lect 3- Carbohydrates.pdf

Carbohydrates The main energy food  What are the different types of dietary CHO? ✓ Formed when the E from the sun is harnessed in plants through the process of photosynthesis. Monosa- Disaccha- Polysacc- Other Dietary Functional Dietary/ ccharides rides...

Carbohydrates The main energy food  What are the different types of dietary CHO? ✓ Formed when the E from the sun is harnessed in plants through the process of photosynthesis. Monosa- Disaccha- Polysacc- Other Dietary Functional Dietary/ ccharides rides harides (> CHO fiber fiber functional 10 glc) fiber Glucose Sucrose Plant starch Sorbitol. Hemicellulose Polydextrin B-glucans (dextrose) (table sugar) Amylose (glc + fru) Amylopectin Ribose (5- Resistant Psyllium Cellulose Fructose Resistant C sugar). starch (levulose Maltose starch Resistant Gums/ or fruit (glc + glc) Animal starch pectins sugar) starch Lactose (glc Glycogen Galactose + gal). (milk sugar) What are some common foods high in CHO content?  What are some common foods high in CHO content? ✓Sports drinks (e.g: Gatorade) (6-8% CHO): mixture of glc, fru, sucrose and/or glc polymers. ✓Sports gels (e.g: power Gel, ReLode): same types of CHO in a more solid form; 1 oz = 20-30 g CHO. ✓Sports bars: 20-45 g CHO. ✓E drinks: 30-50 g/8 oz.  How much CHO do we need in the diet? ✓ RDA = 130 g/d for adults and children ( +++ for the brain who accounts for 50% of total body glu utilization). ✓AMDR (acceptable macronutrient distribution range) = 45-65 % of daily energy intake. ✓Normal training: 55-60% of total calories. ✓Prolonged heavy exercise: 60-70% or more of total calories. ✓DV on food labels is based on a recommendation of 60% of caloric intake. ✓No more than 25% of total calories should come from added sugars). ✓AI of fibers : 38 g/d for men up to age 50 30 g/d for men over age 50 25 g/d for women up to age 50 21 g /d for women over age 50.  Metabolism and function ✓ Digestion = process by which food is broken down mechanically and chemically in the digestive tract and converted into absorbable forms. ✓Absorption = may occur in the stomach and large intestine, but the majority through the millions of villi lining the small intestine [passive diffusion v/s facilitated diffusion]. Some starch is broken down to maltose in the mouth by salivary amylase Salivary amylase is inactivated by strong acid in the stomach Pancreatic amylase breaks down starch into maltose in small intestine Enzymes in the wall of SI break down the disaccharides into monosaccharides Glu, fru, Gal are absorbed into blood to be taken to liver by portal vein Some soluble fiber is fermented into various acids and gases by bacteria in large intestine. Insoluble fiber escapes digestion and excreted in feces  How are dietary CHO digested and absorbed ? ✓ Composition of dietary CHO may influence delivery into body. E.g.: sports drinks may be designed to take advantage of the different monosaccharides receptors in the villi. ✓Certain dietary practices may predispose individuals to GI distress ➔ compromise exercise performance. E.g.: high concentrations of simple sugars +++ fru may exert reverse osmotic effect in intestine, drawing water from circulatory system into lumen of intestine ➔ dumping syndrome (weakness, sweating, diarrhea). ✓Lactose may also cause a problem to some athletes. Foods containing CHO and sodium enhance the absorption of H2O.  What happens to the CHO after it is absorbed into the body ? ✓ Most of the CHO and the majority of the absorbed fru and gal are converted to glucose (it’s the blood sugar). ✓GI = ranking system relative to the effect that consumption of 50 g of a particular CHO food has upon the blood glu response over the course of 2 h. Normal : 50 g glu ➔ glu response of 100. ✓ ≥ 70 : high GI. ✓ 69- 55 : medium GI ✓ ≤ 55: low GI. ✓GL = includes also the portion size = (GI * g of non-fiber CHO in 1 serving) / 100. ✓ ≥ 20 : high GL ✓ 19-11 : medium GL ✓ ≤ 10: low GL  What is the metabolic fate of blood glucose ? ✓ Normoglycemia = 80-100 mg/dl. ✓ If blood glucose increases : ✓ Secretion of insulin by pancreas ➔ activation of GLUT 4 Rc in fat and muscle cell membranes ➔ uptake and utilization of glucose. ✓ Exercice has the same effect (activation of GLUT 4 Rc).. ✓ Foods with high GI ➔ rapid high BG ➔ enhanced secretion of insulin ➔ rapid transport of glucose into tissues ➔ reactive hypoglycemia.  