HMB472H1 Study Guide - Final Guide: Altitude Training, Ventricular Hypertrophy, Cardiac Output

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Published on 15 Apr 2013
School
UTSG
Department
Human Biology
Course
HMB472H1
Professor
Functional capacity of the cardiovascular system
Direct fick method
VO2= Q× avO2
Q=VO2mL × min
a-VO2 difference
Untrained characteristics of Q
HR=70 BPM
SV=70ml
Average women 25% lower due to smaller size
Endurance athletes
Characteristics of Q
o HR= 50 BPM
o SV= 100mL
Mechanisms explaining increased Qmax:
o Increased vagal tone with decreased sympathetic drive
o Increased blood volume
o Increased myocardial contractility and compliance of left ventricle
Cardiac output during exercise
Q increases rapidly during transition from rest to exercise
Q at max exercise increases up to 4 times
Stroke volume is higher
Acute response to CV exercise
HR increases as exercise intensity increases up to maximal heart rate
Stroke volume (SV) increases up to 40% to 60% VO2 max in untrained individuals and up to
maximal levels in trained individuals
Increases in HR and SV during exercise cause cardiac output (Q) to increase
Blood flow and blood pressure change
All result in allowing the body to efficiently meet the increased demands placed on it.
Maximum heart rate
The highest rate value one can achieve in all-out effort to the point of exhaustion
Remains constant day to day and changes slightly from year to year
Can be estimated: HRmax=220-age in years or HRmax=208 (0.7×age)
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Steady-state heart rate
Heart rate plateau reached during constant rate of submaximal work
Optimal heart rate for meeting circulatory demands at the rate of work
The lower the steady-state heart rate ,the more efficient the heart
Stroke volume and cardiac output
Stroke volume
o Volume of blood pumped per contraction
o End-diastolic volumevolume of blood in ventricle before contraction
o End-systolic volumevolume of blood in ventricle after contraction
o Sv=edv-esv
Cardiac output
o Total volume of blood pumped by the ventricle per minute
o Q=HR×SV
Stroke Volume
Determinant of cardiorespiratory endurance capacity at maximal rates of work
Increases with increasing rates of work up to intensities of 40% to 60% of max or higher
May continue to increase up through maximal exercise intensity, generally in highly trained
athletes
Magnitude of changes in SV depends on position of body during exercise
Stroke volume during exercise
Frank starling mechanism-more blood in the ventricle causes it to stretch more and
contract with more force
Increased ventricular contractility (without end-diastolic volume increases)
Decreased total peripheral resistance due to increased vasodilation of blood vessels to
active muscles.
Ventricular contractility
Increased contractility results in higher stroke volume
o Circulating epinephrine and nor epinephrine
o Direct sympathetic stimulation of heart
Frank starling
Degree of stretching or lengthening of myocardial fibers during filling
Frank-starling law of the heart: increased filling leads to greater ejection
Result: increase in stroke volume and cardiac output
Cardiovascular drift
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Results from
o Dehydration
o Reduction in SV
HR drifts upward to maintain same cardiac output
Cardiac output distribution
Blood flows to tissues in proportion to their metabolic activity
BUT: what if blood flow increases everywhere? What happens to BP?
Cardiac output and oxygen transport
Rest cardiac output =5L
O2 transport= 1.34 ml/gm/Hb × 15gm/100ml
o 20ml O2/100ml blood
1000ml O2
Exercise
Max Q averages 16L min (untrained)
O2 transport= 20ml/100ml blood
Result
o 3200mL O2
Training enables Q to increase up to 40L min, increasing O2 transport up to 8000mL
Close association between max Q and VO2 max
An almost proportionate in max Q accompanies increases in VO2 max with training
Slope is approximately 5-6L cardiac output/L of O2 consumption
Av-O2 difference during exercise
20mL O2 dL arterial blood
5-15 ml O2 dL venous blood
Up to a threefold increase in O2 extraction (via increased BF)
Factors that regulate cardiac output
Cardiac output= cardiac rate × stroke volume
Thermal regulation in the heat and cold
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Document Summary

Average women 25% lower due to smaller size. Characteristics of q: hr= 50 bpm, sv= 100ml. Increased myocardial contractility and compliance of left ventricle. Q increases rapidly during transition from rest to exercise. Q at max exercise increases up to 4 times. Hr increases as exercise intensity increases up to maximal heart rate. Stroke volume (sv) increases up to 40% to 60% vo2 max in untrained individuals and up to maximal levels in trained individuals. Increases in hr and sv during exercise cause cardiac output (q) to increase. All result in allowing the body to efficiently meet the increased demands placed on it. The highest rate value one can achieve in all-out effort to the point of exhaustion. Remains constant day to day and changes slightly from year to year. Can be estimated: hrmax=220-age in years or hrmax=208 (0. 7 age) Heart rate plateau reached during constant rate of submaximal work.

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