Energy Transfer during Long Duration/Low Intensity Exercise

Energy Transfer during Long Duration/Low Intensity Exercise

1. Oxygen consumption during exercise

   • Oxygen consumption: the amount of oxygen we use to produce ATP
     • VO2
   • At rest, approx 0.3-0.4 litres of oxygen consumed per min
   • Start of exercise, more oxygen used to provide more ATP so oxygen consumption increases
   • As intensity increases, oxygen consumption increases until max oxygen consumption
     • VO2 max
     • 3-6 litres per min
   • Start of exercise, insufficient oxygen distributed to tissues for all energy to be provided aerobically
     • Takes time for circulatory system to respond to increase in demand for oxygen
     • Takes time for mitochondria to adjust rate of aerobic respiration
     • Energy provided anaerobically so satisfy increase in demand for energy until circulatory system & mitochondria can cope
       • Sub-maximal oxygen deficit

2. Oxygen consumption during recovery

   • Excess Post-exercise Oxygen Consumption (EPOC)
   • Fast component
     • Uses extra oxygen taken in during recovery to restore ATP & PC, and to re-saturate myoglobin with oxygen
     • Complete PC restoration takes 3 mins, 50% restoration takes 30 secs
       • Approx 3 litres oxygen consumed
     • Myoglobin has high affinity for oxygen
       • Stores oxygen in sarcoplasm that has diffused from haemoglobin in blood
         • After exercise oxygen stores in the myoglobin are limited
           • Surplus of oxygen supplied through EPOC helps replenish oxygen stores, taking 2 mins using 0.5L of oxygen
   • Slow component
     • Removal of lactic acid
       • When oxygen is present, lactic acid can be converted back into pyruvate & oxidised into CO2 & H2O in the inactive muscles and organs. Can then be used by the muscles as an energy source
       • Transported in the blood to liver where it's converted to blood glucose & glycogen
         • Cori Cycle
       • Converted into protein
       • Removed in sweat and urine
       • Majority of lactic acid can be oxidised into mitochondria
         • Cool-down can accelerate its removal
           • Exercise keeps metabolic rate of muscles high and keeps capillaries dilated
             • Oxygen can be flushed through, removing accumulated lactic acid
     • Begins as soon as lactic acid appears in muscle cell
       • Will continue using breathed oxygen until recovery is complete
         • Can take up to 5-6L of oxygen in first half hour recovery, removing up to 50% of lactic acid
     • Maintenance of breathing and heart rates
       • Maintaining breathing and heart rates requires extra oxygen to provide energy needed for respiratory and heart muscles
         • Assists recovery as extra oxygen used to replenish ATP & PC stores, re-saturate myoglobin and remove lactic acid, returning body back to pre-exercise state
     • Glycogen replenishment
       • Glycogen main energy provider and is fuel for aerobic and lactic acid systems
         • Will be depleted during exercise
       • Replacement of glycogen stores depends on type of exercise undertaken and when & how much carbohydrate is consumed following exercise
       • May take several days to complete restoration of glycogen after a marathon, but in less than 1 hour after high duration, short intensity exercise
       • Significant amount of glycogen can be restored as lactic acid and is converted back to blood glucose & glycogen in liver via Cori cycle
       • Eating high carbohydrate meal will accelerate glycogen restoration, as will eating within 1 hour of following exercise
       • 2 nutritional windows for optimal recovery
         • 30 mins after exercise
           • Both carbohydrates & proteins should be consumed in 3:1 or 4:1 ratio
             • Combination helps body to re-synthesise muscle glycogen more efficiently than just consuming carbohydrates on their own
         • 1-3 hours after exercise
           • Meal high in protein, carbohydrate, and healthy fat should be consumed
     • Increase in body temperature
       • When temp remains high, respiratory rates will remain high
       • Will help performer take in more oxygen during recovery
       • Extra oxygen from EPOC needed to fuel increase in temp until body returns to normal