What is the metabolic fate of blood glucose ? Energy Storage Fat deposits Kidney excretion in urine +++ brain that Liver glycogen When dietary If excessive rely primarily on that can be later CHO and energy amounts in blood glucose reconverted to exceeds E due to rapid blood glu. demands and ingestion of Muscle gly (less storage capacity. simple sugars. amounts to blood).  How much total E do we store as CHO ? ✓ Mole = weight in g of a particular substance. ✓ Glu = C6H12O6 ➔ atomic weight of C = 12 atomic weight of H = 1 atomic weight of O = 16. ➔ [( 6*12) + (12*1) +(6*16)] = 180. ✓ 1 mol of glu = 180 g. ✓1 mmol of glu = 180 mg. ✓ Normal BG concentration = 5 mmol/l = 90 mg/100 ml. ✓ 5 L of blood = 4.5 g of glucose.  How much total E do we store as CHO ? ✓BG = 5 g = 20 Cal. ✓ Liver gly = 75- 100 g (greatest concentration). ✓1 h of aerobic exercise uses over half of the liver gly supply. ✓ Can be decreased by starvation (15 h starvation deplete stores) or increased by CHO rich diet (stores can double). ✓ Muscle gly = 360 g for 30 kg of body muscles (greatest amount because big mass). ✓Can be increased or decreased ( +++ by effect of PA). ✓ Total body storage of CHO = 1800- 1900 Cal (not appreciable amounts). ✓ One full day of starvation could reduce it considerably.  Can the human body make CHO from protein and fat ? ✓ The body is able to produce glu internally if the stores are depleted by starvation or zero- CHO diet = gluconeogenesis = new formation of glucose. ✓Takes place +++ in liver. Its sources: 1. Protein → a.a. (+++ alanine) → glucose (glu-alanine cycle) (1 g prot gives 0.56 g glu). 2. TG → FA + glycerol → glycerol converted to glu ( 1 g glycerol gives 1 g glu). 3. By-products of CHO metabolism (+++ pyruvate & lactate) → glu. 4. Some of lactic acid produced in muscles during intense exercise → glu → returns back to muscles (E or storage) : Cori cycle.  What are the major functions of CHO in human nutrition ? ✓ Nerve cells in brain + retina + RBC : totally dependent on glu for energy. ✓ Not a major fuel when body is at rest (15-20%). ✓ Source of energy: ✓Anaerobic glycolysis → production of lactic acid. ✓ Aerobic glycolysis → acetyl CoA → krebs cycle. ✓ Formation of glycolipids or glycoproteins.  CHO for exercise Some sports authorities indicate that CHO is the master fuel for athletes !!  In what types of activities does the body rely heavily on CHO as an E source? ✓ Rest : 40% of total E from CHO. ✓ Very light exercise : fat is the most important E source. ✓ Intense exercice (65-85% of capacity): CHO are the preferred E source (cross over concept). ✓ Maximal & supramaximal exercice: CHO is used almost exclusively. CHO is the prime E source for high intensity anaerobic events lasting for less than 1 min, & high intensity aerobic events lasting over 1 or 2 hours.  In what types of activities does the body rely heavily on CHO as an E source? ✓ A normal person can exercice at 40-50% of VO2 max for 1-2 hours, or at 70-80% of VO2 max only for minutes (exhaustion occurs sooner with intense exercise).. ✓ Fatigue in: ✓ Very high intensity exercice of short duration (e.g: 400 m run) may be associated with accumulation of H, a by-product of lactic acid production. ✓ More prolonged exercice may be connected with depleted supplies of liver and muscle glycogen. ✓CHO intake is most important for prolonged endurance events lasting more than 90-120 minutes.  In what types of activities does the body rely heavily on CHO as an E source? ✓CHO is also an essential E fuel for prolonged sports involving many intermittent bouts of high-intensity exercice (soccer, rugby, hockey, tennis…). ✓ Environmental conditions may also increase CHO use during exercise. ✓CHO oxidation is increased during exercice in the heat. ✓Exercising at high altitude increase BG compared to sea level.  Why is CHO an important E source for exercice ? ✓ It’s the only food used for anaerobic E production (lactic acid system). ✓Most efficient fuel for the O2 system. ✓ Fat needs more O2 to be metabolized (CHO are 7% more efficient than fat). ✓ATP production from glu is better than from fatty acids. ✓ Metabolic pathways for CHO are more efficient than fat. ✓ physical performance uses +++ muscle glycogen → BG enters muscles → liver release some glu to prevent hypoglycemia [ in moderate ex, muscle and liver glycogen contribute equally to CHO oxidation; at higher intensities, muscle gly use increases]. All body stores of CHO –BG, liver gly, and muscle gly- are important for energy production during various forms of exercise.  