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GR. 12 FITNESS
ENERGY SYSTEMS
Mr. Mackay
MUSCULAR SYSTEM
• Energy in the human body is derived from the
breakdown of macronutrients like: carbohydrates,
fats, and proteins.
• The end result of this breakdown is the
production of ATP molecules.
• ATP provides energy for body functions.
Breakdown of
Energy currency
Carbohydrates
Fats
Proteins
Biochemical processes
Muscular Work
ATP
Thermoregulation
Digesting Food
ATP Breakdown
+ H 2O
ATP
ADP
+ Energy + P
ATP Resynthesis
ADP
+ Energy + P
ATP
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ANAEROBIC ALACTIC SYSTEM
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ANAEROBIC ALACTIC SYSTEM
Primary energy source:
Stored ATP, CP
Duration of activity:
7-12 s
Sporting events:
Weight lifting, high jump, long jump,
100m run, 25m swim
Advantages:
Produce very large amount of energy
in a short amount of time
Limiting factors:
Initial concentration of high energy
phosphates (ATP, PC)
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TRAINING
• Interval training:
– 20% increase in CP (creatine phosphate) stores.
– No change in ATP stores.
– Increase in ATP function (ATP -> ADP+P)
– Increase in CP (creatine phosphate) and
allows ATP resynthesis.
• Sprint training:
– Increase in CP stores up to 40%.
– 100% increase in resting ATP stores.
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ANAEROBIC LACTIC SYSTEM
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ANAEROBIC LACTIC SYSTEM
Primary energy source:
Stored glycogen, blood glucose
Duration of activity:
12 s – 3 min
Sporting events:
800m run, 200m swim, downhill ski
racing, 1500 speed skating
Advantages:
Ability to produce energy under conditions
of inadequate oxygen
Limiting factors:
Lactic acid build up, H+ ions build up
(decrease of pH)
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Lactic Acid Threshold
• The exercise intensity at which lactic
acid begins to accumulate within the
blood.
• The point during exercise where the
person begins to feel discomfort and
burning sensations in their muscles.
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TRAINING
• Rate of lactic acid accumulation is decreased in the
trained individual.
• This rate can be decreased by:
– Reducing the rate of lactate production.
– Increasing the rate of lactate elimination
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AEROBIC SYSTEM
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AEROBIC SYSTEM
Primary energy source:
Glycogen, glucose, fats, proteins
Duration of activity:
> 3 min
Sporting events:
Walking, jogging, swimming,
walking up stairs
Advantages:
Large output of energy over a long
period of time, removal of lactic acid
Limiting factors:
Lung function, max.blood flow, oxygen
availability, excess. energy demands
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AEROBIC SYSTEM
• The most important energy system in the human
body.
• Blood lactate levels remain relatively low.
• Primary source of energy (70-95%) for exercise
lasting longer than 3 minutes provided that:
– Working muscles have sufficient mitochondria to
meet energy requirements.
– Sufficient oxygen is supplied to the mitochondria.
– Enzymes or intermediate products do not limit the
Kreb’s cycle.
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TRAINING
• Endurance training is the most effective method (long
duration several times per week):
• Increases vascularization within muscles.
• Increases number and size of mitochondria within the
muscle fibres.
• Preferential use of fats over glycogen during exercise.
• Endurance training increases the max aerobic power
of a sedentary individual by 15-25% regardless of age.
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