cardiovascular response to exercise

Question 1

acute cardiovascular responses to exercise

Answer 1

• heart rate
• stroke volume
• cardiac output
• blood flow
• blood pressure
• arteriovenous oxygen difference

Question 2

acute response: heart rate

Answer 2

• HR typically increases in a linear fashion with work rate and oxygen uptake during exercise
• magnitude of increase depends on the age, body position, fitness level, type of activity, presence of disease, medications, blood volume, and environmental factors
• HRmax=220-age
• at submaximal work we can use HR to estimate VO2 max due to direct relationship
• beta blockers inhibit sympathetic nerve activity

Question 3

acute response: stroke volume

Answer 3

• SV=volume of blood ejected per heart beat
• SV=EDV-ESV
• varies between 60 and 100ml per beat
• maximum SV=100-120 ml per beat

Question 4

stroke volume

Answer 4

mechanisms that increase the heart’s stroke volume during exercise:

• enhanced cardiac filling in diastole followed by a more forceful systolic contraction
• normal ventricular filling with a subsequent forceful ejection and emptying during systole
• training adaptations that expand blood volume and reduce resistance to blood flow in peripheral tissues

Question 5

enhanced diastolic filling

Answer 5

any factor that increase venous return or slows the heart produces greater preload during the cardiac cycle’s diastolic phase
-an increase in end-diastolic volume stretches myocardial fibers and initiates a powerful ejection stroke during contraction
-this ejects the normal stroke volume plus additional blood that entered the ventricles in diastole
Frank-starling law of the heart states that the force of contraction of the cardiac muscle remains proportional to its initial resting length
-greater preload=greater contraction

Question 6

acute response: stroke volume

Answer 6

• during exercise in normal healthy adults, SV increases CURVILINEARLY with work rate until it reaches near maximum at approximately 50% of aerobic capacity (VO2 max)
• at higher intensities (=higher HR), SV may actually decrease (not likely)

Question 7

cardiac output

Answer 7

• cardiac output (Q) expresses the amount of blood pumped by the heart during a 1 minute period
• reflects the functional capacity of the cardiovascular system
• cardiac output=heart rate (bpm)xstroke volume(milliliters)