CHO products marketed to athletes Sports drinks (14-18 g/8oz): Gatorade. PowerAde Sport Ade. Sports gels (20-30 g/pkt) Reloade Powergel Clif-Shot Sports bars (20-50 g CHO/bar) Power bar  What effect does endurance training have on CHO metabolism? ✓ Initiation of an endurance exercise → production of GLUT 4 Rc → insulin-type effect & glucose enters into the muscles. ✓ As the exercise continues, tissues begin to adapt to accommodate the exercise stress ( ≈ 5 days of training can decrease the production of lactic acid for standardized exercise task). ✓ Changes that occur after months of endurance training: ✓Increase VO2 max → body deliver & utilize more O2 at the muscle tissue. ✓Able to work at a greater %age of VO2 max without fatigue. ✓ Improves insulin sensitivity by increasing GLUT-4. ✓ Increases maximal capacity to utilize CHO. ✓ Enhance use of fat during exercise. ✓More glycogen stored in the muscles.  How is hypoglycemia related to the development of fatigue ? ✓ Hypoglycemia usually identified at 45 mg/ 100 ml: dizziness, muscular weakness, fatigue. ✓As BG is being used during exercice, it must be replenished from liver gly stores. ✓A depletion of liver glycogen may lead to hypoglycemia during high-intensity aerobic exercice because gluconeogenesis normally cannot keep pace with glucose utilization by the muscles. ✓ Exercice: * Increases muscle glu uptake ( increase GLUT 4 Rc). * Increases sensitivity to insulin. * So during ex, insulin levels decrease to maintain normal serum glucose. * Secretion of epinephrin, glucagon & cortisol to increase BG.  How is hypoglycemia related to the development of fatigue ? Hormone Gland Stimulus Action Insulin Pancreas Increase in BG Helps transport glu into cells; decrease BG levels. Glucagon Pancreas Decrease in BG; Promotes gluconeogenesis in liver; exercice stress helps increase BG levels. Epinephrine Adrenal Exercice stress; Promotes gly breakdown & glu release decrease in BG from liver; helps inc. BG levels. Cortisol Adrenal Exercice stress; Promotes breakdown of prot & decrease in BG resultant gluconeogenesis; helps inc. BG levels.  How is hypoglycemia related to the development of fatigue ? ✓Hypoglycemia may be a concern of athletes in several situations: ✓ Reactive hypoglycemia following a high CHO meal 30-60 min or more prior to an athletic event. ✓ Prolonged exercice tasks but dependant on the intensity level of exercice. ✓ In latter stages of an endurance task when muscle gly stores are depleted (fat oxidation increases and BG become the main E source/ gluconeogenesis cannot completely compensate for decreased liver glycogen availibility). With increased exercise duration there is a progressive decrease in muscle gly and a progressive increase in BG uptake by the muscle. However, liver supplies of gly are limited, and thus BG levels eventually fall.  How is lactic acid related to fatigue ? ✓ High intensity exercice → anaerobic glycolysis to replenish ATP & PCr → lactic acid production. ✓ Lactate molecule does not cause fatigue, but rather that its accumulation in blood reflects a disturbance of muscle cell homeostasis due to: ✓ Increased concentration of H ions that increase acidity (affect muscle contraction). ✓ Na bicarbonate, a buffer of acidity in the muscle, may be an effective mean to enhance performance in high-intensity exercice tasks. ✓Lactate produced during exercise is not a waste product; it’s a CHO that contains half the energy of one molecule of glucose.  How is low muscle gly related to the development of fatigue ? I. In aerobic exercices: a. Muscle gly is the major energy source for prolonged, moderatly high to high intensity aerobic exercice. b. In case of insufficient CHO oxidation often coupled with hypoglycemia, we will need to reduce exercice intensity from 70-85% to 40-60% of VO2 max. c. Some gly remains in muscles even though subjects were exhausted: i. Location of gly: gly located where it is not readily available for glycolysis. ii. Rate of E production: at low concentration, there is not enough gly to supply milliseconds E needs. It interferes with maintenance of optimal levels of krebs cycle intermediates. How is low muscle gly related to the development of fatigue ? III. Muscle fiber type: fatigue may be related to the depletion of muscle glycogen from specific muscle fiber types. Gly depletion in the slow-twitch muscle fibers, necessitating recruitement of fast-twitch muscle fibers and increased E demands, is a factor that may predispose to fatigue. IV. Use of fat for energy as muscle gly is depleted: fat is less efficient fuel than CHO. V. Role of the brain: low gly level invoke neural response causing fatigue.  