MODULE 5 - CARBOHYDRATE METABOLISM IN

EXERCISE(Anandini)

MACRONUTRIENTS AND EXERCISE

Macronutrients1. Carbohydrates (made up of saccharides/

sugars)2. Proteins (made up of amino acids)3. Lipids/ Fats (made up of glycerol + fatty acid)

What do they do?

1. Provide energy2. Maintain structure3. Provide functional integrity

Pathways by which ATP is produced from Macronutrients

Carbohydrate to ATP - Glycolysis

Non-Carbohydrate to ATP- Gluconeogenesis

Production of ATP from food

CLASSIFICATION OF CARBOHYDRATES

About Monosaccharides

1. Glucose - used directly by the cell for energy, stored as glycogen in the liver & muscles, converted to fat & stored as energy

2. Fructose - Converted to glucose in the liver

3. Galactose - Forms milk sugar (lactose), converted to glucose for energy

About Disaccharides

Di = Mono + Mono

Sucrose - Glucose + FructoseLactose - Glucose + GalactoseMaltose - Glucose + Glucose

About Polysaccharides

Formed by glycosidic bonds linking monosaccharides

Classified into 1. Plant polysaccahrides - Starch & Fibre

Starch is known as complex carbohydrate.Fibre is not digested in the human gut.

2. Animal Polysaccharides - Glycogen

Roles of Fibre

1. Retains water - gives bulk to food - SATIETY2. Binds/ dilutes harmful chemicals3. Shortens transit time for food residues to pass through the

digestive tract

Recommended intake of Carbohydrate

Regular physical activity - 60% of total intake

During intense training - 70% of total intake

Glycemic Index

The glycemic index (GI) is a ranking of carbohydrates on a scale from 0 to 100 according to the extent to which they raise blood sugar levels after eating.

Foods with a high GI are those which are rapidly digested and absorbed and result in marked fluctuations in blood sugar levels.

Low-GI foods, by virtue of their slow digestion and absorption, produce gradual rises in blood sugar and insulin levels, and have proven benefits for health.

Hyper & Hypo glycaemia

Hyperglycaemia

• Consuming high glycaemic load food

• Insulin resistance

• Metabolic syndrome

Hypoglycaemia

• Low blood levels of glucose

• Result in weakness, hunger, dizziness

• Impairs exercise performance

• Prolonged - loss of consciousness and brain damage

a) CARBOHYDRATE AS AN ENERGY SUBSTRATE FOR EXERCISE

CARBOHYDRATE AS AN ENERGY SOURCE

Carbohydrates - most important source of energy in the form of ATP (Adenosine Triphosphate)

• Broken down to glucose/ fructose and absorbed in the body

• Glucose/ fructose that is not utilized is stored in the liver as glycogen

• 1 g of carbohydrate gives 4KCal

• Failure to sustain continuous delivery of glucose to working muscles will cause cessation of high intensity activity.

• Avoiding glucose depletion should be a major nutritional focus.

• Unlike protein and fat the storage capacity of carbohydrate in the body is limited.

• Humans can store 350 g of glycogen in the muscles, 90 g in the liver and about 5g of free glucose in the blood

stream.

Activity:

Given the amount of carbohydrate stored in different parts of the body, calculate the number of calories that will be available from glycogen stores in the liver, muscle and blood stream.

b) EFFECT OF EXERCISE INTENSITY, DURATION AND TRAINING ON

CARBOHYDRATE NEEDS

High intensity, low duration

• More calories burned in less timeMore carbohydrate (glycogen) is utilized when:1. Type II muscle fibres are utilized - contain high amount of

glycolytic enzymes2. Increased blood epinephrine - increase muscle glycogen

breakdown, glycolysis and lactate production3. Increased lactate production - inhibits fat metabolism

EFFECT OF EXERCISE INTENSITY & DURATION OF CARBOHYDRATE UTILIZATION

EFFECT OF EXERCISE INTENSITY & DURATION OF CARBOHYDRATE UTILIZATION

• At high intensity of exercise (>70%VO2max) carbohydrate is used as the energy source.

• When the duration of activity is short, carbohydrate is taken from glycogen for energy.

