Carbohydrates

What are Dietary Carbohydrates? Organic compounds containing –Carbon –Oxygen –Hydrogen Formed naturally in nature Synthesized ~4 kcal/gram

Types of Carbohydrates Simple CHO – Monosaccharides Glucose (dextrose, grape sugar) Fructose (levulose, fruit sugar) Galactose (bonds with glucose to form lactose) – Disaccharide Maltose (malt sugar, glucose & glucose)- comes from starch breakdown Lactose (milk sugar, glucose & galactose) Sucrose (cane or table sugar, glucose & fructose)

CHO Types Complex CHO – 3 or more sugar molecules – Oligosaccharides (3-10 sugar molecules) Maltodextrins Corn syrup High fructose corn syrup

Complex CHO – cont’d – Polysaccharide (>10 sugar molecules) Plant starches – Amylose – unbranched chains – Amylopectin – branched chains Animal starch (glycogen) – or glucose polymer (10 or more molecules) Maltodextrin polycose – Fiber

Concentration Units Mole = gram molecular weight A mole is the weight in grams of a particular substance, like glucose Example – Glucose is C 6 H 12 O 6 – Atomic weight of C is 12, H is 1, O is 16 – Multiply the atomic weight X the number of that element in the molecule and sum it up. - 1 mole glucose is 180 grams

TABLE 4.7 Major hormones involved in regulation of blood glucose levels HormoneGlandStimulusAction InsulinPancreasIncrease in blood glucose Helps transport glucose into cells; decreases blood glucose levels. GlucagonPancreasDecrease in blood glucose; Exercise stress Promotes gluconeogenesis in liver; helps increase blood glucose levels. EpinephrineAdrenalExercise stress; decrease in blood glucose Promotes glycogen breakdown and glucose release from the liver: helps increase blood glucose levels CortisolAdrenalExercise stress; decrease in blood glucose Promotes breakdown of protein and resultant gluconeogenesis; helps increase blood glucose levels

Causes of Muscular Fatigue Related to CHO Use Muscle Glycogen Depletion – Fatigue begins to occur at approx mmole/kg – Short duration high intensity (<60 sec) not affected until glycogen drops below 20 mmole/kg

Causes of Fatigue Continued Liver Glycogen Depletion – Normoglycemia: mg/dl – Hyperglycemia: >140 mg/dl – Hypoglycemia: <45 mg/dl – Decreased levels of BCAA in blood Reactive Hypoglycemia

Glycemic Index (GI) The GI reflects the rate of digestion and absorption of CHO GI = Blood glucose area after test food Blood glucose area after reference food X 100

Glycemic Load Glycemic index relative to the serving size Some CHO have high GI but are consumed in small quantities per serving GL = (GI x CHO/serving)/100 Ratings of glycemic loads – High GL = >20 – Medium GL = – Low GL = <11

Major Factors Influencing Skeletal Muscle CHO Metabolism During Exercise Exercise Intensity Exercise Duration Training Diet – Feeding schedule – Type and amount of CHO]

Effect of Intensity of Exercise on CHO Utilization

Effect of Exercise Duration on CHO Utilization

Effect of Training on CHO Utilization

Effect of Diet on CHO Utilization

How Much and What Kind of CHO? Minimum of100 grams CHO/day necessary for nervous system Type of CHO varies with timing – High glycemic CHO get on board faster – Low glycemic CHO have more sustained effect

Table 4.8 CHO Loading Original Classic Method Day 1Depletion exercise Day 2High-protein/fat, 15-20% CHO Day 3High-protein/fat, 15-20% CHO Day 4High-protein/fat, 15-20% CHO Day 5High CHO (70-80%) Day 6High CHO Day 7High CHO Day 8Competition

Table 4.8 CHO Loading Contemporary Recommended Method Day 1Depletion exercise (optional) Day 2Mixed diet (50-55% CHO) Day 3Mixed diet Day 4Mixed diet Day 5High CHO (70-80%) Day 6High CHO Day 7High CHO Day 8Competition

Alcohol As An Energy Substrate 7 kcal/gram By-products of alcohol metabolism released in blood appear to be of little importance to exercising muscle Alcohol consumed prior to exercise may contribute 5% of energy over 90 min of exercise Alcohol requires more O 2 for metabolism than CHO or fat

Effects of Alcohol on Exercise Performance Interfere with glucose metabolism May reduce rate of gluconeogenesis Induces hypoglycemia Inhibit sarcolemmal calcium channel actions Depresses myocardial contractility Reduces psychomotor skill Reduces aerobic performance capacity