Transcript Anaerobic Threshold - York Catholic District School Board

Oxygen Uptake and
Performance
PSE 4U1
Exercise Science
Unit 6
Energy and Performance
• Major function of the cardiovascular
system during exercise is to deliver
oxygen to working muscles
• Cardiovascular endurance depends on
how efficiently the Cardiorespiratory
system works, that is, the ability of the
lungs, heart and blood vessels to take
oxygen and process it and deliver it to
working muscles
Performance depends on:
1. Availability of oxygen in the air (approx. 20%)
2. Diffusion of oxygen from lungs into blood
3. Chemical binding of oxygen with hemoglobin
(CO has 200-250 times greater affinity to heme
than does O2)
4. Ability of cells to pick up oxygen from the blood
in exchange for carbon dioxide and other
waste products
5. Ability to eliminate carbon dioxide through the
lungs and start over
Maximal Oxygen Consumption
•
•
•
•
The rate at which oxygen is delivered and
used by the body
Abbrev. VO2max or MVO2
Best indicator of cardiovascular (aerobic)
fitness expressed relative to body weight,
measured as ml/kg/min
The higher the value, the higher the oxygen
available for each unit of body weight;
therefore, more work can be performed
MVO2 / VO2max depends on
1. Ventilation: the volume of air that can be taken
into the lungs/min
2. Pulmonary Diffusion: oxygen and carbon
dioxide exchange in and out of blood
(capillaries)
3. Transportation of Gases: the ability of blood to
carry oxygen (hemoglobin)
4. Cardiac Output: amount of blood that can be
circulated per minute (SV x HR)
5. Ability of muscles to use delivered oxygen
(anaerobic threshold-mitochondria)
Indices of Cardiorespiratory Fitness
•
•
•
•
•
Maximum oxygen uptake (MVO2 / VO2max)
Resting HR
HR during fixed submaximal exercise/load
Endurance performance
Recovery HR
Correlation between HR and O2 uptake
• As HR increases so too does O2 uptake
Anaerobic Threshold
• Onset of blood lactate accumulation
• Percent of VO2 maximum at which one can
exercise without producing lactic acid
• Anaerobic threshold is approximately 50% of
VO2max in an untrained individual and 65% in a
trained individual
• 10-15% increase in VO2max with training
compared to an 80-90% increase in anaerobic
threshold
Lactate Threshold
Testing for Anaerobic Threshold
1. Talk Test:
•
•
•
Difficult to talk because CO2 is held in
Decrease in O2 uptake; therefore, lactic acid
increases
Breathing in interrupts speech; therefore, the talk
test is effective
2. Heart Rate:
•
Percent of max HR will help determine anaerobic
threshold
Testing for Anaerobic Threshold
3. Breath Sound Check
•
•
•
O2 binds with hydrogen ion to form H2O
Hydrogen ions produced by lactic acid increases
ventilation thereby increasing oxygen uptake
Hearing your breath during exercise allows you to
train at your ventilatory threshold
Training Adaptations
1.
2.
3.
4.
5.
6.
Increase in the amount of hemoglobin
Increase in maximal cardiac output as heart
becomes stronger
Capillarization
• Increase in size and number of capillaries around
muscle fibres, therefore, increasing blood flow
and O2 uptake
Increased efficiency in gas exchange
Increase ability of muscle to use oxygen
Increase in Mitochondria
– ATP production increases; therefore, you can
train longer and harder aerobically (Krebs, Beta
Oxi, ETC)
– Can increase about 120% after 24 months
7. Increase a-vO2 difference
8. Conversion of FT(b) to FT(a)
– Fast twitch muscle fibres become more aerobic
9. VO2max increase in 10-15%
– Increase in anaerobic threshold
10. Fibre size (muscle)
– Increase; therefore, more actin and myosin
available for contraction
a-vO2 Difference
Arteriovenous oxygen difference, or a-vO2 diff, is the difference in the
oxygen content of the blood between the arterial blood and the venous blood.
It’s a good way to see how much O2 is delivered and used by muscle
Physiological Adaptations Due to
Endurance Training
Factors affecting MVO2 / VO2max
• Diet
• Exercise
• Lifestyle