Carbohydrates Flashcards
What is Anaerobic Glycolysis?
- Carbohydrates are broken down to release energy to phosphorylate ADP and form ATP.
- Final product = lactate + H+
What is Aerobic Metabolism?
- Oxidative phosphorylation - carb, protein, fat.
- Continuous supply of ATP as long as oxygen is available
- Occurs in the mitochondria
- 30-32 ATP
What are the 3 phases of aerobic metabolism?
- Preparation
- Krebs cycle/TCA cycle - oxidises, removes, electrons
- Electron Transport Chain - electrons undergo a number of reactions releasing energy to rephosphorylate ADP to ATP
What are the 4 processes of carbohydrate digestion?
- Mouth: salivary amylase hydrolyses dietary starch
- Stomach: stomach acid temporarily inhibits amylase and stops carb digestion
- Pancreas: Bicarbonate secretion from pancreas neutralises the stomach contents and pancreatic amylase continues to digest starch
- Small Intestine: Several disaccharidase enzymes breakdown disaccharides in the brush border of the small intestine producing monosaccharides
What are the 4 processes of intestinal carbohydrate absoprtion?
- Glucose is absorbed in the small intestine via a sodium glucose transporter
- Fructose is absorbed via a different transporter, GLUT5
- GLU and FRU are transported across the basolateral membrane via the transporter GLUT-2
- GLU and FRU are transported to the liver where fructose is removed from the circulation
What are the 3 processes of Glycogensis?
- CHO ingestion stimulates the release of insulin from the pancreas
- Insulin stimulates GLUT-4 translocation to muscle membrane
- Glucose-6-phosphate stimulates the production of glycogen
How much carbs are stored in blood?
~5g
How much carbs are stored in muscle?
~350g
How much carbs are stored in liver?
~100g
What can affect carb stores in the body?
Fasting, exercise and diet
Why do we need carbs?
- Fuel for the muscle and brain during exercise
- Low levels of carb stores are a factor in fatigue and reduced performance
- Ensuring that stores are increased result in performance enhancements
What is athlete knowledge on CHO like?
- Athletes often lack basic knowledge and applied guidelines for CHO
- Understanding current behaviour is the first step in changing future behaviour
What happens when insufficient CHO ingested?
- Progressive decrease in muscle glycogen with low carbohydrate diet
- CHO attenuates the decline in performance and maintains mood
Why do you need CHO before exercise?
- High pre-exercise muscle and liver glycogen concentrations are believed to be essential for optimal performance
- Fatigue during prolonged exercise is often associated with muscle glycogen depletion and reduced blood glucose concentrations
What is gastrointestinal distress?
May be related to the intake of:
- Highly concentrated carb solutions
- Hyperosmotic drinks
- The intake of fibre, fat and protein ie. a low residue = low fibre diet
When does gastrointestinal distress occur?
- GI problems occur frequently, especially in long-distance races
- Problems seem to be highly individual and perhaps genetically determined
What sort of nutrition strategy should be developed for CHO?
An individualised strategy that aims to deliver carbohydrate to the working muscle at a rate that is dependent on the absolute exercise intensity as well as the duration of the event
What are the aims of pre-exercise fueling?
- Prevent muscle and liver glycogen depletion
- Prevent hypoglycaemia
- Prevent gastrointestinal problem
How can you train the gut to handle CHO?
- Suggestions that the gut is able to increase uptake with exposure
- Gradually increase intake overtime, you can handle it better
How much CHO do you need in exercise recovery?
- Muscle and liver glycogen levels to pre-exercise
- A carb intake of 1.5g/kg during the first 30mins and again every 2hours for 4-6 hours will be adequate to replace glycogen stores
What do you need to consider in CHO intake post-exercise?
- Time to next exercise session
- Intensity of session just completed
- What’s the overall nutrition strategy
- Demands of the next training session
- Tolerance of gut to meet fueling needs
- Logistics
What is oestrogen needed for?
- Important for muscle mass
- Inhibits bone resorption
What is progesterone needed for?
- Increases muscle protein synthesis rates
- Stimulates osteoblasts
How many elite female athletes are eumenorrheic?
67-91%
How does estrogen and progesterone effect fat oxidation?
- Estrogen may increase free fatty acids availability during exercise and promote lipid oxidation
- Progesterone may limit fat oxidation
How does hormonal contraception impact reliance on fat?
Elevated plasma estrogen concentrations increase the reliance on fat as an energy source during endurance exercise
