Energy for Movement 2

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Energy for Movement 2
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Kinetic Energy (Movement) Heat Energy
Chemical Energy
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Energy pathways
? Aerobic CHO Fat (Protein)
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? The most immediate source of ATP is the small
store of ATP within skeletal muscle.
? Phospho-Creatine (PCr) is the next most
immediate way of resynthesising ATP.
? The anaerobic breakdown of Carbohydrate (CHO)
is a slightly slower way of resynthesising ATP.
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In the first 1-2 s of a maximum sprint energy for
muscle contraction is supplied from stored ATP
and PCr.
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? The splitting of phosphate and creatine
releases chemical energy.
? This process is speeded by the enzyme creatine
kinase.
? The chemical energy released from PCr can be
used to resynthesise ATP from ADP and Pi.
? This process occurs in the main body of the
cell (called the cytoplasm).
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In the later stages of 100m the major energy
source is PCr.
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Energy pathways
? Aerobic CHO Fat (Protein)
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Metabolism of CHO
Anaerobic glycolysis
Muscle Fibre
2 ATP
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Metabolism of CHO
Anaerobic - Aerobic
Pyruvate only passes into the mitochondria in the
presence of oxygen.
? If there is insufficient oxygen then pyruvate
does not pass into the mitochondria.
This is why aerobic metabolism is limited by
oxygen.
If there is not sufficient O2 then the excess
pyruvate is converted to lactic acid.
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Lactic acid quickly dissociates (splits) into
hydogen ions (H) and lactate.
It is the H particularly that cause fatigue, by
1. Inhibiting the cross-bridge cycle and muscle
contraction.
2. Preventing the resynthesis of ATP.
? Fatigue limits the duration of high intensity
exercise.
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In the later stages of a 400m race the major
energy source is anaerobic glycolysis - the
anaerobic breakdown of CHO.
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Pyruvate
2 ATP
34 ATP
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Aerobic metabolism of CHO
Aerobic metabolism can only take place
? After anaerobic glycolysis.
? In the mitochondria.
? If sufficient oxygen is present.
From 1 glucose molecule.
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Aerobic metabolism of Fat
Aerobic metabolism can also only take place in
the mitochondria - this includes fat CHO.
? Free fatty acid (FFA) molecules are large e.g.
C16H32O2 and can resynthesise many ATP.
? However the maximum rate of Fat metabolism is
much slower than CHO metabolism.
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Central Limitations to Aerobic Metabolism
The ability to supply oxygen to the muscles.
1. The oxygen carrying capacity of the blood -
haemoglobin .
2. The delivery of the blood (and oxygen it
contains) to the muscles. - the pumping of
the heart.
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Peripheral limitations to aerobic metabolism
The ability of the muscles to use oxygen.
1. The muscles extraction of oxygen from the
blood. - capillary density.
2. The muscles ability to produce energy
aerobically. - mitochondria. - aerobic enzymes.
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Intensity of exercise energy pathways
Primary Energy Pathway
Steady State - easy
Fat
Aerobic CHO
Steady State - hard
Aerobic CHO with some anaerobic CHO
VO2max
Mostly ATP PCr.
Max Sprint
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Wilmore, J.H. Costill, D.L. (1999) Physiology
of Sport and Exercise. Human Kinetics,
Champaign, IL, USA. Chapter 4, Metabolism
and basic energy systems, p115-130.
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The Supply and Use of Oxygen
? Oxygen in the air is taken into the lungs.
? Diffuses into the capillaries and combines with
haemoglobin on the red blood cells.
? The red blood cells travel back to the heart
and are pumped around the body in the
vascular circulation.
? When the red blood cells travel through the
muscle capillaries oxygen diffuses into the
muscle.
? Within the muscle cell O2 combines with
myoglobin, which transports it to the
mitochondria.
? Oxygen ( substrate) are used to produce energy
(ATP) in the mitochondria.