Exercise Physio 1-3

Question 1

Respiratory Exchange Ratio

Answer 1

the ratio of CO2 production to O2 consumption at the mouth

Question 2

Relationship between VO2 and work rate

Answer 2

Oxygen uptake increases with increasing work rate. Rate does not increase indefinitely.

Question 3

Relationship between Vo2 and exercise intensity

Answer 3

Vo2 increases linearly with exercise intensity to VO2max (the best indicator of aerobic fitness)

Question 4

What limits VO2max?

Answer 4

1) pulmonary factors (ventilatory capacity, diffusion)
2) cardiovascular factors (cardiac output, distribution of CO, capillarity of skeletal muscle)
3) muscle factors (mitochondria content)

Question 5

Changes in respiratory parameters with increasing exercise intensity

Answer 5

• total minute ventilation increases linearly to the point of the ventilatory threshold, then increases out of proportion to VO2 at high work intensities (NOT due to stimulation of arterial receptors)…hyperventilation at high intensities is costly but useful b/c it decreases alveolar and consequently arterial PCO2, helping manage arterial pH

Question 6

Relationship between CO and work intensity

Answer 6

CO increases linearly with work intensity (max is 4-5x resting)

Question 7

Relationship between HR and VO2

Answer 7

HR increases linearly with VO2 (sympathetic input increases, parasympathetic input decreases)

Question 8

Relationship between stroke volume and VO2

Answer 8

SV initially increases with VO2, then levels off or maybe even declines at higher work rates

Question 9

Distribution of CO during exercise

Answer 9

Arterioles delivering blood to active skeletal muscles dilate and may receive up to 80-85% of CO. Blood flow to inactive muscles and splanchnic area decreases due to vasoconstriction in these arteriolar beds

Question 10

Oxygen extraction and exercise intensity

Answer 10

A-V O2 difference widens with progressively increasing exercise intensity due to:

1) better capillary perfusion
2) a decreased myocyte PO2
3) a right shift in the oxygen-hemoglobin dissociation curve

Question 11

What limits VO2 max?

Answer 11

• Limited by CO (left ventricular output) –> if the heart could deliver more O2 to the tissues, it would.

Question 12

Does skeletal muscle’s ability to consume O2 ever limit VO2 max?

Answer 12

In normal, healthy people, NO. The exception is highly deconditioned people (COPD, dialysis, bedrest).

Question 13

Effect of exercise on BP

Answer 13

Blood pressure response depends on factors such as:

1) the muscle mass being used in the exercise,
2) whether the exercise is static or dynamic,
3) body position
4) temperature

In general CO increases more than TPR decreases so MAP rises. This increases is due to an increase in SBP rather than DBP which is expected to remain near resting levels during exercise in a healthy individual.

Question 14

Why does MAP increase more during arm work than leg work?

Answer 14

MAP = SV * HR * TPR

Leg exercise: vasodilation in large active muscle groups and vasoconstriction in small, inactive muscle groups

Arm exercise: vasodilation in small, active muscle groups and vasoconstriction in large, inactive muscle groups

Question 15

Where does energy for muscle contraction come from?

Answer 15

Anaerobically: 	
	“stored” ATP
	ADP + ADP--->ATP + AMP
	creatine phosphate (CP + ADP--->ATP + C)
	glycolysis

Aerobically:
carbohydrate, fatty acid and amino acid oxidation

Question 16

What is O2 deficit?

Answer 16

Aerobic O2 supply does not immediately meet demand during the transition from rest to steady stare exercise. Anaerobic ATP sources are mobilized creating an “O2 deficit” which is repaid post-exercise.

Question 17

Relationship between RER and Exercise Intensity

Answer 17

The RER increases as VO2 increases. Under steady state conditions this reflects increased CHO use. At high intensities (or any non steady state conditions) the RER also indicates that hyperventilation is occurring.