Carbohydrates Flashcards
Name the locations of CHO stores
Liver - 80-110g
Skeletal muscle - 300-600g
Blood glucose - 3-5g
What type of intensity is CHO recruited for?
High intensity - can be metabolised faster than fat
What initiates the breakdown of glycogen via glucagon?
Epinephrine
What can help maintain blood glucose levels during exercise?
Energy drinks, gels, snacks
What does a higher &VO2max mean in athletes?
Quicker decline to fatigue
What diet improved athletes time to fatigue regarding glycogen?
High CHO diet improved time to fatigue
What does CHO not slow down in terms of fatigue?
The rate of muscle glycogen breakdown - glucose digestion is not quick enough to offset muscle glycogen breakdown
What does CHO during exercise actually slow down?
The rate of liver glycogen depletion
What are the every day recommendations for CHO intake?
Light - 3-5g/kg
Moderate - 5-7g/kg
High - 6-10 g/kg
Very high - 10-12g/kg
What are the consequences of insufficient glycogen stores?
Poor recovery after a training session, which leads to early fatigue in the following session
When is CHO loading recommended? Include the amounts
For events lasting over 90 minutes
10-12 g/kg/dm 36-48 hours before event
What are the general CHO fuelling guidelines prior to competiton?
7-12g/kg/d
What are the CHO guidelines for day of the event?
1-4 g/kg/d 1-4 hours prior
Why should fat be considered in pre-event meal?
Slow-releasing energy that can be used during prolonged exercise
How long is the golden window post-exercise for CHO consumption and why?
First 30 minutes, but within 4 hours
Greatest rates of muscle glycogen synthesis
How much CHO is recommended for recovery?
1.2-1.4 g/kg/dm/h
Name 5 fast CHO.
- Glucose
- Maltose
- Sucrose
- Maltodextrins
- Amylopectin
Name 4 slow CHO.
- Fructose
- Galactose
- Isomaltulose
- Amylose
Why aren’t the recommended guidelines for CHO during exercise higher?
Oxidation rates stay constant, so no point in increasing
Higher amounts increases likelihood of adverse effects
What do the updated guidelines for CHO during exercise suggest?
> 45 mins = no CHO
1hr = 10-15g
1-3hr = 30-60g/hr fast CHO
3+ hr = up to 90g/hr multiple transporters
Where is glycogen spared in the body?
Fed CHO passes the liver before entering the blood, therefore spared in the liver and not skeletal muscle
Is there any non-metabolic effects of CHO?
Yes - CHO in the mouth inputs to the brain, reducing fatigue
What transporter takes up glucose?
SGLT1
What transporter takes up fructose?
GLUT5
Why are multi transporters favoured?
- Greater sugar uptake
- Potential to reduce GI distress
What are the recommendations for CHO after exercise? - LT and ST
LT - normal everyday
ST -
What enzymes are used in glycogen synthesis?
- Glycogen synthase
- Branching enzyme
What is insulin independent glucose uptake?
Exercise activates AMPK which allows the translocation of GLUT4 transporters to the cell membrane
What is insulin dependent glucose uptake?
After a meal beta cells secrete insulin, which binds to the cell receptor, stimulating translocation of GLUT4 to cell membrane
Describe glycogen recovery.
Rapid phase - insulin independent
Slow phase - insulin independent
What are the recommendations for CHO after exercise for rapid recovery?
1.2 g/kg bw/h for 4-6 hr
Are there any added benefits of protein co-ingestion? Why?
No, unless CHO intake is low
Bc protein has stimulatory effects on insulin
What effect does glucose-fructose uptake have on the body?
No increase in glycogen synthesis in muscle, but does increase in the liver
Why is the upper limit for CHO 1g/hr during exercise?
Gastrointestinal carbohydrate absorption
