chapter 7 Flashcards
Oxygen Uptake At Rest
-When at rest, the body’s need for ATP is low, therefore the individual requires low levels of oxygen consumption.
-As exercise intensity increases, oxygen consumption increases to allow greater amounts of ATP to be produced at the muscle level.
Oxygen Deficit
definition:
- The state in which the oxygen supply fails to meet the body’s demand for oxygen.
-It typically occurs at the start of exercise and during this time, the body relies on the anaerobic energy systems to provide ATP for muscle contractions.
Oxygen Deficit
Explanation:
-The oxygen deficit occurs because it takes some time for the respiratory and cardiovascular systems to respond to the demand for oxygen.
-During this time, the oxygen demands of the body are greater than the supply.
Oxygen Deficit
Performance:
-Oxygen deficit usually occurs at the start of exercise.
-However, any sudden increase in intensity can create an oxygen deficit. For example, an athlete running up hill (increase in intensity) will experience oxygen deficit.
- During these times, the anaerobic energy systems will meet the ATP demands.
- The size of the oxygen deficit can be reduced by decreasing intensity, completing a warm-up and completing aerobic training.
Steady State
Definition:
-The state in which oxygen supply equals oxygen demand.
-During this time, the athlete works aerobically, with the aerobic energy system meeting the ATP demands.
- On any oxygen consumption graph, steady state will be represented by plateaus of unchanging oxygen demands.
- During this time, there will also be a plateau in heart rate and ventilation.
steady state
Explanation:
-Steady state only occurs during submaximal continuous activity.
-When the body is in steady state, the oxygen available is used to breakdown lactate and convert it to glycogen.
- It is also used to buffer H+ ions.
steady state
performance:
-In trained endurance (aerobic) athletes, the oxygen deficit is reduced due to these athletes achieving steady state sooner than untrained athletes.
Excess Post-Exercise Oxygen Consumption (EPOC)
definition:
-The amount of oxygen consumed during the recovery period which exceeds the amount of oxygen consumed at rest.
Excess Post-Exercise Oxygen Consumption (EPOC)
explanation:
The extra oxygen consumed during recovery is used to:
FAST REPLENISHMENT (0-3 MINS):
- ATP resynthesis
- Creatine Phosphate replenishment
- Restore oxygen to myoglobin
SLOW REPLENISHMENT (0-HOURS):
-Return core temperature to pre-exercise levels
- Convert lactate to carbon dioxide and water.
- Buffer H+ ions.
- Convert lactate to glycogen
- Restore heart rate, ventilation and other body systems to pre-exercise levels.
Excess Post-Exercise Oxygen Consumption (EPOC)
performance:
-The size of EPOC is directly proportional to the size of oxygen deficit throughout the event. For example, exhausting, maximal (high-intensity) exercise, will result in larger periods of oxygen deficit and therefore a larger EPOC.
- Exercising in hot conditions will create greater periods of oxygen deficit and a larger EPOC.
- Performing an active recovery which involves oxygen consumption levels being elevated will extend EPOC compared to a passive recovery.
- In trained endurance (aerobic) athletes, the oxygen deficit is reduced due to these athletes achieving steady state sooner than untrained athletes. This results in a smaller EPOC.
The Three Causes of Fatigue
Fuel Depletion:
- Intramuscular ATP
- Creatine Phosphate / Phosphocreatine (PC)
- Glycogen
Accumulation of Metabolic By-Products:
- Hydrogen Ions (H+ ions)
- Inorganic Phosphates (Pi)
- Adenosine Diphosphate (ADP)
Thermoregulatory Fatigue:
- Elevated body temperature / Dehydration
Fuel Depletion
-When we refer to fuel depletion as a fatigue-causing mechanism, we are in fact referring to the depletion of energy fuels or substrates that serve to power muscle contractions.
-They include intramuscular ATP, creatine phosphate (PC) and glycogen.
Creatine Phosphate Depletion
When does it occur?
-Creatine phosphate stores deplete rapidly during maximal intensity, short duration, anaerobic-type activities.
-After about 10 seconds of a maximal effort, the muscle stores of creatine phosphate are almost fully depleted.
Creatine Phosphate Depletion
How does this impact on performance?
- As creatine phosphate stores deplete, the ability to rapidly replenish ATP is reduced and thus, the activity cannot be sustained at the same intensity.
- When creatine phosphate stores deplete, there is an increased reliance on the slower anaerobic glycolysis energy system to sustain maximal intensity.
