Health & Medicine

1. NUTRITION
&
ENERGY METABOLISM
DURING EXERCISE
AZIMAH AHMAD, PHD

2. Nutrient Consumption: Fit
Active people do not require additional nutrients beyond those obtained in a nutritionally well
balanced diet.
What physically fit actually eat.
◦ Small differences in energy intake (low v high)
◦ Higher dietary fiber & lower cholesterol intakes
◦ Diets more closely approach recommendations
Sound human nutrition represents sound nutrition for athletes.

3. DEFINITION
a) Nutrition
• The processes involved in the use of food
by living organism including food intake,
digestion, absorption and metabolism of
food
• Influenced by various factors such as
psychology, sociology and economics.

4. …DEFINITION
b) Focus of Sports Nutrition:
• Health promotion
• Nutrition adaptation for training
• Reduce recovery time after training
• Improve optimal performance during training
and competition

6. ENERGY CONCEPT
ENERGY INTAKE > ENERGY EXPENDITURE =
INCREASE IN WEIGHT
ENERGY INTAKE < ENERGY EXPENDITURE =
LOSS IN WEIGHT
ENERGY INTAKE = ENERGY EXPENDITURE =
MAINTAIN IN WEIGHT

7. Dietary Reference Intakes
Recommendation Nutrient Intake (RDI) Malaysia
Same as ordinary people.
Need to meet exercise requirement

8. Malaysia
n Food
Pyramid
2020

9. Malaysian
Food
Pyramid
2010

10. How Do We Go From Eating Food to Powering
Muscles?
•Digestion of food
•Absorption of nutrients from intestine into blood
•Uptake of nutrients from blood into muscle cells
•Use of nutrients to generate adenosine
triphosphate (ATP)the energy currency of cells

11. Pathways for Your Body to Generate ATP
From Nutrients
•Which process is dominant during exercise?
•Depends on oxygen availability
•Affected by training and nutrient stores available

12. Anaerobic Metabolism
•Anaerobic metabolism refers to the transfer of energy when there is a limited amount of oxygen
available.
•This occurs when we are first starting to move and also when we are active at high intensity.
Anaerobic refers to activities that are high in intensity, but short in duration
•At these times, the need for energy is greater than the speed at which the blood can deliver
oxygen.
•ATP-PC and Glycolysis are the pathway of anerobic metabolism

13. Creatine Phosphate Pathway
•Creatine stores may be a limiting factor for adenosine triphosphate (ATP) synthesis during
explosive, high-intensity activities
•Creatine plays a role in maximal effort lasting up to 10 sec
Lasts for only 3 - 15 seconds.
•Key dietary issues include maintaining and maximizing creatine stores in muscle

14. Glycolysis
•The glycolytic system involves the process of glycolysis, through which
glucose is broken down to pyruvic acid via glycolytic enzymes.
•When conducted without oxygen, the pyruvic acid is converted to lactic
acid.
•One mole of glucose yields 2 moles of ATP, but 1 mole of glycogen yields
3 moles of ATP.

15. Anaerobic metabolism
•When we use carbohydrate anaerobically, one of the by-products is an accumulation of
lactic acid.
•The hydrogen ions released during the formation of lactic acid upset the acid-base balance
in the body, leading to muscle fatigue.
OBLA, or the onset of blood lactic acid, occurs when oxygen delivery does not catch up with
energy demand (intensity too high)
•Lactate threshold is the point at which blood lactate begins to rapidly accumulate above
resting levels during exercise.
•This explains why we can only be active at high intensities for short periods of time.
•As the intensity of the activity diminishes, adequate amounts of oxygen are delivered and
the lactic acid is reconverted to pyruvic acid, which can then be used as a fuel source.
•Individuals with higher lactate thresholds or OBLA values, expressed as a percent of their
VO2max, are capable of the best endurance performance.

16. Aerobic Activities
•The oxidative system involves breakdown of fuels with the aid of oxygen
•This system yields much more energy that the ATP-PC (phosphogens) or glycolytic systems
•Aerobic refers to activity that are low-to-moderate in intensity and longer in duration
•Your muscles oxidative capacity (QO2) depends on its oxidative enzyme levels, its fiber-type
composition, and oxygen availability.
•The greater the QO2 the more fit the muscle.

