Carbohydrates

Question 1

What is the crossover concept?

Answer 1

As intensity increases we have to rely on CHO as fat burns too slowly

Question 2

What is Glycogen?

Answer 2

Deposited in muscle and liver

Muscle for exercise liver for brain

Question 3

Muscle glycogen

Answer 3

Quickly mobilized

300-400g of CHO

Question 4

Blood glucose

Answer 4

maintained around 4-6mmol/l

balance between liver and muscle

Question 5

Endogenous Glucose production

Answer 5

Glycogenolysis - generation of glucose by splitting complex carbs
Glyconeogenesis - Making new glucose from 3 carbon units

Question 6

Lactate

Answer 6

Lactate is used by the muscle as a CHO source and used by the liver to make new glucose

Question 7

CHO before exercise

Answer 7

Important for a one day event

Can fully top up glycogen stores and can even super compensate.

Question 8

CHO supercompensation

Answer 8

Where an athlete depletes all their glycogen stores and then eats a lot of carbs to supercompensate so the amount of glycogen in the muscle increases considerably. Better to supercompensate to only 50% CHo in diet to 70%CHo in diet in order to not become hypoglycemic in that time and to avoid GI distress

Question 9

Benefits/limitations of CHO loading

Answer 9

Benefits =
increase time to exhaustion by about 20%
Improves time trial performance
improves skill

Limitations =
Exercise needs to be for at least 90min in order to be of any benefit
does not have a benefit for short high intensity exercise

Question 10

Formula for the GI index

Answer 10

IAUC of test food/IAUC of reference food (glucose) x 100

Question 11

CHO 3-5 hours before exercise

Answer 11

increases CHO availability for muscle

Some will remain in blood and some will go to liver/muscle

Question 12

CHO intake 30-60 before exercise

Answer 12

Large rise in blood glucose and insulin
Does cause intake of glucose which is not what you want
System then thinks that it doesn’t need to make any more glucose
Leads to reactive hypoglycaemia
Need to eat low GI foods to prevent this

Question 13

CHO intake during exercise

Answer 13

Improves performance
Spares glycogen
Increases motor skills

Question 14

CHO oxidation rate

Answer 14

> 2g CHO ingested
1.2-1.7 appears in GI tract
1g from liver
rest into muscle. So the liver becomes the ‘bottleneck’

Question 15

What are maltodextrins?

Answer 15

short chain glucose polymers used to increas CHO of sports drinks

Question 16

CHO after exercise

Answer 16

You need to eat immediately afterwards in order to really provide CHO for your muscles especially if you have a short recovery time. So you need to do another race etc

Question 17

What happens in the muscle during exercise

Answer 17

GLUT 4 is inserted into the membrane
This brings in more glucose
The glucose is broken down by Hexokinase to Glucose-6-phosphate
and is turned into glycogen by glycogen synthase. Glycogen synthase is automatically upregualted during exercise

Question 18

How much CHO is recommended?

Answer 18

`1.2 g/kg/hr

Question 19

What are the factors dictating the glycogen synthesis threshold?

Answer 19

How much is stored by muscle
How much is taken up by other tissue
How much is oxidized immediately

Question 20

What are the daily CHO recommendations for a person undergoing moderate training?

Answer 20

5-7g/kg bw/day

Question 21

What are the daily CHO recommendations for someone undergoing hard training?

Answer 21

7-10 g/kg bw/day

Question 22

What are the daily CHO recommendations for someone undergoing very hard training?

Answer 22

10-13 g/kg bw/day