BPK 142 Lecture Notes - Lecture 12: Vo2 Max, Monark, Cardiac Output

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Direct Measurement of Maximal Aerobic Power
Physiological Determinants of VO2max.
The maximum oxygen uptake provides important information on the capacity
of the oxygen transport system.
The most important factors that determine VO2max. in a given person are:
1. The ability to ventilate the lungs and oxygenate the blood
passing through the lungs
2. The ability of the heart to pump blood: Cardiac output
3. The oxygen carrying capacity of the blood
4. The ability of the working muscles to accept a large blood
supply
5. The ability of muscle fibers to extract oxygen from the capillary
blood and use it to produce energy (oxidative enzyme levels, etc)
As the duration of events requiring heavy continuous energy
expenditure becomes progressively greater than one minute, aerobic
capacity becomes increasingly important as a determining factor for
success.
Test Protocols
1. The test protocol should exceed 6 minutes but be less than approximately
15 min.
2. Incorporate a warmup period: First stage of test
3. The test protocol should be arranged in stages, with each stage
progressively increasing in intensity until the termination criteria is reached.
Criteria For Attainment of VO2max
1. The oxygen consumption ceases to increase linearly with increasing work
rate and approaches a plateau, the last two values agreeing within + 2 ml/kg/min.
2. Heart rate should be close to the age-predicted maximum (220 - age).
3. Blood lactate levels should be 8 millimoles/liter or greater, 3-5 minutes post
exercise.
4. Respiratory exchange ratio (VCO2 divided by VO2) should be greater than 1.10.
5. Subjective observations: Did the subject look exhausted at the end of the test?
Factors affecting Maximal Aerobic Power
Mode of Exercise Since local muscle capillarization and aerobic enzyme levels are
important determinants of VO2max., athletes should ideally be tested in the mode of
exercise used in their sport, i.e., rowers should be measured while rowing, cyclists
while cycling, etc.
In most subjects, the highest VO2max. values can be obtained during uphill
treadmill running - 5-7% higher than on a bicycle ergometer due to activation
of a larger muscle mass on the treadmill. However, competitive cyclists
pedalling at a high frequency are able to achieve VO2max. values equal to
their treadmill scores while cycling.
Bicycle ergometers are of two main types:
■ Mechanical: Monark ergometers in Kines 142 lab 2.
Electrically braked bicycle ergometer: Resistance is provided by
moving a conductor through a magnetic field.
Advantages of bicycle ergometers as compared to treadmills for
exercise testing:
1. Less expensive
2. Portable: Can be used in field studies
3. Don't require electricity
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