Week 3 - Carbohydrate feeding during exercise

Question 1

Examples of monosaccharides

Answer 1

Galactose, glucose, fructose

Question 2

Examples of disaccharides

Answer 2

lactose, maltose and sucrose

Question 3

Examples of more complex carbohydrates

Answer 3

• Amylose starch
• Amylopectin starch
  (banana, bread, potato)

Question 4

What does fast and slow carbohydrates refer to?

Answer 4

Fast and slow carbs refer to the speed at which these carb types are digested, absorbed and made available to the body for energy provision.

Question 5

Give examples of slow and fast carbohydrates.

Answer 5

Fast carbs
- Glucose
- Maltose
- Sucrose
- Maltodextrins
- Starches rich in amylopectin

Slow carbs
- Fructose
- Galactose
- Isomaltulose
- Starches rich in amylose

Question 6

What are the classical guidelines for carbohydrate feeding during exercise?

Answer 6

60grams per hour (1g/min) during exercise

Ex: 1litre/h of sports drink or 80g of Jelly babies

Question 7

What are the updated guidelines for carb feeding at 30-75mins, 1-2hours, 2-3hours, and >2.5hours?

Answer 7

30-75mins: small amounts such as single or multiple transportable carbohydrates

1-2hours: 30g/hour such as single or multiple transportable carbohydrates (advise fast absorbed carbs - glucose, sucrose)

2-3hours: 60g/hour such as single or multiple transportable carbohydrates (advise fast absorbed carbs - glucose, sucrose)

> 2/5hours: 90g/hour and only multiple transportable carbohydrates

Question 8

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

Answer 8

• Improve endurance capacity and performance
• Effects of carb feeding during exercise increase with exercise duration
• May also benefit other aspects of sport performance such as motor skills during prolonged sports events (pen)

Question 9

What are the metabolic effects (benefits) of carb feeding during exercise?

Answer 9

• Maintains plasma glucose concentration and helps to sustain high rates of carbohydrate oxidation
• Spares liver glycogen stores which can be used during later stages of exercise and helps to sustain plasma glucose and carbohydrate oxidation
• May spare muscle glycogen in certain situations

Question 10

What are multiple transportable carbohydrates?

Answer 10

Refer to sugars that are transported across the intestine and into the blood by stimulating more than one protein transporter (e.g. glucose {via SGLT1} and fructose {via GLUT5}).

Question 11

Why is using multiple transporters carbohydrates beneficial for prolonged exercise?

Answer 11

It increases rates of exogenous carbohydrate oxidation by 20-50% above single transported carbohydrates.
It does this by reducing competition for SGLT1 transport (glucose) in the intestines due to stimulating other protein transporters (GLUT5 for fructose).

Question 12

When are multiple transporter carbohydrates required?

Answer 12

when we need to achieve the high ingestion rates of up to 90g/h recommended for sustained exercise of >2.5-3h.