How is low muscle gly related to the development of fatigue ? II. In anaerobic exercice: a) Maximal high-intensity exercice, lasting only about 60 sec., is not impaired by a very low muscle gly concentration. b) It’s possible that performance in such exercice may be impaired with extremely low muscle gly in the fast twitch muscle fibers. c) Slower overall sprint speed ( e.g.: latter parts of prolonged athletic contests like soccer), may be due to muscle gly depletion. d) Low muscle gly level is a major cause of the overtraining syndrome in endurance athletes. Low levels of gly in the white, fast-twitch IIb muscle fibers may limit performance in intermittent, anaerobic type exercice tasks. Hypoglycemia and low gly in red mucle fiber type are contributing factors to fatigue in prolonged endurance exercices.  How are low endogenous CHO levels related to the central fatigue hypothesis ? I. After prolonged exercise bouts → low muscle gly + hypoglycemia → gluconeogenesis from muscle protein ( +++ BCAA will be used). With decreased release of BCAA from liver or increased uptake by muscle → decreased blood concentration of BCAA. ➔ The decrease in blood BCAA concentration causes fatigue. II. On the other hand, tryptophan increase and compete with BCAA for similar Rc that facilitate their entry into the brain. An increase in Trp:BCAA ratio → increase entry of trp to the brain → increase formation of serotonin → fatigue sensation.  Will eating CHO immediately before or during an event improve physical performance ? I. Use of the ingested CHO: I. Studies indicate that exogenous CHO may be used as an E source within 5-10 min. II. Peak of use occurs at 75-90 min after ingestion. II. Possible fatigue-delaying mechanisms: I. Maintenance of BG levels (important for muscles and brain). II. Reduction of psychological effort by reducing the rate of perceived exertion. III. Sparing of muscle glycogen: contradictory results.  Will eating CHO immediately before or during an event improve physical performance ? III.Limitations to prevent fatigue: a. Glucose ingestion cannot totally prevent fatigue. Limitations are: a. Intestines: maximum rate in CHO absorption (Maximal amount of energy derived from exogenous carbohydrate is approximately 1.5-1.7 gram per minute [lower than that required at 65-85% VO2 max]). b. Liver: maximum rate of releasing glucose into blood.  Will eating CHO immediately before or during an event improve physical performance ? iv. Initial endogenous stores: a. Normal liver and muscle glycogen stores are enough for continuous moderately high-intensity exercise bouts lasting 60-90 min or less → no glc feedings. b. But for higher intensities, the critical point is to consume substantial amounts of CHO a day or two prior to the event and to decrease the duration and the intensity of training to assure ample endogenous gly supplies. c. Consumption of glc, fru, sucrose, maltodextrin… immediately prior to events of short or moderate duration has a negligible effect upon performance. d. If muscle levels of gly are low and the exercise is somewhat prolonged ➔ CHO ingestion prior to exercise may improve performance.  V. Exercise intensity and duration: Exercice During intensity/ Duration Before exercice After exercice exercice sport < 30 min None needed None needed None needed Very high intensity (unless there is aerobic muscle or liver gly deficiency) High intensity 30-90 min 20-25 g 30-60 g 60-80 g/h aerobic (10 km for 3-4 h run) Intermittent high- 60-90 min 20-25 g 30-60 g 60-80 g/h intensity for 3-4 h Moderate to high > 90 min 20-50 g CHO 60-80 g/h 60 g/h intensity aerobic loading for 3-4 h Moderate >6h 20-50 g CHO 60-80 g/h 60-80 g/h intensity aerobic loading for 3-4 h High intensity 1-2 h None needed None needed 60-80 g/h resistance training for 3-4 h  Will eating CHO immediately before or during an event improve physical performance ? VI. Timing of CHO intake: for prolonged endurance events, CHO intake several hours before, immediately before, and during the event may be recommended. a. 4 hours or less before exercise: enhance performance. b. less than 1 h before exercise: 1. Prudence suggests that individuals who may be prone to reactive hypoglycemia should avoid CHO intake, +++ high glycemic index food, 15-60 min prior to performance. 