Factors affecting increased reliance on carbohydrate as an energy source:

1. High intensity activity2. Long duration activity3. Exercise in hot and cold temperature extremes4. Exercise in high altitude5. Age (higher in young boys than men)

Factors that decrease the relative energy expenditure from carbohydrate:

6. Endurance training7. Good aerobic conditioning8. Temperature adaptation9. Gender

c) CARBOHYDRATE LOADING

CARBOHYDRATE LOADING

A strategy involving changes to training and nutrition that can maximise muscle glycogen (carbohydrate) stores prior to endurance competition.

Carbohydrate loading procedure

Cons of Carbohydrate Loading

Modified Procedure

Gender Differences During Carbohydrate Loading

ACTIVITY:

Some common foods and their carbohydrate content:FOOD Carbohydrate Content (g) Calories (KCal)

Skimmed milk (360mL) 18 125

Peanut Butter (1 tablespoon) 3 94

Honey (1 tbsp) 17 64

Oats (4 tbsp) 23 200

Fig bar (3 inches) 40 198

Raisins (30g) 34 129

Whole wheat bread 25 180

Chicken breast (1/2)/ Salmon (100g) 0 142

Baby carrots (12) 10 48

Thin tomato slices 2 44

Digestive biscuit (1) 8.5 90

Apple 25 95

Brown rice (1.5 cups) 69 328

Yoghurt - fat free (1 cup) 12

Activity:

What would be a suitable menu plan for an athlete to carbohydrate load up to about 70% energy coming from carbohydrate rich food?

Activity:

An athlete weighs 80kg. How much carbohyrdate will be require 3 hours before the competition?

After training daily for a moderate intensity endurance program, how much carbohydrate will he require for recovery?

Also from the above scenarios, how many calories will the carbohydrate give the athlete?

d) CARBOHYDRATE INTAKE BEFORE, DURING AND AFTER EXERCISE

e) PRE-GAME AND POST-GAME MEALS

Carbohydrates before Exercise

The ideal pre-competition meal should:

• Contain about 150 to 300g of carbohydrate

• Be consumed 3 to 4 hours before the competition

• Be low in fibre

• Be low in fat

• Have low to medium GI

CARBOHYDRATE INTAKE - PRE GAME

It is vital that athletes have a sufficient carbohydrate intake prior to exercise so that the total energy requirement is met.

The following foods are suitable to eat 3-4 hours before exercise:

• crumpets with jam or honey + flavoured milk

• baked potato + cottage cheese filling + glass of milk

• baked beans on toast

• breakfast cereal with milk

• bread roll with cheese/meat filling + banana

• fruit salad with fruit-flavoured yoghurt

• pasta or rice with a sauce based on low-fat ingredients (e.g. tomato, vegetables, lean meat)

The following snacks are suitable to eat 1-2 hours before exercise:

• liquid meal supplement

• milk shake or fruit smoothie

• sports bars (check labels for carbohydrate and protein content)

• breakfast cereal with milk

• cereal bars

• fruit-flavoured yoghurt

• fruit

The following foods are suitable to eat if there is less than 1 hour before exercise:

• sports drink

• carbohydrate gel

• cordial

• sports bars

• jelly lollies

Carbohydrates during Exercise

• Allows for greater intensity during prolonged activity

• Consuming about 60g of liquid/ solid carbohydrate each hour will benefit :

1. High intensity, long duration aerobic exercise2. Repetitive short bouts of near-maximal effort

• Spares muscle glycogen

• Maintains more optimal blood glucose level

CARBOHYDRATE INTAKE - DURING THE ACTIVITY

The carbohydrate stores have to be replenished during exercise as well. The foods given below are some of the options:

• Banana

• Nuts

• Dry fruits

Carbohydrates after Exercise

• High glycemic carbohydrate - rich foods

• Either a single large meal or small frequent meals will replenish glycogen stores

• Should be consumed as soon as possible after the activity

• Avoid legumes, fructose and milk products

CARBOHYDRATE INTAKE - POST GAME

After exercise the glycogen stores will have depleted and need to be replenished. These are some of the food options:

• Fruit

• Yoghurt

• Sandwiches

• Corn flakes with milk

Activity

Activity

From the examples given, suggest a plan for an athlete to receive sufficient carbohydrates before, during and after activity