemia and fatigue following a carbohydrate feeding
Choose low GI sources (more stable glucose and insulin response)
Consume carbs a few minutes before exercise
Consume carbs during exercise
What hormones inhibit the release of insulin?
Epinephrine
Norepinephrine
Growth hormone
Consuming carbohydrates during exercise negates the glycemic effects of the pre exercise meal on performance and metabolism. T/F
True
What are the benefits of consuming carbs during exercise?
Primarily metabolic:
Prevents hypoglycemia
Maintains high rates of carb oxidation
Improves endurance
During prolonged exercise, what becomes an increasingly important fuel source?
Blood glucose
Because muscle glycogen stores decreased. By consuming carbs during exercise, carb oxidation (and therefore ATP production) remains high
How do carbohydrate feedings improve performance in intermittent, high intensity sports?
Decrease muscle glycogen utilization
Increase muscle glycogen resynthesis during rest or low intensity periods
Increase blood glucose
Maximum amount of glucose absorption during exercise
1 g/min
How to exceed maximum carbohydrate absorption rate?
Pair glucose with FRUCTOSE
At what hour of exercise does multiple transportable carbohydrates provide benefits?
2.5 hours or longer
Same benefit is provided as other carbohydrate sources lasting under 2.5 hours
Recommended carbohydrate intake:
- Exercise lasting less than 30 minutes
- High intensity exercise lasting 30-75 minutes
- Endurance and intermittent, high intensity exercise lasting 1-2 hours
- Endurance exercise lasting 2-3 hours
- Endurance and ultra endurance exercise lasting 2.5 hours or more
30 or less: Not necessary or practical
30-75 minutes: Small amounts or a mouth rinse
1-2 hours: 30 g/hr and single or multiple
2-3 hours: 60 g/hr and single or multiple
2.5 or more: 90 g/hr and multiple transportable carbs
Post exercise carbohydrate refueling recommendations
1.0-1.2 g/kg per hour for the first 4 hours
There is no difference in glycogen resynthesis when liquid or solid forms of carbs are consumed.
T/F
True
Why does glycogen depletion occur faster after exercise?
Blood flow to the muscles is greater immediately following exercise
Muscle cells are more likely to take up glucose
Muscle cells are more sensitive to the effects of insulin, which enhances the action of glycogen synthase
Post exercise refueling recommendations for both carbs and protein
Carbs: 0.8 g/kg/hr
Protein: 0.3 g/kg/hr
Consumption of 1-4 g/kg of carbs 1-4 hours prior to exercise results in __% improvement to ___________ performance
Improved endurance performance by as much as 14%
List 3 examples of non-commercial intraworkout beverages
Fruit juice diluted in water (4 oz juice in 4 oz water = 6% solution)
Low sodium vegetable juices, such as carrot juice (7% solution)
Honey or solid foods ingested with water (8 oz for every 15 g of carbs = 6.3% solution)
Why is maltodextrin no longer used
Causes GI upset