2. For individuals not prone to reactive hypoglycemia, the consumption of CHO within 15-60 min prior to performance may confer some benefits. Possible increase in liver and muscle gly may offset the reported increase in muscle gly utilization.  Will eating CHO immediately before or during an event improve physical performance ? VI. Timing of CHO intake: for prolonged endurance events, CHO intake several hours before, immediately before, and during the event may be recommended. c. Immediately before exercise: 1. Consuming CHO immediately before exercise of short duration or less than 90 min, normally will not enhance performance. 2. CHO intake immediately prior to prolonged endurance exercise tasks of 2 h or more may help delay the development of fatigue and improve performance if the athlete is exercising at a level greater than 50% VO2 max (60-75%). d. During exercise: CHO ingested during prolonged exercise can help maintain BG levels and reduce the psychological perception of effort.  When, how much and in what form should CHO be consumed before or during exercice ? ✓ Exercises that may benefit from CHO feedings are those of long duration (90-120 min) at moderate to high intensity levels (marathon, cross-country skiing…) and those with bouts of intensive exercises over a prolonged period (soccer…). ✓ During these types of exercise, fluid supplementation is even more important than CHO.  When, how much and in what form should CHO be consumed before or during exercice ? ✓ General recommendations for individuals who are exercising at 60-80% of their VO2 max for 1-2 h or longer: ✓ Pre-ex: 4 h prior to performance → 4-5 g/kg (fiber intake minimized). 1 h prior to performance → 1-2 g/kg (Glucose polymers or foods with low glycemic index ). within 10 min of the start → 50-60 g of glucose polymer (40-50% solution) ✓ During ex: feedings every 15-20 min appear to be a reasonable schedule. Sports drinks averaging 6-10% CHO have been found to enhance prolonged endurance performance. Recently, we recommend the following to have less risk to cause GI disturbances:  When, how much and in what form should CHO be consumed before or during exercice ? Type of exercice CHO needs Maximal ex lasting less than 45 min None required Maximal ex lasting about 45-60 min < 30 g /h Team sports lasting about 90 min Up to 50 g/h Submaximal ex lasting more than 2 h Up to 60 g/h Near max and max ex lasting more than 2 h Up to 50-70 g/h Ultraendurance events 60-90 g/h  When, how much and in what form should CHO be consumed before or during exercice ? Best effect observed when CHO were consumed both before and during exercise  Glucose Polymer 1 T = 15 g 50% solution containing 50 g 3T + 100 ml water 7.5% solution containing 15 g 1T + 200 ml water  When, how much and in what form should CHO be consumed before or during exercice ? ✓ Type of CHO: no difference between the different types of CHO to enhance endurance performance when used appropriately. ✓ CHO combinations: combination of CHO, +++ glu + fru, result in higher oxidation rates than a single CHO. ✓ Fru: absorbed slowly and doesn’t create an insulin response and the potential reactive hypoglycemia → stable BG during early stages of prolonged ex when ingested 45 min before ex (N.B: no large amounts). When, how much and in what form should CHO be consumed before or during exercice ? ✓ Solid and liquid CHO: no difference seen between these 2 forms (Composition of pre-exercise meal has little effect on performance). ✓ Low GI food: no significant difference between low and high GI food. ✓ CHO with prot: no diff between CHO alone and CHO + prot. ✓ Some studies have demonstrated that combination of CHO and protein increase fat oxidation; increase recovery and improve performance. ✓ In the recovery period, the chocolate milk drink is more effective than CHO replacement drink (good CHO/protein ratio + high concentration of electrolytes + feeling of fullness). ✓ Individuality: try the different types and amounts of CHO during training before competition.  