1. 4-utilization of carbohydrates
during exercise
Sport Nutrition
Prepared by De. Siham Gritly
Dr. Siham Gritly

2. 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

3. Carbohydrate Needs
the diet for athletes and active people is that it should include
more carbohydrate-containing foods that recommended by the
health professionals.
Dr. Siham Gritly
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 energy
It also fueling the central nervous system (CNS)
and brain
During 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

4. 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.
Dr. Siham Gritly

5. • *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
Dr. Siham Gritly

6. • 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
Dr. Siham Gritly

7. 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
Dr. Siham Gritly

8. Muscle glycogen store is the first source of
glucose for the exercising muscle
Dr. Siham Gritly
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)

9. 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
Dr. Siham Gritly

10. Aerobic physical activity
and 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
Dr. Siham Gritly

11. Carbohydrate diets and endurance performance
Endurance performance such as (cycling,
swimming or running
• aerobic Exercise
Dr. Siham Gritly

12. • 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
Dr. Siham Gritly

13. 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
Dr. Siham Gritly

14. Low- to moderate-intensity aerobic exercises that
can be sustained for a long time (more than 20
minutes) use some glucose, but more fat for fuel.
Dr. Siham Gritly
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

15. 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.
Dr. Siham Gritly

16. 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.
Dr. Siham Gritly

17. 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.
Dr. Siham Gritly

18. Anaerobic exercise
• Anaerobic exercise include, strength-based
activities, such as sprinting or bodybuilding,
Dr. Siham Gritly

19. Anaerobic exercise is high in intensity and short
in duration
Ref. 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
Dr. Siham Gritly

20. 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
Dr. Siham Gritly
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).

21. 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).Dr. Siham Gritly

22. • 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)
Dr. Siham Gritly

23. 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.
Dr. Siham Gritly
The cycle's importance is
based on the prevention
of lactic acidosis in the
muscle under anaerobic
conditions

24. 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
Dr. Siham Gritly

25. 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
Dr. Siham Gritly

26. • 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
Dr. Siham Gritly

27. • 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.
Dr. Siham Gritly

28. 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 Pancrea
s
Increase in blood
glucose
Helps transport glucose into
cells; decrease blood glucose
levels
Glucagon Pancrea
s
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
levelsDr. Siham Gritly

29. 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
Dr. Siham Gritly

30. 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
Dr. Siham Gritly

31. • 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?
.
Dr. Siham Gritly

32. 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

33. 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.
Dr. Siham Gritly

34. 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.
Dr. Siham Gritly

35. • 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.
Dr. Siham Gritly

36. • 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
Dr. Siham Gritly

37. 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 ?
Dr. Siham Gritly

38. 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 .
Dr. Siham Gritly

39. • 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
Dr. Siham Gritly

40. • 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
Dr. Siham Gritly

41. 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
Dr. Siham Gritly

42. *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

43. • *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
Dr. Siham Gritly