17. Aerobic Metabolism
•Aerobic metabolism refers to the process whereby energy is transferred in the presence of oxygen.
•In aerobic metabolism, energy demand does not outpace oxygen delivery.
•Your heart and circulatory system are able to deliver oxygen in sufficient quantities to meet the body's
needs for energy transfer.
•In this circumstance, you initially use carbohydrate as a fuel source and then shift to fat as the primary
source.
•If the intensity remains relatively low, this type of activity can go on indefinitely.
•The only limiting factors will be orthopedic stress and low levels of carbohydrate (fat burns in a CHO
flame).
•Oxidation of CHO involves glycolysis, the Krebs cycle, and the electron transport system.
•The end result is water, CO2 and 36 or 38 ATP per molecule of glucose (38 or 39 per molecule of
glycogen).
•Fat oxidation begins with oxidation of free fatty acids, then follows the same path as CHO oxidation the
Krebs cycle and the electron transfer system.
•The energy yield for fat oxidation is much higher than for CHO oxidation, and it varies with the free fatty
acid being oxidized.

18. Electron Transfer System
•Final metabolic pathway in the production of ATP
•Series of chemical reactions in the mitochondria that transfer electrons from the hydrogen atom
carriers NAD and FAD to oxygen
•Accounts for the majority of the ATP formation

19. Aerobic metabolism-Protein
•Protein oxidation is more complex because protein (amino acids) contains nitrogen, which
cannot be oxidized.
•Protein contributes relatively little to energy production, so its metabolism is often overlooked.
•Protein can supply up to 5 to 10 of the energy needed to sustain prolonged exercise.
•Only the most basic units of protein – amino acids can be used for energy.

20. Energy sources Summary
•CHO
◦ Used anaerobically and
aerobically
◦ Low amount stored in body
•Fats
◦ Used only aerobically
◦ Large amounts stored in body
◦ Can only be used if CHO is
available
•Protein
◦ Only used in starvation states

21. Anaerobic vs aerobic
•The key factor that differentiates the two is how quickly you are able to circulate oxygen to your
muscles (cardiorespiratory fitness) versus how quickly you are transferring energy
•If energy demand exceeds oxygen delivery, you are performing anaerobic exercise
•If oxygen delivery meets or exceeds energy demand, you are performing aerobic exercise

22. Energy selection and duration

24. EPOC(Excess Post Exercise Oxygen
Consumption)
•When we start exercise, we initially have difficulty getting enough oxygen to our muscles
•Therefore, when we start exercise, we are performing anaerobic exercise
•Eventually, if the intensity is not too high, we are able to get the necessary amount of oxygen to the
muscles
•This is why the initial moments of exercise feel uncomfortable and why within a few moments we get
our second wind
•Our fitness level determines how quickly this occurs
•However, the energy used anaerobically at the start needs to be eventually replaced
•This is why we breathe hard after exercise
Excess post-exercise oxygen consumption (EPOC) is the elevation above resting oxygen consumption
that occurs after exercise.

26. Delayed onset muscle soreness (DOMS)
•is caused by an inflammation response triggered by microscopic damage to muscles caused by
stressing them beyond their capabilities
•The inflammation response causes swelling, tenderness, heat production, and pain.

27. Daily Energy Expenditure
•Resting metabolic rate (RMR).
•Thermic effect of activity (TEA).
•Thermic effect of feeding (TEF).
•Thermic effect of a meal is the energy that is expended to digest, metabolize, and store ingested
macronutrients.

28. Resting Metabolic Rate
•This is the rate of energy expenditure when you are in an awake, resting state.
•Differs from Basal Metabolic Rate

29. How Does the Body Decide What to
Burn for Fuel at a Given Time?
•Influenced by a number of factors
•Intensity of exercise and oxygen availability
•Fuel stores available (carbohydrate depletion)
•Hormonal influences (insulin, epinephrine, cortisol)
•Training effects regarding ability to deliver and use oxygen
•Muscle fiber make-up

30. Classification of Human Skeletal Muscle Fiber