What is the importance of CHO replenishment after prolonged exercise ? ✓ 3 cases: ✓ Between 2 prolonged ex with a rest period of 1-4 h. ✓ Intense training everyday with one day rest interval. ✓ CHO loading. ✓ After prolonged ex → increased levels of GLUT 4 Rc in muscle → BG enters to resynthesize muscle gly → intake of CHO help restore BG &may be used to resynthesize muscle gly. ✓ In case where rate of muscle gly resynthesis is important, high GI foods are preferred. ✓ For repeat prolonged ex with 4 h interval → consume 1 g CHO/kg immediately after 1st event & again 2h prior to second event.  What is the importance of CHO replenishment after prolonged exercise ? ✓ Consuming a prot/CHO mixture after ex would promote gly resynthesis more effectively compared to CHO alone (eg: 3-4 g CHO for each g of prot). ✓ For athlete who train intensely on a daily basis with either restrictive or aerobic ex that leads to muscle gly depletion ➔ 8-10 g CHO/ kg daily (≈ 65-80% of total caloric intake). ✓ If rapid resynthesis of muscle gly is not important, it’s good to note that studies have shown that consumption of adequate amouts of CHO over 24 h period will restore muscle gly levels to normal. ✓ Sports drinks may be a convenient means to consume CHO immediately after exercise. The remaining should be derived from other natural sources in the diet.  Will a high CHO diet enhance my daily exercise training ? ✓ Athletes in general training should consume daily approximately 5-7 g CHO / kg BW, but endurance athlete should consume 7-10 g/ kg. ✓ Athletes consumption of CHO increased from 40-45% to 55-70% of total daily calories (upper limits of AMDR recommendations). ✓ For trained athletes, a moderate- CHO diet may be adequate (45%) ✓ Mood state seems better maintained with a high CHO diet rather than with a moderate CHO diet (reduce symptoms of overreaching and overtraining). CHO loading What is CHO or glycogen loading ? Carbohydrates loading = glycogen loading = glycogen super compensation= Dietary technique designed to promote a significant increase in the glycogen content in both the liver and the muscles in an attempt to delay the onset of fatigue.  What type of athlete would benefit from CHO loading ? ✓ High levels of continuous energy expenditure for prolonged periods (swimmers, bicyclists... ), prolonged stop-and-go activities (soccer, handball…), body builders attempting to appear more muscular due to water retention. ✓ Long continuous exercise depletes gly principally in the slow-twitch red and fast-twitch red fibers, whereas fast, intermittent bouts of exercise with periods of rest primarily deplete gly in the fast-twitch white fibers. ✓ N.B: gly depletion may occur in all types of fibers in either prolonged continuous or intermittent exercise. ✓ Both types of physical exercise benefits from CHO loading.  How do you carbohydrate load ? ✓ Classic technique (Scandinavian research): ✓ First step: glycogen depletion stage (prolonged exercise). ✓ 2nd step: CHO deprivation (restricted diet + tapering exercise) (2-3 days). ✓ 3rd step: loading stage: more than 70% CHO from total E intake + reduce ex intensity (2-3 days). Negative side effects: Risk of hypoglycemia in the first phase. Muscle trauma that can impair the storage of extra glycogen.  How do you carbohydrate load ? ✓ Recent data suggest that simply changing to a very-high CHO diet, combined with 1 or 2 days of rest or reduced activity levels (tapering), will effectively increase muscle and liver glycogen. ✓ Continuing endurance training during the 7-14 days before competition will serve in maintaining adequate levels of GLUT-4 receptors to transfer BG into muscle cell, and of gly synthase that synthesizes glycogen from glucose. ✓ If the total CHO content is consumed over the entire week, the result will be similar to that of concentrating it in 2-3 days.  How do you carbohydrate load ? ✓ During CHO loading, CHO intake = 8-10 g/kg BW = 400-800 g/d. ✓ These intakes + total energy intake should be adjusted according to individual needs. ✓ Excess CHO consumption may lead to formation of body fat. ✓ Diet should contain simple and complex CHO, and an adequate intake of fat and protein. ✓ If the CHO load for 3-7 days is impossible, one day of high-CHO intake (10g/ kg BW high GI) can double the muscle gly concentration.  How do you carbohydrate load ? ✓ Most prolonged endurance events begin in the morning: ✓ Last large meal: 15 hours prior to race time. ✓ Some athletes drink a glucose polymer for the last major meal to avoid presence of intestinal residue in the morning of the competition. ✓ A CHO breakfast of CHO and protein may be eaten 3-4 hours prior to competition.  