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History. Krogh and Lindhardt 1920 RER change after high fat diet Levine, Gordon and Derick 1924 Boston marathon, blood glucose decline Christensen 1932 Exercise intensity increased, carbohydrate utilization increased Bergstrom and Hultman 1966-67 Muscle biopsy technique Muscle glycogen
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Ex Nutr c5-CHO History • Krogh and Lindhardt 1920 • RER change after high fat diet • Levine, Gordon and Derick 1924 • Boston marathon, blood glucose decline • Christensen 1932 • Exercise intensity increased, carbohydrate utilization increased • Bergstrom and Hultman 1966-67 • Muscle biopsy technique • Muscle glycogen • Costill, Coyle, Sherman 1980’s • High carbohydrate diet vs endurance capacity • Costill 1973 • Isotope technique 同位素 (2H, 3H) (13C, 14C)
Ex Nutr c5-CHO Role of Carbohydrate • Glycogen – • Muscle glycogen • 12~16 g/kg • Liver glycogen 80~100g • Maintain blood glucose level • Fuel for brain ~0.1 g/min • May down to < 20 g after overnight fast • Hepatic glucose output • liver +kidney
Ex Nutr c5-CHO Sources of blood glucose
Ex Nutr c5-CHO Hypoglycemia • blood glucose < 3 mM • During exercise, when liver glycogen depleted • Glucose production rate insufficient for glucose uptake by muscle • Symptoms: • Rate of glucose uptake by brain insufficient • Dizziness, nausea, cold sweat, reduced mental alertness, loss of motor skill, increased heart rate
Ex Nutr c5-CHO Carbohydrate Before Exercise • Carbohydrate Supercompensation • Carbohydrate loading 肝醣超載 • Classic protocols • Low CHO diet (25%) for 3 days, followed by 3 days high CHO diet (75%) • Moderate protocols • Mixed diet 3 days (50% CHO) followed by 3 days high CHO diet (70%) • During taper period, gradually decreased training: 75%VO2max for 90 min on 1st day, to complete rest on 6th day
Ex Nutr c5-CHO Classical vs moderate protocol
Ex Nutr c5-CHO Stage 1: 100 g CHOstage 2: 400-625 g CHO (classical)
Ex Nutr c5-CHO Moderate protocol
Ex Nutr c5-CHO Carbohydrate Supercompensation • Classic protocols disadvantages • Hypoglycemia • Practical problems • GI problem • Poor recovery • Uncomfortable on training • Mood disturbance
Ex Nutr c5-CHO Benefits • 20% increases time to exhaustion • ↑2%-3% in Time trial • At least 90 min before the benefits • Improve performance in team sports involving high-intensity intermittent exercise and skills • Soccer, hockey • No effect on Sprint performance, or repeated bouts of high-intensity ex • Athletes in high-intensity training still need high CHO in diet • Low CHO diet impaired endurance capacity
Ex Nutr c5-CHO CHO loading improve soccer performance In second match (3 days after 1st match)
Ex Nutr c5-CHO Supercompensation Strategies in Sport • Endurance sports • Consecutive days • May be difficult for supercompensation • Marathon and triathlon • High intensity exercise (95-100% VO2max) not a limit factor • 1 g glycogen – 3 g water……increase mass
Ex Nutr c5-CHO Carbohydrate Intake 3-5 hour before Exercise • Can ↑muscle and liver glycogen • CHO within 1 hr before exercise only ↑liver glycogen • Overnight fasting – liver glycogen depleted • CHO-rich meal (140-330 g) • Bread, jam, honey, cereals, bananas, canned fruits, juice • increase muscle glycogen • improved endurance performance • For practice • 200-300 g CHO 3-4 hours before exercise • Especially when CHO is unavailable during exercise
Ex Nutr c5-CHO Carbohydrate Intake 3-5 hour before Exercise • Transient fall in plasma glucose at onset of exercise • ↑CHO oxidation,↑glycogenolysis • Compensated by ↑CHO availability • Blunting FA mobilization and fat oxidation • NO detrimental effect to exercise performance
Ex Nutr c5-CHO Carbohydrate Intake 30-60 min before Exercise • Ingestion CHO Within 1 h before exercise • Largely elevated blood glucose and insulin • Transient fall in plasma glucose with the onset exercise • Increased CHO oxidation rate • Blunting of FA mobilization (insulin-mediated inhibition of lipolysis), and ↓fat oxidation in muscle • Transient fall in plasma glucose with the onset exercise • Hyperinsulinemia • Muscle contraction stimulate muscle glucose uptake • Exercise-induced normal liver glycogen output inhibited by CHO ingestion • Still improved endurance exercise performance • Individual variations, try and error