- The athlete will start to slow down or jumps a shorter distance as they cannot produce the same rate/force of muscle contractions.
Creatine Phosphate Depletion
How do you replenish creatine phosphate stores?
A passive recovery consisting of sitting, standing still or lying down will assist with the replenishment of creatine phosphate stores.
During a passive recovery:
- 70% of creatine phosphate stores are replenished in 30 seconds.
- 97% of intramuscular ATP and creatine phosphate stores are replenished within 3 minutes.
- It is important to be aware that the passive recovery occurs during EPOC.
-With the extra oxygen consumed used to restore intramuscular ATP and creatine phosphate stores.
Depletion of Glycogen Stores
When does this occur?
-During prolonged submaximal intensity aerobic (endurance) exercise, the body uses glycogen stores as the fuel for providing energy for ATP synthesis.
- These stores of glycogen, found in the muscle and liver, deplete after 90-120 minutes of continuous submaximal exercise.
Depletion of Glycogen Stores
How does this impact on performance?
-Depletion of glycogen stores results in a decrease in exercise intensity as the athlete will start to rely on fats to resynthesise ATP (aerobic lipolysis).
- Fats resynthesise ATP at a slower rate compared to glycogen and require more oxygen.
- ‘Hitting the wall’ is a term used in endurance sports to describe a condition caused by the depletion of glycogen stores in the muscles and liver, which results in significant levels of fatigue and loss of energy.
Depletion of Glycogen Stores
What strategies do endurance athletes use to prolong their glycogen stores?
-Endurance athletes will carbohydrate load, increase their intake of carbohydrates 3-4 days prior to an event, to increase their glycogen stores.
-During an event, endurance athletes will consume carbohydrate gels or sports drinks (which contain carbohydrates).
-This allows them to top up their glycogen stores during an event.
-Aerobic training leads to an increase in muscle glycogen stores.
-It also assists the athlete to ‘glycogen spare’ – this involves the athlete using fats stores early in an event and more readily, and saving glycogen stores for later in the event.
Accumulation of Fatiguing Metabolic By-Products
- Metabolic by-products are substances that are produced as a result of the chemical reactions involved in producing energy for ATP synthesis.
-They are the ‘left overs’ and include hydrogen ions (H+) as well as inorganic phosphates (Pi) and adenosine diphosphate (ADP).
Accumulation of Hydrogen Ions (H+ ions)
Why does this occur?
- Hydrogen ions are a by-product of the anaerobic glycolysis energy system.
-An increased reliance on the anaerobic glycolysis energy system will lead to the accumulation of hydrogen ions in the muscle.
Accumulation of Hydrogen Ions (H+ ions)
How does the accumulation of hydrogen ions impact on performance?
-When hydrogen ions accumulate to a level the athlete can no longer tolerate, fatigue will occur as the accumulation of hydrogen ions inhibits muscle contraction.
- The accumulation of hydrogen ions results in an increase in muscle acidity (decrease muscle pH).
-This inhibits the action of the glycolytic enzymes and prevents the breakdown of glycogen. It also interferes with the role that calcium (Ca2+) play in muscle contractions. - This will cause the athlete to reduce their intensity and/or slow down.
- The athlete will not be able to generate as forceful muscle contraction. For example, a long jumper may not be able to jump as far or an AFL footballer may not be able to kick a football as far.
Accumulation of Hydrogen Ions (H+ ions)
What recovery method assists athletes to remove hydrogen ions from the muscle?
- An active recovery assists athletes to remove hydrogen ions from the muscle.
- It is usually 5-10 minutes in length and consists of low intensity activity (60-70% maximum heart rate).
- During an active recovery oxygen consumption levels remain elevated.
- The higher levels of oxygen that are available at the muscles are used to buffer H+ ions and remove them from the muscle.
Accumulation of Inorganic Phosphates (Pi)
Why does this occur?
- Inorganic phosphates are a by-product of the breakdown of ATP (the breakdown of ATP produces the by-products of ADP and Pi).
-They are also a by-product of the breakdown of creatine phosphate that is used by the ATP-PC system to provide the energy for muscle contraction.
Accumulation of Inorganic Phosphates (Pi)
How does the accumulation of inorganic phosphates (Pi) impact on performance?
-The accumulation of inorganic phosphates contributes to muscle fatigue.
-Inorganic phosphates can interfere with the role that calcium plays in muscle contractions.
-Thus, the athlete will not be able to generate as forceful muscle contractions (decreased muscle contractile force).
