This slide give a complete introduction on how energy plays an important role in sports athletes, types of energy system, how body responds to energy system and Vo2max and its importance.

1. Energy metabolism
Sports Nutrition

2. Exercise
 When we perform any form of exercise or
movement it is a co-ordinated physical response
that provides the skeletal muscle with:
Energy
Oxygen &
Appropriate nutrients
 At the same time metabolic waste & heat need to
be removed and the person’s fluid and
electrolyte balance must be maintained.

3. Sports nutrition
 The IOC describes sports nutrition as a
combination of healthy eating habits,
supplements and sports foods that are needed
to support energy needs for:
Training hard
Achieving performance goals
Reducing incidence of illness & injury

4. Difference between Athlete and an Exerciser
 According to the American college of cardiology, in order
to be classified as an athlete one must meet all of the
following criteria:
Be training in sports aiming to improve performance/
results
To be actively participating in sports competitions
To be formally registered in sports federation
To have sports training and competition as his/ her major
activity, devoting several hours in all or most days for
these activities.

5.  It is vital to remember that athlete’s make up < 1%
of the population.
 Many of us are not actually athletes but are rather
‘exerciser’. An exerciser does not meet these
criteria.
 The term exerciser is now used to replace the
outdated terms ‘recreational’ athlete
 In this group of individuals, often health
promotion and body aesthetics are the primary
goal (not necessarily an improvement in
performance). This is a great population to benefit
from medical advice.

6. Types of athletes: 3 types
1. Endurance athletes:
 These athletes exercise for long durations and
beneficial metabolic adaptations for this group
includes methods to increase oxygen supply to
their muscles and reduce their body fat.
 The lighter these athletes are, the greater their
power to weight ratio is and the faster and further
they can typically go.

7. 2. Resistance athletes:
 Use short, intense bursts of power output.
Metabolic adaptations that suit them are an increase
in strength, power & muscle mass.
 These are the athlete’s that are typically quite
heave and would benefit from ‘bulking up’.
3. Sports athletes:
 Take part in stop start activities and utilize a
combination of endurance and resistance metabolic
adaptations.

8. Muscle fibres
 Understanding muscle fibre types will help to
understand which energy systems and nutrients best
fuel muscles for chosen activity.
 A muscle biopsy gives definitive answer to this
question.
 There ae 2 types of muscle fibers:
Slow twitch fibres
Fast twitch fibres

9. Slow twitch fibres
 Slow twitch muscle fibres are known to be:
Fatigue resistant
Rely heavily on the aerobic/ oxidative energy system
Are well supplied by capillaries also known as blood
vessels meaning that they are primed for optimal oxygen
supply.
This type of muscle fibre is ideal for prolonged low
intensity activity like running a marathon

10. Fast twitch fibres
 There are two subsets in this group: Fast twitch A and Fast
twitch B.
 They are known to be:
More fatigable
Utilise energy more from the anaerobic/ glycolytic energy
system
Rely less on the aerobic/ oxidative energy system and are
thus Better suited to high intensity exercise of a shorter
duration, like weightlifting

11.  Individuals have both types of fibers, but genetically
some have more of one than another.
 Factor that can determine this depends on the training
that one routinely take part in. In maximal exercise all
fibres are involved.
Elite endurance athletes have been found to have
between 70 – 90% slow twitch muscle fibres and
Sprint and explosive sports athletes have been found to
have more fast twitch fibres, with champion sprint
runners having an average of 70% fast twitch muscle
fibres.

12. Energy metabolism
 There are 3 metabolic systems that supply energy to the
body:
• The ATP-PC system (independent of oxygen)
• The Anaerobic/ or glycolytic system (independent of
oxygen)
• The Aerobic or oxidative system (dependent on
oxygen)
 The type of system utilized, depends on the duration,
intensity and type of physical activity.

13.  Skeletal muscle is the tissue responsible for the
generation of the force needed to move joints needed
for exercise.
 Any muscle contraction needs a molecule called ATP
which is found within the mitochondria of the cells.
 Body relies on a continuous supply of fuel through ATP,
regardless of which energy system is used. The energy
systems should be seen as a continuum.
 Body uses all of them in different amounts depending
on the duration and intensity of the exercise.

15. 1. ATP-ADP cycle
 ATP adenosine triphosphate is made up of a molecule
called adenosine with 3 phosphates attached to it.
 At any given time, body contains about 90g of ATP
that can be used for a sudden burst of energy.
 The bond between the last 2 phosphates of this
molecule is a volatile one and when it breaks,
energy is released (and is subsequently used for
muscle contraction).

16.  After one phosphate is utilized for energy,
adenosine and two phosphates (or adenosine
di-phosphate) are left.
 In order to continue to provide muscle with
energy the ATP must be replenished.
 The ATP is replenished through the various
energy systems and the substrates that fuel
these energy systems either come directly
from food (exogenous) or from the body stores
(endogenous).