Ex Nutr c5-CHO Carbohydrate Intake 30-60 min before Exercise • Glycemic Index (GI) 升糖指數 • [Area under curve (AUC) (X) / AUC (glucose)] x 100
Ex Nutr c5-CHO Carbohydrate during Exercise • Ingestion CHO during exercise (>45 min) improved endurance capacity and performance • Mechanisms • Maintaining blood glucose and high level of CHO oxidation • Glycogen Sparing • Promoting glycogen synthesis during exercise • ↓glycogen breakdown, ↑glycogen syn in low-intensity ex • Affecting motor skill • Especially involving fast running, rapid movement, explosive • Affecting the central nervous system
Ex Nutr c5-CHO Carbohydrate during Exercise • Feeding schedule: bolus vs intervals • Little effect on exogenous CHO oxidation • Amount of CHO • Maximal exogenous CHO oxidation rate 1-1.2 g/min • 70 g/h = 1L sports drink = 600 ml cola = 3 banana = 1.5 power bar, energy bar • Type of CHO • Glucose, maltose, sucrose, maltodextrins: up to ~1 g/min • Fructose, galactose: up to ~0.6 g/min, usually GI discomfort • Inclusion of 2-3 different CHO result in exogenous CHO oxidation rates ~1.3 g/min • Glucose, fructose, sucrose • Separate transporters across intestinal wall
Ex Nutr c5-CHO CHO consumption CHO oxidation
Ex Nutr c5-CHO Hr of exercise at ~60% VO2max
Ex Nutr c5-CHO Results in time trial and total power output during the time trial
Ex Nutr c5-CHO endogenous exogenous
Ex Nutr c5-CHO Carbohydrate during Exercise • Exercise intensity • <50%VO2max, exogenous CHO oxidation rate increase with increasing total CHO oxidation rate • >60%VO2max, no further increase of CHO oxidation • Limitation to Exogenous CHO oxidation • Gastric emptying not a limiting factor • Limited by rate of digestion, absorption, transport of glucose into systemic circulation • > 80% VO2max reduce blood flow to gut • Hepatic glucose output highly regulated, if supply from intestine too large, glycogen synthesis may be stimulated in liver • Infusion of glucose (> 10 mM in blood) can make Exogenous CHO oxidation >> 1 g/min
Ex Nutr c5-CHO Metabolic effects of CHO intake during exercise • CHO ingested at onset of exercise • ↑ insulin in first minutes of exercise • ↓lipolysis, ↓ FA, ↓fat oxidation rates • Also ↓transport of FA into mitochondria • CHO ingested later during exercise • Fat oxidation less affected because insulin release is inhibited by epinephrine
Ex Nutr c5-CHO Female runner in 100 Km run, Moran ST, 2011
Ex Nutr c5-CHO Carbohydrate After Exercise • Replenishment of muscle glycogen • Regulation of Glucose uptake and Glycogen Synthesis • Glucose uptake - GLUT-4 • Muscle contraction (Ca+) • Insulin secretion • Glycogen synthesis depends on • enzyme activity, especially glycogen synthase • transport glucose into cell, influenced by muscle glycogen concentration and insulin
Ex Nutr c5-CHO Glycogen synthesis • Rapid phase of glycogen synthesis • Glycogen synthase : Inactive D-form active I form • Exercise, low muscle glycogen activate glycogen synthase • GLUT-4 translocation: last for only few hours in the absence of insulin • When muscle glycogen level low, enhanced glucose uptake may last longer • Slow phase of glycogen synthesis • Depends on insulin concentration • Muscle contraction increases insulin sensitivity, lasted for several hours • Increased GLUT-4 expression
Ex Nutr c5-CHO Carbohydrate After Exercise • Postexercise feeding and rapid recovery • Glycogen resynthesis very low without CHO ingestion • Timing of CHO intake • As soon as possible after exercise • Rate of CHO ingestion: up to 2 g/kg/h (1.2-2.0 g/min) • Type of CHO ingested: High GI • Especially in the first hours after exercise, ↑glucose availability • glycogen synthesis rate for fructose: 50% of glucose • Protein and CHO ingestion • Additive effect (< 1.2-2 g/kg/h CHO), certain amino acids stimulate insulin secretion • Some study showed no additional effect when CHO ingestion at 1.2 g/kg/h, some study showed addition effect even in high CHO intake • Solid versus Liquid • Similar results • High-GI
Ex Nutr c5-CHO Post-exercise recovery
