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Lecture 4

Kinesiology 2230A/B Lecture Notes - Lecture 4: Change No Change, Exercise Intensity, Partial Pressure

Course Code
Kinesiology 2230A/B
Glen Belfry

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CV Lecture 4
Exercise - Arm vs. Leg
Systolic and diastolic BPs are higher during arm work
o Mechanism is the radius of the vasculature in the upper body compared to the larger
muscles in the lower body
Arms have a smaller radius, , which means there is greater pressure required to maintain the same
If the radius is doubled, there is a 16x change in flow
Pressure and Radius
Small arterial occlusion can have a surprisingly large effect
20% reduction in radius needs roughly 2.5 x more pressure to maintain blood flow
50% reduction needs 1920mmHg to maintain flow
Steady State Exercise
Power output isn't changing and exercise intensity is below lactate threshold
Cardiovascular drift - change in HR over time with no change in CO
o With systolic pressure during moderate intensity, blood stretches/compresses over time and
radius starts to increase
o This causes the pressure to drop
o HR must be increased to maintain flow
SV decreases in response to pressure and radius changes, HR increases
o Less blood returns to the heart because of the decrease in SV
o HR needs to be increased to maintain CO
Duration, Heat, and Exercise
Prolonged exercise and heat can lead to cardiovascular drift
o Insufficient venous return, hence a decrease in EDV
Increased core temperature - overheating
Disrupts enzyme function
Cardiac Performance and Oxygen Uptake
VO2diff = O2 extraction (offloading) from hemoglobin at tissue
At rest, a small portion (25%) of available O2 is used
o VO2 is low
With exercise, an increased amount of O2 is dropped off
Not much is used at rest
During exercise, becomes large
o Offload is more because more O2 is needed
o Even if CO doesn't change
No Change in AO2, Change in Venous O2
High partial pressures during maximal exercise
Partial pressure dictates oxyhemoglobin saturation
o High pressures = full saturation
As exercise increases, there is less blood on the venous side of circulation
Exercise in the Trained and Untrained
A-VO2diff compares how much O2 is arriving vs. how much is leaving
Resting values are similar in trained and untrained (0.225 l/min)
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