4-utilization of carbohydrates during exercise

Sport NutritionPrepared by De. Siham Gritly

Dr. Siham Gritly

Dr. Siham Gritly

objectives

• At the end of the lecture student should be able to understand;

*Utilization of Carbohydrate diets during endurance performance

* Utilization Carbohydrate diets and high intensity exercise

*Concepts of Glycemic Index and Glycemic load

Dr. Siham Gritly

Carbohydrate Needsthe diet for athletes and active people is that it should include more

carbohydrate-containing foods that recommended by the health professionals.

Their diets should be about 60-70% of their daily energy intake obtained from carbohydrates, 30 % or less from fat and 10 to 15 % from proteins Adequate carbohydrate intake also helps prevent protein from being used as energyIt also fueling the central nervous system (CNS) and brainDuring heavy training kcal must be increased specially from carbohydrates (CHO), to meet the energy demands. Low intake may result in: Chronic muscular fatigue.Weight and muscle mass loss Ellie Whitney and Sharon Rady

Rolfes; Under standing Nutrition, Twelfth Edition. 2011, 2008 Wadsworth, Cengage Learning

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Carbohydrates utilized by the body in different ways;

• *for the immediate energy needs through oxidation to carbon dioxide and water via the processes of glycolysis and tri-carboxylic acid cycle or Kerb cycle

• *stored as glycogen in the liver and muscles tissue through the process glycogenesis.

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• *converted to fatty acids and stored as triglyceride.

• *convert to other necessary CHO such as ribose, fructose and deoxyribose which is necessary for the formation of genetic material DNA.

• *some become the carbon skeletons for production of essential amino acids

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• Carbohydrates can produce nearly 20 times more energy (in the form of ATP) per gram when metabolized in the presence of adequate oxygen (aerobic oxidation).

• CP, creatine phosphate (also called phosphocreatine): a high-energy compound in muscle cells that acts as a reservoir of energy that can maintain a steady supply of ATP. CP provides the energy for short bursts of activity

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Carbohydrates come in two sources during

exercises ;

Carbohydrates utilization during Exercise

1-Simple sugar glucose

2-Storage form of glucose –glycogen; Glycogen is stored in Muscles and Liver

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Muscle glycogen store is the first source of glucose for the exercising muscle

when no glycogen;- the process of glycogenolysis started and follow by gluconeogenesis in the liver to make glucose available (main function of the liver is to release glucose through glycogenolysis and gluconeogenesis )

if no enough glucose after 3 hours of heavy exercise athletes enter to a condition known as hoypglycemia (low glucose level in the blood)

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Muscle glycogen breakdown during exercise

• It is needed for any short, intense short period of exercise from sprinting (running) to weight lifting

• Two main factors lead to the Muscle Glycogen Depletion

1- intensity of exercise

2-duration of exercise

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Aerobic physical activityand carbohydrate

• Aerobic physical activity: activity in which the body’s large muscles move in a rhythmic manner for a sustained period of time. Aerobic activity, also called endurance activity, improves cardiorespiratory fitness. Brisk(fast) walking, running, swimming, and bicycling are examples

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Carbohydrate diets and endurance performanceEndurance performance such as (cycling, swimming or

running

• aerobic Exercise

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• The endurance capacity of an individual on a high-CHO diet is approximately 3 times greater than on a high-fat diet.

When CHO intake is low, several days of exact training will deplete muscle CHO (glycogen) stores and eventually impair performance.

CHO should supply 60 -65% of the total daily kcal intake

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Moderate-intensity physical activity:

• moderate-intensity physical activity: physical activity that requires some increase in breathing and/or heart rate and expends 3.5 to 7 kcalories per minute.

• Walking at a speed of 3 to 4.5 miles per hour (about 15 to 20 minutes to walk one mile) is an example

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Low- to moderate-intensity aerobic exercises thatcan be sustained for a long time (more than 20

minutes) use some glucose, but more fat for fuel.Nutrient Density A healthful diet is based on nutrient-dense foods—foods that supply adequate vitamins and minerals for the energy they provide. Active people need to eat both for nutrient adequacy and for energy. A diet that is high in carbohydrate (60 to 70 percent of total kcalories), moderate in fat (20 to 35 percent), and adequate in protein (10 to 20 percent) ensures full glycogen and other nutrient stores

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Carbohydrate diets and high intensity exercise intensity exercise such as( soccer,

hockey, tennis, basketball and rugby)

• Muscle glycogen provides the main contribution of energy during high-intensity exercise that lasts more than about 30 seconds.

• As the exercise duration increases, the muscle

glycogen stores are diminished, and the ATP comes from the contribution

of fatty acid oxidation.

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CHO for Strength Training (weight lifting)

• CHO are required for strength training because the exercises rely on muscle glycogen stores for energy.

• CHO should supply 55-60% of the total daily caloric intake. This is slightly lower than the requirements for endurance activities because the total amount of energy expended is less.

