BLOOD FLOW AND GAS TRANSPORT
I. CARDIAC OUTPUT DURING EXERCISE
A. Cardiac Output and Oxygen Transport
Cardiac output ("Q") - the amount of __blood___ pumped by either the left
or right ventricle of the heart per _minute___.
Both the left and right ventricles must have the __same___ cardiac output so
that blood flow through the pulmonary and systemic circuits is maintained
[Rate per minute]
Stroke volume - the amount of __blood__ pumped by either the left or right
ventricle per __beat__.
[Amount pumped per beat]
Cardiac output = ___heart rate____ X __stroke volume____
Since the blood transports __oxygen___, when cardiac output increases in
exercise more ___oxygen___ will be transported to the working muscles.
This relationship can be expressed by the Fick equation:
VO = HR X SV X (a-vO ) diff
where: VO 2 _oxygen__ uptake or utilization by the tissues in the body
(a-vO diff = arterial-mixed venous __oxygen__ difference
Therefore, in order to increase oxygen uptake, you must increase ___cardiac
output___ and/or extract more __oxygen___ from the arterial blood.
In general, the higher the maximal _stroke__ volume --> higher maximal
cardiac output --> higher maximum oxygen uptake (VO 2ax.)
B. Exercise Heart Rate
For any given subject, heart usually increases linearly with increasing
__workload___ until the subject's maximum heart rate is reached.
The heart rate at a given oxygen uptake is higher when the exercise is
performed with the _arms__ than with the legs. 2
Since: (1) the cardiac output required for a given workload is reasonably
__similar__ for trained and untrained subjects, and (2) trained subjects have
a higher __stroke__ volume than untrained subjects --> then, for any given
workload, trained subjects will have a lower exercise _heart rate_.
Cardiac output = HR[Heart rate] x SV [Stroke volume]
C. Stroke Volume During Exercise
Stroke volume = __end-disastoolic___ volume minus __end-systolic___
Systole - the __contraction___ phase of the cardiac cycle, when the
ventricles pump out their stroke volumes.
Diastole - the __resting___ phase of the cardiac cycle, between heart beats
End-diastolic volume (EDV) – the volume of blood in each ventricle at the
end of __diastole___ – 120 ml in an untrained person at rest
End-systolic volume (ESV) – the volume of blood that remains in each
ventricle after the ventricles have finished _contracting___ – 50 ml in an
untrained person at rest
Ejection fraction – the __percentage___ of EDV ejected with each
Ejection fraction = stroke volume/end-diastolic volume
Stroke volume increases to its __highest____ values during submaximal
exercise (40% of VO 2max, HR = 110 - 120) and then remains __constant____
during the progress ion from moderate to maximal work.
Mechanism of increase in stroke volume during exercise:
- greater __systolic_____ emptying = greater ejection fraction.
The heart has a functional residual volume - at rest in the upright position,
only ___50-60%____ of the blood in the ventricle is pumped out of the
ventricle during the contraction - 50 to 80 ml of blood remains in the
During graded exercise, the heart progressively increases stroke volume by
means of a more complete ___emptying_ during systole - due to effect of
II. DISTRIBUTION OF BLOOD FLOW DURING EXERCISE
At rest __15-20%____ of the systemic blood flow goes to the skeletal
During maximal exercise __85%__ of the cardiac output can be diverted to
the working skeletal muscles. This increased blood flow to the working
muscles is caused by:
1. Increased blood __pressure__
2. ___Dilation__ of arterioles in working muscles due to
___relaxation____ of the smooth muscle in the walls of the arterioles.
3.___Constriction____ of arterioles in the gut area (liver, intestines,
stomach, kidneys) and non-working muscles.
Resistance to flow = Fluid viscosity X Tube length
Radius of tube 4
[Don’t need to memorize this equation]
[[This is here to explain how a small change in diameter can impact the
Thus decreasing tube radius by a factor of 2 will increase resistance to flow
by a factor of 16, decreasing flow by a factor of 16. It has been calculated
that a 33 % decrease in the radius of the arterioles will produce a 400 %
increase in resistance to flow.
Conclusion – only a small change in blood vessel _radius__ dramatically
alters blood _flow__.
MAXIMAL AEROBIC POWER
I. DIRECT MEASUREMENT OF MAXIMAL AEROBICPOWER 4
A. Physiological Determinants of VO max.
Definition – VO2 max provides an integrated measurement of your
physiological systems that contribute to O2 transport and O2 utilization
including the cardiovascular, respiratory, neural and muscular systems while
maintaining body homeostasis
The maximum oxygen uptake provides important information on the
capacity of the __oxygen____ transport system.
The most important factors that determine VO m2x. 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.
B. Typical Values for VO ma2 (ml∙kg ∙min )
1. Untrained Canadian male (20-29 years) _40-50_
2. Untrained Canadian female (20-29 years) _30-50_
3. World class endurance athlete (M) 80-90
4. World class endurance athlete (F) 65-75
5. Soccer, ice hockey, basketball (M) 54-60
6. Baseball, football, thrower, sprinter 40-50
C. VO max. Test Protocols
1. The test protocol should ex