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  • Created by: Evie
  • Created on: 06-08-14 17:24

Energy, Work and power

Energy = the ability to perform work. (measured in joules)

Work = Ability to apply a force over a distance. Force x distance moved (Newtons x Meters)

Power = Rate at which work can be done. Force x distance / time (measured in watts)

1 Joule = the energy expended in applying a force of 1 newton over a distance of 1 meter.

1 Newton = the amount of force required to accellerate a mass of 1 kg at a rate of 1m per second squared.

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Adenosine Triphosphate (ATP)

A - P - P - P <--- phosphates held by high energy bonds.

The only immediately useable source of energy in the body for muscle contractions.

Energy is released as the enzyme ATPase breaks the bonds.

This only provides energy for 2 seconds and leaves behind ADP (can't provide energy) --> additional energy from 3 energy systems is required.

3 Energy systems 

  • ATP PC system 
  • lactic acid system
  • Aerobic system 

The systems dont work in isolation. The predominant system used is dependant on the intensity and duration of the activity.

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ATP PC system

Used for high intensity short duration activities that last longer than 2 seconds (100m sprint).

ATP is resynthesised using PC (Phosphate - Creatine) which is stored in the muscles.

PC stores are limited therefore ATP can only be resynthesised in this way for up to 10 seconds.

The enzyme creatine kinase breakes the P-C bond to release energy.

This reaction is anaerobic therefore no oxygen is used 

Advantage - Very immediate source of energy.

Disadvantage  - Only suitable for short duration activities.

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Lactic Acid System

Used in activities lasting longer than 10 seconds without oxygen.

Carbohydrates are broken down into glucose and then stored as glycogen.

Anaerobic Glycosis 

PFK breakes down glucose to produce pyruvic acid which releases enough energy to resynthesis ATP twice (x2).

LDH stimulates the production of lactic acid which causes muscle pain.

Advantage - no delay in oxygen being supplied to the lungs. used for up to 3 minutes.

Disadvantage - lactic acid reduces PH of muscle cells causing fatigue.

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Aerobic System

Requires oxygen and glycogen or fat to resynthesis ATP.

Used when oxygen is readily availiable and the intensity is moderate. mostly the same process as the lactic acid system adding -

Krebs cycle 

Pyruvic acid is converted into Acetyl co-A which combines with oxaloacetic acid to form citric acid. This releases enough energy to resynthesis ATP twice.

Electron Transfer Chain.

Hydrogen ions released enter the chain which occurs in the mitochondria cristae. electrons are removed from hydrogen and passed down the chain providing 34 ATP. hydrogen combines with oxygen to produce water which is then expelled out of the body.

Advantage - activity lasts for hours as large amounts of ATP are resynthesised. no harmful by products

Disadvantage - cant be used at high intensity (delay in O2 transportation). not instant. 

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The relative contribution of each system to ATP resynthesis is determined by the intensity and duration of the activity. 

Threshold = point at which an energy system cannot provide energy.

OBLA = the point at which the concentration of lactic acid rapidly increases. (4mmol per litre of blood)

Oxygen Deficit = occurs when we cannot provide enough oxygen for the demands of the activity. Our breathing rate will increase until the demand is met.

The greater the intensity of the activity the greater the oxygen deficit. The extra oxygen taken in after exercise = EPOC (recovery process). It allows the body to return to its normal state and replenish energy stores.

Fast componant of EPOC = resaturate myoglobin to become oxymyoglobin.

Slow componant of EPOC = removal of lactic acid (converted to protein, glucose, CO2 and H20) 

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