Lecture 35

Question 1

Two competing needs during large‑muscle exercise?

Answer 1

Match skeletal muscle blood flow to metabolic demand AND maintain arterial blood pressure.

Question 2

Resting VO₂ values?

Answer 2

0.15–0.40 L/min (3–4 ml/kg/min).

Question 3

Which organs use >80% of resting O₂?

Answer 3

Brain, heart, kidneys, liver.

Question 4

How much does VO₂ increase during exercise?

Answer 4

10–15× in untrained (30–50 ml/kg/min). Up to 70–85+ ml/kg/min in elite athletes.

Question 5

Why is VO₂max lower in women?

Answer 5

Less muscle mass and lower hemoglobin.

Question 6

Resting cardiac output?

Answer 6

Q ≈ 5 L/min (70 ml × 70 bpm).

Question 7

O₂ content of arterial blood?

Answer 7

~200 ml O₂/L.

Question 8

Fick equation?

Answer 8

VO₂ = Q × (CaO₂ – CvO₂).

Question 9

Mixed venous saturation at rest?

Answer 9

≈75% (≈150 ml O₂/L).

Question 10

Oxygen extraction at rest?

Answer 10

Most tissues extract only 20–30%, except heart (~70%).

Question 11

Implication of low extraction in many organs?

Answer 11

Blood flow can be redistributed away from kidney/liver during exercise.

Question 12

Max exercise HR & SV in untrained?

Answer 12

HR ≈ 200 bpm, SV ≈ 100 ml.

Question 13

Mixed venous saturation during maximal exercise?

Answer 13

Falls to 25–30%.

Question 14

Oxygen extraction during max exercise?

Answer 14

≈140–150 ml O₂/L of blood.

Question 15

Sympathetic vasoconstriction effect?

Answer 15

Reduces flow globally but overridden locally in active muscle by vasodilators.

Question 16

Renal + splanchnic flow during heavy exercise?

Answer 16

Reduced to ~25% of rest (~2.8 L → 0.7 L/min).

Question 17

Blood flow shift from kidney/liver during exercise?

Answer 17

≈2.1 L/min redistributed to muscle.

Question 18

Cerebral blood flow?

Answer 18

~0.75 L/min; relative contribution falls during exercise.

Question 19

Coronary blood flow during max exercise?

Answer 19

Increases 3–4× (0.15–0.20 → 0.50–0.80 L/min).

Question 20

Endurance training effect on heart?

Answer 20

Eccentric hypertrophy increases SV; max HR unchanged.

Question 21

Training effect on muscle extraction?

Answer 21

Increased capillary density improves O₂ extraction.

Question 22

Training effect on mitochondria?

Answer 22

Large increases lower lactate at submax workloads; key for endurance.

Question 23

Elite athlete SV and Q?

Answer 23

SV ≈ 200 ml; Q ≈ 40 L/min.

Question 24

Elite athlete VO₂max?

Answer 24

Typically 70–85 ml/kg/min (highest recorded ≈97+).

Question 25

Total skeletal muscle blood flow during exercise?

Answer 25

18 L/min possible in untrained (if Q=20 L/min).

Question 26

Skin blood flow in heat?

Answer 26

6–8 L/min for thermoregulation.

Question 27

Total muscle flow in elite athletes?

Answer 27

30–35+ L/min in men; 20–25+ L/min in women.

Question 28

O₂ extraction in maximal exercise?

Answer 28

~90% extracted by contracting muscle.

Question 29

Muscle mass in young men?

Answer 29

~30 kg total; 10–15 kg active in running/cycling.

Question 30

MAP during exercise?

Answer 30

≈100 mmHg; little increase due to baroreflex resetting & vasodilation.

Question 31

Primary driver of exercise hyperemia?

Answer 31

Local vasodilation > changes in blood pressure.

Question 32

Key vasodilators in active muscle?

Answer 32

Nitric oxide and metabolic byproducts.

Question 33

Peak muscle flow in untrained male example?

Answer 33

Q=22 L/min → ~15 kg muscle → compute ml/min/100 g based on distribution.

Question 34

Peak muscle flow in elite male example?

Answer 34

Q=38 L/min with 15 kg active muscle → higher ml/min/100 g.