Classic method 1st day Depletion exercise 2nd day High prot/fat diet; low CHO; tapering exercise 3rd day High prot/fat diet; low CHO; tapering exercise 4th day High prot/fat diet; low CHO; tapering exercise 5th day High CHO diet; tapering ex 6th day High CHO diet; tapering ex or rest 7th day High CHO diet; tapering ex or rest 8th day competition  Recommended method 1st day Depletion exercise (optional) 2nd day Mixed diet; moderate CHO; tapering exercise 3rd day Mixed diet; moderate CHO; tapering exercise 4th day Mixed diet; moderate CHO; tapering exercise 5th day High CHO diet; tapering ex 6th day High CHO diet; tapering ex or rest 7th day High CHO diet; tapering ex or rest 8th day competition  Will CHO loading increase muscle glycogen concentration ? ✓ YES. ✓ No gender differences noted. ✓ Muscle gly increases 2-3 times beyond normal. ✓ Liver gly nearly doubles. ✓ It’s important to taper and rest 2 days before events. ✓ CHO loading become inefficient if repeated within a 5-days period.  How do i know if my muscles have increased their glycogen stores ? ✓ Best way: muscle biopsy. ✓ Practical way: monitor changes in body weight. ✓ 3 g of water are bound to each gram of stored glycogen. ✓ If you store an additional 300-400 g of gly, along with 900-1200 g of water ➔ BW will increase about 1200-1600 g above the normal training weight during the loading phase.  Will CHO loading improve exercise performance ? ✓ Contradictory studies. ✓ Although CHO loading may be an effective technique to enhance performance in prolonged aerobic endurance events, research suggests the most effective protocol is to CHO load and use CHO supplements during the event.  Are there any detrimental effects relative to CHO loading ? ✓ The extra BW may be a disadvantage. ✓ In most performance events where CHO loading is advocated, benefits are more than disadvantages. ✓ Role of the extra water in temperature regulation during exercise is not fully understood. ✓ For diabetic people, or people suffering from dyslipidemia, this technique is to be avoided. ✓ Possible destruction of muscle fibers by excess storage of CHO. ✓ Diarrhea, nausea, cramping (+++ with simple CHO) Case Study Mr. X entered the stadium for the final lap of his marathon race. He was well ahead of his competitors. In the last few minutes, he became confused. In the stadium, he started running around the track in the wrong direction and then collapsed. What went wrong? Sports drinks  Best Sports drinks: 5-8% carbohydrates or 50-80 calories per 8 oz with 120-170 mg sodium  To prepare your own sports drink:  8 oz ice water or caffeine-free lemon tea  1 tablespoon sugar  Pinch of salt (1/16 teaspoon)  1 ounce orange juice or 2 tablespoons lemon juice.  Dissolve the sugar and salt in the hot tea or a little hot water. Add juice and remaining ice water or tea Beverage Cal. CHO g CHO% Na (mg) K(mg) CHO Ing. Gatorade® 50 14 6 110 30 Sucrose, glucose, fructose AllSport® 70 19 8 55 55 HFCS Coca-Cola® 103 27 11 6 0 HFSC, sucrose Orange Juice 104 25 10 6 436 Fructose, sucrose, glucose Water 0 0 0 Low Low None  Question 1  Calculate the percent of CHO in a sports drink which contains 14 g of CHO in 240 ml = 8 oz.  14g/240 g fluid X 100 = 5.8 or 6%  Question 2  Give three reasons why a cola beverage would not be a good sports drink…  8 oz of cola contain 26 g of CHO so what is the CHO% = 11% so stomach upset can occur  Contain caffeine  Carbonation can cause the athlete to feel full and stop drinking Question 3  A cross country skier is participating in a 3 hr endurance exercise training session. He needs to consume 30-60 g CHO each hr during exercise (ACSM.) How much of a 6% CHO-containing sports drink will he need to consume each hour to obtain recommended amount of CHO?  6% = 6 g CHO in 100 g fluid.  To Obtain 30 g CHO you need to divide 30 by 6 and multiply by 100  so you need 500 g of fluid or 2 cups each hr  How much does he need to consume to obtain 60g CHO?  The following may benefit from CHO supplementation before exercise:  Soccer match  Very high intensity ex less than 30 min  Resistance training.  High intensity 30-60 min  All of the above.  Consumption of CHO during prolonged ex may delay fatigue.  Simple sugar should be taken 15-60 min before ex.  Moderate exercise: