3 - Energy Transfer During Long Duration/Lower Intensity Exercise

Question 1

Define oxygen consumption?

Answer 1

The amount of oxygen we use to produce ATP.

Question 2

Define the VO2 max?

Answer 2

The maximum volume of oxygen that can be taken up by the muscles per minute.

Question 3

Explain sub-maximal oxygen deficit?

Answer 3

• When we start to exercise, insufficient oxygen is distributed to the tissues for all the energy to be provided aerobically. This is because it takes time for the circulatory system to respond to the increase in demand for oxygen and it also takes time for the mitochondria to adjust to the rate of aerobic respiration needed.
• As a result, energy is provided anaerobically to satisfy the increase in demand for energy until the circulatory system and mitochondria can cope.

Question 4

Explain EPOC?

Answer 4

Excess Post-exercise Oxygen Consumption is the amount of oxygen consumed during recovery above that which would have been consumed at rest during the same time.

• Recovery involves returning the body to it’s pretty-exercise state. When a performer finishes exercise, oxygen consumption still remains quite high in comparison with oxygen consumption at rest. This is because extra oxygen needs to be taken in and used to try to help the performer recover. This breathlessness after exercise is often referred to as EPOC.
• There are two main components to EPOC; Fast component (alactacid) and slow component (lactacid).

Question 5

Explain the Fast component (alactacid) of EPOC?

Answer 5

The fast component is the restoration of ATP and phosphocreatine stores and the re-saturation of myoglobin with oxygen.

• The fast replenishment stage uses the extra oxygen that is taken in during recovery to restore ATP and phosphocreatine and to re-saturate myoglobin with oxygen.
• Complete restoration of PC takes up to 3 minutes but 50% of stores can be replenished after only 30 seconds, during which time approx 3 litres of oxygen are consumed.
• Myoglobin has a high affinity for oxygen. It stores oxygen in the sarcoplasm that has diffused from the haemoglobin in the blood. After exercise, oxygen stores in the myoglobin are limited. The surplus of oxygen supplied through EPOC helps replenish these stores, taking up to 2 minutes and using approx 0.5 litres of oxygen.

Question 6

Explain the Slow Component (lactacid) of EPOC?

Answer 6

The oxygen consumed at the slow replenishment stage has several functions:

• Removal of lactic acid: lactic acid accumulates during exercise and during recovery needs to be removed, full recovery can take up to an hour or longer. Lactic acid is removed in a number of ways; converted back into pyruvate and oxidised into co2 and water, transported to blood and liver where its converted to blood glucose and glycogen (the cori cycle), converted into protein, or removed in sweat and urine.
• Maintenance of breathing and heart rates: Maintaining breathing and heart rate requires extra oxygen, this assists recovery as the extra oxygen is used to replenish ATP and phosphocreatine stores, re-saturate the myoglobin and remove lactic acid, therefore returning the body back to its pre-exercise state.
• Glycogen replenishment: Glycogen is the main energy provider and, as it is the fuel for both the aerobic system and anaerobic glycolytic system, it will be depleted during exercise.
• Increase in body temperature: When temperature remains high, respiratory rates will also remain high and this will help the performer take in more oxygen during recovery.