MODULE 5 -CARBOHYDRATEMETABOLISM 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 fromMacronutrientsCarbohydrate to ATP - GlycolysisNon-Carbohydrate to ATP- Gluconeogenesis
Production of ATP from food
About Monosaccharides1. Glucose - used directly by the cell for energy, stored as glycogen in the liver & muscles, converted to fat & stored as energy2. Fructose - Converted to glucose in the liver3. Galactose - Forms milk sugar (lactose), converted to glucose for energy
About PolysaccharidesFormed by glycosidic bonds linking monosaccharidesClassified into1. Plant polysaccahrides - Starch & FibreStarch is known as complex carbohydrate.Fibre is not digested in the human gut.2. Animal Polysaccharides - Glycogen
Roles of Fibre1. 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 CarbohydrateRegular physical activity - 60% of total intakeDuring intense training - 70% of total intake
Glycemic IndexThe 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 HypoglycaemiaHyperglycaemia • Low blood levels of glucose• Consuming high • Result in weakness, glycaemic load food hunger, dizziness• Insulin resistance • Impairs exercise performance• Metabolic syndrome • Prolonged - loss of consciousness and brain damage
a) CARBOHYDRATE AS AN ENERGY SUBSTRATE FOR EXERCISE
CARBOHYDRATE AS AN ENERGY SOURCECarbohydrates - 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
EFFECT OF EXERCISE INTENSITY &DURATION OF CARBOHYDRATEUTILIZATIONHigh 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 CARBOHYDRATEUTILIZATION• 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 activity 2. Long duration activity 3. Exercise in hot and cold temperature extremes 4. Exercise in high altitude 5. Age (higher in young boys than men)Factors that decrease the relative energy expenditure from carbohydrate: 1. Endurance training 2. Good aerobic conditioning 3. Temperature adaptation 4. Gender
c) CARBOHYDRATE LOADING
CARBOHYDRATE LOADINGA strategy involving changes to training and nutrition that can maximise muscle glycogen (carbohydrate) stores prior to endurance competition.
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 EXERCISEe) PRE-GAME AND POST-GAME MEALS
Carbohydrates before ExerciseThe 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 GAMEIt 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 THEACTIVITYThe 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 GAMEAfter 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
ActivityFrom the examples given, suggest a plan for an athlete to receive sufficient carbohydrates before, during and after activity