W4-L7: CVD System

Question 1

How is Blood Flow to the Heart and Brain regulated?

Answer 1

• The heart & brain cant tolerate compromised blood supply
• At rest, the myocardium uses ~75% of O2 in blood flowing through the coronary circulation
• During exercise, the coronary circulation has a four- to fivefold increase in blood flow
• Cerebral blood flow increases during exercise by ~25-30% compared with the resting flow

Question 2

How does cardiac output and oxygen transport at rest ensure an oxygen reserve in the body?

Answer 2

At rest, arterial blood carries 200 mL of O2 per liter, and with a cardiac output of ~5 L/min, 1000 mL of O2 are available to the body. Resting VO2 averages 250-300 mL/min, leaving 750 mL of O2 unused and in reserve for increased demands.slide 80

Question 3

How are maximal cardiac output and VO2max related, and what are the implications for endurance athletes?

Answer 3

Maximal cardiac output and VO2max are closely linked, as low VO2max corresponds with low maximal cardiac output.

Each 1-L increase in VO2 above rest results in a 5- to 6-L increase in blood flow, a consistent ratio across exercise modes.

High VO2max and maximal cardiac output are key traits of endurance athletes, and endurance training proportionately increases both VO2max and maximal cardiac output.

Question 4

Close Relationship Between Maximal Cardiac Output and VO2max

Answer 4

Question 5

What are the Cardiac Output Differences Among Men and Women and Children?

Answer 5

• Cardiac output and VO2 are linearly relate during graded exercise for boys and girls and men and women
• Teenage and adult women exercise at submaximal VO2 with 5 to 10% larger cardiac output than males due to their 10% lower Hb concentration
• Higher submaximal exercise HR in children do not compensate for a smaller SV
• Produces smaller cardiac output for children
• a-vO2 diff expands to meet the O2 requirements

Question 6

a-vO2 Difference During Physical Activity

Answer 6

• Arterial blood O2 content varies little from 20 mL/dL at rest throughout the exercise intensity range
• Mixed-venous O2 content varies between 12 to 15 mL/dL during rest to 2 to 4 mL/dL during maximal exercise
• Progressive expansion of a-vO2diff results from an increased cellular O2 extraction leading to a reduced venous O2 content

Question 7

a-vO2 Difference During Exercise, cont.

Answer 7

During exercise, the oxygen-carrying capacity of arterial blood increases slightly due to hemoconcentration. Hemoconcentration results from fluid moving from plasma to interstitial spaces due to:

1. Increased capillary hydrostatic pressure from rising blood pressure.
2. Metabolic byproducts drawing fluid osmotically from plasma into tissues.

Question 8

How does VO2 max differ in upper and lower body exercise?

Answer 8

• Highest VO2 during arm exercise averages 20 to 30% lower than leg exercise
• Arm exercise produces lower maximal values for HR and pulmonary ventilation compared to leg exercise
• Differences relate to smaller muscle mass activated in arm exercise

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Question 9

How does O2 consumption differ in upper body exercise? Why might this me the case? (2)

Answer 9

Submaximal oxygen consumption is higher during upper-body exercise at all power outputs due to:

1. Lower mechanical efficiency, as static muscle actions add to the O2 cost without contributing to external work.
2. Additional muscles recruited to stabilize the torso during arm exercise.

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Question 10

What are the Physiologic Responses during Upper-Body Exercise, when compared to lower body?

Answer 10

Upper-body exercise induces greater physiological strain than lower-body exercise at the same VO2 or power output, leading to higher heart rate, ventilation, perceived effort, and blood pressure.

This elevated heart rate is due to increased feed-forward stimulation from the brain’s central command and heightened feedback from peripheral receptors in active muscles.

Question 11

What are the Implications of Upper-Body Exercise?

Answer 11

• Upper-body exercise causes greater metabolic and physiological strain than leg exercise at the same submaximal load.
• Exercise prescriptions for running and cycling are not suitable for arm exercise.
• Low correlations between VO2max for arm and leg exercises prevent accurate VO2max predictions across these modes, supporting the concept of exercise specificity.