Cardiovascular Response to Activity Flashcards
HR Response
Linear increase with work rate and O2 uptake
Magnitude of increase depends on multiple factors
HR max=
220 - age (+/- 10 bpm)
SV
Stroke Volume
SV =
End diastolic volume - End systolic volume
Maximum SV =
100-120 ml per beat
SV response
Enhanced diastolic filling
More forceful systolic contraction
Peripheral adaptations reduce resistance to blood flow
Frank-Starling Law
The force of contraction of the cardiac muscle remains proportional to its initial resting length
Enhanced systolic emptying
Occurs because the ventricles always have residual volume; catecholamine release enhances myocardial contractile force to augment stroke power
During exercise in healthy adults, SV increases _____ with work rate until it reaches near maximum at ~____ of aerobic capacity
curvilinearly; 50%
At higher intensities, SV may actually ____
Decrease
Cardiac Ouput
(Q)
The amount of blood pumped by the heart during a 1-minute period
Reflects functional capacity of the cardiovascular system
Cardiac Output at rest
Varies considerably at rest
5L average for males
4L average for females
Cardiac Output distribution at rest
1/5 to muscle tissue
4/5 to digestion, liver, spleen, brain, and kidneys
Cardiac Output during exercise
Increases linearly with increases in work rate
HR increases above 50% VO2 max, combination of HR and SV below
Hormonal vascular regulation of blood flow
Decreased PO2 and increased norepinephrine and endothelial shear stress, NO is released causing vasodilation
During exercise, blood flow increases to…
Muscles; Heart; Brain; skin
Maximal Cardiac Output and VO2 Max
Low maximal oxygen consumption corresponds with low maximal cardiac output
5-6L increase in blood flow accompanies each 1-L increase in oxygen consumption above resting value
Blood Pressure acute response
Linear increase in systolic BP
Max systolic is 190-220 during exercise, shouldnt exceed 250
Diastolic should not change much but shouldnt exceed 115
a-v O2 difference during exercise
Blood O2 in arterioles doesnt change much, but gets reduced in veins
Factors affecting a-v O2 difference
Cardiac output diverted to active tissue
Some tissues temporarily reduce blood supply
Training redirects a greater portion of circulation to muscle
Factors affecting a-v O2 difference 2
Increase in skeletal muscle microcirculation
Increased capillary to fiber ratio
Increase in size and number of mitochondria
Augmenting aerobic enzyme activity
Improvement of muscle ability to produce ATP
Cardiovascular Drift
Downward drift in cardiovascular response during prolonged steady rate exercise
Lower stroke volume from lower plasma volume leads to increased HR to maintain cardiac output
Resistance Exercise
HR and BP increase
SV increases significantly during eccentric phase
Isometric Contractions
Increases in BP and HR at 20%
Above 20% contraction, sharp increase in SBP
Factors that produce additional oxygen cost at higher intensities of arm exercises
Lower mechanical efficiency
Recruitment of additional stabilizing musculature
Changes in cardiovascular function results from
Increased plasma volume Decreased HR Increased SV Increased Maximum CO Increased O2 extraction Increased Blood flow Decreased BP
