fuels for exercise

• Fuels


  When exercising, the body requires fuel to allow muscular contractions to occur
• Types of fuels


  • Chemical (fuels synthesised in the body)
  • Food (fuels that come from food sources)
• PC (phosphocreatine)


  A chemical fuel that is synthesised in the body and stored in the muscles
• PC breakdown


  1. Bond between phosphate and creatine molecules split

  2. Phosphate used to turn ADP back into ATP
• PCcharacteristics


  • Preferred during explosive movements that are short in duration
  • PC stores are very limited (~10 secs) and deplete quick - low yield
  • PC has a very simple chemical structure so it provides ATP at the fastest rate (break bonds quickly)
• Food fuels


  • Carbohydrates (preferred during exercise)
  • Fats (preferred during rest or low intensity exercise)
  • Proteins (rarely used for energy)
• Protein


  A food fuel that is consumed, then broken into amino acids, and stored around the body as muscle
• Characteristics of protein


  • Building blocks for muscle tissue
  • Not preferred fuel source
  • Require a significant amount of time and oxygen for ATP production
  • Only relied on during survival situations to produce ATP
  • The body uses protein to repair + build new muscle tissue
• Carbohydrates


  A food fuel that is consumed, then broken into glucose, and stored in the muscles & liver as glycogen
• Carbohydratescharacteristics


  • More complex structure than PC, but simplest chemical structure out of food fuels
  • Most versatile fuel source
  • Can provide energy under anaerobic + aerobic conditions
  • Have limited stores within the muscles - cannot fuel exercise forever
• Anaerobic breakdown of carbohydrates


  1. Glycogen can be partially broken down without the use of oxygen

  2. Allows ATP to be re-synthesised at a fast rate (fuels high intensity movements - generally after PC has depleted)

  3. The incomplete breakdown of carbohydrates is accompanied by H+ ions which inhibit muscular contractions and cause fatigue

  4. Results in low yield - hence only fuel short bursts of exercise
• Aerobic breakdown of carbohydrates


  1. Glycogen can be completely broken down with the use of oxygen

  2. ATP re-synthesised at a moderate (or slower rate)

  3. The complete breakdown of glycogen produces a significant amount of ATP - leads to a high yield (allows athletes to exercise for longer periods of time: > 1 min)
• Fats (triglycerides)


  A food fuel that is broken into triglycerides, and stored around the body as adipose tissue
• Characteristics of fats


  • Energy rich food fuel
  • Preferred fuel source during rest and low intensity exercise
  • Require a significant amount of time and oxygen for ATP production
  • Provide the greatest yield of ATP at the slowest rate
  • The body has relatively infinite stores of fats (can fuel exercise indefinitely)
• When do we use fats


  1. Rest to low intensity (very complex chemical structure - takes a long time and lots of oxygen to produce ATP)

  2. Very long/endurance duration (the complete breakdown of fats produces a very high yield of ATP, allows athletes to exercise for extended periods of time, used when exercise intensity and ATP demand is low)