1. Carbohydrates (CHO) C:H:O ratio of 1:2:1 Sugars and starches Functions –Predominant fuel in high-intensity exercise, intermittent-intensity and cause of fatigue (due to lack of CHO) in prolonged exercise –Fuel for CNS and blood cells Intake –West 40-50% (300g/day) 50% simple –Athletes 60% (up to 1000g/day)

2. Monosaccharides (simple sugars) 3 – 7 C atoms The most important to humans are the hexose sugars eg. Glucose C 6 H 12 O 6 Straight chain or ring (more common in body) Fructose same formula, diff structure (ie. Isomer)

3. Dehydration vs hydrolysis

4. Polysaccharides Complex carbohydrates Chains of sugars are straight or highly branched. Eg. –Cellulose (indigestible - fibre) or starch (digestible) in plants –Glycogen in animals (highly branched) All must be broken down to monosaccharides before absorption

5. Oligosaccharides 3-15 monosaccharide units joined to form polysaccharides Maltodextrins – partially hydrolysed starch –Include starch oligosaccharides and maltose –Less osmotically active than glucose and less sweet

6. Glycogen

8. Muscle –Rate of depletion relates to exercise intensity High intensities glycogen is broken down v rapidly Liver –Main role is to maintain blood glucose – stored as glycogen  glucose and released –80-100g, but reduced to <20g after overnight fast –Also produces glucose via gluconeogenesis fom lactate, glycerol, pyruvate, alanine, glutamine +other amino acids

9. Function of CHO 1.Energy source 2.Metabolic primer ‘fat burns in a CHO flame’ 3.Protein sparer 4.Fuel for CNS

10. CHO digestion Saliva contains – α-amylase – breaks down starch into maltose, trisaccharides and small oligosaccharides Amylase less active due to acid in stomach Pancreatic juice contains –α-amylase Disaccharides further digested by lactase, sucrase and maltase in brush border

11. CHO Absorption Monosaccharides absorbed by carrier- mediated transport Glucose and galactose taken into epithelial cell with 2 x Na+ (SGLT) –Na is then actively pumped back into lumen Fructose – Na-independent facilitated diffusion transporter (GLUT 5) GLUT 2 transporter on contra-luminal side accepts all 3 monosaccharides  hepatic portal vein.

12. Hormones Insulin –At rest increases glucose uptake by liver, muscle –Increases glycogen synthase activity, inhibits glycogen phosphorylase Glucagon –Breakdown liver glycogen and release of glucose Catecholamines –In exercise reduce release of insulin Blood glucose kept fairly constant except: –High intensity exercise  liver produces more glucose than taken up by muscle --. Elevated blood glucose –Prolonged exercise – rate of production less than utilisation  hypoglycaemia

13. Effect of exercise intensity As intensity ↑ so do adrenaline/noradrenaline  glucose release from liver and glycogen b’down in muscle So post sprint levels are 40/50%+ Muscle uses own glycogen stores before blood glucose in short intense exercise Post exercise it enters muscle to replace glycogen stores

14. Glycaemic Index (GI) & glycaemic load Based on ingestion of food containing 50g CHO with reference food (usually 50g glucose or white bread) Measure area under glucose curve over 2-hr period GI = area under curve for test food area under curve for ref food x 100 Low GI 71 But GI does not take into account serving size e.g. 50g of CHO from carrots = 750g of carrots Glycaemic Load (GL) is more practical and takes into account GI and serving size.