Transcript Aerobic system - Oxygen deficit_EPOC

Training Effects – linked with Aerobic System
• At the end of this section, you should be able to:
• Define and explain the term Oxygen Deficit
• Understand the recovery process and explain Slow and
Fast systems
• Identify the different characteristics of the slow and fast
component of the recovery process
• Explain the relationship between VO2 Max and sporting
performance
September 2011
Physiological effects of training…
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Why do you train?
What differences do you notice?
Internal/External?
• When training stresses the aerobic system, adaptations
make ‘systems’ more effective:
- Cardiac hypertrophy = RSV
- RHR = reduced exercising and maximal HR
- blood volume and haemoglobin
- Muscle stores of glycogen/triglycerides, myoglobin
content
Capilliarisation of muscle, number/size of mitochondria
Concentration of oxidative enzymes
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Maximal Oxygen Consumption
• As a result – VO2 Max also increases
• What is VO2 max?
Maximum amount of Oxygen
taken in
transported
used (ml)
• During rest/exercise, we require Oxygen to resynthesise
ATP
• Heart, contraction of muscles during respiration, brain function
• The total amount required is known as Oxygen Consumption
• During the onset of exercise, there is insufficient oxygen available to
produce the amount of ATP required aerobically
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Oxygen consumption during exercise
• When oxygen consumption is lower than the amount
actually required, it creates an oxygen deficit
• Insufficient oxygen available at the start of exercise to
provide all the ATP needed aerobically
• (See next side)
• Amount of ATP required for muscles to contract varies =
VO2 varies
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Graph showing Oxygen consumption during rest and
exercise
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• Why do we take in more Oxygen when we exercise
than when at rest?
• To supply mitochondria in muscle fibres, to manufacture
ATP aerobically.
• If the level of exercise intensity increases, so does the
level of oxygen uptake ……..until….
• Extreme exercise where we reach a level of Maximal
Oxygen Consumption – the maximum amount of oxygen
an individual can consume during strenuous exercise
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VO2 and sustained performance
• The greater amounts of Oxygen taken to and used within the
Mirochondria, the longer a performer can work without accumulating
Lactic Acid
• LA accumulates because there is insufficient oxygen to combine
with the hydrogen released during the breakdown of glucose.
Excess Hydrogen combines with Pyruvic acid produced during
glycolysis to form LA
• Swimming example – p.23:
• When swimming at a faster pace, lactic acid is accumulating, which
will eventually cause fatigue
• If fatigue hits too early, she will have to slow her pace – which could
mean the difference between gold and silver
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Lactate Threshold/OBLA
• You do not work at your VO2 max – this intensity can only be
tolerated for few seconds – a lack of fitness/motivation plays a part
• The harder you exercise, the more LA you generate within your
muscles, eventually your blood
• Athletes must monitor the intensity of their exercise, to ensure they
do not accumulate too much lactic acid within their blood, but at the
same time, working at an intensity close to their VO2 max
high VO2 Max
• Highly trained endurance athlete
ability to work closer to VO2
before LA threshold occurs
September 2011
Lactate Threshold/OBLA
• As we begin to exercise more intensely, a point is reached at which
lactate starts to accumulate:
Onset of Blood Lactacid Accumulation
• The point at which LA starts to accumulate within the blood.
• As a performer increases their level of intensity, they cross a point
known as the LA Threshold
• Why does it happen?
• The anaerobic lactate energy system produces more LA than can be
dealt with – therefore acid starts to accumulate in the muscles and
the blood
September 2011
Fatigue and Lactate tolerance
• Lactate tolerance, is about how well an athlete can withstand the
effects of the accumulation of lactic acid
• Evidence suggests that L.T is linked with psychological factors –
elite athletes more highly motivated more willing to ignore the
fatiguing effects of LA
• Bicarbonates combine with the free Hydrogen ions, making them
less acidic – as bicarbonates have an alkalising affect
• The alkalising agents draw the hydrogen ions and the lactic acid
from the muscle cell into the blood – reducing the effects of fatigue
• Blood flow away from muscles also contributes to the process –
which can be improved through training by increasing capillary
density at muscle site
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After Intense exercise
What is
happening to the
athletes body at
this point?
September 2011
• Alister Brownlie collapses
• (://news.bbc.co.uk/sport1/hi/other_sports/triathlon/88531
23.stm)
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Restore levels of ATP and PC
Reduce levels of Lactic Acid back to normal
Reload Myoglobin
Restore levels of muscle glycogen
Oxygen
Recovery
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• When the body is recovering from intense exercise,
MORE Oxygen is required ABOVE the normal level used
at that workload
“Excess Post-Exercise Oxygen Consumption”
(EPOC)
September 2011
• What happens during EPOC:
September 2011
• Restoring ATP levels:
- Constantly restoring ATP by resynthesis – 48/72 hrs to restore to
normal.
- This requires:
Glucose
which in turn requires:
Oxygen
• Restoring PC:
- When energy for ATP resynthesis is requires rapidly (sprinting), it is
provided by the breakdown of PC – a
reaction
The energy provided for the PC resynthesis comes from the breakdown
of glucose – therefore making an oxygen demand
September 2011
• Dealing with Lactic Acid:
• As a result of the body moving from working aerobically to
anaerobically – the lactate threshold point is crossed – this is the
point at which OBLA is reached.
• The amount of LA accumulating depends on HOW LONG you work
above the threshold.
• This has to be monitored because:
1) It will cause muscle fatigue
2) Lactic Acid can be a useful source of energy
September 2011
2 methods for dealing with excess LA
1) Converting LA to Pyruvate (oxidation)
Pyruvate then goes through
reformation
to produce energy for ATP
Process requires oxygen and occurs in the mitochondria
2) Transporting LA to the liver via bloodstream – reconverted to
glucose via CORI cycle
(Series of chemical reactions in which LA is converted to blood glucose
in the liver)
Also indirectly involved the use of Oxygen.
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Recovery – 2 components:
• The alactacid debt – (fast component)
• The Lactacid decbt – (slow component)
• Graph – p91
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The alactacid (fast)Component
• Restoration on muscle phosphagen stores (ATP/PC)
(broken down and energy used)
Oxygen consumption remains high to allow elevated rates of aerobic
respiration to continue.
Energy released aerobically is used to continue ATP production – then
to reform stores of PC depleted by exercise
Uses up to 4 litres of oxygen
Takes 2-3 minutes to complete restoration after intense exercise
Stores are replaced to 50% of normal levels after 30 secs
September 2011
The alactacid (fast)Component
• If exercise was submaximal – replenishment is even quicker
• Muscle phosphagen stores provide energy for short intensive bouts
of exercise – therefore stores can be replenished quickly.
• Link to performance: See Video clip
• In a game that relies heavily on the anaerobic energy systems such
as Basketball – the coach may schedule T.O’s to help the team
recover.
• Time available may not be sufficient to gain full recovery, but the
athlete will be able to ‘offset’ fatigue
• PC stores will reduce contribution from LA – limit amount being
produced
Sept-Oct 2011
The lactacid (slow) component
• Responsible for the removal of LA
• Full recovery can take up to 1 hr – depending on duration and
intensity
• LA accumulates in the working muscles/blood. It can be removed in
4 ways:
• Removed by cells - using it as a metabolic fuel (Pyruvic acid)
• Conversion to protein or to glycogen in muscle/liver or excretion
via urine or sweat
• Elevated breathing and heart rates – CO2 expelled through
increased circulation and respiration
• Body temp – remains high, therefore keeps respiratory and
metabolic rates higher than normal
September 2011