Energy Systems

1
Energy Systems
2

• Some basic truisms
• 1. All energy systems are on at all times,
  relative contributions of each one will change
• 2. As intensity ?, energy supplied by CHO ?
• 3. As duration ?, energy supplied by fat ?.
• 4. As glycogen ?, energy supplied by protein ?.
• 5. Training ? fat use at any given intensity.
• 6. Heat, cold, altitude, other stress ? CHO use.
• 7. Effects of diet ? as exercise intensity ?

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HUMAN ENERGY SYSTEMS
SPRINT (10 seconds of maximal exercise)
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HUMAN ENERGY SYSTEMS
800 METER RUN (50 seconds)
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HUMAN ENERGY SYSTEMS
ADENOSINE TRIPHOSPHATE (ATP)
PHOSPHO- CREATINE (PCr)
GLYCOLYSIS (ANAEROBIC CHO BREAKDOWN)
KREBS CYCLE (AEROBIC CHO, FAT, AND
PROTEIN BREAKDOWN)
MARATHON 2.5 hours of exercise
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• Some basic truisms
• 1. All energy systems are on at all times,
  relative contributions of each one will change
• 2. As intensity ?, energy supplied by CHO ?
• 3. As duration ?, energy supplied by fat ?.
• 4. As glycogen ?, energy supplied by protein ?.
• 5. Training ? fat use at any given intensity.
• 6. Heat, cold, altitude, other stress ? CHO use.
• 7. Effects of diet ? as exercise intensity ?

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energy from CHO 40 60 80
100
energy from FAT 40 30 20 10
increasing intensity of exercise

• As exercise gets harder, the energy from
• oxidation of CHO goes UP sharply while the
• energy from fat goes DOWN

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Exercise Intensity Fuel Source
100
80
60
FAT
( Total Kcal)
CHO
40
20
0
25 MAX
85 MAX
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Misinterpretation

• The graph on the previous slide indicates that if
  you
• exercise at very low intensity levels (25 MAX)
  you
• will burn a great deal more fat for energy
• However, at the end of the day, body weight is
• determined by how many TOTAL calories were
• ingested vs. how many TOTAL calories were
  expended
• Consider the next slide which is the same
  exercise
• scenario now expressed in absolute (calorie) terms

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Exercise Intensity Fuel Source
600
500
400
FAT
(kcal)
300
CHO
200
100
0
25 MAX
85 MAX
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• Some basic truisms
• 1. All energy systems are on at all times,
  relative contributions of each one will change
• 2. As intensity ?, energy supplied by CHO ?
• 3. As duration ?, energy supplied by fat ?.
• 4. As glycogen ?, energy supplied by protein ?.
• 5. Training ? fat use at any given intensity.
• 6. Heat, cold, altitude, other stress ? CHO use.
• 7. Effects of diet ? as exercise intensity ?

12
90
FAT being used
80
70
60
50
CHO FAT Use in Exercise
40
30
20
CHO being used
10
0
0
30
60
90
120
Exercise Time (min)
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• WHY does the of energy from CHO go
• down as the exercise duration gets longer?
• Glycogen supplies getting low remember
• that use of glycogen
• is related
• to how much
• you have.

rate of glycogen use
amount of glycogen remaining
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• So, as exercise progresses, the use of
• glycogen lessens and use of fat goes up.
• What happens to intensity?
• When glycogen supplies become very low, it
• is no longer possible to provide enough
• glycogen to sustain high intensity exercise.
• How does that make you feel?

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• Inability to maintain
• a high exercise
• intensity when
• muscle glycogen
• supplies get low is
• called bonking,
• hitting the wall,
• going down in
• flames and other
• colorful expressions.

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• So, there is always a trade-off between
• exercise intensity and duration
• High intensity (fast, hard) requires a lot of
• glycogen so duration has to be short
• Low-intensity (slow, easy) requires little
• glycogen so duration can be long
• What can you do to improve ability to maintain
• a higher intensity for a longer period of time?

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• Some basic truisms
• 1. All energy systems are on at all times,
  relative contributions of each one will change
• 2. As intensity ?, energy supplied by CHO ?
• 3. As duration ?, energy supplied by fat ?.
• 4. As glycogen ?, energy supplied by protein ?.
• 5. Training ? fat use at any given intensity.
• 6. Heat, cold, altitude, other stress ? CHO use.
• 7. Effects of diet ? as exercise intensity ?