Carbohydrate Supplementation Flashcards
What are the three general locations glycogen/glucose can be stored?
- liver
- muscle
- blood
Which glycogen store provides the largest amount for exercise duration?
- liver
- muscle
- blood
- muscle
In grams in the average person how much glycogen is found in the liver?
80-100g
In grams in the average person how much glycogen is found in the blood?
20g- 4-5mmol/l
In grams in the average person how much glycogen is found in the muscle?
300-800g
In which parts of the GI tract does CHO digestion take place?
Buccal cavity/mouth
Small intestine
True or False: There is a small amount of CHO digestion in the stomach
False- no CHO digestion occurs here
Give 3 types of CHO, and the enzymes needed to break them down
Starch –> Amylase
Maltose –> Maltase
Lactose –> Lactase
Sucrose –> Sucrase
Which CHO forms glucose and fructose when digested
Sucrose
Which CHO forms glucose when digested
Maltose
How is glucose absorbed into the intestine
Co-transported with Na
How is fructose absorbed into the intestine
Co-transported with GLut-5
Which Glut transporter do glucose/fructose use to enter the blood
Glut 2
What is the maximal rate of CHO absorption
60g/h
Give an overview of the glycolysis process
Glucose –> G-1-P –> G-6-P –> F 1,6-BP –> Glyceraldehyde-3-P ——-> Pyruvate
What are the products of glycolysis
Pyruvate
NADH
ATP
How is pyruvate converted into acetyl co-A
Pyruvate + CoA + NADH -CO2 = Acetyl CoA
What are the products of the krebs cycle
CoA CO2 NADH GTP FADH2
What is the final electron acceptor in the ETC
Oxygen
What are the products of the ETC
NAD FAD H20 ATP H+
How does increased CHO affect time to exhaustion
Greater time to exhaustion
Which fuel is predominant >60% VO2 max
Fat
Which fuel is predominant <60% VO2 max
CHO
Describe the classic supercompensation CHO loading protocol
Intense training 7 days prior to event to deplete CHO stores with low CHO diet. Then 3 days before the race, have a high CHO diet (supercompensation)
Give 2 disadvantages of the classic supercompensation CHO loading protocol
could lead to hypoglycaemia in the low CHO phase, GI distress, poor recovery and a negative mental state
Describe the moderate supercompensation CHO loading protocol
Gradually increase the CHO quantity consumed in the 7 days prior to the race, as well as decreasing the intensity of training
How do CHO levels differ between the classic and moderate supercompensation protocols- study results not protocol type
the classic protocol boosts higher CHO levels, 60 minutes into performance,
Otherwise there is no observed difference in CHO levels between the 2 protocols.
True or False: studies suggest 1 day of high CHO consumption prior to exercise may be enough for these performance benefits
True- As long as there wasn’t exercise performed the day before.
Everyday, what is a sufficient CHO intake level (g/kg/d)
5-7 g/kg/day
What is one negative of CHO generally
• GI problems- so athletes need to be careful about how much/the form
3-5 hours prior to performance, what are the benefits of a large CHO rich meal
- Should maximise glycogen in liver and muscle
- Can improve performance
- Decreased fat and fibre- effects length of time in intestine
At exercise onset, what happens to plasma glucose levels
Transient fall
When increased CHO oxidation occurs, giving an accelerated glycogen breakdown- how does this effect fat
blunting of FA mobilisation and fat oxidation
What is the issue with taking in a large amount of CHO 30-60 mins prior to exercise
Causes a large rise in plasma glucose and insulin
Can lead to reactive/rebound hypoglycaemia during exercise
Define the Glycaemic Index
Response to 50g CHO compared to 50g glucose
Give 2 factors which influence the glycaemic index
o Food particle size
o Biochemical structure
o Co-ingestion of fat/fibre/protein
o Gastric emptying, digestion and absorption
A lower GI gives a ——- insulin response?
lower
Does glucose or fructose have a lower GI. How is this beneficial?
Fructose lower. Reduces likelihood of crashing.
Can CHO be beneficial for intermittent exercise as well as endurance?
Yes by feeding CHO during exercise, muscle glycogen levels reduced less than the placebo.
Can CHO be beneficial for technical skills i.e. tennis serve?
CHO supplementation increased stroke quality in tennis, and was beneficial for high pressure situations, or those which require explosiveness.
GIve 3 examples of rapidly oxidised CHOs
Glucose Sucrose Maltose Lactose Maltodextrins Soluble Starch (amylopectin)
GIve 3 examples of less rapidly oxidised CHOs
Fructose (liver)
Galactose (liver)
Insoluble starch (amylose)
At what g/min does rapidly oxidised mean
up to 1g/min
At what g/min does less rapidly oxidised mean
up to 0.5g/min
To what g/min rate is oxidation limited too
1g/min
Why can glucose levels become fully saturated
Only utilises 1 transporter
How can we improve CHO oxidation rates
Ingesting both glucose and fructose increases oxidation rates (1.26g/min), as they use different transporters.
True or False: the form of CHO ingested affects the performance of CHO oxidation
False
What can be used for those who suffer GI distress from glucose
CHO mouth rinse
What % glucose is often found in a mouth rinse?
12.5%
Why is performance enhanced with multiple sources of CHO
They use different transporters, so more CHO generally can be absorbed in a time
At <30min duration how much CHO is needed
None
At 30-75 min duration, how much CHO is needed
Small amounts i.e. mouthrinse
AT 1-2h duration, how much CHO is needed
30g/h most types
At 2-3h duration, how much CHO is needed
60g/h rapidly oxidised forms
At >3h duration, how much CHO is needed
Up to 90g/h multiple CHO transporters
With CHO supplementation, how might a diet change fat, fibre and protein consumption
should be low in fat and fibre and contain protein if it can be tolerated
True or False: CHO ingested during exercise will “spare” liver glycogen and can completely block hepatic glucose output
True
True or False: Ingestion of multiple transportable CHO can increase exogenous carbohydrate oxidation rates by 40-60%
False- 20-50%
Why should CHO be used during recovery?
to maintain/restore muscle glycogen concentrations for future performance.
Give 3 factors that may affect glycogen resynthesis
- Timing
- Amount
- Form
- Type
- Other nutrients
What glut receptor response does exercise stimulate
Glut 4 translocation
How does glycogen resynthesis affect the insulin response, and why
Increases insulin response, as it stimulates glycogen synthase
What are the maximal glycogen resynthesis rates
1.2-1.4g/min ~70-90g/hour
Why could liquid forms of CHO be preferential?
liquid forms are fluid, so contribute to rehydration. They are easier to consume when appetite is reduced, and easy to digest.
Which two CHO’s are most favourable for recovery:
- Glucose, Sucrose
- Glucose, fructose,
- Fructose, sucrose
- Glucose, Sucrose
Why is fructose less favourable for recovery
absorbed slower. It has a lower GI, and minimal insulin response (which is not favourable as we want to stimulate glut-4 translocation, which require the insulin response)
Where can fructose be more favourable during recovery
The liver
For recovery, do we want foods with a high or lower GI
Higher