Preview - Energy Systems

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Study Notes

ENERGY Production

  • ATP is made up of two types of molecules: adenosine (big) and three phosphates (small).
  • The ATP stores energy within it’s bonds. Energy is released when the connection between the last two phosphates is broken. This release of energy makes movement possible.
  • However, now ATP is ADP (adenosine diphosphate) = powerless to supply energy.
  • ADP needs to be rebuilt back to ATP for muscles to keep working.
  • Rebuilding of the ADP molecule back to ATP = re-synthesis.

– Alactacid System

Source of fuel

Creatine Phosphate

Efficiency of ATP production

Rapid supply of ATP through the availability of PC and short explosive movements (e.g. sprinting)

Duration that the system can operate

ATP exhausted after 1-2 seconds

Further activity relies on CP (creatine/phosphate molecule) which is bound by high-energy bonds, when bonds break, energy released. This energy is used to join the phosphate molecule back to ADP so it becomes ATP again (re-synthesis) – CP exhausted after 10-12 seconds

Cause of fatigue

At maximal/near maximal HR (effort), fatigue caused by inability to continually re-synthesise = ATP from PC, because PC supplies are quickly exhausted

By-products of energy production

No by-products in Alactacid system

Process and rate of recovery

At rest, CP supplies fully restored within 2 minutes

– Lactic Acid System

Source of fuel

Sugar supplies (carbohydrates)

– As glucose (in blood)

– As glycogen (stored in muscle cells and liver)

Use of glucose/glycogen is glycolysis

Breakdown of glucose/glycogen occurs without O2

Glycogen much more plentiful than CP

Higher quantity of glycogen = more energy available

Efficiency of ATP production

Provides ATP quickly, but requires large amounts of glucose

Duration that the system can operate

High intensity activities lasting 10-30 seconds

Moderate intensity lasting approx. 3 minutes(e.g. 400/800m)

Cause of fatigue

Build up of lactic acid in the muscle

By-products of energy production

Lactic acid

Process and rate of recovery

Depends on intensity/duration of activity. Somewhere around 20 mins – 2 hours, with shorter recovery assisted by active cool down. After exercise, lactic acid leaves muscles and returns to bloodstream to be stored in kidney, for fuel later on.

– Aerobic System

Source of fuel

Carbs preferred fuel, fats become important after an hour, also protein (all broken down by oxygen)

Virtually unlimited fats in well trained athlete, body will mix carbs/fats

Efficiency of ATP production

Extremely efficient for activity of a lower intensity and prolonged duration

Duration that the system can operate

More than a few minutes

Hours if individual is trained

Cause of fatigue

Depletion of carbs

Depletion of glucose to working muscles

Poor circulation/respiration (fats require more oxygen, thus faster breathing is needed)

By-products of energy production

Water and Carbon Dioxide

Process and rate of recovery

Rate of recovery depends on the duration/intensity of the activity.

Could take longer than 24 hours.

Replenishment of glycogen is required, which can take several days to digest