9/30b Acute and Chronic Responses to Aerobic Activity (Examination, Evaluation, Intervention)

Question 1

determinants of VO2

Answer 1

VO2 = CO x a-vO2diff = CO x (CaO2-CvO2)

Question 2

Cardiac Output determinants

Answer 2

CO = HR x SV = L/min

Question 3

when does HR increase?

Answer 3

Initially: (<100bpm) because of parasympathetic withdrawal
Later: Increased beta1 receptor activation by SNS stimulation and circulating catecholamines

Question 4

with SCI vs HTx, what accounts for the differences in resting HR and the initial HR response? what accounts for increase in HR response?

Answer 4

Higher resting HR in HTx b/c no parasympathetic innervation. Early withdrawal of PNS innervation explains the early rise in SCI

Question 5

with SCI vs HTx, what accounts for the similar values of max HR

Answer 5

max HR is blunted in SCI and HTx due to lack of direct SNS stimulation, only circulating catecholamines

Question 6

with HTx vs sedentary, what accounts for the differences in HR response?

Answer 6

lack of innervation in HTx causes:

1. higher resting HR
2. slowed initial response
3. blunted max hr response

Question 7

what is the difference in HR for sedentary vs athlete

Answer 7

Lower resting and submax HR in athlete due
to ↑ parasympathetic activity/↓ sympathetic activity at all
submaximal workloads. Max HR is similar

Question 8

what is stroke volume affected by?

Answer 8

Preload - initial stretching of cardiac myocytes, related to ventricular filling
Afterload - force or load against which the heart has to contract to eject blood
Contractility - innate ability of heart muscle to contract
-Sympathetic Stim
-Circulating Catecholamines

Question 9

SV of SCI vs. HTx

Answer 9

SCI has no venous muscle pump to
augment venous return with exercise. This blunts the SV
response compared to HTx

Question 10

SV of sedentary vs. HTx

Answer 10

Initial similar increase due to intact venous muscle pump/↑ preload/Frank-Starling mechanism. Later increase in sedentary due to sympathetic innervation, which increases contractility. HTx has no direct innervation

Question 11

SV of sedentary vs. athlete

Answer 11

Athlete has larger ventricular volume and slower HR at all submaximal workloads, allowing longer filling time and a greater SV.

Question 12

what impacts cardiac output

Answer 12

increased due to both HR and SV

• SV contributes to up to 45% of VO2max
• Further increase due solely to HR

Question 13

CO of SCI vs HTx

Answer 13

Lack of muscle pump blunts SV increase in SCI, and therefore CO. Also, VO2 max limited due to less activated muscle mass

Question 14

CO of Sedentary vs HTx

Answer 14

Initially similar due to similar SV response. But blunted HR response in HTx due to lack of sympathetic innervation of heart limits later increases

Question 15

CO of Sedentary vs Athlete

Answer 15

Similar at low workloads. However, athlete can achieve

higher CO because SV is much higher than sedentary at all workloads

Question 16

a-vO2 difference significance

Answer 16

increases in VO2 due to increases in CO and Oxygen Extraction by Muscle

• Oxygen extraction increases because of:
  1. increased oxygen consumption in active muscle due to aerobic metabolsm
  2. restribution of blood to working muscle

Question 17

athlete vs sedentary a-vO2 difference

Answer 17

Maximal oxygen extraction is similar. Higher CO in
athlete allows him to achieve same VO2 with less
oxygen extraction.

Question 18

Mean Arterial and Pulse Pressure

Answer 18

Pulse Pressure = Psystolic - Pdiastolic

MAP = Pdiastolic + 1/3(Pulse Pressure)

Question 19

Pulse Pressure

Answer 19

1. directly proportional to SV
   - decrease SV due to ischemia -> decrease pulse pressure
   - increase SV during exercise -> increase pulse pressure
2. Inversely proportional to vessel compliance
   - arterial stiffening with aging and arteriosclerosis -> increase pulse pressure

Question 20

Systolic Blood Pressure

Answer 20

Affected by:
• Stroke volume
• Arterial compliance
• Diastolic pressure

Question 21

SBP of SCI vs HTx

Answer 21

Lack of a muscle pump in SCI blunts the SV response, and therefore the SBP response.

Question 22

SBP of HTx vs sedentary

Answer 22

SV, and therefore SBP, doesn’t increase as much in HTx

because of lack of sympathetic innervation

Question 23

SBP of athlete vs sedentary

Answer 23

Athlete has greater increase in SV, so greater SBP

response

Question 24

Diastolic Blood Pressure

Answer 24

Primarily related to:

• CO, primarily HR
• TPR

Question 25

DBP of athlete vs HTx

Answer 25

• DBP falls in the athlete because the fall in TPR is greater than the increase in CO. TPR falls due to vasodilation in skeletal muscle via vasodilator metabolites produced
  -In HTx, DPB is elevated at rest because resting HR is
  higher than the athlete. During exercise, DBP stays
  the same or increases slightly. This indicates that
  the fall in TPR is balanced by the increase in CO.
  by muscle.

Question 26

Effects of Training

Answer 26

• increase VO2 max
• increase maximal CO
  > decrease HR at rest and submaximal workloads due to increased PNS and Decreased SNS
  >SV due to ventricular filling (large chamber) and slower HR = longer filling time for diastolic filling
  -no change or slight increase in max a-v02 diff
  -Decrease myocardial oxygen demand during exercise decrease Rate pressure product
  -decrease resting BP