1.3 Energy For Exercise

ATP

• ATP = energy currency of the body – only usable source of energy which is readily available in the human body

• ATP – Adenosine triphosphate (one adenosine molecule and 3 phosphate molecules)

• Phosphate = P

• The energy stored in the phosphate bonds is released to cause muscular contractions

• Measured

ATP Breakdown

• The chemical reaction which causes the molecules to split - enzyme ATPase

• Exothermic (releases energy to the muscles) - 2/3 seconds

• ATP = ADP + P + energy

• ADP = Adenosine diphosphate (1 mol adenosine and 2 mol phosphate )

• P = Phosphate

ATP Resynthesis

• ADP + P + energy = ATP (endothermic)

• To replace the bond between two molecules, an energy is required from an alternative source - endothermic

• COUPLED REACTION – continual breakdown and resynthesis of ATP

Phosphocreatine(PC) - stored in the sarcoplasm - broken down with the enzyme Creatine Kinase - makes creatine and phosphate – this phosphate is the P in the reaction

The phosphate lost in the breakdown goes back into the phosphocreatine stores

• High intensity (under 10 second)

• Immediately available

• No harmful by-products

• Type 2b – Fast Glycolytic – high phosphocreatine stores

Glycolytic System (Lactic Acid System)

• Used when the ATP/PC system is exhausted

• Glucose is the next source of energy available to resynthesis ATP

• Triggered by the rise of ADP in muscle cells

• GPP = Glucose Phosphorylase

• Glycogen breaks down to glucose - enzyme GPP

• Glucose breaks down to pyruvic acid/ pyruvate - enzyme PFK - releases 2mol energy (pyruvate)

• In high intensity exercise and during the early phases of ATP resynthesis, oxygen is not available

• Lactate Dehydrogenase only appears without oxygen (anaerobic respiration)

• Pyruvic acid combines with the enzyme LDH - produces lactic acid

• Lasts for around 3 minutes at moderate intensity

• Lactic acid is created – inhibits the release of enzymes and causes pain receptors in the muscles to be stimulated

One molecule of pyruvate goes to the lactic system, the other goes to the aerobic system

Aerobic System

• Aerobic Glycolysis

• Krebs cycle

• Electron Transfer Chain

• Glucose turns into pyruvic acid

• With oxygen, it turns into energy

• At rest the main system is the aerobic system – plentiful supply of oxygen

• Intensity and duration will determine the main system

• Point B = anaerobic threshold

• Threshold – point at which the energy systems change

1) Aerobic Glycolysis

• Glucose breaks down to glycogen - enzyme GPP

• Glycogen breaks down to pyruvic acid/ pyruvate - enzyme PFK

2) Krebs Cycle

• Pyruvate breaks down to acetyl COA - enzyme Coenzyme A

• This combines with oxaloacetic acid to create citric acid

• Citric acid gets oxidised – carbon dioxide is released as a bi-product

• The resynthesis of 2 ATP moles can then happen

• This occurs in the matrix of the mitochondria

• Hydrogen atoms are removed and transported to the cristae of the mitochondria

• By the hydrogen carriers NAD and FAD

3) Electron Transport Chain

• Hydrogen atoms are split into ions and electrons

• Some ions are oxidised and released as H2O

• Pairs of hydrogen ions carried by NAD release enough energy to resynthesis 30 ATP

• FAD carries enough pairs to resynthesis another 4 molecules of ATP

• = 38 moles of ATP are produced from 1 mole of glucose

Energy Systems Recap

Describe the predominant energy system which resynthesises ATP while performing the long jump in athletics

The main energy system used to resynthesis ATP in a long jump would be the ATP/PC system, as a long jump would not take longer than 10 seconds to complete, and therefore would not cross the threshold into the lactic acid system. The ATP/PC system uses adenosine triphosphate which is broken down by the enzyme ATPase, into ADP and one phosphate molecule. This releases energy which was stored in the bonds between the molecules, and this energy allows the molecules to contract, and create movement. Energy is used to resynthesis ATP– energy + ADP + P  forms ATP, the energy is absorbed from the surroundings, creating an endothermic reaction.The breakdown of ATP is an exothermic reaction, as it releases energy to its surroundings. The continual breakdown and resynthesis of ATP is a coupled reaction. Theses reactions are anaerobic, as oxygen is not required. The enzyme used in the resynthesis of ATP is creatine kinase, and it occurs in the sarcoplasm.

The Recovery Process

• Fast Component - alactacid

• Slow Component - lactacid

• EPOC = Excess Post-Exercise Oxygen Consumption

Alactacid Component

• PC stores are restored 
  

  • 3 minutes to recover fully, 30 seconds for 50%, and 60 seconds for 75%

  • Requires 1-4L of oxygen

• Replenishment of blood and muscle oxygen
  

  • Within 1 minute, oxygen resaturates the bloodstream - associates with haemoglobin

  • Within 3 minutes, the oxygen link to muscle cells is restored

Lactacid Component

- needs 5-8 litres of O2

- takes hours to complete

• Elevated ventilation and circulation
  

  • Respiratory rate, depth, and HR remain elevated - gradually decrease to maximise O2 delivery, and bi-product removal

• Elevated body temperature
  

  • Increases metabolic rate - 60-70% of the slow lactacid component

• Removal of lactic acid
  

  • 50-75% is converted back into pyruvic acid and used in the Krebs Cycle

  • 10-25% is converted back to glucose

  • Can be converted to proteins by the Cori Cycle

  • Can be removed via sweating and in urine

Implications of Recovery

• Warm Up = minimise time spent using anaerobic aerobic system - reduces oxygen deficit

• Active Recovery = maintains respiratory rate, and HR -  speeds up the removal of lactic acid

• Cooling Aids = used post-event to speed up the removal of lactic acid and to reduce muscle soreness and DOMS - ice baths

• Intensity of Training = high intensity training will increase ATP/PC storage - boosts efficiency of the fast component, increases tolerance of lactic acid and buffering capacity, and delays OBLA - reduces demand on the slow component. Low intensity exercise will increase aerobic capacity - delays OBLA - maximises oxygen delivery to working muscles - higher intensity takes longer to recover, and low intensity allows for a faster recovery

• Work:Relief Ratios = can maximise recovery - 1:1 /1:2 / 1:3

• Strategies and Tactics = using time-outs and substitutions - delays OBLA and fatigue

• Nutrition = maximise fuel stores - delays fatigue - reduces lactic acid - speeds up recovery - creatine supplements