Carbohydrates During And After Exercise

Question 1

What is the effect (results) of carbohydrate feeding during exercise on performance?

Answer 1

• 61 studies
• 0% reduced
• 18% no effect
• 82% improved

Question 2

Examples of ‘fast’ carbohydrates?

Answer 2

Glucose
Maltose
Sucrose

Question 3

Examples of ‘slow’ carbohydrates?

Answer 3

Fructose alone
Galactose
Starches rich in amylose

Question 4

Guidelines for carbohydrate feeding during exercise?

Answer 4

1.0g/min (60g/h) during exercise

For example:
1 litre/h of a typical sports drink
2 gels/h (containing 30g each)
0.5 litre sports drink plus 1 gel
80g of jelly babies (78g carb per 100g)

Question 5

Guidelines of carbohydrate consumption of exercise lasting 30-75 minutes?

Answer 5

• Small amounts of mouth rinse

Question 6

Guidelines of carbohydrate consumption of exercise lasting 1-2 hours?

Answer 6

• 30g/hour

Question 7

Guidelines of carbohydrate consumption of exercise lasting 2-3 hours?

Answer 7

• 60g/hour

Question 8

Guidelines of carbohydrate consumption of exercise lasting > 2.5 hours?

Answer 8

• 90g/hour

Question 9

What are the metabolic effects (benefits) of carbohydrate feeding during exercise? (Glucose, oxidation, glycogen)

Answer 9

• Maintains plasma glucose
• helps to sustain high rates of carbohydrate oxidation
• Spares liver glycogen

Question 10

What is the research around performance with glucose vs glucose + fructose?

Answer 10

• 8% faster with glucose + fructose compared to glucose, and 19% faster compared to water (placebo)

Question 11

What are multiple transportable carbohydrates? (Sugars, oxidation, performance)

Answer 11

• sugars transported across intestine by stimulating more than one protein transporter
• increases exogenous carbohydrate oxidation by 20-50%
• In exercise (>2.5-3h), this contributes to higher performance

Question 12

How does timing of carbohydrate ingestion affect rate of glycogen synthesis?

Answer 12

• Carbohydrate ingested immediately post exercise has roughly double the rate of glycogen synthesis than carbohydrates ingested 2 hours after exercise

Question 13

What is the recommended amount/maximum carbohydrate consumption post exercise for maximum glycogen synthesis?

Answer 13

• Above 1.2g/kg bw/h, there is little or no further benefit

Question 14

What is the optimal steps to speedy refuelling after exercise?

Answer 14

• Early and frequent carbohydrate feeding
• 1.2g/kg CHO/h for first 4 hours, of moderate-to-high glycaemic index CHO’s

Question 15

How can carbohydrate type affect short-term exercise recovery?

Answer 15

• fructose with glucose-based carbohydrates = quickest replenishment of glycogen stores
• it can also enhance subsequent time-to-fatigue

Question 16

What is the main limitation to exogenous oxidation when a single carbohydrate source is ingested during exercise with the upper limit being 1g/min (60g/h)?

Answer 16

Intestinal carbohydrate absorption

Question 17

Combining glucose and fructose can increase exogenous carbohydrate oxidation above the so called upper limit of 1g/min. What are the most likely mechanisms for this? (4 points)?

Answer 17

• Glucose and fructose would stimulate multiple carbohydrate transport mechanisms
• Glucose transported by SGLT1
• Fructose transported by GLUT5
• This increases the amount of carbs that can be absorbed into the circulation and delivered to the muscle

Question 18

What is Glucose transported by?

Answer 18

Sodium-dependent glucose cotransporter (SGLT1)

Question 19

What is fructose transported by?

Answer 19

Penrose transporter (GLUT5)

Question 20

What effect does carbohydrate feeding during exercise have on liver glucose metabolism?

Answer 20

• Suppresses liver glucose output
• and spares liver glycogen