Exercise Physiology

Question 1

Factors influencing venous return

Answer 1

-vasoconstriction -muscle pump -respiratory pump –> negative pressure

Question 2

Major factors that effect stroke volume

Answer 2

-preload: increased preload –> increased SV -afterload: decreased afterload –> increased SV -contractility: increased contractility –> increased SV (controlled by autonomic NS)

Question 3

Enhanced contractility –> enhanced stroke volume

Answer 3

-enhance sympathetic activity

Question 4

Stroke volume response to exercise

Answer 4

-SV increases up to 40-60% of maximal excercise and then reaches plateau -all people ~double resting SV during exercise, however: -sedentary resting SV < endurance athlete resting SV -elite athletes have ability to continue to increase SV up until maximal exercise

Question 5

CO response to exercise

Answer 5

-CO responds to metabolic rate required to perform exercise -6L of CO required for each 1L increase in O2 uptake above rest -@ 50% VO2max: CO is increased by increases in HR ONLY (except in elite athletes)

Question 6

CO @ rest

Answer 6

-male co=5 L/min and female=4.5L/min -no difference in resting CO btwn trained and untrained -trained = lower HR and higher SV

Question 7

Blood flow during exercise

Answer 7

-increase in blood flow achieved by decrease in vascular resistance (not increase BP) -increase in SBP due to increased CO -local blood flow regulation

Question 8

BP during excercise

Answer 8

-systolic pressure increases -pressure during diastole should stay the same -increase in mean arterial pressure (MAP=diastole + 1/3 (systolic-diastolic))

Question 9

Blood flow to organs during excercise

Answer 9

-skeletal muscle blood flow increases -splanchnic blood flow –> decreases -brain blood flow –> slight absolute increase (though percent of total output goes down)

Question 10

Regulation of redistribution of blood flow during excercise

Answer 10

-non-exercising vascular beds: vasoconstriction via SNS -exercising: autoregulation –> vasodilation; intrinsic metabolic control, regulation by arterioles; 100% recrutiment of capillaries (vs. 5-10% @ rest)

Question 11

Sympathetic activity impact on blood vessels during exercise

Answer 11

-moderate to heavy: vasodilation @ muscle bed and vasoconstriction elsewhere to maintain MAP -very heavy: vasodilation may exceed heart’s capacity –> sympathetic can control and increase vasoconstriction in order to maintain MAP/avoid syncope

Question 12

Coronary blood flow during exercise

Answer 12

-coronary blood flow increases w/increased CO

Question 13

Methods of increasing O2 delivery

Answer 13

-exercise training -blood doping: transfusion or EPO -high altitude exposure

Question 14

O2 extraction during exercise

Answer 14

-@ rest: a[O2]=20 and v[O2]=15 –> extracted [02]=5 -exercise: a[O2]=20 and v[O2]=5 –> extracted [02]=15 -3-fold increase in O2 extraction < 5-fold increase in CO –> O2 consumption influenced more by CO than O2 extraction

Question 15

Fick equation

Answer 15

-VO2=CO x { [O2]a - [O2]v } -VO2=myocardial oxygen consumption

Question 16

Mechanisms for increased O2 extraction during exercise

Answer 16

-increase in skeletal Increase in skeletal muscle microcirculation -Increase in aerobic activity of skeletal muscle -Increase in size and number of mitochondria -Local vascular and metabolic improvements in skeletal muscle -NO increase in arterial O2 content

Question 17

Influences on myocardial O2 sypply

Answer 17

-CBF -perfusion pressure -vascular resistance

Question 18

Influences on myocardial O2 demand

Answer 18

-wall stress -HR -contractility

Question 19

Factors that decrease myocardial oxygen supply

Answer 19

-Hypotension (MAP < 60 mmHg) -Decreased Oxygen Content (anemia, hypoxia) -Decrease Coronary Blood Flow: -Fixed Coronary Stenosis -Abnormal Vessel Reactivity: -Failure to vasodilate – endothelial dysfunction -Inappropriate vasoconstriction

Question 20

Factors that increase myocardial oxygen demand

Answer 20

Exercise Fever Acute Hypertension Emotional Distress Cardiac Disease Enlarged left ventricle Drugs

Question 21

Consequences of Myocardial ischemia

Answer 21

-angina -electrical abnormalities: ST depression, arrhythmias -mechanical abnormalities: decreased fxn, mitral regurgitation -hemodynamic abnormalities: increased HR, BP

Question 22

Stenosis severity impact on O2 supply (exercise vs. rest)

Answer 22

• need 90% stenosis to decrease CBF @ rest -70% stenosis –> decreased CBF w/exercise
• exercise can help dx presence of occlusion

Question 23

RPP=

Answer 23

-“rate pressure product” - =HR x SBP = HR x CO x PVR = HR x HR x SV X PVR -index of MVO2

Question 24

“ischemic threshold”

Answer 24

-RPP (heart rate) where ischemia occurs -leads to ST-segment changes -O2 supply cannot meet myocardial demand b/c inadequate increase in coronary perfusion

Question 25

CAD impacts on physiology of exercise

Answer 25

-stroke volume/systolic BP will start to increase but plateau and fall –> “exertional hypotension” -chronotropic incompetence

Question 26

Benefits of exercise in CAD patients

Answer 26

1. Improve aerobic capacity (peak VO2) 2. Increase in peripheral O2 extraction 3. Possible increase in stroke volume 4. Decrease in sympathetic activity 5. Decrease in heart rate and BP at submaximal exercise 6. No change in total body VO2 at given workload 7. Decrease in myocardial VO2 at given workload

Question 27

Effects of exercise training on coronary circulation

Answer 27

-by increasing overall maximal exercise capacity –> given amount of work requires less O2 demand -decreased O2 demand leads to less requirement of blood flow for a certain level of work

Question 28

Less common effects of exercise training on CAD patients

Answer 28

-increasing ischemic -help endothelial dysfxn -regression of coronary

Question 29

VO2 definition/characteristics

Answer 29

Directly related to workload and energy requirement during aerobic exercise Linear increase through mild – intense exercise VO2 max – plateau of VO2 despite continued work VO2 max – indicator of aerobic capacity Quantitative measure of person’s capacity for aerobic ATP resynthesis

Question 30

Use of cardiopulmonary exercise testing in CHF

Answer 30

Accurate assessment of functional limitations (LVEF alone not a good indicator of severity of disease) Predictor of prognosis in severe heart failure Assessment of response to medical or device therapy Pre-transplantation Evaluation

Question 31

Artificial HR increase vs. Exercise HR increase impact on stroke vole

Answer 31

-artificially increasing HR at rest will result in a decreased CO due to decreased diastolic filling time -w/exercise there is an increase in stroke volume caused by factors that affect increased venous return

Question 32

HR response during exercise

Answer 32

• Resting heart rate: 60-80 bpm (untrained) or 28-40 bpm (elite athlete) • anticipatory response = sympathetic stimulation prior to exercise that prepare circulatory system • HR increase –> linear response of heart rate to workload/exercise intensity • Maximal exercise HR = 220 – age • @ lower levels of exercise the increase in HR up to 100 bpm is related to parasympathetic withdrawal; above this level it is controlled by sympathetic input

Question 33

CO output response to exercise in untrained vs. trained person

Answer 33

-untrained: ~5L/min –> ~20L/min -trained: –> 34L/min (males) or 24L/min (females)