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vigorous-intensity physical activity: physical activity

Intensity refers to the rate at which the activity is being performed

• vigorous-intensity physical activity: physical activity that requires a large increase in breathing and/or heart rate and expends more than 7 kcalories per minute.

• Walking at a very brisk pace (>4.5 miles per hour) or running at a pace of at least 5 miles per hour are examples.

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Anaerobic exercise

• Anaerobic exercise include, strength-based activities, such as sprinting or bodybuilding,

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Anaerobic exercise is high in intensity and short in durationRef. http://www.livestrong.com/article/500155-example-of-anaerobic-exercise/#ixzz2S1NYa5jd

• Anaerobic exercises may last only two minutes or less, but this type of workout actually burns more calories than aerobic exercise.

• Unlike aerobic exercise, anaerobic exercise burns a higher percentage of calories from glycogen

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Intense activities; such as a quarter-mile race—use glycogen quickly. In such activities, the muscles break down glucose to pyruvate anaerobically, producing ATP quickly. (anaerobically glycolysis) Lactate is the product of anaerobic glycolysis

sprinting, strength/resistance training and other intense activities that require more energy than can be provided in a lower intensity aerobic activity would be anaerobic (no oxygen).

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Lactate

• Lactate; When the rate of glycolysis exceeds the capacity of the mitochondria to accept hydrogens with their electrons for the electron transport chain, the accumulating pyruvate molecules are converted to lactate.

• At low intensities, lactate is readily cleared from the blood, but at higher intensities, lactate accumulates.

• When the rate of lactate production exceeds the rate of clearance, intense activity can be maintained for only one to three minutes (as in a 400- to 800-meter race or a boxing match).

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• Working muscles may produce lactate and experience fatigue, but the lactate does not cause the fatigue.

• Lactate quickly leaves the muscles and travels in the blood to the liver.

• liver enzymes convert the lactate back into glucose. • Glucose can then return to the muscles to fuel

additional activity. (The recycling process that regenerates glucose from lactate is known as the Cori cycle)

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The Cori cycle (also known as Lactic acid cycle), refers to the metabolic pathway in which lactate produced by anaerobic

glycolysis in the muscles moves to the liver and is converted to glucose, which then returns to the muscles and is converted

back to lactate.

The cycle's importance is based on the prevention of lactic acidosis in the muscle under anaerobic conditions

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Hypoglycemia

• During intensity of exercise and long duration;

• Glycogen supplies energy within the first few minutes of any sport, If no glucose within hours athletes enter a condition known as hypoglycemia

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Hypoglycemia and the development of Fatigues during exercise

• Hypoglycemia occurs when a person's blood sugar levels are low, the normal blood glucose level is usually ranges from 80-120 mg of glucose per 100 ml of blood

• Usually hypoglycemia occur during high intensity aerobic exercise when no glycogen storage in the liver

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• blood glucose is very short supply during exercise, and should be replenish from glycogen storage in the liver

• ATP that supply the muscle decreased thus athletes become fatigue

• The symptoms of hypoglycemia rarely develop until the level of sugar in the blood falls below 60 milligrams per deciliter of blood

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• Hypoglycemia impair the function of central nervous system (brain and spinal cord) thus acute feeling of dizziness, muscular weakness, sweating and fatigue developed

• severe hypoglycemia causes symptoms such as confusion, seizure, and coma

• Symptoms of hypoglycemia are treated by consuming sugar in any form.

• the sugar levels in the blood become too high, a condition called hyperglycemia.

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Major hormones involved in regulation of blood glucose levels

adapted from; Melvin H Williams 2010; Nutrition for Health, Fitness and Sport.

hormone Gland stimulus action

Insulin Pancreas

Increase in blood glucose

Helps transport glucose into cells; decrease blood glucose levels

Glucagon Pancreas

Decrease in blood glucose; exercise stress

Promotes gluconeogenesis in liver; helps increase blood glucose

Epinephrine Adrenal Exercise stress; decrease in blood glucose

Promote glycogen breakdown and glucose release from the liver; helps increase blood glucose levels

cortisol adrenal Exercise stress; decrease in blood glucose

Promotes breakdown of protein and resultant gluconeogenesis; helps increase blood glucose levels

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Glycemic Index (GI)• Glycemic index represents a ranking system

relative to the effect that consumption of 50 grams of particular carbohydrates that influence blood glucose within 2 hours.

In other words;-• glycemic index; Carbohydrates which produce

a large increase in blood glucose concentration, in response to a standard amount of carbohydrate (50g), are classified as having a high glycemic index

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Glycemic Index values

• The values that used to rank glycemic index of food as follows;-

*70 or more------high GI

*69-55------------medium GI foods

*55 or less--------low GI foods

Factors other than CHO might influence the GI;-

*physical form (coarse or fine)

*serving mode (raw or cooked)

A glycemic index GI value tells you only how rapidly a particular carbohydrate turns into sugar

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• The carbohydrate in watermelon or grapes, for example, both have a high GI (food which have refined sugars). Foods high in fiber such as beans have low GI

• GI in fructose has a low GI used as primary source in sports drinks. Why?

