Energy For Muscular Activity

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Energy for Muscular
Activity
Chapter 5
1
Where do we get Energy for our
working muscles?
The Three Energy Nutrients
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 Fats
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 Carbohydrates
 Proteins
Carbohydrates
Carbohydrates are broken down into
glucose and stored into the muscle as
glycogen.
 Most easily broken down into this state
which is why they are the first thing our
body uses as a form of energy.

Proteins
Proteins are broken down into amino acids.
 Proteins are used for energy when the body
is in starvation mode.

Fats
Fats are broken down in to fatty acids and a
glycerol.
 Fats are the LAST energy source which is
used.

Metabolism
Metabolism
• All the chemical reactions in the body that
occur in the production of energy to do
work (i.e. muscle work,
7
Bioenergetic Conversion
The process by which our body converts the
energy found in carbohydrates, proteins and
fats into a more usable form, Adenosine
Triphosphate (ATP).
8
ATP = Adenosine TRI Phosphate
3 phosphates are present
Adenosine Triphosphate (ATP)
 Adenosine triphosphate (ATP)
 ATP is a usable form of energy for
the body.
 Made in the mitochondrion
 Resynthesized in two ways
Aerobically
Anaerobically
ATP
ADP + Pi + ENERGY
Recall the Hydrolysis of
ATP Equation
ATP + H20
ADP + Pi + Energy
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 ATP
is the molecule that gives every cell in
our body energy to function.
 All things in our body require energy in
order to be able to function properly.
– Food metabolism
– Heart beat
– Muscles contract
 When
you need energy it is on.
 When you don’t need energy it is being
stored and not used.
2 ways to re-synthesize ATP
Aerobic System
Two Energy Systems
 Aerobic System
In the presence of oxygen (O2)
All of its metabolic activity will involve O2
Occurs in the mitochondria
Leads to the complete breakdown of glucose
Lag period (slow to reach peek production)
Longer duration activities
 With
the presence of oxygen you are able to
perform an activity over a long period of
time with a balanced intensity.
 What
is an example of “aerobic activity”
– Requires oxygen
 How
does your body react?
– Heart rate increases
– Breathing increases
Anaerobic
Without oxygen (O2)
 Occurs in cytoplasm
 Produces ATP immediately when needed
 Fast rate of ATP production
 Quick burst & shorter duration activities
 Needed for short and medium length
activities.

– Ex: weight lifting, short shifts in hockey
Energy spectrum:
Anaerobic <------------------------------> Aerobic
• These systems are not in opposition
• These systems do not work in isolation, both
systems are always contributing to some extent.
• All sporting events require some contribution
from both systems.
• The body has three (3) primary metabolic
pathways to resynthesizing ATP as it is used up
and/or needed during exercise.
21
Three Metabolic
Pathways
22
Three Metabolic Pathways

Within the ANAEROBIC and AEROBIC
systems, there are 3 metabolic pathways by
which ATP energy reserves are restored:
– ATP-PC pathway (anaerobic alactic)
– Glycolysis pathway (anaterobic lactic)
– Cellular respiration (aerobic)
23
High Energy Phosphate System
P
ENERGY
Creatine
ADP + Pi  ATP
24
ATP-PC System
 ATP-PC System (anaerobic alactic)
 First of two anaerobic energy
pathways
 Relies on the action of stored
ATP and phosphocreatine
 Yields enough ATP for 7-12
seconds of energy
 Provides highest rate of ATP
synthesis
PC + ADP
ATP + CREATINE
ATP-PC

Plays an important role in sporting events
which only last a few seconds, but require
large bursts of energy.
– Ex: Olympic weight lifting, high jump, 50-100
m dash.

HOWEVER – muscles do not have large
supplies of phosphocreatine, and after about
10-15 seconds, body begins to rely on the
second system.
High Energy Phosphate System
Overview
Primary energy source:
Stored ATP, CP
Duration of activity:
7 to 12 s
Sporting events:
Weightlifting, high jump, long jump, 100
m run, 25 m swim
Advantages:
Produces very large amount of energy
in a short amount of time
Limiting factors:
Initial concentration of high energy
phosphates (ATP, PC)
27
The Anaerobic Glycolytic System
Glycogen
ENERGY
Lactic Acid
ADP + Pi  ATP
28
Glycolysis



A biochemical process that releases energy in the form of
ATP from glycogen and glucose
anaerobic process (in the absence of oxygen)
The products of glycolysis (per molecule of glycogen):
- 2 molecules of ATP
- 2 molecules of pyruvic acid

The by-product of glycolysis (per molecule of glycogen):
- 2 molecules of lactic acid
29
The Anaerobic Glycolytic System

Starts when:
– the reserves of high energy phosphate
compounds fall to a low level
– the rate of glycolysis is high and there is a
buildup of pyruvic acid
30
Anaerobic Threshold



The exercise intensity at which lactic acid begins to accumulate within
the blood
The point during exercise where a person begins to feel discomfort and
burning sensations in the muscles
Lactic acid is used to store pyruvate and hydrogen ions until they can
be processed by the aerobic system
31
Substrates for the anaerobic energy system


The primary source of
substrates is carbohydrate
Carbohydrates:
– primary dietary source
of glucose
– primary energy fuels for
brain, muscles, heart,
liver
32
Carbohydrate breakdown and storage
Complex
Carbohydrates
Digestive
system
Glucose
Blood
Stream
Circulation of glucose
throughout body
Glucose stored
in blood
Glucogenesis
Glycogen
Glycogen stored
in muscle or liver
33
LACTIC ACID CHALLENGE 
What is lactic acid challenge?

This is a class challenge.
– Find an place on the wall, and the person who
can perform a wall sit for the longest – will win
a prize!

Describe what you felt that made you want
to stop?
What is lactic acid?

After 2 or 3 minutes of a sustained activity
the body can not break down glucose fast
enough to keep up.

Lactic Acid builds up in the muscle fibers

You are forced to slow down/stop – as it
causes pain/discomfort in the muscle.
The Anaerobic Glycolytic System Overview
Primary energy source:
Stored glycogen, blood glucose
Duration of activity:
12 s to 3 min
Sporting events:
800 m run, 200 m swim, downhill ski
racing, 1500 m speedskating
Advantages:
Ability to produce energy under
conditions of inadequate oxygen
Limiting factors:
Lactic acid build up, H+ ions build
up (decrease of pH)
37
The Role of Three Energy Systems During an All-out
Exercise Activity of Different Duration
38
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