18. ATP- Creatine phosphate (CrP) system
 CrP is a high energy compound and there is 5 x
more in body than ATP (but still limited).
 It occurs in the absence of oxygen and is the
fastest way to replenish ATP but because there
is a limited amount available in the body it is
quickly depleted (within 8 seconds
approximately).

19.  Creatine is made from amino acids and so one
can replenish used creatine sources by
consuming protein rich foods (or alternatively
using creatine supplements).
 In order for CrP to give ADP one of its
phosphates to create ATP, it must first be
broken down by an enzyme called creatine
kinase.
 Creatine kinase take CrP and breaks it into
creatine and one phosphate.
 The phosphate will bond to ADP to make ATP.

21. Anaerobic/ glycolytic system
 Anaerobic means without oxygen. Glyco means glucose
and lysis is breaking down. So, glycolysis is the
breakdown of glucose to form ATP in the absence of
oxygen.
 The glucose is obtained from two main sources:
1.When glycogen from muscles stores is broken down into
glucose and
2.Glucose obtained directly from dietary sources of
carbohydrates.

22.  This system
supplies energy
for short
intense bursts
of
approximately
60-120 seconds
and at the end
of the process,
a substance
called lactic
acid/ lactate is
produced.

23. Lactic acid/ lactate
 Lactic acid is not just a waste product but is an
important intermediate nutrient that enters through the
Cori cycle.
 The lactic acid moves from the muscle to the liver and is
converted into glucose which can then be used again in
the anaerobic energy system.
 Unfortunately, this pathway is energy insufficient and
can thus not be sustained for long periods of time.
 When there is insufficient energy to convert the lactic
acid to glucose, the lactic acid builds up and causes the
muscle to fatigue which will slow or halt the activity.

24. Aerobic/ oxidative system
 This system is dependent on oxygen (it cannot
function without oxygen) and is accessed when
a person takes part in prolonged exercise.
 The substrates used to fuel this system
includes carbohydrates and lipids and to a
much lesser extent, amino acids (from
protein).

25.  The amount of CHO used vs lipids depends on
a variety of factors, including:
Exercise intensity & duration
Preceding diet
Substrate availability
Training status
Environmental factors

27. Summary of energy metabolism

28. Exercise intensity & energy systems
 For high intensity, short duration exercise,
body use the anaerobic system (no oxygen) an
example of this is weightlifting.
 For this system body will use only glucose or
stored glycogen as fuel.
 Having a high muscle glycogen level will fuel
the activity for longer.

29.  For stop-start sports body will use a
combination of anaerobic & aerobic energy
systems.
 Examples of these includes: Basketball,
football, soccer, tennis and cricket.
 Having a high muscle glycogen levels for these
sports will also fuel the activity for longer.

30.  For moderate intensity activity body will
utilize the aerobic energy system as well as
blood glucose and circulating fatty acids.
 Examples include jogging, hiking, aerobic
dance, gymnastics and cycling.

31.  In moderate to low intensity activity, body will
predominantly use the aerobic pathway. The
duration of the activity will depict which fuel is
utilized.
 For example, walking for a shorter duration will use
the aerobic glycolysis pathway and walking for a
long duration will access the aerobic lipolysis
pathway.
 The longer one walk or exercise at a lower intensity,
the more fat is used to create ATP for energy.

32. UTILISATION OF MACRONUTRIENTS DURING
VARIOUS INTENSITIES OF EXERCISE

33. Effects of training on energy systems
 The type of energy system body will use also depends on
how well trained the muscle are. In athlete’s who are well
trained or very fit, they have:
• Improved oxygen delivery (due to better cardiovascular
health)- Oxygen is a rate limiting substrate in the aerobic
system, without oxygen the aerobic system cannot replenish
ATP and body will revert to the anaerobic system which is very
quickly depleted.
• They also have more mitochondria means more ATP
generation and thus more energy and power.

34. Oxygen uptake
 Energy intensity is assessed by measuring
oxygen uptake –VO2
 Maximal oxygen uptake (VO2max), it is
the amount of oxygen that can be
consumed by a person
 VO2max is related to heart rate.Measured
as ‘mL/kg/min’
 It is considered best indicator of an
athlete’s cardiovascular fitness and
aerobic endurance. The more oxygen
body can use the more ATP can be
produced.

35. Sedentary individuals: 30-40 ml/kg/min
High trained individuals: 80-90ml/kg/min
Oxygen uptake can depend on:
Training
Body size
Red blood cell count
Genetic
 It is calculated by measuring the
volume (V) of oxygen (O2) that one
consume while running on a treadmill.

37. Light intensity exercise
20-50% VO2max
 Increase in fat oxidation as
aerobic exercise increases
 Primary fuel for energy is fatty
acids in blood
 Muscle glycogen is used very
slowly

38. Moderate intensity exercise
65% VO2max
 Fat and carbohydrate
contribute equally to providing
fuel for exercise

39. High intensity exercise
> 85% VO2max
 Oxidation of carbohydrates
will provide approx. 2/3 of
energy needs at this intensity
 Fats serve as a vital
secondary fuel source
 Reduced ability to sustain
intensity and eventual halt
will occur upon depletion of
muscle glycogen

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