• the low glycemic index carbohydrate improve endurance capacity more than the high glycemic index food. Why?

.

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Glycemic load (GL)

• The glycemic load represents a ranking system relative to the effect that eating a carbohydrates food has on the blood glucose level, but also includes the portion size

• The glycemic load (GL) is a relatively new way to assess the impact of carbohydrate consumption that takes the glycemic index into account, but gives a fuller picture than does glycemic index alone

Dr. Siham Gritly

Glycemic index and glycemic load

• glycemic index is the rate at which food is converted into glucose, glycemic load is the total amount (load) of glucose provided by the food. Glycemic index is an absolute value

• while glycemic load depends on the serving size of the food in question. Glycemic load values are always quoted in reference to a serving size in grams.

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Glycemic load values

• Values are used to rank the glycemic load food;-

*20 or more----high GL

*19-11----------medium GL food

*10 or less------low GL foods

Foods that have a low GL almost always have a low GI is more healthful source of CHO.

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• The glycemic load of a food is calculated by multiplying the absolute GI value by the grams of available carbohydrate in the serving, and then dividing by 100.

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• The glycemic load can be calculated by the following equation;-

• GL= GI × gms of CHO in one serving ÷ 100

• Note that Available Carbs is equal to the total carbohydrate content minus the fiber content.

• For example, a 225 g (1 cup) serving of Bananas with a GI of 52 and a carbohydrate content of 45.5 g (51.4 g total carbohydrate - 5.9 g fiber) makes the calculation GL = 52 * 45.5 / 100 = 24, so the GL is 24.

• Adapted from; www.glycemicgourmet.com/how-calculate-glycemic-index.html

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Exercise;- calculate the Glycemic Load of the following carbohydrates;-adapted from; Melvin H Williams 2010; Nutrition for Health, Fitness and Sport.

COH Glycemic index CHO in grams Gycemic loadL

1-baked potato 1 cup 85 57 ?

2-white bread 1 slice;- 70 10 ?

3-orange 1 medium 44 15 ?

4-fructose 1 tsp 23 5 ?

5-wafers (5 cookies) 77 15 ?

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Carbohydrate diets and Recovery from exercise

• recovery from exercise by resynthesize of the body's carbohydrate stores & rehydration

• Recovery of muscle glycogen can be achieved in 24h when sufficient dietary carbohydrate is ingested

• Within 30 minutes of completing an extended or intense exercise session, consumption of at least 50 grams of CHO (roughly 200 kcals) is recommended .

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• Some expertise suggested that; the optimal amount of carbohydrate is about 1 to 1.5 g of carbohydrate/kg body weight, consumed immediately after exercise and at 2-h intervals until the next meal

• The most important effect of such a diet is to maximize the stores of glycogen in the muscles.

• recover of muscle glycogen stores may take longer when exercise causes muscle damage and pain

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• Rehydration• Immediately after exercise most athletes

generally prefer to drink fluids rather than to consume solid foods.

• Drinking fluids helps rehydrate the athlete,

which is an essential part of the recovery process

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references

*Ellie Whitney and Sharon Rady Rolfes; Under standing Nutrition, Twelfth Edition. 2011, 2008 Wadsworth, Cengage Learning

*Sareen Gropper, Jack Smith and James Groff, Advanced Nutrition and Human Metabolism, fifth ed. WADSWORTH

*Melvin H Williams 2010; Nutrition for Health, Fitness and Sport. 9th ed, McGraw Hill

*Heymsfield, SB.; Baumgartner N.; Richard and Sheau-Fang P. 1999. Modern Nutrition in Health and Disease; Shils E Maurice, Olson A. James, Shike Moshe and Ross A. Catharine eds. 9th edition

*Guyton, C. Arthur. 1985. Textbook of Medical Physiology. 6th edition, W.B. Company

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*LEMON, P. W. R. Protein and exercise: update 1987. Med Sci. Sports Exerc., Vol. 19, No. 5

*FAO FOOD AND NUTRITION TECHNICAL REPORT SERIES 1

*Human energy requirements Report of a Joint FAO/WHO/UNUExpert Consultation Rome, 17-24 October 2001

*Burke LM et al. (2004). Carbohydrates and fat for training and recovery. J Sports Sci 22:15-30

Dr. Siham Gritly

• *Power sports;- Olympic weight lifting• *Very high-intensity sports;- 100-meter dash• *High-intensity, short duration sports;- 5,000-

meter run• *Intermittent high-intensity sports;- soccer• *Endurance sports;- marathon running• *Low-endurance, skill sports;- golf• *Weight-control and body image sports;- body

building